Radiation Dose to Patients from Radiopharmaceuticals: a Compendium of Current Information Related to Frequently Used Substances

Internal dosimetry study of [82Rb]Cl using a long axial field-of-view PET/CT

PURPOSE

Long axial field-of-view (LAFOV) positron emission tomography (PET) systems allow to image all major organs with one bed position, which is particularly useful for acquiring whole-body dynamic data using short-lived radioisotopes like 82Rb.

METHODS

We determined the absorbed dose in target organs of three subjects (29, 40, and 57 years old) using two different methods, i.e., MIRD and voxel dosimetry. The subjects were injected with 407.0 to 419.61 MBq of [82Rb]Cl and were scanned dynamically for 7 min with a LAFOV PET/CT scanner.

RESULTS

Using the MIRD formalism and voxel dosimetry, the absorbed dose ranged from 1.84 to 2.78 μGy/MBq (1.57 to 3.92 μGy/MBq for voxel dosimetry) for the heart wall, 2.76 to 5.73 μGy/MBq (3.22 to 5.37 μGy/MBq for voxel dosimetry) for the kidneys, and 0.94 to 1.88 μGy/MBq (0.98 to 1.92 μGy/MBq for voxel dosimetry) for the lungs. The total body effective dose lied between 0.50 and 0.76 μSv/MBq.

CONCLUSION

Our study suggests that the radiation dose associated with [82Rb]Cl PET/CT can be assessed by means of dynamic LAFOV PET and that it is lower compared to literature values.

EANM practice guidelines for an appropriate use of PET and SPECT for patients with epilepsy

Epilepsy is one of the most frequent neurological conditions with an estimated prevalence of more than 50 million people worldwide and an annual incidence of two million. Although pharmacotherapy with anti-seizure medication (ASM) is the treatment of choice, ~30% of patients with epilepsy do not respond to ASM and become drug resistant. Focal epilepsy is the most frequent form of epilepsy. In patients with drug-resistant focal epilepsy, epilepsy surgery is a treatment option depending on the localisation of the seizure focus for seizure relief or seizure freedom with consecutive improvement in quality of life. Beside examinations such as scalp video/electroencephalography (EEG) telemetry, structural, and functional magnetic resonance imaging (MRI), which are primary standard tools for the diagnostic work-up and therapy management of epilepsy patients, molecular neuroimaging using different radiopharmaceuticals with single-photon emission computed tomography (SPECT) and positron emission tomography (PET) influences and impacts on therapy decisions. To date, there are no literature-based praxis recommendations for the use of Nuclear Medicine (NM) imaging procedures in epilepsy. The aims of these guidelines are to assist in understanding the role and challenges of radiotracer imaging for epilepsy; to provide practical information for performing different molecular imaging procedures for epilepsy; and to provide an algorithm for selecting the most appropriate imaging procedures in specific clinical situations based on current literature. These guidelines are written and authorized by the European Association of Nuclear Medicine (EANM) to promote optimal epilepsy imaging, especially in the presurgical setting in children, adolescents, and adults with focal epilepsy. They will assist NM healthcare professionals and also specialists such as Neurologists, Neurophysiologists, Neurosurgeons, Psychiatrists, Psychologists, and others involved in epilepsy management in the detection and interpretation of epileptic seizure onset zone (SOZ) for further treatment decision. The information provided should be applied according to local laws and regulations as well as the availability of various radiopharmaceuticals and imaging modalities.

Non-invasive quantitative assessment of induced component displacement can safely and accurately diagnose tibial component loosening in patients: A prospective diagnostic study

PURPOSE

Aseptic loosening often requires major, expensive and invasive revision surgery. Current diagnostic modalities merely show indirect signs of loosening. A recent proof of concept study proposed a non-invasive technique for the quantitative and visual assessment of implant movement as a diagnostic aid for tibial component loosening. The primary research question addressed is whether this novel diagnostic modality can safely and effectively aid the diagnosis of aseptic loosening.

METHODS

This clinical study included patients suspected of aseptic total knee arthroplasty (TKA) loosening listed for revision surgery and asymptomatic patients. Safety was evaluated using a numerical rating scale (NRS) for discomfort and by registration of adverse events. Feasibility was assessed by recording the duration and ease of the procedure. Intra- and interrater reliability were evaluated. In symptomatic patients, diagnostic accuracy metrics were evaluated with intra-operative assessment as a reference test.

RESULTS

In total, 34 symptomatic and 38 asymptomatic knees with a TKA were analysed. The median NRS for discomfort during loading was 6 (interquartile range [IQR]: 3.75-7.00) in symptomatic patients and 2 (IQR: 1.00-3.00) in asymptomatic patients. No adverse events were reported. The majority of users found the use of the loading device easy. The median time spent in the computed tomography room was 9 min (IQR: 8.00-11.00). Excellent to good intra- and interrater reliabilities were achieved. Diagnostic accuracy analysis resulted in a sensitivity of 0.91 (95% confidence interval [CI]: 0.72-0.97) and a specificity of 0.72 (95% CI: 0.43-0.90).

CONCLUSIONS

The proposed diagnostic method is safe, feasible, reliable and accurate in aiding the diagnosis of aseptic tibial component loosening.

LEVEL OF EVIDENCE

Level II.

Clinical Feasibility of Deep Learning-Based Attenuation Correction Models for Tl-201 Myocardial Perfusion SPECT

PURPOSE

We aimed to develop deep learning (DL)-based attenuation correction models for Tl-201 myocardial perfusion SPECT (MPS) images and evaluate their clinical feasibility.

PATIENTS AND METHODS

We conducted a retrospective study of patients with suspected or known coronary artery disease. We proposed a DL-based image-to-image translation technique to transform non-attenuation-corrected images into CT-based attenuation-corrected (CT AC ) images. The model was trained using a modified U-Net with structural similarity index (SSIM) loss and mean squared error (MSE) loss and compared with other models. Segment-wise analysis using a polar map and visual assessment for the generated attenuation-corrected (GEN AC ) images were also performed to evaluate clinical feasibility.

RESULTS

This study comprised 657 men and 328 women (age, 65 ± 11 years). Among the various models, the modified U-Net achieved the highest performance with an average mean absolute error of 0.003, an SSIM of 0.990, and a peak signal-to-noise ratio of 33.658. The performance of the model was not different between the stress and rest datasets. In the segment-wise analysis, the myocardial perfusion of the inferior wall was significantly higher in GEN AC images than in the non-attenuation-corrected images in both the rest and stress test sets ( P < 0.05). In the visual assessment of patients with diaphragmatic attenuation, scores of 4 (similar to CT AC images) or 5 (indistinguishable from CT AC images) were assigned to most GEN AC images (65/68).

CONCLUSIONS

Our clinically feasible DL-based attenuation correction models can replace the CT-based method in Tl-201 MPS, and it would be useful in case SPECT/CT is unavailable for MPS.

Diagnostic Performance of Perfusion-Only SPECT/CT for Chronic Thromboembolic Pulmonary Hypertension in Comparison With Ventilation-Perfusion Planar, SPECT, and SPECT/CT Imaging

PURPOSE

The aim of this study was to assess the diagnostic performance of perfusion-only SPECT/CT (Q SPECT/CT) in comparison with that of ventilation/perfusion planar scintigraphy (V/Q planar), perfusion SPECT with ventilation scan (V/Q SPECT), and perfusion SPECT/CT with ventilation scan (V/Q SPECT/CT) in chronic thromboembolic pulmonary hypertension (CTEPH).

PATIENTS AND METHODS

Patients with pulmonary hypertension who underwent ventilation-perfusion planar and SPECT/CT were retrospectively recruited. Two nuclear medicine physicians interpreted V/Q planar, V/Q SPECT, V/Q SPECT/CT, and Q SPECT/CT according to the European Association of Nuclear Medicine criteria. The diagnostic accuracy of these modalities for CTEPH was compared using a composite reference standard of pulmonary angiography, imaging test, cardiorespiratory assessment, and follow-up.

RESULTS

A total of 192 patients were enrolled, including 85 with CTEPH. The sensitivity of Q SPECT/CT was 98.8%, which similar to that of V/Q planar (97.6%), V/Q SPECT (96.5%), or V/Q SPECT/CT (100.0%). In contrast, Q SPECT/CT exhibited significantly lower specificity (73.8%) compared with V/Q planar (86.9%, P = 0.001), V/Q SPECT (87.9%, P < 0.001), and V/Q SPECT/CT (88.8%, P < 0.001). The significantly lower specificity of Q SPECT/CT, compared with the 3 others, was observed in the subgroup aged ≥50 years ( P < 0.001 for all), but not in those <50 years.

CONCLUSIONS

Q SPECT/CT exhibited lower specificity compared with V/Q planar, V/Q SPECT, and V/Q SPECT/CT in diagnosing CTEPH. It might underscore the essential role of a ventilation scan in patients with PH, even with the introduction of SPECT/CT.

Joint EURADOS-EANM initiative for an advanced computational framework for the assessment of external dose rates from nuclear medicine patients

BACKGROUND

In order to ensure adequate radiation protection of critical groups such as staff, caregivers and the general public coming into proximity of nuclear medicine (NM) patients, it is necessary to consider the impact of the radiation emitted by the patients during their stay at the hospital or after leaving the hospital. Current risk assessments are based on ambient dose rate measurements in a single position at a specified distance from the patient and carried out at several time points after administration of the radiopharmaceutical to estimate the whole-body retention. The limitations of such an approach are addressed in this study by developing and validating a more advanced computational dosimetry approach using Monte Carlo (MC) simulations in combination with flexible and realistic computational phantoms and time activity distribution curves from reference biokinetic models.

RESULTS

Measurements of the ambient dose rate equivalent Ḣ*(10) at 1 m from the NM patient have been successfully compared against MC simulations with 5 different codes using the ICRP adult reference computational voxel phantoms, for typical clinical procedures with 99mTc-HDP/MDP, 18FDG and Na131I. All measurement data fall in the 95% confidence intervals, determined for the average simulated results. Moreover, the different MC codes (MCNP-X, PHITS, GATE, GEANT4, TRIPOLI-4®) have been compared for a more realistic scenario where the effective dose rate Ė of an exposed individual was determined in positions facing and aside the patient model at 30 cm, 50 cm and 100 cm. The variation between codes was lower than 8% for all the radiopharmaceuticals at 1 m, and varied from 5 to 16% for the face-to face and side-by-side configuration at 30 cm and 50 cm. A sensitivity study on the influence of patient model morphology demonstrated that the relative standard deviation of Ḣ*(10) at 1 m for the range of included patient models remained under 16% for time points up to 120 min post administration.

CONCLUSIONS

The validated computational approach will be further used for the evaluation of effective dose rates per unit administered activity for a variety of close-contact configurations and a range of radiopharmaceuticals as part of risk assessment studies. Together with the choice of appropriate dose constraints this would facilitate the setting of release criteria and patient restrictions.

Hyperpolarized 129Xe MRI, 99mTc scintigraphy, and SPECT in lung ventilation imaging: a quantitative comparison

RATIONALE AND OBJECTIVES

The current clinical standard for functional imaging of patients with lung ailments is nuclear medicine scintigraphy and Single Photon Emission Computed Tomography (SPECT) which detect the gamma decay of inhaled radioactive tracers. Hyperpolarized (HP) Xenon-129 MRI (XeMRI) of the lungs has recently been FDA approved and provides similar functional images of the lungs with higher spatial resolution than scintigraphy and SPECT. Here we compare Technetium-99m (99mTc) diethylene-triamine-pentaacetate scintigraphy and SPECT with HP XeMRI in healthy controls, asthma, and chronic obstructive pulmonary disorder (COPD) patients.

MATERIALS AND METHODS

59 subjects, healthy, with asthma, and with COPD, underwent 99mTc scintigraphy/SPECT, standard spirometry, and HP XeMRI. XeMRI and SPECT images were registered for direct voxel-wise signal comparisons. Images were also compared using ventilation defect percentage (VDP), and a standard 6-compartment method. VDP calculated from XeMRI and SPECT images was compared to spirometry.

RESULTS

Median Pearson correlation coefficient for voxel-wise signal comparison was 0.698 (0.613-0.782) between scintigraphy and XeMRI and 0.398 (0.286-0.502) between SPECT and XeMRI. Correlation between VDP measures was r = 0.853, p < 0.05. VDP separated asthma and COPD from the control group and was significantly correlated with FEV1, FEV1/FVC, and FEF 25-75.

CONCLUSION

HP XeMRI provides equivalent information to 99mTc SPECT and standard spirometry measures. Additionally, XeMRI is non-invasive, hence it could be used for longitudinal studies for evaluating emerging treatment for lung ailments.

Theranostics of Thyroid Cancer

Molecular imaging is pivotal in evaluating and managing patients with different thyroid cancer histotypes. The existing, pathology-based, risk stratification systems can be usefully refined, by incorporating tumor-specific molecular and molecular imaging biomarkers with theranostic value, allowing patient-specific treatment decisions. Molecular imaging with different radioactive iodine isotopes (ie, I131, I123, I124) is a central component of differentiated carcinoma (DTC)'s risk stratification while [18F]F-fluorodeoxyglucose ([18F]FDG) PET/CT is interrogated about disease aggressiveness and presence of distant metastases. Moreover, it is particularly useful to assess and risk-stratify patients with radioiodine-refractory DTC, poorly differentiated, and anaplastic thyroid cancers. [18F]F-dihydroxyphenylalanine (6-[18F]FDOPA) PET/CT is the most specific and accurate molecular imaging procedure for patients with medullary thyroid cancer (MTC), a neuroendocrine tumor derived from thyroid C-cells. In addition, [18F]FDG PET/CT can be used in patients with more aggressive clinical or biochemical (ie, serum markers levels and kinetics) MTC phenotypes. In addition to conventional radioiodine therapy for DTC, new redifferentiation strategies are now available to restore uptake in radioiodine-refractory DTC. Moreover, peptide receptor theranostics showed promising results in patients with advanced and metastatic radioiodine-refractory DTC and MTC, respectively. The current appropriate role and future perspectives of molecular imaging and theranostics in thyroid cancer are discussed in our present review.

Nuclear medicine and pediatric nephro-urology: a long-lasting successful partnership

Congenital anomalies of the kidney and urinary tract, as well as urinary infections, are very frequent in children. After the clinical and laboratory evaluation, the first imaging procedure to be done is a renal and bladder ultrasound, but afterwards, a main contribution comes from nuclear medicine. Through minimally invasive and sedation-free procedures, nuclear medicine allows the evaluation of the functional anatomy of the urinary tract, and the quantification of renal function and drainage. If pediatric dosage cards provided by scientific societies are used, radiation exposure can also be low. In the pediatric conditions previously mentioned, nuclear medicine is used both for initial diagnosis and follow-up, mostly in cases of suspicion of ureteropelvic or ureterovesical junction syndromes, as well as vesicoureteral reflux or renal scars of febrile infectious episodes. Pediatric nephro-urology constitutes a significant workload of pediatric nuclear medicine departments. The following paragraphs are a revision of the renal radiopharmaceuticals, as well as the nuclear nephro-urology procedures - dynamic and static renal scintigraphy, and direct and indirect radionuclide cystography. A summary of the techniques, main indications, interpretation criteria and pitfalls will be provided. Some future directions for the field are also pointed out, among which the most relevant is the need for nuclear medicine professionals to use standardized protocols and integrate multidisciplinary teams with other pediatric and adult health professionals that manage these life-long pediatric pathologies, which are recognized as an important cause of adult chronic kidney disease.

Administered dosage and effective dose estimated from 81Rb-rubidium hydroxide for lung ventilation scintigraphy using 81mKr noble gas

The aim of this study was to estimate the administered dosage of 81mKr noble gas as calculated by the radioactivity of 81Rb-rubidium hydroxide (81RbOH). The administered dosage was regarded as the total amount of 81mKr noble gas. The radioactivity of 81mKr was calculated using the radioactivity of 81RbOH at the examination, the beginning of inhalation, the inhalation duration and the attenuation volume from the generator to the patient for 81mKr noble gas. In addition, we created an Internet survey and asked National University Hospital in Japan to respond to questions regarding the parameters of concern. Survey responses were provided by 38 hospitals (response rate was 90.5%). Twenty-seven hospitals (64.3%) examined lung ventilation scintigraphy using 81mKr noble gas. The mean administered dosage and the effective dose of lung ventilation scintigraphy using 81mKr noble gas were 35.8 ± 22.1 GBq and 0.97 ± 0.60 mSv, respectively.

Absorbed dose coefficients for pediatric differentiated thyroid cancer patients undergoing radioiodine therapy

The escalating incidence of differentiated thyroid cancer (DTC) in pediatric patients and the resultant growing use of radioactive iodine (RAI) reinforce the need to evaluate radiation exposure to normal tissues and radiation-induced health risks in pediatric patients undergoing RAI therapy. In the current study, we calculated absorbed dose coefficients (i.e. absorbed dose per unit activity administered, mGy MBq-1) specific for pediatric patients with localized DTC undergoing RAI therapy following total thyroidectomy for use in epidemiological studies. We first modified previously-published biokinetic models for adult thyroid cancer patients to achieve a reasonable agreement with iodine biokinetics observed in pediatric patients or design principles addressed in the International Commission on Radiological Protection (ICRP) reference age-specific biokinetic models. We then combined the biokinetic models in conjunction withSvalues derived from ICRP reference pediatric voxel phantoms. The absorbed dose coefficients for pediatric patients were overall greater than those for adults with a ratio (pediatric/adult) up to 11.6 and rapidly decreased with increasing age. The sensitivity analysis showed that the renal clearance rate andSvalues may have the greatest impact on the absorbed dose coefficients with the rank correlation coefficients ranging from -0.53 to -0.82 (negative correlations) and from 0.51 to 0.80 (positive correlations), respectively. The results of the current study may be utilized in clinical or epidemiological studies to estimate organ-specific radiation absorbed doses and radiation-associated health risks among pediatric thyroid cancer patients.

Ejection fraction and ventricular volumes on rubidium positron emission tomography: Validation against cardiovascular magnetic resonance

BACKGROUND

Cardiovascular magnetic resonance (CMR) is the non-invasive gold standard for non-invasively determining left ventricular volumes (LVVs) and ejection fraction (EF). We aimed to assess the accuracy of LVV and left ventricular ejection fraction measured by positron emission tomography (PET) as compared to CMR.

METHODS

Patients who underwent both PET and CMR within 1 year were identified from prospective institutional registries. Analysis was performed to evaluate the agreement between the raw and body-surface-area-normalized left ventricular volume (LVV) and EF derived from PET vs. those derived from CMR.

RESULTS

The study population consisted of 669 patients (mean age 62 ± 13 years, 65% male). The median (interquartile range [IQR]) duration between CMR and PET imaging was 36 (7-118) days. The median (IQR) EF values were 52% (38-63%) on CMR and 53% (37-65%) on PET (mean difference: 0.53% ± 9.1, P = 0.129) with a strong correlation (Spearman rho = 0.84, P < 0.001; Intraclass Correlation Coefficient 0.84, 95% confidence interval [CI]: 0.82-0.86, P < 0.001; Lin's concordance correlation coefficient was 0.844, 95% CI: 0.822 to 0.865). Results were similar with LVV, normalized LVV/EF, and in subgroups of patients with reduced EF, coronary artery disease scar, and LV hypertrophy as well as in patients with defibrillators. However, PET tended to underestimate LVV compared to CMR.

CONCLUSION

Our analysis showed a strong correlation of EF and LVV by PET against a reference standard of CMR, whereas PET significantly underestimated LVV, but not EF, compared to CMR.

MIB Guides: Preclinical Radiopharmaceutical Dosimetry

Preclinical dosimetry is essential for guiding the design of animal radiopharmaceutical biodistribution, imaging, and therapy experiments, evaluating efficacy and/or toxicities in such experiments, ensuring compliance with ethical standards for animal research, and, perhaps most importantly, providing reasonable initial estimates of normal-organ doses in humans, required for clinical translation of new radiopharmaceuticals. This MIB Guide provides a basic protocol for obtaining preclinical dosimetry estimates with organ-level dosimetry software.

Impact of medical radionuclide discharges on people and the environment

We present a novel methodology to dynamically calculate dose rates to people and wildlife from hospital-released radionuclides reaching the environment through water treatment plants (WTPs), using the biokinetic model D-DAT for aquatic wildlife, applied to 18F, 123I, 131I, 153Sm, 99mTc and 201Tl. We have also developed a method to calculate doses to WTP workers and to farmers from agricultural practices. This proof-of-concept study simulates a generic source term of radionuclide levels in the Belgian Molse Nete River during the year 2018, chosen because the river flow was very low during that year, which constitutes a very conservative, bounding case. The dose rates to wildlife calculated for this hypothetical scenario under conservative assumptions, are well below the ERICA predicted no effects dose rate to wildlife of 10 μGy h-1. Human exposures are also very low, in most cases not exceeding 10 μSv y-1. This work identifies important data gaps and areas of uncertainty in the assessment of radiopharmaceutical effluents. The study, which is part of the EC project SINFONIA, paves the way for a dynamic screening assessment methodology able to perform consistently assessments of the impact of radiopharmaceuticals on people and wildlife. This is particularly relevant since discharges of radiopharmaceuticals in rivers are on the increase and it is necessary to explicitly demonstrate that people and the environment are adequately protected.

Radiation Exposure from GEP NET Surveillance

BACKGROUND

Neuroendocrine tumors (NET) are neoplasms that secrete peptides and neuroamines. For gastroenteropancreatic (GEP) NET, surgical resection represents the only curative option. Ten-year imaging surveillance programs are recommended due to long time-to-recurrence following resection. We performed retrospective chart review evaluating radiation exposure and practice patterns from surveillance of completely resected GEP NET.

METHODS

We performed a retrospective cohort study of cases with well-differentiated GEP NET from January 2005 to July 2020. Location of primary, modality of imaging, and duration of follow-up were collected. Dosimetry data was collected to calculate effective dose.

RESULTS

62 cases were included with 422 surveillance scans performed. Cross-sectional imaging was used in 82% and functional imaging was used in 18% of scans. Mean number of scans per year was 1.25 (0.42-3). Mean total effective dose was 56.05 mSv (SD 45.56; 0 to 198 mSv) while mean total effective dose per year was 10.62 mSv (SD 9.35; 0 to 45 mSv). Over the recommended ten years of surveillance the estimated total effective dose was 106 mSv.

CONCLUSIONS

Surveillance of completely resected GEP NET results in cumulative radiation doses in the range associated with secondary malignancy development. Strategies to minimize radiation exposure in surveillance should be considered in future guideline development.

Analysis of image data from the EuroNet PHL-C2 trial indicates a potential reduction in injected F-18 FDG activities in children: a proposal to update the EANM Paediatric Dosage Card

BACKGROUND

The aim of this work is to provide the currently missing evidence that may allow an update of the Paediatric Dosage Card provided by the European Association of Nuclear Medicine (EANM) for conventional PET/CT systems.

METHODS

In a total of 2082 consecutive [18F]FDG-PET scans performed within the EuroNet-PHL-C2 trial, the administered [18F]FDG activity was compared to the activity recommended by the EANM Paediatric Dosage Card. None of these scans had been rejected beforehand by the reference nuclear medicine panel of the trial because of poor image quality. For detailed quality assessment, a subset of 91 [18F]FDG-PET scans, all performed in different patients at staging, was selected according to pre-defined criteria, which (a) included only patients who had received substantially lower activities than those recommended by the EANM Paediatric Dosage Card, and (b) included as wide a range of different PET systems and imaging parameters as possible to ensure that the conclusions drawn in this work are as generally valid as possible. The image quality of the subset was evaluated visually by two independent readers using a quality scoring system as well as analytically based on a volume-of-interest analysis in 244 lesions and the healthy liver. Finally, recommendations for an update of the EANM Paediatric Dosage Card were derived based on the available data.

RESULTS

The activity recommended by the EANM Paediatric Dosage Card was undercut by a median of 99.4 MBq in 1960 [18F]FDG-PET scans and exceeded by a median of 15.1 MBq in 119 scans. In the subset analysis (n = 91), all image data were visually classified as clinically useful. In addition, only a very weak correlation (r = 0.06) between activity reduction and tumour-to-background ratio was found. Due to the intended heterogeneity of the dataset, the noise could not be analysed statistically sound as the high range of different imaging variables resulted in very small subsets. Finally, a suggestion for an update of the EANM Paediatric Dosage Card was developed, based on the analysis presented, resulting in a mean activity reduction by 39%.

CONCLUSION

The results of this work allow for a conservative update of the EANM Paediatric Dosage Card for [18F]FDG-PET/CT scans performed with conventional PET/CT systems.

Investigation of the quarter-dose 18 F-FDG total-body PET in routine clinical practice and its clinical value

OBJECTIVE

The purpose of the study was to evaluate the routine clinical application of total-body PET with quarter-dose 18 F-FDG.

METHODS

The contrast recovery coefficient (CRC) and coefficient of variation (COV) were evaluated among full-, half-, and quarter-dose groups with an acquisition duration of 10-, 5-, 3-, and 1-min in the NEMA (IQ) phantom test. Fifty patients undergoing total-body PET/CT with quarter-dose (0.925MBq/kg) of 18 F-FDG were included in the prospective study. The acquisition time was 10 min, divided into duration groups of 5-, 3-, and 1-min, referred to as G10, G5, G3, and G1. Visual scores were assessed based on overall visual assessment, noise scoring, and lesion conspicuity. Lesion SUV max and TBR were evaluated in semi-quantitative analysis. G10 was used as the gold reference to evaluate lesion detectability.

RESULTS

In the phantom study, the COV value of the images with quarter-dose 18 F-FDG and 10-min acquisition time was 11.52%. For spheres with 10 mm diameter, the CRC of quarter-dose PET images was relatively stable compared to that of full-dose groups with all acquisition durations. In the human study, the visual score in G10, G5, and G3 was significantly higher than that in G1. The differences in lesion SUV max and TBR for G1-G10 were significantly higher than that for G5-G10 and G3-G10. All lesions in G10 could be identified in G5 and G3.

CONCLUSION

The phantom and human findings demonstrated the feasibility of quarter-dose 18 F-FDG PET with 3-min acquisition time, which can maintain image quality with reduced radiation dose.

Exponential dosing to standardize myocardial perfusion image quality with rubidium-82 PET

BACKGROUND

82Rb PET is commonly performed using the same injected activity in all patients, resulting in lower image quality in larger patients. This study compared 82Rb dosing with exponential vs proportional functions of body weight on the standardization of myocardial perfusion image (MPI) quality.

METHODS

Two sequential cohorts of N = 60 patients were matched by patient weight. Rest and dipyridamole stress 82Rb PET was performed using 0.1 MBq·kg-2 exponential and 9 MBq·kg-1 proportional dosing. MPI scans were compared qualitatively with visual image quality scoring (IQS) and quantitatively using the myocardium-to-blood contrast-to-noise ratio (CNR) and blood background signal-to-noise ratio (SNR) as a function of body weight.

RESULTS

Average (min-max) patient body weight was 81 ± 18 kg (46-137 kg). Proportional dosing resulted in decreasing CNR, SNR, and visual IQS with increasing body weight (P < 0.05). Exponential dosing eliminated the weight-dependent decreases in these image quality metrics that were observed in the proportional dosing group.

CONCLUSION

82Rb PET dosing as an exponential (squared) function of body weight produced consistent stress perfusion image quality over a wide range of patient weights. Dramatically lower doses can be used in lighter patients, with the equivalent population dose shifted toward the heavier patients to standardize diagnostic image quality.

Association between body mass index (BMI) and [123I]Ioflupane (DaTSCAN) availabilities in patients with parkinsonism using single-photon emission computed tomography-computed tomography (SPECT-CT)

AIM

[123I]Ioflupane (DaTSCAN) has a high binding affinity to the dopamine (DA) transporter (DaT) and tenfold less affinity to serotonin (5-HT) transporter (SERT). Both neurotransmitters are considered to contribute to body weight regulation. This study assesses the association between body mass index (BMI) and DaTSCAN availability in brain.

METHOD

Scans from 74 consecutive patients who had undergone DaTSCAN single-photon emission computed tomography-computed tomography (SPECT-CT) were used to obtain semi- and absolute quantitative data in several volumes of interest (VOIs). Relative semi-quantitative specific binding ratios (SBRs) from Chang attenuated SPECT were obtained from GE DaTQUANT. Absolute normalised concentration (NC) was calculated from attenuation/scatter corrected SPECT-CT images, using an adapted version of the EARL Ltd (European Association of Nuclear Medicine (EANM) Research 4 Life) template. Scans were subdivided into either degenerative parkinsonism (abnormal = 49), borderline (n = 14) or scan without evidence of dopaminergic deficit (SWEDD = 11) using visual assessment and SBR values by two nuclear medicine consultants.

RESULTS

SBRs did not correlate with BMI. However, NC values correlated negatively in the entire cohort, with the strongest correlation in the frontal (r = - 0.649. p = 0.000), occipital (r = - 0.555, p = 0.000) regions and pons (r = - 0.555, p = 0.000). In the abnormal (n = 49) and SWEDD group (n = 11), NC of the frontal region was the most correlated with BMI (r = - 0.570, p = 0.000; r = - 0.813, p = 0.002, respectively). In the borderline group (n = 14), the left posterior putamen displayed the strongest correlation (r = - 0.765, p = 0.001).

CONCLUSION

Absolute NC values demonstrate a strong inverse correlation with BMI, strongest in the extrastriatal regions. Due to the predominately non-overlapping distribution of DaT and SERT, this study suggests greater involvement of SERT in obesity with possible interplay with DA transmission.

Identifying and troubleshooting the pitfalls of ictal/interictal brain perfusion SPECT studies

Epilepsy is a prevalent condition, and surgical intervention can benefit patients with refractory seizures. Single photon emission computed tomography (SPECT) using 99mTc-HMPAO or 99mTc-ECD provides assessment of regional cerebral blood flow and is the primary non-invasive approach for imaging brain perfusion in ictal and interictal states. Ictal/interictal SPECT is valuable in localising epileptogenic foci, particularly when MRI and electroencephalography are negative. However, to obtain accurate images reflecting brain perfusion in both states, meticulous preparation of the patient, timely radiotracer injection and close coordination between neurology and nuclear medicine teams are essential. Tracers also have inherent limitations, and patients may present with coexisting brain pathologies for which coregistration of SPECT images with MRI is recommended to improve diagnostic accuracy. Inconclusive SPECT findings may require repeating the exam or considering additional investigations. A comprehensive approach, considering various factors, is crucial for accurate interpretation of SPECT studies in presurgical epilepsy evaluations. This article provides a summary of the organisation and key challenges involved in conducting ictal/interictal SPECT studies, covering the entire process from a patient's hospital arrival to the integration of results within their presurgical pathway and using our experience of 182 patients over 10 years.

Use of ionizing radiation in a Norwegian cohort of children with congenital heart disease: imaging frequency and radiation dose for the Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy in Pediatrics (HARMONIC) study

BACKGROUND

The European-funded Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy in Pediatrics (HARMONIC) project is a multicenter cohort study assessing the long-term effects of ionizing radiation in patients with congenital heart disease. Knowledge is lacking regarding the use of ionizing radiation from sources other than cardiac catheterization in this cohort.

OBJECTIVE

This study aims to assess imaging frequency and radiation dose (excluding cardiac catheterization) to patients from a single center participating in the Norwegian HARMONIC project.

MATERIALS AND METHODS

Between 2000 and 2020, we recruited 3,609 patients treated for congenital heart disease (age < 18 years), with 33,768 examinations categorized by modality and body region. Data were retrieved from the radiology information system. Effective doses were estimated using International Commission on Radiological Protection Publication 60 conversion factors, and the analysis was stratified into six age categories: newborn; 1 year, 5 years, 10 years, 15 years, and late adolescence.

RESULTS

The examination distribution was as follows: 91.0% conventional radiography, 4.0% computed tomography (CT), 3.6% diagnostic fluoroscopy, 1.2% nuclear medicine, and 0.3% noncardiac intervention. In the newborn to 15 years age categories, 4-12% had ≥ ten conventional radiography studies, 1-8% underwent CT, and 0.3-2.5% received nuclear medicine examinations. The median effective dose ranged from 0.008-0.02 mSv and from 0.76-3.47 mSv for thoracic conventional radiography and thoracic CT, respectively. The total effective dose burden from thoracic conventional radiography ranged between 28-65% of the dose burden from thoracic CT in various age categories (40% for all ages combined). The median effective dose for nuclear medicine lung perfusion was 0.6-0.86 mSv and for gastrointestinal fluoroscopy 0.17-0.27 mSv. Because of their low frequency, these procedures contributed less to the total effective dose than thoracic radiography.

CONCLUSION

This study shows that CT made the largest contribution to the radiation dose from imaging (excluding cardiac intervention). However, although the dose per conventional radiograph was low, the large number of examinations resulted in a substantial total effective dose. Therefore, it is important to consider the frequency of conventional radiography while calculating cumulative dose for individuals. The findings of this study will help the HARMONIC project to improve risk assessment by minimizing the uncertainty associated with cumulative dose calculations.

Image Quality and Quantitative PET Parameters of Low-Dose [18F]FDG PET in a Long Axial Field-of-View PET/CT Scanner

PET/CT scanners with a long axial field-of-view (LAFOV) provide increased sensitivity, enabling the adjustment of imaging parameters by reducing the injected activity or shortening the acquisition time. This study aimed to evaluate the limitations of reduced [18F]FDG activity doses on image quality, lesion detectability, and the quantification of lesion uptake in the Biograph Vision Quadra, as well as to assess the benefits of the recently introduced ultra-high sensitivity mode in a clinical setting. A number of 26 patients who underwent [18F]FDG-PET/CT (3.0 MBq/kg, 5 min scan time) were included in this analysis. The PET raw data was rebinned for shorter frame durations to simulate 5 min scans with lower activities in the high sensitivity (HS) and ultra-high sensitivity (UHS) modes. Image quality, noise, and lesion detectability (n = 82) were assessed using a 5-point Likert scale. The coefficient of variation (CoV), signal-to-noise ratio (SNR), tumor-to-background ratio (TBR), and standardized uptake values (SUV) including SUVmean, SUVmax, and SUVpeak were evaluated. Subjective image ratings were generally superior in UHS compared to the HS mode. At 0.5 MBq/kg, lesion detectability decreased to 95% (HS) and to 98% (UHS). SNR was comparable at 1.0 MBq/kg in HS (5.7 ± 0.6) and 0.5 MBq/kg in UHS (5.5 ± 0.5). With lower doses, there were negligible reductions in SUVmean and SUVpeak, whereas SUVmax increased steadily. Reducing the [18F]FDG activity to 1.0 MBq/kg (HS/UHS) in a LAFOV PET/CT provides diagnostic image quality without statistically significant changes in the uptake parameters. The UHS mode improves image quality, noise, and lesion detectability compared to the HS mode.

Tc-99m DMSA SPECT for Follow-Up of Non-Operative Treatments in Renal Injuries: A Prospective Single-Center Study

OBJECTIVE

The assessment of cortical integrity following renal injuries with planar Tc-99m dimercaptosuccinic acid (DMSA) scintigraphy depends on measuring relatively decreased cortical uptake (i.e., split renal function [SRF]). We analyzed the additive values of the volumetric and quantitative analyses of the residual cortical integrity using single-photon emission computed tomography (SPECT) compared to the planar scintigraphy.

MATERIALS AND METHODS

This prospective study included 47 patients (male:female, 32:15; age, 47 ± 22 years) who had non-operatively managed renal injuries and underwent DMSA planar and SPECT imaging 3-6 months after the index injury. In addition to planar SRF, SPECT SRF, cortical volume, and absolute cortical uptake were measured for the injured kidney and both kidneys together. The correlations of planar SRF with SPECT SRF and those of SRF with volumetric/quantitative parameters obtained with SPECT were analyzed. The association of SPECT parameters with renal function, grades of renal injuries, and the risk of renal failure was also analyzed.

RESULTS

SPECT SRF was significantly lower than planar SRF, with particularly higher biases in severe renal injuries. Planar and SPECT SRF (dichotomized with a cutoff of 45%) showed 19%-36% of discrepancies with volumetric and quantitative DMSA indices (when dichotomized as either high or low). Absolute cortical uptake of the injured kidney best correlated with glomerular filtration rate (GFR) at follow-up (ρ = 0.687, P < 0.001) with significant stepwise decreases by GFR strata (90 and 60 mL/min/1.73 m²). Total renal cortical uptake was significantly lower in patients with moderate-to-high risk of renal failure than those with low risk. However, SRF did not reflect GFR decrease below 60 mL/min/1.73 m² or the risk of renal failure, regardless of planar or SPECT (count- or volume-based SRF) imaging.

CONCLUSION

Quantitative measurements of renal cortical integrity assessed with DMSA SPECT can provide more clinically relevant and comprehensive information than planar imaging or SRF alone.

The burden of radiation exposure in children requiring percutaneous nephrolithotomy

BACKGROUND

Children undergoing investigation and management for complex upper tract urolithiasis often require multimodal imaging. The significance of related radiation exposure in stone care pathways has received little attention in the published literature.

STUDY DESIGN

Medical records of paediatric patients undergoing percutaneous nephrolithotomy were retrospectively analysed to ascertain the modalities used and determine extent of radiation exposure occurring during each care pathway. Radiation dose simulation and calculation was performed a priori. The cumulative effective dose (mSv) and cumulative organ dose (mGy) for radiosensitive organs was calculated.

RESULTS

A total of 140 imaging studies were included from the care pathways of 15 children with complex upper tract urolithiasis. Median follow-up was 9.6 years (range: 6.7-16.8 years). The average number of imaging studies with ionising radiation per patient was nine, with a cumulative effective dose of 18.3 mSv across all modalities. The most common modalities were: mobile fluoroscopy (43%), x-ray (24%), and computed tomography (18%). The cumulative effective dose per study type was greatest for CT (4.09 mSv), followed by fixed and mobile fluoroscopy (2.79 mSv and 1.82 mSv, respectively).

CONCLUSION

There is high general awareness of radiation exposure involved in CT scanning with resultant caution in employing this modality in paediatric patients. However, the significant radiation exposure relating to fluoroscopy (whether fixed or mobile) is less well documented in children. We recommend implementing steps to minimise radiation exposure by optimisation and avoidance of certain modalities where possible. Paediatrics urologists must employ strategies to minimise radiation exposure in children with urolithiasis, given the significant exposures encountered.

Quantitative [123]I-Ioflupane DaTSCAN single-photon computed tomography-computed tomography in Parkinsonism

AIM

[123]I-Ioflupane (DaTSCAN) binds to the presynaptic dopamine transporter (DAT) and with a lower affinity to the serotonin transporter (SERT). We aimed to develop a novel method to quantify absolute uptake in the striatal (predominantly DAT binding) and extra-striatal regions (mainly SERT binding) using single-photon computed tomography-computed tomography (SPECT-CT) DaTSCAN and to improve DaTSCAN image quality.

METHOD

Twenty-six patients with Parkinsonism underwent DaTSCAN SPECT-CT prospectively. The scans were visually analyzed independently by two experienced reporters. Specific binding ratios (SBRs) from Chang attenuation corrected SPECT were obtained using GE DaTQuant. Normalized concentrations and specific uptakes (NSU) from measured attenuation and modelled scatter-corrected SPECT-CT were obtained using HERMES Hybrid Recon and Affinity and modified EARL volumes of interest.

RESULTS

Striatal NSU and SBR positively correlate ( R  = 0.65-0.88, P  = 0.00). SBR, normalized concentrations, and NSU box plots differentiated between scans without evidence of dopaminergic deficit and abnormal scans. Interestingly, body weight inversely correlated with normalized concentrations values in extra-striatal regions [frontal ( R  = 0.81, P  = 0.00); thalamus ( R  = 0.58, P  = 0.00); occipital ( R  = 0.69, P  = 0.00)] and both caudate nuclei [ R  = 0.42, P  = 0.03 (Right), R  = 0.52, P  = 0.01 (Left)]. Both reporters noted improved visual quality of SPECT-CT versus SPECT images for all scans.

CONCLUSION

DaTSCAN SPECT-CT resulted in more accurate quantification, improved image quality, and enabled absolute quantification of extra-striatal regions. More extensive studies are required to establish the full value of absolute quantification for diagnosis and monitoring the progression of neurodegenerative disease, to assess an interplay between DAT and SERT, and to verify whether serotonin and DATs are potentially dysfunctional in obesity.

Assessment of Radiation Exposure in a Nuclear Medicine Department during 99mTc-MDP Bone Scintigraphy

This study measured 99mTc-MDP bone scintigraphy radiation risks, as low-dose radiation exposure is a growing concern. Dosimeter measurements were taken at four positions (left lateral, right lateral, anterior, and posterior) around the patients at 30, 60, 100, and 200 cm at 0, 1.5, and 3 h. The highest dose rates were recorded from 51% of the patients, who emitted ≥ 25 µSv/h up to 49.00 µSv/h at the posterior location at a distance of 30 cm. Additionally, at the anterior location at a distance of 30 cm, 42% of patients emitted ≥ 25 µSv/h up to 38.00 µSv/h. Furthermore, at 1.5 h after the tracer injection, 7% of the dose rates exceeded 25 µSv/h. There was a significant reduction in mean dose rates for all positions as distance and time increased (p-value < 0.05). As a result, radiation levels decreased with increased distance and time as a result of radiation decay, biological clearance, and distance from the source. In addition, increasing the distance from the patient for all positions reduced the radiation dose, as was substantiated via exponential regression analysis. Additionally, after completing the bone scintigraphy, the patients' dose rates on discharge were within the current guidelines, and the mean radiation doses from 99mTc-MDP were below occupational limits. Thus, medical staff received less radiation than the recommended 25 μSv/h. On discharge and release to public areas, the patients' mean dose rates were as follows: 1.13 µSv/h for the left lateral position, 1.04 µSv/h for the right lateral, 1.39 µSv/h for the anterior, and 1.46 µSv/h for the posterior. This confirms that if an individual was continuously present in an unrestricted area, the dose from external sources would not exceed 20 µSv/h. Furthermore, the patients' radiation doses were below the public exposure limit on discharge.

Cumulative radiation exposure from radiological imaging in patients with Hodgkin and diffuse large b-cell lymphoma not submitted to radiotherapy

OBJECTIVE

To assess the cumulated exposure to radiation due to imaging in Hodgkin (HL) and diffuse large B-cell (DLBCL) lymphoma patients who were not submitted to radiotherapy.

METHODS

The study population included 51 and 83 adult patients with HL and DLBCL, with a follow-up duration >1 year. The cumulated exposure was expressed using patient-specific data as cumulated effective dose (CED).

RESULTS

Fifty-one HL patients (median age 47 years) were followed for a median of 3.5 years. The median total CED per subject was 104 mSv. CT and PET/CT examinations accounted for 75 and 25% of the total CED, respectively. 26 patients (49%) had a total CED ≥ 100 mSv and the maximum CED was 302 mSv. Eighty-three DLBCL patients (median age 66 years) were followed for a median of 3.7 years. The median total CED per subject over the study period was 134 mSv. CT and PET/CT for 86% and 13% of the total CED, respectively. 56 patients (67%) had a total CED ≥100 mSv. The maximum CED was 557 mSv.

CONCLUSION

Our study demonstrated the large number of imaging procedures performed for patients with lymphoma. Overall, 61% of the patients accrued a CED ≥ 100 mSv. Imaging policies were only in a partial agreement with current international guidelines.

ADVANCES IN KNOWLEDGE

The cumulated exposure radiation exposure may be of concern in HL patients and the contribution of CT procedures to the total CED is significant. The standardisation of clinical guidelines for managing patients with lymphoma is warranted.

Predictive value of a positive stress single-photon emission computed tomography or stress cardiac magnetic resonance for ruling in obstructive coronary artery disease in a real-world setting

INTRODUCTION AND OBJECTIVES

Randomized controlled trials comparing stress cardiac magnetic resonance (CMR) and single-photon emission computed tomography (SPECT) suggest similar diagnostic accuracy for detecting obstructive coronary artery disease (CAD). There are few data on whether this remains true in routine clinical practice. The aim of this study was to assess clinical and angiographic characteristics of patients undergoing invasive coronary angiography (ICA) after stress CMR or SPECT, and to compare their positive predictive value with published results from the CE-MARC trial.

METHODS

In this retrospective tertiary-center analysis, we included 429 patients undergoing ICA after a positive stress CMR or positive SPECT performed within the previous 12 months. Obstructive CAD was defined as any coronary artery stenosis ≥50% in a vessel compatible with the ischemic territory on stress testing.

RESULTS

Of the total 429 patients, 356 (83%) were referred after a positive SPECT, and 73 (17%) after a positive stress CMR. Patients did not differ according to age, cardiovascular risk factors, previous revascularization or left ventricular dysfunction, but patients with SPECT were more frequently male (p=0.046). The prevalence of obstructive CAD was similar in patients with positive SPECT vs. positive stress CMR (76.1% vs. 80.8%, respectively, p=0.385). The positive predictive values of both techniques were similar to those reported in the CE-MARC trial.

CONCLUSION

In this tertiary center analysis, stress CMR and SPECT showed similar positive predictive values, comparable to those reported in the CE-MARC trial. This finding supports the emerging adoption of CMR in clinical practice for the diagnosis and management of CAD.

Normal organ dosimetry for thyroid cancer patients treated with radioiodine as part of the multi-centre multi-national Horizon 2020 MEDIRAD project

PURPOSE

Dosimetry is rarely performed for the treatment of differentiated thyroid cancer patients with Na[131I]I (radioiodine), and information regarding absorbed doses delivered is limited. Collection of dosimetry data in a multi-centre setting requires standardised quantitative imaging and dosimetry. A multi-national, multi-centre clinical study was performed to assess absorbed doses delivered to normal organs for differentiated thyroid cancer patients treated with Na[131I]I.

METHODS

Patients were enrolled in four centres and administered fixed activities of 1.1 or 3.7 GBq of Na[131I]I using rhTSH stimulation or under thyroid hormone withdrawal according to local protocols. Patients were imaged using SPECT(/CT) at variable imaging time-points following standardised acquisition and reconstruction protocols. Whole-body retention data were collected. Dosimetry for normal organs was performed at two dosimetry centres and results collated.

RESULTS

One hundred and five patients were recruited. Median absorbed doses per unit administered activity of 0.44, 0.14, 0.05 and 0.16 mGy/MBq were determined for the salivary glands of patients treated at centre 1, 2, 3 and 4, respectively. Median whole-body absorbed doses for 1.1 and 3.7 GBq were 0.05 Gy and 0.16 Gy, respectively. Median whole-body absorbed doses per unit administered activity of 0.04, 0.05, 0.04 and 0.04 mGy/MBq were calculated for centre 1, 2, 3 and 4, respectively.

CONCLUSIONS

A wide range of normal organ doses were observed for differentiated thyroid cancer patients treated with Na[131I]I, highlighting the necessity for individualised dosimetry. The results show that data may be collated from multiple centres if minimum standards for the acquisition and dosimetry protocols can be achieved.

MIB Guides: Preclinical radiopharmaceutical dosimetry

Preclinical dosimetry is essential for guiding the design of animal radiopharmaceutical biodistribution, imaging, and therapy experiments, evaluating efficacy and/or toxicities in such experiments, ensuring compliance with ethical standards for animal research, and providing reasonable initial estimates of normal-organ doses in humans, required for clinical translation of new radiopharmaceuticals. This MIB guide provides a basic protocol for obtaining preclinical dosimetry estimates with organ-level dosimetry software.

Influence of the natural radon radiation on the spread of the COVID 19 pandemic

The statistics of COVID-19 accumulated in Ukraine show areas with a significantly lower incidence of diseases. The purpose of the study was to identify factors that could influence the pattern of the pandemic in a particular area. Within the study it was assumed that the level of health care is approximately the same throughout the country. Population density was considered the main factor influencing the dynamics of the spread of infection. To reduce the impact of changes in population density across regions, it was normalized by the average population density in the country. The normalization of statistics for the country resulted in a model in the form of a linear relationship between the normalized values of the number of COVID-19 cases in the region and the size of the region. Subsequent analysis of the graphical data made it possible to identify four regions with the lowest incidence of COVID-19. The geographical proximity of these regions Dnipro, Kherson, Vinnytsia and Kirovograd, indicates the presence of a common factor for them, not typical for the rest of Ukraine. Such a factor may be the location of 83% of Ukraine's uranium deposits in the territories around Kirovohrad. Radon is one of the decay products of uranium, so the population of these areas may experience increased exposure to radon. This noble gas has more than a century of medical use, in particular for pulmonary diseases, although there is still no consensus about its effectiveness and side effects. Considering that COVID-19 was often complicated by pulmonary diseases, it can be assumed that the geological specificity of these four regions of Ukraine had an impact on the course of the COVID-19 pandemic in their territories. The study findings are important in terms of further COVID-19 research and prevention strategies.

Venous Thromboembolism Management in Pregnant Patients

Pulmonary embolism (PE) in pregnancy accounts for 10% of maternal deaths in the United States. As maternal morbidity and mortality continue to increase, it is imperative for all specialties interfacing with pregnant patients to understand the current research and guidelines surrounding risk stratification, diagnosis, and treatments of PE in pregnancy. Given the complexity of high-risk pregnancy-associated PE (PA-PE), that is, which is associated with hemodynamic instability or collapse, and the rising popularity of new technologies to treat high-risk PA-PE in the nonpregnant population, this review aims to emphasize the differences in diagnosis, risk stratification, and management of the pregnant and nonpregnant PE patients. Furthermore, this review will cover treatment paradigms that include anticoagulation versus advanced therapies such as systemic thrombolysis, surgical embolectomy, extracorporeal membrane oxygenation, and inferior vena cava disruption as well as the more novel therapies which fall under the umbrella term of catheter-based treatments. Finally, this review will include a case-based review of 2 patients with PA-PE requiring catheter-based therapies and their ultimate clinical outcomes.

CANCER RISK ESTIMATION FOR PATIENTS UNDERGOING WHOLE-BODY PET/CT SCANS

The objective of this paper was to compute the effective dose, as well as the lifetime attributable risk (LAR) of cancer related to whole-body positron emission tomography (PET)/computed tomography (CT) scan for 193 adult patients. The mean effective dose for all patients from a single PET/CT scan was 20.6 mSv. For males aged 40 y, a single PET/CT scan is associated with a LAR of cancer incidence of 0.169%. This risk increased to 0.85% if an annual surveillance protocol for 5 y was performed. For female patients aged 40 y, the LAR of cancer mortality increased from 0.126 to 0.63% if an annual surveillance protocol for 5 y was performed. Since PET/CT scans are associated with a high dose and a risk of developing cancer, it was important to balance the advantages and risks before conducting any scans. This is especially important for younger patients and those who are overweight.

Safety, biodistribution and radiation dosimetry of [123I]ioflupane in healthy Chinese volunteers

BACKGROUND

[¹²³I]ioflupane is a radiopharmaceutical used to visualise the dopaminergic neuron terminals in the striata, to aid in the differential diagnosis among Parkinsonian syndromes (e.g., Parkinson's disease). However, nearly all of the subjects in the initial development studies of [¹²³I]ioflupane were Caucasian.

METHODS

8 Chinese healthy volunteers (HVs) received a single 111 MBq ± 10% dose of [¹²³I]ioflupane and had simultaneous whole-body (head to mid-thigh) anterior and posterior planar scintigraphy scans at 10 min and 1, 2, 4, 5, 24, and 48 h. To estimate biodistribution, dosimetry was evaluated for the Cristy-Eckerman female and hermaphrodite male phantoms. Single-photon emission computed tomography (SPECT) images of the brain were acquired at 3 and 6 h after injection. Blood samples and all voided urine were collected for 48 h for pharmacokinetic analysis. The results were then compared with those of a similar European study.

RESULTS

There were strong similarities in uptake and biodistribution between the Chinese and European studies. Excretion was primarily renal, and the values were similar for the first 5 h but diverged after that, possibly because of differences in subjects' height and weight. Tracer uptake in regions of interest in the brain was stable over the imaging window of 3 to 6 h. The difference in mean effective dose for Chinese HVs vs European HVs (0.028 ± 0.00448 vs 0.023 ± 0.00152 mSv/MBq) was not clinically significant. The [¹²³I]ioflupane was well tolerated.

CONCLUSION

This study demonstrated that a single 111 MBq ± 10% dose of [¹²³I]ioflupane injection was safe and well tolerated, and the SPECT imaging window of 3 to 6 h after injection of [¹²³I]ioflupane was appropriate in Chinese subjects. Trial registration number ClinicalTrials.gov: NCT04564092.

Validation of the DoseCalcs Monte Carlo code for estimating the 18F S-values for ICRP adult and 15-year-old male and female phantoms

Internal radiation exposure using radiopharmaceuticals, as in nuclear medicine procedures, necessitates the estimation of the S-value to determine and improve the estimates of absorbed doses in at-risk organs and tissues. The S value is defined as the absorbed dose in the target organ per unit of nuclear transformation in the source organ. It is calculated using the specific absorbed fraction, which is an important quantity that connects the deposited energy in the target and emitting source organs. In this study, we applied DoseCalcs, a new Geant4-based tool, to estimate the S values of [Formula: see text]F using nuclear data from ICRP Publication 107. Geometrical data from ICRP Publications 110 and 143 were used to select four models representing male and female phantoms for adults and 15 years old to study the variability in the S-values arising from variations in anatomy and initial energy validations, because we used the [Formula: see text] mean energy instead of the full beta spectrum. The [Formula: see text]F-released photons and [Formula: see text] from 26 source organs were tracked using the Geant4 Livermore package. Accordingly, the S-values were calculated for 141 target organs. The results for the adult male and female phantoms were compared with the OpenDose reference data. These results agreed well with OpenDose, the average ratio for self-absorption S-values was 1.015, and the average ratios for the cross-irradiation were 1.2 and 1.22 for the AM and AF, respectively. This indicates the accuracy of DoseCalcs for subsequent use in estimating [Formula: see text]F S-values using voxelized geometries.

18F-alfatide II internal dosimetry using the ICRP 110 adult reference phantoms and the ICRP 103 tissue weighting factors

PURPOSE

¹⁸F-alfatide II is an arginine-glycine-aspartate (RGD) peptide-based PET tracer with promising imaging properties and pharmacokinetics. This study aims to calculate the absorbed and effective doses of ¹⁸F-alfatide II using the ICRP 110 adult reference phantoms and the ICRP 103 tissue weighting factors.

METHODS

The MIRD method was used in this study to calculate the absorbed dose of organs and tissues. The biokinetic data were taken from a previous study. These data are based on the whole-body PET imaging of mice.

RESULTS

The results show that the effective dose per unit activity administered of ¹⁸F-alfatide II is 1.33E-02 mSv/MBq. The urinary bladder wall receives the highest absorbed dose due to the administration of this radiopharmaceutical. Also, the effective dose of ¹⁸F-alfatide II is lower than that of ¹⁸F-FDG and some other RGD peptide-based tracers.

CONCLUSIONS

Dose calculation using ICRP 110 voxelized adult reference phantoms and ICRP 103 tissue weighting factors leads to more realistic and accurate results for 18F-alfatide II compared to the stylized phantoms. The calculated effective dose of ¹⁸F-alfatide II in the present study is lower than that of previously published data.

Dose evaluation of the one-year-old child in PET imaging by18F-(DOPA, FDG, FLT, FET) and68Ga-EDTA using reference voxel phantoms

Because of more sensitive organs due to high growth rates, evaluating the absorbed dose is essential for children to prevent irreparable damage. Therefore, to this aim, a one-year-old child's whole-body effective dose and organ absorbed dose were evaluated for various PET imaging Radiopharmaceuticals such as:¹⁸F-DOPA,¹⁸F-FDG,¹⁸F-FLT,¹⁸F-FET, and⁶⁸Ga-EDTA. For this aim, one-year-old child reference voxel phantoms and GATE Monte Carlo simulation were used, and the results were compared with the ICRP128 report (for stylized phantom). The highest absorbed dose was related to bladder wall (for¹⁸F-DOPA,¹⁸F-FET, and⁶⁸Ga-EDTA), heart wall (for¹⁸F-FDG), and liver (for¹⁸F-FLT) between 30 organs that have been studied. Comparing the results with the ICRP128 report values for a one-year-old child show a significant difference in some organs. Comparison of the effective dose with the ICRP128 report shows a relative difference of 22%, 12.5%, 11.8%, 10.8% and 8.6% for¹⁸F-DOPA,⁶⁸Ga-EDTA,¹⁸F-FDG,¹⁸F-FET,¹⁸F-FLT, respectively. In conclusion, using new one-year-old voxel phantoms could provide a better estimate of organs absorbed dose and whole-body effective dose due to its exact structure.

Fetal Dose from PET and CT in Pregnant Patients

When pregnancy is discovered during or after a diagnostic examination, the physician or the patient may request an estimate of the radiation dose received by the fetus as per guidelines and standard operating procedures. This study provided the imaging community with dose estimates to the fetus from PET/CT with protocols that are adapted to University of Michigan low-dose protocols for patients known to be pregnant. Methods: There were 9 patients analyzed with data for the first, second, and third trimesters, the availability of which is quite rare. These images were used to calculate the size-specific dose estimate (SSDE) from the CT scan portion and the SUV and ¹⁸F-FDG uptake dose from the PET scan portion using the MIRD formulation. The fetal dose estimates were tested for correlation with each of the following independent measures: gestational age, fetal volume, average water-equivalent diameter of the patient along the length of the fetus, SSDE, SUV, and percentage of dose from ¹⁸F-FDG. Stepwise multiple linear regression analysis was performed to assess the partial correlation of each variable. To our knowledge, this was the first study to determine fetal doses from CT and PET images. Results: Fetal self-doses from ¹⁸F for the first, second, and third trimesters were 2.18 mGy (single data point), 0.74-1.82 mGy, and 0.017-0.0017 mGy, respectively. The combined SSDE and fetal self-dose ranged from 1.2 to 8.2 mGy. These types of images from pregnant patients are rare. Conclusion: Our data indicate that the fetal radiation exposure from ¹⁸F-FDG PET and CT performed, when medically necessary, on pregnant women with cancer is low. All efforts should be made to minimize fetal radiation exposure by modifying the protocol.

Diagnostic performance of prospective same-day 18F-FDG PET/MRI and 18F-FDG PET/CT in the staging and response assessment of lymphoma

BACKGROUND

Accurate staging and response assessment are essential for prognosis and to guide treatment in patients with lymphoma. The aim of this study was to compare the diagnostic performance of FDG PET/MRI versus FDG PET/CT in adult patients with newly diagnosed Hodgkin and Non- Hodgkin lymphoma.

METHODS

In this single centre study, 50 patients were prospectively recruited. FDG PET/MRI was performed after staging FDG PET/CT using a single injection of 18F-FDG. Patients were invited to complete same-day FDG PET/MRI with FDG PET/CT at interim and end of treatment response assessments. Performance was assessed using PET/CT as the reference standard for disease site identification, staging, response assessment with Deauville score and concordance in metabolic activity.

RESULTS

Staging assessment showed perfect agreement (κ = 1.0, P = 0) between PET/MRI and PET/CT using Ann Arbor staging. There was excellent intermodality correlation with disease site identification at staging (κ = 0.976, P < 0.001) with FDG PET/MRI sensitivity of 96% (95% CI, 94-98%) and specificity of 100% (95% CI, 99-100%). There was good correlation of disease site identification at interim assessment (κ = 0.819, P < 0.001) and excellent correlation at end-of-treatment assessment (κ = 1.0, P < 0.001). Intermodality agreement for Deauville scores was good at interim assessment (κ = 0.808, P < 0.001) and excellent at end-of-treatment assessment (κ = 1.0, P = 0). There was good-excellent concordance in SUV max and mean between modalities across timepoints. Minimum calculated radiation patient effective dose saving was 54% between the two modalities per scan.

CONCLUSION

With high concordance in disease site identification, staging and response assessment, PET/MR is a potentially viable alternative to PET/CT in lymphoma that minimises radiation exposure.

UK audit of variation in nuclear medicine occupational exposure calculations in 2021

It is a core requirement of UK ionising radiations regulations 2017 (IRR17) compliance for radiation risk assessments and the investigation of accidental exposure scenarios that the magnitude of doses likely to be encountered are evaluated. A novel national audit was undertaken to investigate the variation in dose estimations for a range of foreseeable accidental exposure scenarios in nuclear medicine (NM). Participants were asked to estimate the levels of exposure in 15 foreseeable scenarios; covering whole-body and extremity exposures from external sources, internal exposure and exposures from skin (surface contamination and needle-stick injury) and eye contamination. Questions were intentionally simplified to reduce variation from assumptions made by the participants and to focus more on the underlying gross systematic variation. Twenty-seven centres participated. There was generally a very wide variation in the estimated exposures across all the categories of exposures, apart from internal exposure estimates. Whilst there was no ground truth for each individual question, the variation in results itself often exceeded the relevant threshold for classification and annual dose limits. The majority of variation was due to differences in methods, models and assumptions used by each participant. This audit raises questions around how IRR17 compliance can be universally demonstrated with such wide national variation. It evidences the need for a more standardised practice in NM radionuclide exposure estimates through national consensus guidelines or standards etc.

Incremental prognostic value of digital positron emission tomography derived myocardial flow reserve: A prospective cohort study

BACKGROUND

Positron Emission Tomography (PET) Myocardial Perfusion Imaging (MPI) is a robust diagnostic and prognostic test in patients with suspected or known coronary artery disease (CAD). We aimed to assess the incremental prognostic value of myocardial flow reserve (MFR) using the latest generation of digital PET scanners.

METHODS

Consecutive patients with clinically indicated PET MPI for suspected or known CAD were included. Myocardial blood flow (MBF) in ml/min/g was obtained from dynamic images at rest and peak hyperemia, and the myocardial flow reserve (MFR) was calculated as the ratio of stress to rest MBF. Patients were followed from the date of PET imaging for the occurrence of the primary outcome (composite of all-cause death, myocardial infarction, and Percutaneous Coronary Intervention or Coronary Artery Bypass Graft occurring >90 days after imaging). Nested multivariable Cox regression models were used to assess the incremental prognostic role of MFR over traditional risk factors and PET relative perfusion parameters.

RESULTS

The final cohort consisted of 3534 patients (mean age 67 ± 12 years, 48% female, 67% Caucasian, 53% obese, 55% hypertension, 32% diabetes, 42% dyslipidemia). During a median follow-up of 8.5 (3.0-15.4) months, 229 patients (6.5%, 6.4 per 1000 person-years) experienced the primary outcome. In nested multivariable Cox models, impaired MFR (MFR < 2) was significantly associated with the primary outcome (HR 2.9, 95% CI 2.0-4.1, p < 0.001) and significantly improved discrimination (Harrell's C 0.77, p = 0.002).

CONCLUSION

MFR derived from digital PET scanners has an independent and incremental prognostic role in patients with suspected or known CAD.

Radiation exposure from radiological procedures in liver transplant candidates with hepatocellular carcinoma

PURPOSE

Candidates for liver transplantation (LT) with hepatocellular carcinoma (HCC) undergo a large number of diagnostic and interventional radiology procedures. A significant proportion of such procedures involve ionizing radiation with increased lifetime risk of cancer. The objective of our study was to review LT candidates with HCC to quantify ionizing radiation doses from different radiology procedures performed at a single transplant center.

METHOD

We retrospectively reviewed 179 adult patients with HCC (median age 58.6 years [IQR, 55-62]; 155 [86.6%] males) who were accepted for LT between April 2010 and Dec 2018. Radiology procedures and radiation doses were retrieved and the total and median radiation effective dose in millisieverts (mSv) were calculated for different procedures. Exposure to ionizing radiation was categorized based on previously reported thresholds.

RESULTS

We assessed 9,986 radiology procedures for our cohort. Patients had a median effective dose prior to transplantation of 254 mSv (IQR, 130-421) with an annualized rate of 152 mSv (IQR, 92-266). Patient median dose increased to 316 mSv (IQR, 159-478) when including exposures post-LT within the study period. 85% of overall exposure was in the extremely high exposure category (>100 mSv). Interventional procedures represented 13% of procedures with substantial radiation and contributed to 45% of radiation exposure while abdominal CTs represented 39% of total procedures and contributed to 45% of radiation exposure.

CONCLUSIONS

Patients with HCC considered for LT undergo radiology procedures with significant cumulative radiation exposure. Attempts to reduce radiation exposure are suggested by minimizing unnecessary procedures and utilizing ones without ionizing radiation. Improving interventional techniques to reduce radiation doses is needed without compromising treatment delivery.

Nuclear medicine in the assessment and prevention of cancer therapy-related cardiotoxicity: prospects and proposal of use by the European Association of Nuclear Medicine (EANM)

Cardiotoxicity may present as (pulmonary) hypertension, acute and chronic coronary syndromes, venous thromboembolism, cardiomyopathies/heart failure, arrhythmia, valvular heart disease, peripheral arterial disease, and myocarditis. Many of these disease entities can be diagnosed by established cardiovascular diagnostic pathways. Nuclear medicine, however, has proven promising in the diagnosis of cardiomyopathies/heart failure, and peri- and myocarditis as well as arterial inflammation. This article first outlines the spectrum of cardiotoxic cancer therapies and the potential side effects. This will be complemented by the definition of cardiotoxicity using non-nuclear cardiovascular imaging (echocardiography, CMR) and biomarkers. Available nuclear imaging techniques are then presented and specific suggestions are made for their application and potential role in the diagnosis of cardiotoxicity.

89Zr-Labeled High-Density Lipoprotein Nanoparticle PET Imaging Reveals Tumor Uptake in Patients with Esophageal Cancer

Nanomedicine holds promise for the delivery of therapeutic and imaging agents to improve cancer treatment outcomes. Preclinical studies have demonstrated that high-density lipoprotein (HDL) nanoparticles accumulate in tumor tissue on intravenous administration. Whether this HDL-based nanomedicine concept is feasible in patients is unexplored. Using a multimodal imaging approach, we aimed to assess tumor uptake of exogenously administered HDL nanoparticles in patients with esophageal cancer. Methods: The HDL mimetic CER-001 was radiolabeled using ⁸⁹Zr to allow for PET/CT imaging. Patients with primary esophageal cancer staged T2 and above were recruited for serial ⁸⁹Zr-HDL PET/CT imaging before starting chemoradiation therapy. In addition, patients underwent routine ¹⁸F-FDG PET/CT and 3-T MRI scanning (diffusion-weighted imaging/intravoxel incoherent motion imaging and dynamic contrast-enhanced MRI) to assess tumor glucose metabolism, tumor cellularity and microcirculation perfusion, and tumor vascular permeability. Tumor biopsies were analyzed for the expression of HDL scavenger receptor class B1 and macrophage marker CD68 using immunofluorescence staining. Results: Nine patients with adenocarcinoma or squamous cell carcinoma underwent all study procedures. After injection of ⁸⁹Zr-HDL (39.2 ± 1.2 [mean ± SD] MBq), blood-pool SUV_mean decreased over time (11.0 ± 1.7, 6.5 ± 0.6, and 3.3 ± 0.5 at 1, 24, and 72 h, respectively), whereas liver and spleen SUV_mean remained relatively constant (4.1 ± 0.6, 4.0 ± 0.8, and 4.3 ± 0.8 at 1, 24, and 72 h, respectively, for the liver; 4.1 ± 0.3, 3.4 ± 0.3, and 3.1 ± 0.4 at 1, 24, and 72 h, respectively, for the spleen) and kidney SUV_mean markedly increased over time (4.1 ± 0.9, 9.3 ± 1.4, and 9.6 ± 2.0 at 1, 24, and 72 h, respectively). Tumor uptake (SUV_peak) increased over time (3.5 ± 1.1 and 5.5 ± 2.1 at 1 and 24 h, respectively [P = 0.016]; 5.7 ± 1.4 at 72 h [P = 0.001]). The effective dose of ⁸⁹Zr-HDL was 0.523 ± 0.040 mSv/MBq. No adverse events were observed after the administration of ⁸⁹Zr-HDL. PET/CT and 3-T MRI measures of tumor glucose metabolism, tumor cellularity and microcirculation perfusion, and tumor vascular permeability did not correlate with tumor uptake of ⁸⁹Zr-HDL, suggesting that a specific mechanism mediated the accumulation of ⁸⁹Zr-HDL. Immunofluorescence staining of clinical biopsies demonstrated scavenger receptor class B1 and CD68 positivity in tumor tissue, establishing a potential cellular mechanism of action. Conclusion: To our knowledge, this was the first ⁸⁹Zr-HDL study in human oncology. ⁸⁹Zr-HDL PET/CT imaging demonstrated that intravenously administered HDL nanoparticles accumulated in tumors of patients with esophageal cancer. The administration of ⁸⁹Zr-HDL was safe. These findings may support the development of HDL nanoparticles as a clinical delivery platform for drug agents. ⁸⁹Zr-HDL imaging may guide drug development and serve as a biomarker for individualized therapy.

Biokinetics and dosimetry of 18 F-PSMA-1007 in patients with prostate cancer

PURPOSE

Positron emission tomography-computed tomography (PET-CT) using prostate-specific membrane antigen (PSMA) ligands is a method for imaging prostate cancer. A recent tracer, ¹⁸ F-PSMA-1007, offers advantages concerning production and biokinetics compared to the standard tracer (⁶⁸ Ga-PSMA-11). Until now, radiation dosimetry data for this ligand was limited to the material of three healthy volunteers. The purpose of this study is to study the biokinetics and dosimetry of ¹⁸ F-PSMA-1007.

METHODS

Twelve patients with prostate cancer were injected with 4 MBq/kg ¹⁸ F-PSMA-1007. Eight PET-CT scans with concomitant blood sampling were performed up to 330 min after injection. Urine was collected until the following morning. Volumes of interest for radiation-sensitive organs and organs with high uptake of ¹⁸ F-PSMA-1007 were drawn in the PET images. A biokinetic compartment model was developed using activity data from PET images and blood and urine samples. Time-activity curves and time-integrated activity coefficients for all delineated organs were calculated. The software IDAC-dose 2.1 was used to calculate the absorbed and effective doses.

RESULTS

High concentrations of activity were noted in the liver, kidneys, parts of the small intestine, spleen, salivary glands, and lacrimal glands. The elimination through urine was 8% of injected activity in 20 h. The highest absorbed doses coefficients were in the lacrimal glands, kidneys, salivary glands, liver, and spleen (98-66 µGy/MBq). The effective dose coefficient was 25 µSv/MBq.

CONCLUSION

The effective dose of ¹⁸ F-PSMA-1007 is 6.0-8.0 mSv for a typical patient weighing 80 kg injected with 3-4 MBq/kg.

Notes for the general paediatrician: managing thyrotoxicosis in children and young people

Thyrotoxicosis due to hyperthyroidism is a serious disorder in childhood often presenting to general paediatricians with a range of clinical manifestations. The commonest cause is Graves' disease, an autoimmune disorder resulting from thyrotropin receptor stimulation by autoantibodies. Early recognition and accurate interpretation of investigations are essential to achieve and maintain a euthyroid state. This will not only optimise growth, development and transition from childhood to young adult life but also avoid the potentially severe and life-threatening complications of acute thyrotoxicosis. In this review, we have focussed on the general paediatrician's perspective of the presentation and management of thyrotoxicosis and the need to network with specialist paediatric endocrine centres to optimise patient care. We have discussed nuances of therapy, side effects and long-term outcomes, while recognising that limited remission rates in this age group often necessitate more definitive management. While carbimazole is usually used as first-line medical therapy, we have provided useful information to guide paediatricians in the discussion of individualised safe and effective treatment plans for both short-term and long-term management.

Assessment of total annual effective doses to representative person, for authorised and accidental releases from the Nuclear Medicine Department at Cattinara Hospital (Trieste, Italy)

PURPOSE

Clinical procedures in a Nuclear Medicine Department produce radioactive liquid and solid waste. Regarding waste release into the environment from an authorised hospital, it is mandatory to verify the compliance with European Directive 2013/59/EURATOM, adopted by the Italian Government via the Legislative Decree 101/2020.

METHODS

Different activity release pathways into the environment from Trieste Nuclear Medicine Department have been analysed: liquid waste from patients' excreta discharged by sewage treatment system into the sea, and atmospheric releases following solid waste incineration. Reference models, provided by NCRP and IAEA guidelines, have been implemented to assess the impact of the discharged radioactivity for coastal waters and atmospheric transport conditions. Finally, an accidental fire event occurring in Radiopharmacy Laboratories has been simulated by HotSpot software.

RESULTS

Advanced screening models give an effective dose to population of 5.3 · 10^-3 µSv/y and 1.4 · 10^-4 µSv/y for introduction by sewage system into coastal waters and atmospheric releases by the incinerator, respectively. Workers involved in the maintenance of the sewage treatment plant receive a total annual effective dose of 3.8 µSv/y, while for incinerator staff the total annual exposure is 5.9 · 10^-8 µSv/y. For the accidental fire event the maximum total effective dose to an individual results 3.8 · 10^-8 Sv with mild wind, and 4.1 · 10^-7 Sv with strong wind.

CONCLUSIONS

The total annual effective doses estimated to representative person, due to both Nuclear Medicine authorised clinical practices and in case of an accidental fire event, are in compliance with regulatory stipulations provided by Directives.

Optimized low-dose positron emission tomography/computed tomography schemes in pediatric tumor patients: a randomized clinical trial

BACKGROUND

It's clinically relevant to reduce the radiation dose to children while ensuring their positron emission tomography/computed tomography (PET/CT) image quality. The optimal protocol for whole-body PET/CT imaging in children (non-model) has been less studied. In this study, we investigated the optimal protocol for PET/CT imaging of pediatric oncology by analyzing the radiation dose and image quality in18F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) PET/CT imaging of children with oncology.

METHODS

One hundred children with tumors who underwent ¹⁸F-FDG PET/CT were included. CT grouping: randomly divided into 18 groups A-R according to the combination of three parameters: tube voltage (80/120 kV), automatic milliamp range (20-39/40-59/60-80 mA), and noise index (NI) (8/12/14). PET grouping: randomly divided into 9 groups a-i according to the combination of two parameters: the pharmaceuticals injection dose (0.08/0.12/0.15 mCi/kg) and time per bed (120/150/180 s). The effective radiation dose (ED) was calculated separately for each group and the image quality of CT and PET was evaluated subjectively using standard deviation (SD) and coefficient of variation (CV) objective evaluation and 5-point evaluation method, respectively.

RESULTS

Ninety-seven images in CT and 57 images in PET were included. The best quality of CT images was in group K (120 kV/40-59 mA/8); there are 9 groups had good image quality and lower dose length product (DLP) than group K (SD ±10), while the difference in DLP between groups was large. The Kruskal-Wallis (K-W) test showed that the difference in image quality between the 9 groups was not statistically significant. The best PET image quality was in group i [0.15 (mCi/kg)/180 s]; there are four groups had good image quality and lower ED_PET than group i (CV ±3.5%), while the difference in ED_PET between groups was large (4.4-6.5 mSv), and the K-W test showed that the difference in image quality between the four groups was not statistically significant (P>0.05), with the lowest ED_PET being in the g group.

CONCLUSIONS

The optimal protocols for CT scanning and PET imaging in this experiment were group H (80 kV/40-59 mA/14) and group g [0.08 (mCi/kg)/180 s], respectively.Trial Registration: Chinese Clinical Trial Registry ChiCTR2200061386.

Pre-clinic study of radiopharmaceutical for Covid-19 inactivation: Dose distribution with Monte Carlo Simulation

Monte Carlo simulation method and Nuclear Medicine MIRD method were used to evaluate the effect of radiopharmaceuticals on Covid-19 disease. The mean absorbed organ dose in the target organ and gamma radiation emitter attenuation properties such as linear attenuation coefficients, energy absorption build-up factors (EABF), exposure build-up factors (EBF), and relative dose distributions (RDD) were examined. The results showed that radiopharmaceuticals containing gamma radiation emitters which are densely ionizing charged particles induced membrane damage and produced protein damage.