Pharmacology, Part 5: CT and MRI Contrast Media

Evaluation of pathways involved in the protective effect of trans sodium crocetinate against contrast-induced nephropathy in rats

Contrast-induced nephropathy (CIN) is the most important side effect following contrast media application. The purpose of this study was to investigate the nephroprotective effects of trans sodium crocetinate (TSC) against sodium amidotrizoate/meglumine amidotrizoate (SAMA). Wistar rats were classified into eight groups (n = 6, male, 220-250 g) including (1) sham, injection of solvents (intraperitoneally; i.p.), (2) premedication-control, N(ω)-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg, i.p.) + indomethacin (IND, 10 mg/kg, i.p.), (3) model (L-NAME + IND + SAMA (12.5 ml/kg, i.p.)), (4-6) TSC 10, 20, and 40 mg/kg/day, 7 days, i.p., and L-NAME + IND + SAMA, (7) N-acetylcysteine (NAC, 125 mg/kg/day, 7 days, i.p.) and L-NAME + IND + SAMA, (8) TSC alone (40 mg/kg/day, 7 days, i.p.). Rats were injected with L-NAME, IND, and SAMA 40 h after water deprivation. SAMA caused the enhancement of histopathological damage in kidney tissue, biochemical factors (serum blood urea nitrogen and creatinine), and oxidative stress. Moreover, SAMA increased inflammation (TNF-α), apoptosis proteins (Caspase 3-cleaved and Bax/Bcl-2 ratio), and autophagy markers (Beclin-1 and LC3 II/I ratio). TSC declined biochemical factors and oxidative stress. Also, TSC 40 mg/kg decreased histopathological damage, inflammation, apoptosis, and autophagy markers. This study demonstrated that TSC has nephroprotective effects through anti-oxidant, anti-inflammatory, and anti-apoptotic properties, as well as regulating autophagy.

Magnetic resonance angiography in diagnostic long-term follow-up of primary patency of the MOTIV drug-eluting bioresorbable vascular scaffold in the region below the knee: 5 years of experience

PURPOSE

Treatment of peripheral artery disease (PAD) in the region below the knee (BTK) is dissatisfying as failure of treated target lesions (TLF) is frequent and diagnostic imaging is often challenging. In the BTK-region metallic drug-eluting stents (mDES) yielded best results concerning primary patency (PP), but also annihilate signal in magnetic resonance angiography (MR-A). A recently introduced non-metallic drug eluting bioresorbable Tyrocore® vascular scaffold (deBVS), that offers an option for re-treatment of lesions due to its full degradation within 3-4 years after placement, was investigated with respect to its compatibility with MR-A to unimpededly depict previously treated target lesions.

METHODS

Patency of the deBVS in the BTK-region was assessed retrospectively using contrast enhanced MR-A of the lower limbs in patients with PAD of Lafontaine-grades II-IV (n = 19). Clinically driven MR-A censoring was triggered by an assumed target lesion failure (CD-TLF), which served to compute the probability of PP during the observation period of 5 years. Compatibility of this particular deBVS with MRI was additionally proven via in-vitro experiments.

RESULTS

The scaffold was found to be fully compatible with MRI. The normalised intra-luminal signal measured in MR-A increased significantly after successful deBVS-placement. The retrospective 5-years PP-probability was 0.87 (CI95%: [0.71,1.0]) with 2 stent-occlusions observed after 90 days. No major adverse events occurred.

CONCLUSION

Assessment of PAD in the BTK-region after placement of the Tyrocore®-deBVS using MRA is feasible. The promising high PP-probability after 5-years and the persistent full interpretability of treated target lesions by MR-A after stent-placement encourage further prospective assessment of this deBVS in treatment of PAD in the BTK-region.

Active pharmaceutical contaminants in drinking water: myth or fact?

Global water availability has been affected by a variety of factors, including climate change, water pollution, urbanization, and population growth. These issues have been particularly acute in many parts of the world, where access to clean water remains a significant challenge. In this context, preserving existing water bodies is a critical priority. Numerous studies have demonstrated the inadequacy of conventional water treatment processes in removing active pharmaceutical ingredients (APIs) from the water. These pharmaceutical active compounds have been detected in treated wastewater, groundwater, and even drinking water sources. The presence of APIs in water resources poses a significant threat not only to aquatic organisms but also to human health. These emerging contaminants have the potential to disrupt endocrine systems, promote the development of antibiotic-resistant bacteria, and bioaccumulate in the food chain, ultimately leading to unacceptable risks to public health. The inability of current conventional treatment methods to effectively remove APIs from water has raised serious concerns about the safety and reliability of water supplies. This issue requires immediate attention and the development of more effective treatment technologies to safeguard the quality of water resources and protect both aquatic ecosystems and human health. Other treatment methods, such as nanotechnology, microalgal treatment, and reverse osmosis, are promising in addressing the issue of API contamination in water resources. These innovative approaches have demonstrated higher removal efficiencies for a wide range of APIs compared to conventional methods, such as activated sludge and chlorination, which have been found to be inadequate in the removal of these emerging contaminants. The potential of these alternative treatment technologies to serve as effective tertiary treatment. To address this critical challenge, governments and policymakers should prioritize investment in research and development to establish effective and scalable solutions for eliminating APIs from various water sources. This should include comprehensive studies to assess the performance, cost-effectiveness, and environmental sustainability of emerging treatment technologies. The emerging contaminants should be included in robust water quality monitoring programs (Aus der Beek et al. in Environ Toxicol Chem 2016;35(4):823-835), with strict regulatory limits enforced to protect public health and the environment. By doing so, the scientific community and regulatory authorities can work together to develop a multi-barrier approach to safeguarding the water resources and ensuring access to safe, clean water for all. This review explores the potential of alternative treatment technologies to serve as viable solutions in the fight against API contamination. Innovative approaches, including nanotechnology, microalgal treatment, and reverse osmosis, have demonstrated remarkable success in addressing this challenge, exhibiting higher removal efficiencies compared to traditional methods.

Pancreatic fibrosis assessment and association with pancreatic cancer: comparison with the extracellular volume fraction

AIMS

To compare the iodine washout rate (IWR) from multiphasic contrast-enhanced computed tomography (CT) with the extracellular volume fraction (fECV) for assessing pancreatic fibrosis and its association with pancreatic cancer.

MATERIALS AND METHODS

The study included 51 individuals (33 men; median age: 69 years; 21 with pancreatic cancer, 30 with other diseases) who underwent multiphasic contrast-enhanced CT and histological evaluation for fibrotic changes in pancreas. The histological pancreatic fibrosis fraction (HPFF) was assessed on Azan-stained sections. Pancreatic parenchymal enhancement values were measured to calculate IWR and fECV. Statistical methods, such as Spearman's rho and Mann-Whitney U-test, were used. Linear regression models using IWR and fECV were constructed to predict HPFF, with the performance expressed as root mean squared error (RMSE) and Akaike information criterion (AIC).

RESULTS

HPFF correlated with all CT parameters at the estimated transection line, strongest for IWRPPP-EP (r=-0.69, P<0.01). HPFF and fECV values were higher in the pancreatic cancer group than in controls (30% vs. 12.5%, P<0.01; 40.3% vs. 33.0%, P<0.01), whereas IWR values were lower (IWRPPP-EP: 43.3% vs. 55.0%, P<0.01; IWRPVP-EP: 25.0% vs. 33.5%, P<0.01). Linear regression models combining IWRPPP-EP + fECV and IWRPVP-EP + fECV were superior for predicting HPFF, with lower RMSE (9.23-9.35) and AIC (379.38-380.72) values than models with IWR or fECV alone.

CONCLUSION

IWRPPP-EP, IWRPVP-EP, and fECV were reliable biomarkers for noninvasively assessing pancreatic fibrosis and were associated with pancreatic cancer risk. Linear regression combining these variables showed enhanced predictive accuracy for pancreatic fibrosis.

The Diagnostic Value of bpMRI in Prostate Cancer: Benefits and Limitations Compared to mpMRI

Prostate cancer is the second most common cancer in men and a leading cause of death worldwide. Early detection is vital, as it often presents with vague symptoms such as nocturia and poor urinary stream. Diagnostic tools like PSA tests, ultrasound, PET-CT, and mpMRI are essential for prostate cancer management. The PI-RADS system helps assess malignancy risk based on imaging. While mpMRI, which includes T1, T2, DWI, and dynamic contrast-enhanced imaging (DCE), is the standard, bpMRI offers a contrast-free alternative using only T2 and DWI. This reduces costs, acquisition time, and the risk of contrast-related side effects but has limitations in detecting higher-risk PI-RADS 3 and 4 lesions. This study compared bpMRI's diagnostic accuracy to mpMRI, focusing on prostate volume and PI-RADS scoring. Both methods showed strong inter-rater agreement for prostate volume (ICC 0.9963), confirming bpMRI's reliability in this aspect. However, mpMRI detected more complex conditions, such as periprostatic fat infiltration and iliac lymphadenopathy, which bpMRI missed. While bpMRI offers advantages like reduced cost and no contrast use, it is less effective for higher-risk lesions, making mpMRI more comprehensive.

Long-term effects of iopamidol as a contrast medium for computed tomography in Cloudy Catsharks Scyliorhinus torazame

OBJECTIVE

The use of computed tomography (CT) in aquarium animals, including elasmobranchs, has increased dramatically. To take advantage of CT, contrast medium is used to enhance internal organs and provide contrast since elasmobranchs lack visceral fat. In this study, the contrast effects of iopamidol were examined for up to 260 days after intravenous administration to establish the time course of the CT values for the target organs in eight mature Cloudy Catsharks Scyliorhinus torazame.

METHODS

A micro-CT system was used to measure the CT values of the designated region of interest in the target organs (ventricular cavity, kidneys, liver, gallbladder, ovarian follicles, uterine horn cavity) over time and the eggs laid, following administration of iopamidol (700 mg of iodine/kg).

RESULT

The CT values of the ventricular cavity and kidneys peaked at 30 min and showed low values after day 22. The CT values for the liver increased over time and peaked at day 200, whereas values for the gallbladder and ovarian follicles peaked on day 6, with the gallbladder showing a low value and the ovarian follicles still showing a high value on day 260. Computed tomography images with identifiable enhancement within bilateral uterine horns were followed from days 1 to 35. The mean and maximum CT values of yolk and jelly in eggs laid after day 30 were significantly higher than the values for eggs laid up to day 29; embryonic development was confirmed in 88.7% of the eggs.

CONCLUSION

There was no mortality or morbidity of the sharks during the experiment, indicating that the administration of iopamidol at 700 mg of iodine/kg did not result in any adverse effects for 260 days. This is the first study to describe the long-term contrast effects of iopamidol, thus contributing new information about the application of contrast studies in Cloudy Catsharks.

Impact of iodine contrast media on gamma camera-based GFR and factors affecting the difference between serum creatinine-based estimated GFR and Gate's GFR

OBJECTIVE

We aimed to elucidate the factors underlying the difference between estimated glomerular filtration rate (eGFR) calculated from serum creatinine and Gate's GFR (gGFR) measured using technetium-99m diethylene triamine pentaacetic acid ( 99m Tc-DTPA) scintigraphy.

METHODS

This study was based on consecutive patients who underwent 99m Tc-DTPA scintigraphy at our hospital between January 2021 and December 2022 and whose blood serum creatinine data were obtained on the same day as the 99m Tc-DTPA scintigraphy. Relationships between the ratio of gGFR and eGFR (gGFR/eGFR) and age, sex, BMI, visceral fat, psoas muscle index (PMI), serum blood urea nitrogen, and creatinine level were investigated based on 75 patients. Additionally, for 44 patients who had two or more follow-up DTPA studies, we compared gGFR values for studies that used iodine contrast media (ICM) for computed tomography before same-day 99m Tc-DTPA studies and those that did not in the same patients.

RESULTS

Weak correlations were observed between gGFR/eGFR and PMI ( r  = 0.30), BMI ( r  = 0.24), and the visceral fat area ( r  = 0.33). Multi-regression analyses showed that gGFR/eGFR was correlated with PMI ( β  = 0.34, P  < 0.01) and approached significance with the visceral fat area ( β  = 0.24, P  = 0.05). A significant difference was observed in gGFR between patients who received ICM before the 99m Tc-DTPA renogram and those who did not ( P  < 0.001, eGFR 80.5 ± 19.0 vs. 91.7 ± 27.8 ml/min).

CONCLUSION

ICM administration temporarily decreased gGFR, and increased muscle mass increased the difference between eGFR and gGFR values.

Unenhanced computed tomography radiomics help detect endoleaks after endovascular repair of abdominal aortic aneurysm

OBJECTIVES

To explore the feasibility of unenhanced CT images for endoleak detection of abdominal aortic aneurysm (AAA) after endovascular repair (EVAR).

METHODS

Patients who visited our hospital after EVAR from July 2014 to September 2021 were retrospectively collected. Two radiologists evaluated the presence or absence of endoleaks using the combination of contrast-enhanced and unenhanced CT as the referenced standard. After segmenting the aneurysm sac of the unenhanced CT, the radiomic features were automatically extracted from the region of interest. Histogram features of patients with and without endoleak were statistically analyzed to explore the differences between the two groups. Twelve common machine learning (ML) models based on radiomic features were constructed to evaluate the performance of endoleak detection with unenhanced CT images.

RESULTS

The study included 216 patients (69 ± 8 years; 191 men) with AAA, including 64 patients with endoleaks. A total of 1955 radiomic features of unenhanced CT were extracted. Compared with patients without endoleak, the aneurysm sac outside the stent of patients with endoleak had higher CT attenuation (41.7 vs. 33.6, p < 0.001) with smaller dispersion (51.5 vs. 58.8, p < 0.001). The average area under the curve (AUC) of the ML models constructed with unenhanced CT radiomics was 0.86 ± 0.05, the accuracy was 81% ± 4, the sensitivity was 88% ± 10, and the specificity was 78% ± 5. When fixing the sensitivity to > 90% (92% ± 2), the models retained specificity at 72% ± 10.

CONCLUSIONS

Unenhanced CT features exhibit significant differences between patients with and without endoleak and can help detect endoleaks in AAA after EVAR with high sensitivity.

CLINICAL RELEVANCE STATEMENT

Unenhanced CT radiomics can help provide an alternative method of endoleak detection in patients who have adverse reactions to contrast media. This study further exploits the value of unenhanced CT examinations in the clinical management and surveillance of postoperative abdominal aortic aneurysm.

KEY POINTS

• Unenhanced CT features of the aneurysm sac outside the stent exhibit significant differences between patients with and without endoleak. The endoleak group showed higher unenhanced CT attenuation (41.7 vs 33.6, p < .001) with smaller dispersion (51.5 vs 58.8, p < .001) than the nonendoleak group. • Unenhanced CT radiomics can help detect endoleaks after intervention. The average area under the curve (AUC) of twelve common machine learning models constructed with unenhanced CT radiomics was 0.86 ± 0.05, the average accuracy was 81% ± 4. • When fixing the sensitivity to > 90% (92% ± 2), the machine learning models retained average specificity at 72% ± 10.

Myocardial Calcium Handling in Type 2 Diabetes: A Novel Therapeutic Target

Type 2 diabetes (T2D) is a multisystem disease with rapidly increasing global prevalence. Heart failure has emerged as a major complication of T2D. Dysregulated myocardial calcium handling is evident in the failing heart and this may be a key driver of cardiomyopathy in T2D, but until recently this has only been demonstrated in animal models. In this review, we describe the physiological concepts behind calcium handling within the cardiomyocyte and the application of novel imaging techniques for the quantification of myocardial calcium uptake. We take an in-depth look at the evidence for the impairment of calcium handling in T2D using pre-clinical models as well as in vivo studies, following which we discuss potential novel therapeutic approaches targeting dysregulated myocardial calcium handling in T2D.

Heavy Metal-Based Nanoparticles as High-Performance X-ray Computed Tomography Contrast Agents

X-ray computed tomography (CT) contrast agents offer extremely valuable tools and techniques in diagnostics via contrast enhancements. Heavy metal-based nanoparticles (NPs) can provide high contrast in CT images due to the high density of heavy metal atoms with high X-ray attenuation coefficients that exceed that of iodine (I), which is currently used in hydrophilic organic CT contrast agents. Nontoxicity and colloidal stability are vital characteristics in designing heavy metal-based NPs as CT contrast agents. In addition, a small particle size is desirable for in vivo renal excretion. In vitro phantom imaging studies have been performed to obtain X-ray attenuation efficiency, which is a critical parameter for CT contrast agents, and the imaging performance of CT contrast agents has been demonstrated via in vivo experiments. In this review, we focus on the in vitro and in vivo studies of various heavy metal-based NPs in pure metallic or chemical forms, including Au, Pt, Pd, Ag, Ce, Gd, Dy, Ho, Yb, Ta, W, and Bi, and provide an outlook on their use as high-performance CT contrast agents.

DIAGNOSTIC VALUE OF SYSTEMIC IMMUNE–INFLAMMATION INDEX (SIII) IN ACUTE ISCHEMIC STROKE

Background: Calculated based on platelet, neutrophil and lymphocyte counts, the systemic immune-inflammation index is thought to be associated with many malignancies in the literature. Despite the existing investigations on its diagnostic value, there have been no clear results reported regarding its diagnostic value in stroke patients. The current study is therefore intended to demonstrate the diagnostic value of the systemic immune-inflammation index and its prognostic value in cases of acute ischemic stroke. Materials and Methods: A total of 150 cases of acute stroke and a control group of 150 individuals were retrospectively examined. The data recorded for each case included age, gender, history, vital findings, NIHSS, SIII, and outcome. Results: In the current study, the group of stroke patients had significantly higher SIII than the control group. According to the diagnostic examinations, in stroke, the diagnostic value of SIII was greater than that of neutrophil-to-lymphocyte ratio at a statistically significant level. The present study also found that, compared to the SIII, the (Lymphocyte x Platelet)/Neutrophil ratio (called the novel SIII) had a higher statistical significance in diagnosing the stroke and predicting early hospital mortality. Conclusions: The SIII can be a good marker for both diagnostic evaluation and for predicting early hospital mortality in stroke cases. Additionally, it is approved to be a useful index since it can be calculated inexpensively and easily.

V/Q SPECT and SPECT/CT in Pulmonary Embolism

Ventilation and perfusion (V/Q) lung scintigraphy has been used in the assessment of patients with suspected pulmonary embolism for more than 50 y. Advances in imaging technology make SPECT and SPECT/CT feasible. This article will examine the application and technical considerations associated with performing 3-dimensional V/Q SPECT and the contribution of a coacquired CT scan. The literature tends to be mixed and contradictory in terms of appropriate investigation algorithms for pulmonary embolism. V/Q SPECT and SPECT/CT offer significant advantages over planar V/Q, with or without the advantages of Technegas ventilation, and if available should be the preferred option in the evaluation of patients with suspected pulmonary embolism.

Emergency pharmacology for the CT technologist

The scope of practice of the medical radiation practitioner demands knowledge and understanding of the indications, contraindications, warnings, precautions, proper use, drug interactions and adverse reactions of a variety of medications. The risk of patient deterioration or acute emergent event, particularly following contrast administration, makes the command of crash cart medications particularly important. This article explores the pharmacological principles of medications most likely to be required in a medical emergency in the medical radiation department and in particular by the computed tomography (CT) technologist. The article also outlines early warning signs to assist in identifying the emergent or deteriorating patient. The learning outlined is designed to equip medical radiation practitioners with the capacity to identify and respond to a medical emergency typical of the medical radiation department, and to respond to that situation with the appropriate use of emergency medications where appropriate. The ability of medical radiation practitioners to recognise and respond to (including the use of medicines) the deteriorating patient or circumstances of a medically urgent nature are key capabilities required to meet minimum standards for Medical Radiation Practice Board of Australia registration and National Safety and Quality Health Service standards.

Increased Sensitivity of Computed Tomography Scan for Neoplastic Tissues Using the Extracellular Vesicle Formulation of the Contrast Agent Iohexol

Computed tomography (CT) is a diagnostic medical imaging modality commonly used to detect disease and injury. Contrast agents containing iodine, such as iohexol, are frequently used in CT examinations to more clearly differentiate anatomic structures and to detect and characterize abnormalities, including tumors. However, these contrast agents do not have a specific tropism for cancer cells, so the ability to detect tumors is severely limited by the degree of vascularization of the tumor itself. Identifying delivery systems allowing enrichment of contrast agents at the tumor site would increase the sensitivity of detection of tumors and metastases, potentially in organs that are normally inaccessible to contrast agents, such as the CNS. Recent work from our laboratory has identified cancer patient-derived extracellular vesicles (PDEVs) as effective delivery vehicles for targeting diagnostic drugs to patients' tumors. Based on this premise, we explored the possibility of introducing iohexol into PDEVs for targeted delivery to neoplastic tissue. Here, we provide preclinical proof-of-principle for the tumor-targeting ability of iohexol-loaded PDEVs, which resulted in an impressive accumulation of the contrast agent selectively into the neoplastic tissue, significantly improving the ability of the contrast agent to delineate tumor boundaries.

Radiomics of dual-energy computed tomography for predicting progression-free survival in patients with early glottic cancer

Aim: This study aimed to predict progression-free survival (PFS) in patients with early glottic cancer using radiomic features on dual-energy computed tomography iodine maps. Methods: Radiomic features were extracted from arterial and venous phase iodine maps, and radiomic risk scores were determined by univariate Cox proportional hazards regression analysis and least absolute shrinkage and selection operator regression with tenfold cross-validation. The Kaplan-Meier method was used to evaluate the association between radiomic risk scores and PFS. Results: Patients were stratified into low-risk and high-risk groups using radiomics, the PFS corresponding rates with statistical significance between the two groups. The high-risk group showed better survival, benefiting from laryngectomy. Conclusion: Radiomics could provide a promising biomarker for predicting the PFS of early glottic cancer patients.

The interaction between iodinated X‐ray contrast agents and macrocyclic GBCAs provides a signal enhancement in T 1 ‐weighted MR images: Insights into the renal excretion pathways of Gd‐HPDO3A and iodixanol in healthy mice

Purpose

This work aims to investigate the supramolecular binding interactions that occur between iodinated X‐ray contrast agents (CAs) and macrocyclic gadolinium (Gd)–based MRI contrast agents (GBCAs). This study provides some new insights in the renal excretion pathways of the two types of imaging probes.

Methods

The water‐proton relaxivities (r₁) of clinically approved macrocyclic and linear GBCAs have been measured in the presence of different iodinated X‐ray contrast agents at different magnetic field strengths in buffer and in serum. The in vivo MRI and X‐ray CT of mice injected with either Gd‐HPDO3A or a Gd‐HPDO3A + iodixanol mixture were then acquired to assess the biodistribution of the two probes.

Results

A significant increase in r₁ (up to approximately 200%) was observed for macrocyclic GBCAs when measured in the presence of an excess of iodinated X‐ray CAs (1:100 mol:mol) in serum. The co‐administration of Gd‐HPDO3A and iodixanol in vivo resulted in a marked increase in the signal intensity of the kidney regions in T₁‐weighted MR images. Moreover, the co‐presence of the two agents resulted in the extended persistence of the MRI signal enhancement, suggesting that the Gd‐HPDO3A/iodixanol adduct was eliminated more slowly than the typical washing out of Gd‐HPDO3A.

Conclusions

The reported results show that it is possible to detect the co‐presence of iodinated agents and macrocyclic GBCAs in contrast‐enhanced MR images. The new information may be useful in the design of novel experiments toward improved diagnostic outcomes.

Analysis of clinical characteristics of Kounis syndrome induced by contrast media

BACKGROUND

Understanding the relationship between contrast agents and Kounis syndrome (KS) is mainly based on case reports. The purpose of this research is to explore the clinical characteristics of contrast media induced KS.

METHODS

We searched for contrast-induced KS case reports through Chinese and English databases from 1991 to October 31, 2021.

RESULTS

A total of 26 patients (19 men and 7 women,) were included, with a median age of 60 years (range 30-83). The contrast agents that cause KS mainly included gadolinium-based contrast agent (7 cases), iodine-containing contrast media (12 cases). KS mainly occurred within 30 min after administration and mainly manifests as chest pain and allergic reactions. Electrocardiogram (ECG) mainly showed ST elevation. Echocardiography mainly revealed normal. Coronary angiography showed normal, coronary vasospasm, stent thrombosis, occlusion and stenosis. After treatment with steroids, antihistamines and anti-ischemic therapy, 24 patients recovered completely and 2 patients died.

CONCLUSIONS

KS is a rare adverse reaction of contrast media. Radiologists should recognize this rare but serious disease to ensure rapid diagnosis and proper management.

PET/MR Part 3: PET/MRI Protocols and Procedures

The emergence of position emission tomography (PET) and magnetic resonance imaging (MRI) as a hybrid modality has demanded new approaches to protocol and procedure. While protocols for MRI and PET individually lend themselves to synergistic and simultaneous approaches, there are a number if unique challenges and patient preparations that require consideration. This manuscript provides an insight into the protocols, procedures and challenges associated with simultaneous PET/MRI in both adult and pediatric populations. While protocols may be specific to applications or pathologies of interest, a richer discussion of the clinical applications of PET/MRI is beyond the scope of this manuscript and will be detailed in part 4 of the series. The foundations of PET/MRI protocols is an understanding of the various MRI sequences which are outlined succinctly. The principles outlined for protocols and procedures are general in nature and specific application will vary among departments. Given the procedures of PET is well established amongst the readership of this journal, the manuscript provides an emphasis on MR factors unless specific variations in standard PET protocol or procedure are driven by the simultaneous MRI. This manuscript is the third in a four-part integrated series sponsored by the SNMMI-TS PET/MR Task Force in conjunction with the SNMMI-TS Publication Committee.

MRI as a first-line imaging modality in acute ischemic stroke: a sustainable concept

Background:

Computed tomography (CT) scans are the first-line imaging technique in acute stroke patients based on the argument of rapid feasibility. Using magnetic resonance imaging (MRI) as the first-line imaging technique is the exception to the rule, although it provides much more diagnostic information and avoids exposure to radiation. We evaluated whether an MRI-based acute stroke concept is fast, suitable, and useful to improve recanalization rates and patient outcomes.

Methods:

We performed a retrospective observational cohort study comparing patients treated at a comprehensive stroke center (Ulm/Germany) applying an MRI-based acute stroke concept with patients recorded in a large comprehensive stroke registry in Baden-Württemberg (Germany). We analyzed the quality indicators of acute stroke treatment, patient’s outcome, and the rate of transient ischemic attack (TIA) at discharge.

Results:

A total of 2182 patients from Ulm and 82,760 patients from the Baden-Württemberg (BW) stroke registry (including 29,575 patients of comprehensive stroke centers (BWc)) were included. Intravenous thrombolysis rate was higher in Ulm than in BW or the BWc stroke centers (Ulm 27.4% versus BW 20.9% versus BWc 26.1; p < 0.01), while a door-to-needle time <30 min could be achieved more frequently (Ulm 73.6% versus BW 44.1% versus BWc 47.1%; p < 0.01). Thrombectomy rate in patients with a proximal vascular occlusion was higher (Ulm 69.2% versus BW 50.7% versus BWc 59.3; p < 0.01). The number of TIA diagnoses was lower (Ulm 16.2% versus BW 24.6% versus BWc 19.9%; p < 0.01). More patients showed a shift to a favorable outcome (Ulm 21.1% versus BW 16.9% versus BWc 15.3; p < 0.01). Complication rates were similar.

Conclusions:

The MRI-based acute stroke concept is suitable, fast and seems to be beneficial. The time-dependent quality indicators were better both in comparison to all stroke units and to the comprehensive stroke units in the area. Based on the MRI concept, high rates of recanalization procedures and fewer TIA diagnoses could be observed. In addition, there was a clear trend towards an improved clinical outcome. A clinical trial comparing the effects of CT and MRI as the primary imaging technique in otherwise identical stroke unit settings is warranted.

A comparative study between CT, MRI, and intraoral US for the evaluation of the depth of invasion in early stage (T1/T2) tongue squamous cell carcinoma

Objectives

This study aimed to clarify the accuracy of intraoral ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) in preoperative image depth of invasion (DOI) measurement of T1/T2 tongue cancer through comparison with histopathological measurements.

Methods

Imaging of the primary lesions was performed at our hospital; the lesions were classified into T1 and T2 based on the 8th edition of the AJCC/UICC, and surgery performed. There was histopathological confirmation of lesions as squamous cell carcinoma in 48 patients with tongue cancer. T3 and T4 cases, cases in which preoperative chemotherapy and radiation therapy were performed, and cases where biopsy was performed before imaging were excluded. The radiological DOI in US, CT, and MRI and the histopathological DOI as base were comparatively investigated and statistical analyses were performed by Bland–Altman analysis and Spearman's rank correlation coefficient.

Results

Bland–Altman analysis showed that the US radiological DOI was overestimated by an average of 0.2 mm compared to the histopathological DOI, while CT and MRI radiological DOI were overestimated by an average of 2–3 mm. The comparison of CT and MRI revealed that the difference between the MRI and histopathological DOI, as well as the 95% limit of agreement, were smaller than those of the CT radiological DOI.

Conclusions

US is the most accurate preoperative diagnostic tool for T1 and T2 squamous cell carcinoma; CT and MRI tend to have an overestimation of about 2–3 mm and so caution is required.

PET/MRI, Part 2: Technologic Principles

The challenges of hybridizing PET and MRI as a simultaneous modality have been largely overcome in recent times. PET hybridized with MRI has seen the emergence of PET/MRI systems in the clinical setting, and with it comes a responsibility to adapt appropriate facility design, safety practices, protocols and procedures, and clinical opportunity. This article provides an insight into the considerations and challenges associated with PET/MR technology. Given that the nature of PET is well established among the readership of this journal, the article provides an introduction to the foundations of MRI instrumentation and emphasis on specific technologic aspects of PET/MR systems. This article is the second in a 4-part integrated series sponsored by the PET/MR and Publication Committees of the Society of Nuclear Medicine and Molecular Imaging-Technologist Section, building on the previous article (part 1), which was on establishing a facility. In subsequent parts, PET/MRI will be explored on the basis of protocols and procedures (part 3) and applications and clinical cases (part 4).

Contrast and dyes

Contrast agents have long been used for the imaging of anatomic boundaries and to explore normal and abnormal physiologic findings. The introduction of increasingly faster and more discriminating radiographic imaging techniques has resulted in the need for radiation-attenuating contrast agents that can be used in traditional radiographic imaging or, more recently, in subtraction imaging, both of which can be projected and rotated in three dimensions. By far the most successful and widely applied contrast agents in use today are the iodinated contrast agents (ICAs), first introduced into clinical practice in the 1950s. It is estimated that approximately 75 million doses of ICAs are given worldwide each year.