Implementation of xSPECT, xSPECT bone and Broadquant from literature, clinical survey and innovative phantom study with task-based image quality assessment

OBJECTIVE

From patient and phantom studies, we aimed to highlight an original implementation process and share a two-years experience clinical feedback on xSPECT (xS), xSPECT Bone (xB) and Broadquant quantification (Siemens) for 99mTc-bone and 177Lu-NET (neuroendocrine tumors) imaging.

METHODS

Firstly, we checked the relevance of implemented protocols and Broadquant module on the basis of literature and with a homogeneous phantom study respectively. Then, we described xS and xB behaviours with reconstruction parameters (10i-0mm to 40i-20mm) and optimized the protocols through a blinded survey (7 physicians). Finally, the preferred 99mTc-bone reconstruction was assessed through an IEC NEMA phantom including liquid bone spheres. Conventional SNR, CNR, spatial resolution, Q.%error, and recovery curves; and innovative NPS, TTF and detectability score d' were performed (ImQuest software). We also sought to review the adoption of these tools in clinical routine and showed the potential of quantitative xB in the context of theranostics (Xofigo®).

RESULTS

We showed the need of optimization of implemented reconstruction algorithms and pointed out a decay correction particularity with Broadquant. Preferred parameters were 1s-25i-8mm and 1s-25i-5mm for xS/xB-bone and xS-NET imaging respectively. The phantom study highlighted the different image quality especially for the enhanced spatial resolution xB algorithm (1/TTF10%=2.1 mm) and showed F3D and xB shared the best performances in terms of image quality and quantification. xS was generally less efficient.

CONCLUSIONS

Qualitative F3D still remains the clinical standard, xB and Broadquant offer challenging perspectives in theranostics. We introduced the potential of innovative metrics for image quality analysis and showed how CT tools should be adapted to fit nuclear medicine imaging.

Assessment of the Association between Entropy in PET/CT and Response to Anti-PD-1/PD-L1 Monotherapy in Stage III or IV NSCLC

Anti-PD-1/PD-L1 therapy indications are broadened in non-small cell lung cancer (NSCLC) although immune checkpoint inhibitors (ICI) do not provide benefits for the entire population. Texture features based on positron emission tomography/computed tomography (PET/CT), especially entropy (based on a gray-level co-occurrence matrix (GLCM)), could be interesting as predictors in NSCLC. The aim of our retrospective study was to evaluate the association between GLCM-entropy and response to anti-PD-1/PD-L1 monotherapy at the first evaluation in stage III or IV NSCLC, comparing patients with progressive disease (PD) and non-progressive disease (non-PD). In total, 47 patients were included. Response Evaluation Criteria in Solid Tumors (RECIST 1.1) were used to evaluate the response to ICI treatment (nivolumab, pembrolizumab, or atezolizumab). At the first evaluation, 25 patients were PD and 22 were non-PD. GLCM-entropy was not predictive of response at the first evaluation. Furthermore, GLCM-entropy was not associated with progression-free survival (PFS) (p = 0.393) or overall survival (OS) (p = 0.220). Finally, GLCM-entropy measured in PET/CT performed before ICI initiation in stage III or IV NSCLC was not predictive of response at the first evaluation. However, this study demonstrates the feasibility of using texture parameters in routine clinical practice. The interest of measuring PET/CT texture parameters in NSCLC remains to be evaluated in larger prospective studies.

Predicting subacute hematological toxicity of 177Lu-DOTATATE therapy using healthy organs' uptake on post-treatment quantitative SPECT: A pilot study

The aim is to investigate the usefulness of 177Lu-DOTA-0-Tyr3-Octreotate (DOTATATE) healthy organs' (spleen, kidneys, bone marrow) standard uptake value for the prediction of subacute hematological toxicity in patients undergoing 177Lu-DOTATATE treatment. All patients referred from January 2021 to May 2022 for 177Lu-DOTATATE treatment were retrospectively screened. For each treatment session, baseline clinical data including age, sex, weight, delay between 177Lu-DOTATATE treatment and last cold somatostatin analogue intake were collected. Mean standardized uptake value (SUVmean) of healthy organs was measured and analyzed by generalized linear mixed effect models. Outcomes (significant decrease of platelets, hemoglobin levels and neutrophils) were assessed 1 month later, considering their within-subject biological coefficient of variation, published by the European Federation of Clinical Chemistry and Laboratory Medicine. A total of 9 patients (33 treatment sessions) were included. No predictive factors were identified for platelet and neutrophil decrease. Splenic SUVmean was found to be a significant predictor of hemoglobin levels decrease. Using an optimal threshold of ≥6.22, derived sensitivity and specificity to predict hemoglobin decrease were 85.7% [46.4; 99.0] and 76.9% [57.5; 89.2] respectively with an accuracy of 82.4%. Although not significantly predictive of hematological toxicity, bone marrow SUVmean and renal SUVmean were correlated with splenic SUVmean. Quantitative single photon emission computed tomography and healthy organs analysis might help to foresee hematological subacute toxicity in patients undergoing 177Lu-DOTATATE treatment and improve patient management.

Orbital Metastasis: A Rare but Typical Location of Small Intestine Neuroendocrine Tumor on 18F-FDOPA PET/CT

ABSTRACT

Orbital foci of increased uptake are sometimes visualized on 18F-FDOPA PET/CT, but the literature remains poor as to their nature. The orbit is indeed a rare site of metastatic involvement. Given this low probability of metastatic location, the question of an incidental benign finding may arise. We reviewed all 18F-FDOPA PET/CT examinations performed at our institution between January 2015 and May 2021: 4/149 patients presented at least 1 orbital focus of increased uptake, all of them presented a metastatic small intestine neuroendocrine tumor. Somatostatin receptor expression was confirmed using 68Ga-DOTATOC PET/CT supporting the hypothesis of genuine metastases.

Performances of 18F-FDOPA PET/CT in the Preoperative Evaluation of the Peritoneal Cancer Index in Small Intestine Neuroendocrine Tumors

PURPOSE

Peritoneal carcinomatosis (PC) concerns up to 30% of patients with a neuroendocrine tumor (NET), especially of the small intestine. Aggressive management of carcinomatosis seems to be justified, especially with regard to possible mechanical complications. 18F-FDOPA PET/CT is known to be the most sensitive imaging modality for the detection of small bowel NET metastases, yet its performance in the detection of PC is not well studied. The main objective of our study is to evaluate the performances of preoperative 18F-FDOPA PET/CT in the prediction of surgical peritoneal cancer index.

METHODS

All patients referred to our center for an 18F-FDOPA PET/CT from October 2017 to January 2021 were retrospectively screened. Images were analyzed by a blinded nuclear medicine physician, and peritoneal abnormalities were reported to comply with the surgical peritoneal cancer index standard. Per patient analysis and per region analysis were then conducted.

RESULTS

Thirty-three patients were included; 6 patients (35 regions) presented a peritoneal carcinosis. Peritoneal Carcinomatosis Index (PCI) estimated on 18F-FDOPA PET/CT was significantly and strongly correlated to surgical PCI (r = 0.96, P < 0.001). Patient-based sensitivity, specificity, negative predictive value, and positive predictive value for 18F-FDOPA PET/CT were 100%, 93%, 100%, and 75%, respectively. The agreement between 18F-FDOPA and surgery regarding PC was excellent (Cohen κ = 0.82 on per patient analysis, 0.74 on per region analysis).

CONCLUSIONS

A preoperative estimation of PCI is achievable based on 18F-FDOPA PET/CT for small intestine NET and could allow to optimize surgical procedures and patient selection.

Pulmonary cavitations with increased 18F-FDG uptake revealing a thoracic endometriosis: A case report

RATIONALE

Thoracic endometriosis is a rare disorder that can involve airways, pleura and lung parenchyma. It is the most frequent form of extra-abdominopelvic endometriosis. Multiple lung cavitations are a rare feature of thoracic endometriosis.

PATIENT CONCERNS

A 46-year-old woman was referred to our hospital after incidental finding of multiple pulmonary cavitations with surrounding areas of ground glass opacity on a thoraco-abdominal computed tomography-scan performed for abdominal pain. Retrospectively, the patient also reported mild hemoptysis occurring 4 months ago.

DIAGNOSES

Positron emission tomography-computed tomography scan revealed moderate and homogeneous [18F] fluoro-2-deoxy-D-glucose (18F-FDG) uptake in pulmonary cavitations (maximum standardized uptake value 5.7). The diagnosis of thoracic endometriosis was confirmed by histological examination of surgical resection of a left lower lobe cavitation.

INTERVENTIONS AND OUTCOME

Gonadotropin-releasing hormone analogues associated with add-back therapy was started. Four months after initiating pharmacological treatment, the chest computed tomography-scan showed a dramatic decrease in lung cavitations size.

LESSONS

Thoracic endometriosis is a rare disorder requiring a multidisciplinary management including gynaecologist, pulmonologist, radiologist, nuclear physician, pathologist and thoracic surgeon for early diagnosis and treatment. Our case report highlights that an increased 18F-FDG uptake can be found in thoracic endometriosis syndrome presenting as multiple lung cavitations.

Perturbations des glycémies capillaires : un effet indésirable inattendu de l’épidémie COVID-19 en TEP

Un jeûne d’environ 6 heures est requis avant l’injection de 18F-FDG afin d’éviter les états d’hyperinsulinisme susceptibles d’augmenter la captation des tissus non tumoraux, notamment musculaires. Un contrôle de la glycémie capillaire est ainsi recommandé avant toute administration de 18F-FDG. Nous rapportons une courte série de 3 patients présentant des glycémies capillaires faussement basses en lien avec l’utilisation de gel hydroalcoolique pour le lavage des mains. Les appareils de mesure de glycémie capillaire utilisent une réaction enzymatique pour mesurer la glycémie à partir des produits de dégradation de la goutte de sang déposée sur la bandelette. Trois enzymes principales peuvent être utilisées : glucose oxidase, glucose hexokinase et glucose deshydrogénase (comme dans notre appareil de mesure). Ces enzymes sont conditionnées à l’état sec sur la bandelette et sont donc sensibles aux conditions ambiantes. Le gel hydroalcoolique peut ainsi altérer la mesure. Dans notre série, les glycémies étaient artificiellement abaissées lorsque les patients avaient les mains couvertes de gel hydroalcoolique non séché avec potentiellement deux conséquences : la non détection d’une hyperglycémie ou la fausse hypoglycémie. Pour deux de ces patients, tous deux diabétiques, la question d’un resucrage immédiat et d’un report de TEP avait même été soulevée. Les guides de bonnes pratiques préconisent un lavage et un séchage des mains soigneux avant toute mesure de la glycémie capillaire, voire même l’utilisation de la seconde goutte de sang dans les cas où un bon lavage serait impossible. La consommation de gel hydroalcoolique a augmenté avec l’épidémie de COVID-19, ces potentielles interactions avec les appareils de mesure de glycémie doivent être gardées en tête.

Superiority of NaF PET/CT Over Chest CT in a Case of Osteosarcoma

ABSTRACT

We report the case of a 21-year-old man referred to our institution for the initial staging of an osteoblastic osteosarcoma of the right femur. An 18F-NaF PET/CT demonstrated millimetric pleuroparenchymal metastases, later confirmed on follow-up. These lesions were not reported on both dedicated chest CT and 18F-FDG PET/CT.

PET/CT of Duodenal Gangliocytic Paraganglioma

An 87-year-old woman with leg-type lymphoma underwent a staging F-FDG PET/CT, which demonstrated besides leg lymphomatous lesions a round, well-defined, preduodenal mass with moderate FDG uptake. This mass remained unchanged after chemotherapy treatment completion, despite a complete metabolic response of lymphomatous lesions. A biopsy revealed a gangliocytic paraganglioma. Subsequent F-FDOPA PET/CT and somatostatin receptor scintigraphy were positive and did not depict any other lesions.

Added value of 18F-fluorocholine positron emission tomography-computed tomography in presurgical localization of hyperfunctioning parathyroid glands after dual tracer subtraction scintigraphy failure: A retrospective study of 47 patients

Hyperparathyroidism is a common endocrine disorder. The precise localization of causal parathyroid gland is crucial to guide surgical treatment. Several studies report the added value of 18F-fluorocholine (FCH) positron emission tomography-computed tomography (PET/CT) as second line imaging but rely on suboptimal first-line imaging using 99mTc-sestaMIBI dual phase scintigraphy. The aim of this study is to evaluate the percentage of successful parathyroid localization with FCH PET/CT after failure of a more sensitive first-line detection protocol associating neck ultrasonography and 99mTc-Pertechnetate/99mTc-sestaMIBI dual tracer subtraction scintigraphy.We included retrospectively 47 patients who underwent a FCH PET/CT as second line imaging for biologically proven primary hyperparathyroidism from November 2016 to October 2018 in Godinot Institute (Reims, France). 99mTc-Pertechnetate/99mTc-sestaMIBI dual tracer subtraction scintigraphy and neck ultrasonography were used as first-line imaging and failed to localize the causal parathyroid lesion in all cases.FCH PET/CT demonstrated at least 1 parathyroid target lesion in 29 patients (62%). 21/29 patients underwent surgery. Target lesions corresponded histologically to hyperfunctioning parathyroid glands for all 21 patients and surgery was followed by hyperparathyroidism biological resolution. Calcium serum levels were associated to FCH PET/CT positivity (P = .002) and a trend toward significance was seen for Parathyroid hormone (PTH) levels (P = .09).FCH PET/CT is a promising tool in second-line parathyroid imaging. Large prospective studies and cost-effectiveness analyses are needed to precise its role.

A no-reference respiratory blur estimation index in nuclear medicine for image quality assessment

Few indexes are available for nuclear medicine image quality assessment, particularly for respiratory blur assessment. A variety of methods for the identification of blur parameters has been proposed in literature mostly for photographic pictures but these methods suffer from a high sensitivity to noise, making them unsuitable to evaluate nuclear medicine images. In this paper, we aim to calibrate and test a new blur index to assess image quality.Blur index calibration was evaluated by numerical simulation for various lesions size and intensity of uptake. Calibrated blur index was then tested on gamma-camera phantom acquisitions, PET phantom acquisitions and real-patient PET images and compared to human visual evaluation.For an optimal filter parameter of 9, non-weighted and weighted blur index led to an automated classification close to the human one in phantom experiments and identified each time the sharpest image in all the 40 datasets of 4 images. Weighted blur index was significantly correlated to human classification (ρ = 0.69 [0.45;0.84] P < .001) when used on patient PET acquisitions.The provided index allows to objectively characterize the respiratory blur in nuclear medicine acquisition, whether in planar or tomographic images and might be useful in respiratory gating applications.

Everolimus-induced pulmonary toxicity: Findings on 18F-FDG PET/CT imaging

The everolimus-exemestane combination is indicated in advanced breast cancer treatment and usually well tolerated. The objective of the study was to determine the frequency of everolimus lung side effects and investigate their imaging characteristics on positron emission tomography with 18F-fluoro-deoxy-glucose combined with computerized tomography (F-FDG PET/CT).Our single-center retrospective descriptive study systematically included all patients with metastatic breast cancer treated by this combination (n = 29 representing 57 F-FDG PET/CT). Number of segments involved was quantified. Maximum standardized uptake value (SUVmax), average standardized uptake value (SUVmean), metabolic target volume (MTV), and total lesion glycolysis (TLG) were measured. Severe pneumopathy was studied by subgroup analysis.Pleuroparenchymal anomalies rate detected on F-FDG PET/CT was 62%. Alveolar-interstitial lesions were mainly observed (89%) and affected 2.8 segments (0.5-11.5) with a median of 2 segments. S7 and S10 were the most involved segments with SUVmax 3.9 (1.3-8.8) and SUVmean 2.2 (0.7-4.9). Statistically significant difference (P = .02) was found with number of segment involved to characterize severe pneumopathy (average of 6.3 segments [2.5-11.5] vs 1.9 segments [0.5-8] for interstitial lung disease) but not with SUVmax, SUVmean, MTV, TLG (P = .14, 0.22, 0.22, and 0.17, respectively).The F-FDG PET/CT could highlight pulmonary everolimus side effects, with a typical imaging pattern: alveolar-interstitial opacities associated with moderate uptake, more or less extensive, mainly affecting the lower lobes. Rarely, a pseudotumoral aspect may be detected, corresponding to a pitfall. MTV or TLG showed a tendency to differentiate severe pneumopathy vs interstitial lung disease but no statistically significant differences was observed contrarily to the number of segments involved. Further studies are necessary to determine if the F-FDG PET/CT could early predict adverse effects of mTOR inhibitors.

Data-driven respiratory gating for ventilation/perfusion lung scan

BACKGROUND

Ventilation/perfusion lung scan is subject to blur due to respiratory motion whether with planar acquisition or single photon emission computed tomography (SPECT). We propose a data-driven gating method for extracting different respiratory phases from lung scan list-mode or dynamic data.

METHODS

The algorithm derives a surrogate respiratory signal from an automatically detected diaphragmatic region of interest. The time activity curve generated is then filtered using a Savitzky-Golay filter. We tested this method on an oscillating phantom in order to evaluate motion blur decrease and on one lung SPECT.

RESULTS

Our algorithm reduced motion blur on phantom acquisition: mean full width at half maximum 8.1 pixels on non-gated acquisition versus 5.3 pixels on gated acquisition and 4.1 pixels on reference image. Automated detection of the diaphragmatic region and time-activity curves generation were successful on patient acquisition.

CONCLUSIONS

This algorithm is compatible with a clinical use considering its runtime. Further studies will be needed in order to validate this method.

Incidental gastrointestinal 18F-Fluorodeoxyglucose uptake associated with lung cancer

BACKGROUND

F-Fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is increasingly used for the initial staging and restaging of lung cancer. Incidental gastrointestinal findings are often observed on (18)F-FDG PET/CT. The objective of this study was to assess incidental 18F-FDG uptake by the gastrointestinal tract (GIT) in patients with lung cancer.

METHODS

Two hundred thirty consecutive 18F-FDG PET/CT examinations performed for lung cancer over a 3-year period were retrospectively reviewed for the presence of incidental FDG uptake in the GIT. The charts of patients with positive FDG uptake were then reviewed and analysed to determine the GIT uptake sites, the standardized uptake value (SUV) max and the final clinical diagnosis.

RESULTS

Fifty-two patients (52/230, 23%) demonstrated incidental FDG uptake in the GIT. Thirty-three patients (63.5%) had diffuse uptake (oesophagus, n = 2, colon, n = 31) and 19 patients (36.5%) had focal uptake (oesophagus, n = 1, small bowel, n = 1, ascending colon, n = 5, descending colon, n = 4, sigmoid, n = 4, rectum, n = 3, and anal margin, n = 1). Twelve of the 52 patients with GIT uptake were further investigated, revealing, a diagnosis of malignancy in 4 patients with focal FDG uptake. No significant differences in mean SUVmax were observed between patients with malignant and benign GIT diseases.

CONCLUSION

This study demonstrates a high incidence of FDG uptake in the GIT associated with lung cancer. Focal GIT uptake was frequently associated with malignant disease. These results suggest that further GIT investigations should be performed in patients with focal GIT uptake.

Cognitive impairment in systemic lupus erythematosus women with elevated autoantibodies and normal single photon emission computerized tomography

BACKGROUND

Systemic lupus erythematosus (SLE) is known to induce psychiatric disorders, from psychoses to maladaptive coping. Brain autoantibodies were proposed to explain SLE neuropsychiatric disorders and found to be elevated before the onset of clinical symptoms. We assessed cognition in Caucasian SLE women with elevated autoantibodies without overt neuropsychiatric syndromes, in conjunction with single photon emission computerized tomography (SPECT).

METHODS

31 women meeting SLE criteria of the American College of Rheumatology (ACR) were included. Patients who met the ACR neuropsychiatric definition were excluded. Matched controls were 23 healthy women from the Champagne-Ardenne region, France. Participants completed neuropsychological and autoantibodies measurements, and 19 completed SPECT.

RESULTS

61% (19/31) of women with SLE and 53% (9/17) of those with normal SPECT had significant global cognitive impairment defined as 4 T-scores <40 in cognitive tests, compared to 0% (0/23) of controls. SLE women also had significantly greater cognitive dysfunction (mean T-score) on the Wechsler Adult Intelligence Scale (WAIS) visual backspan, Trail Making Test A and B, WAIS Digit Symbol Substitution Test and Stroop Interference, compared to controls. Elevated antinuclear antibody correlated with impairment in the WAIS visual span, WAIS visual backspan, and cancellation task; elevated anti-double-stranded DNA antibody and anticardiolipin correlated respectively with impairment in the Trail Making Test A and WAIS auditive backspan. Two SLE women had abnormal SPECT.

CONCLUSIONS

A high prevalence of cognitive deficits was found in Caucasian SLE women compared to normal women, which included impairment in cognitive domains important for daily activities. Elevated autoantibodies tended to correlate with cognitive dysfunction.

Impact on overall survival of radioactive iodine in low-risk differentiated thyroid cancer patients

CONTEXT

American Thyroid Association and European Thyroid Association guidelines cannot recommend for or against radioactive iodine (RAI) ablation after surgery in low-risk differentiated thyroid cancer (DTC) patients.

OBJECTIVES

The objective of the study was to assess the survival benefit of RAI for these patients.

DESIGN

We identified 1298 DTC patients at low risk treated between 1975 and 2005. Logistic regressions were used to identify variables associated to RAI and to calculate the propensity score to receive RAI after surgery. We compared overall survival (OS) and disease-free survival (DFS) according to RAI with the log-rank tests and univariate and multivariate Cox analyses. Analyses stratified on propensity score were also performed.

RESULTS

Median follow-up was 10.3 yr. Nine hundred eleven patients received RAI after surgery vs. 387 patients without RAI after surgery. Using univariate analysis, 10-yr OS was found to be 95.8% in patients without RAI after surgery vs. 94.6% in RAI after surgery (P = 0.006), and 10-yr DFS was found to be 93.1% vs. 88.7% (P = 0.001). All clinical factors except sex were significantly associated with RAI. Using multivariate Cox analyses, RAI was neither significantly nor independently associated with OS (P = 0.243) and DFS (P = 0.2659). After stratification on propensity score, Cox univariate analyses showed that OS did not differ according to RAI (P = 0.3524), with a hazard ratio for RAI of 0.75 (95% confidence interval 0.40-1.38). Similarly, DFS did not differ (P = 0.48) with a stratified univariate hazard ratio of 1.11 (95% confidence interval 0.73-1.70).

CONCLUSION

With a long-term follow-up of 10.3 yr, we failed to prove any survival benefit of RAI after surgery in a large cohort of low-risk DTC patients.

[Comparison between PET(-FDG) and computed tomography in the staging of lung cancer. Consequences for operability in 94 patients]

INTRODUCTION

Lung cancer, a major application of FDG/PET-CT, has recently been introduced in daily practice in France. The authors retrospectively studied its impact on the management of this disease.

METHODS

The results of PET-CT and conventional assessment (brain imaging, chest and abdominal CT and possibly bone scintigraphy) were compared in 94 patients, referred for the staging of non-small cell lung cancer, or the assessment of a solitary lung lesion. The impact of thoracic lymph node involvement on the operability of patients was studied in 44 patients.

RESULTS

PET-CT revealed metastases in 20% of the patients without metastases found by conventional imaging and modified the stage of the disease in 28% of the cases. It changed the indication of surgical treatment in 19% of the cases and led to induction chemotherapy in two patients. In addition, two synchronous cancers were discovered. Regarding lymph node involvement, PET-CT remains of diagnostic value regardless of the scanner results.

CONCLUSION

The impact of PET-CT in assessing non-small cell lung cancer was confirmed in the authors' practice. Its interest and the consequences in some patients misclassified with conventional assessment have been demonstrated.

Single-photon emission computed tomography combined with computed tomography (SPECT/CT) in bone diseases

Radionuclide bone scanning was proven effective many years ago. Its main advantages are good sensitivity, limited radiation exposure, and noninvasiveness. However, increased radionuclide uptake by a lesion is not specific, and differentiating malignant from nonmalignant disorders may therefore be difficult. An additional structural imaging study is often needed to establish the final diagnosis. Furthermore, the limited resolution of radionuclide bone scanning images does not allow accurate localization of the lesions. Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) provides both structural and functional information. SPECT/CT has been proven useful for interpreting radionuclide bone scan results in patients with bone malignancies, showing far better specificity than planar imaging or SPECT alone, most notably in the evaluation of spinal abnormalities. SPECT/CT provides an accurate evaluation of the site of the lesions and also supplies other information that can be useful in nonmalignant conditions such as injuries, infections, and degenerative disease. Nevertheless, there are only a few published studies on the usefulness of SPECT/CT in nonmalignant conditions. However, SPECT/CT is only starting to become available and may become a routine investigation for a number of rheumatic disorders.

The growing development of multimodality imaging in oncology

The first decade of the century has been the beginning of an era of new practice in daily medical imaging, that is the multimodality involving functional or metabolic imaging brought by nuclear medicine techniques directly associated with anatomical information brought by CT (Computed X-Ray Tomography) devices combined with nuclear medicine detectors. PET (Positron Emission Tomography)/CT and SPECT (Single Photon Emission Computed Tomography)/CT are now established to further increase the interest of PET and SPECT, thanks to improved localization of the pathologic processes, and in many instances thanks to a gain in specificity. An even better use of the combined information will necessitate redefining some protocols and indications, and the future will probably see the continued development of multimodality imaging in practice. Besides the combination with CT, another modality is expected in the future: PET/MRI (Magnetic Resonance Imaging).

SPECT/CT in localization of parathyroid adenoma or hyperplasia in patients with previous neck surgery

PURPOSE

Single photon emission computed tomography/computed tomography (SPECT/CT) now makes it possible to use combined morphologic CT and functional scintigraphy information. It has proved useful for localization of abnormal parathyroid glands, especially in the case of an ectopic gland. We experienced that it was also beneficial for patients with a history of previous neck surgery, and we report 4 cases in this entity.

MATERIALS AND METHODS

Four patients with prior neck surgery and hyperparathyroidism underwent parathyroid Tc-99m MIBI scintigraphy with SPECT/CT. Two patients had undergone surgery for hyperparathyroidism and 2 had undergone thyroidectomy, 1 for thyroid cancer and 1 for multinodular goiter. Parathyroid hormone levels were assessed during surgery, and patients were followed several months after treatment.

RESULTS

SPECT/CT successfully localized the abnormal gland, including an uncommon anterior situation for which previous surgery guided by planar imagery failed to cure the hyperparathyroidism. It allowed efficient surgical treatment, as confirmed by parathyroid hormone level normalization, without complications and with a relatively short operation time in those challenging cases.

CONCLUSIONS

SPECT/CT seems to be a useful tool for presurgical assessment in hyperparathyroidism, not only for ectopic glands but also for patients with previous neck surgery.

Respiratory motion artefact in the liver dome on FDG PET/CT: comparison of attenuation correction with CT and a caesium external source

PURPOSE

Respiratory motion has been reported to be a potential cause of artefacts on PET/CT, and of errors in the quantification of lesion activity due to inaccurate attenuation correction. We examined FDG images corrected for attenuation with CT and a caesium external source in the same patients to study this artefact and to assess its impact on detection of lesions in the upper part of the liver.

METHODS

A total of 122 patients underwent the examination using both attenuation correction techniques, with the Gemini PET/CT scanner. No breathing instructions were given. The images obtained were visually compared, and standardised uptake values (SUVs) in 35 lesions were measured (mean SUV/normal liver SUV) in 14 patients with lesions in the upper part of the liver (less than 5 cm from the upper border).

RESULTS

CT-corrected images of the liver included an artefactual cold area in 84 patients (69%); this area was located in the posterior upper part of the liver (65 patients, 53%), included the top of the liver (ten patients, 8%) or affected both the top and the posterior part (nine patients, 8%). In lesions (and also in normal liver outside the artefactual area), SUVs obtained with CT correction were higher than those obtained with Cs correction (p<0.05), though this was usually without relevance for lesion detection. However, in patients with lesions situated inside the artefactual area, SUVs were lower with CT correction, and ability to detect two lesions (6%) was affected.

CONCLUSION

Failure to detect a liver lesion (especially in the superior and posterior parts) is a rare but possible pitfall when using only CT-corrected FDG images.

High-Grade Lymphoma of the Bladder Visualized on PET

F-18 FDG PET is used for the staging of many cancers. One of its limits is the analysis of the pelvis and the urinary tract because of physiological radiotracer excretion. We report a rare case of an 82-year-old woman in whom intravenous administration of diuretics (furosemide) allowed the identification of a primary diffuse large B-cell lymphoma of the bladder wall. This pharmaceutical increases urine flow and, therefore, reduces the concentration of radiotracer in the urinary tract, improving the visualization of pelvic or urinary tumors. Furosemide administration is an easy, safe, and noninvasive method, even in case of renal insufficiency. Newer PET cameras with high-performance crystals allow rapid acquisitions and improve the tolerance of an examination with diuretic injection. The 3-dimensional reconstruction of images in new PET cameras reduces the occurrence of hyperactive bladder artifacts. The present case illustrates the advantages of furosemide in a rare pathologic entity.

Computer-aided intrapatient comparison of brain SPECT images: the gray-level normalization issue applied to children with epilepsy

A tool was developed for automated intrapatient comparison of brain SPECT images, with specific emphasis on gray-level normalization.

METHODS

Ictal and interictal (99m)Tc-ethyl cysteinate dimer SPECT images were acquired for 6 children with partial epilepsy (age range, 2-10 y). For each patient, 3-dimensional rigid geometric ictal-to-interictal image registration optimizing different classic criteria (correlation coefficient, ratio uniformity) in a multiscale translation-rotation 6-parameter space was first performed. Gray-level normalization was then performed with different methods, using a 1- or 2-parameter linear model. In the 1-parameter case, the scaling factor was equal to the interictal-to-ictal ratio of the maximum, mean, or median values calculated within different reference volumes (whole brain or cerebellum) or obtained by linear regression between ictal and interictal counts in the brain or by maximizing a robust criterion, the number of deterministic sign changes in the subtraction images. In the 2-parameter case, the scaling factor and additive constant were estimated using these last 2 methods. For each patient, registration validity and normalization plausibility were assessed by considering the correlation scatterplot together with the different normalization lines and by comparing interictal and registered normalized ictal images using a twin display (with isocontours) in the 3 orthogonal planes. Three-dimensional volumes of interest could be selected on coupled interictal-subtraction images for further focused numeric comparison.

RESULTS

After a satisfactory and stable geometric registration with both criteria, the different normalization methods led to similar subtraction images for 5 of 6 patients, except the maxima ratio, which gave noticeably different results in 2 patients. For the remaining patient, with highly dissimilar ictal-interictal images, the maxima ratio normalization was obviously wrong and the other 1-parameter methods probably better depicted the data than did the 2-parameter methods.

CONCLUSION

When comparing intrapatient brain SPECT images, one should be aware of the potential impact of the gray-level normalization method on clinical interpretation. For ictal-interictal images, simple robust scaling should be recommended. In particular, image maximum should generally not be considered a valid reference, and no additive constant is needed in the linear gray-level normalization model.

Automated anatomical labeling of activations in SPM using a macroscopic anatomical parcellation of the MNI MRI single-subject brain

An anatomical parcellation of the spatially normalized single-subject high-resolution T1 volume provided by the Montreal Neurological Institute (MNI) (D. L. Collins et al., 1998, Trans. Med. Imag. 17, 463-468) was performed. The MNI single-subject main sulci were first delineated and further used as landmarks for the 3D definition of 45 anatomical volumes of interest (AVOI) in each hemisphere. This procedure was performed using a dedicated software which allowed a 3D following of the sulci course on the edited brain. Regions of interest were then drawn manually with the same software every 2 mm on the axial slices of the high-resolution MNI single subject. The 90 AVOI were reconstructed and assigned a label. Using this parcellation method, three procedures to perform the automated anatomical labeling of functional studies are proposed: (1) labeling of an extremum defined by a set of coordinates, (2) percentage of voxels belonging to each of the AVOI intersected by a sphere centered by a set of coordinates, and (3) percentage of voxels belonging to each of the AVOI intersected by an activated cluster. An interface with the Statistical Parametric Mapping package (SPM, J. Ashburner and K. J. Friston, 1999, Hum. Brain Mapp. 7, 254-266) is provided as a freeware to researchers of the neuroimaging community. We believe that this tool is an improvement for the macroscopical labeling of activated area compared to labeling assessed using the Talairach atlas brain in which deformations are well known. However, this tool does not alleviate the need for more sophisticated labeling strategies based on anatomical or cytoarchitectonic probabilistic maps.

Amplitude measurements of Faraday waves

A light reflection technique is used to measure quantitatively the surface elevation of Faraday waves. The performed measurements cover a wide parameter range of driving frequencies and sample viscosities. In the capillary wave regime the bifurcation diagrams exhibit a frequency independent scaling proportional to the wavelength. We also provide numerical simulations of the full Navier-Stokes equations, which are in quantitative agreement up to supercritical drive amplitudes of epsilon approximately equal 20%. The validity of an existing perturbation analysis is found to be limited to epsilon<2.5%.

A common language network for comprehension and production: a contribution to the definition of language epicenters with PET

In this paper, we report on a PET activation study designed to assess whether functional neuroimaging would help to uncover essential language areas in normal volunteers and to provide a more accurate definition of their localization. Regional cerebral blood flow was repeatedly monitored in eight right-handed male volunteers, while performing a language comprehension task (listening to factual stories) and a language production task (covert generation of verbs semantically related to heard nouns), using silent resting as a control condition. The conjunction analysis, conducted with SPM, was used to uncover the network of activations common to both task that included three left hemisphere areas, namely (1) the pars opercularis and triangularis of the inferior frontal gyrus, (2) the posterior part of the superior temporal cortex centered around the superior temporal sulcus, extending to the planum temporale posterior part but sparing the supramarginalis and angular gyri, and (3) the most anterior part of the left inferior temporal gyrus at the junction with the anterior fusiform gyrus. The inferior and lateral parts of the right cerebellar cortex were also included in the conjunction network. Each of the three cortical areas, when they are site of lesion or electrical stimulation, elicit impairment in both language comprehension and production and can thus be considered as essential to language. Accordingly, the present results provide conservative anatomofunctional definitions of the Broca, Wernicke, and basal language areas. Interestingly, contralateral homologues of Broca's and Wernicke's areas also lighted up in the conjunction analysis that could be related to the interindividual variability of hemispheric language dominance.

Picture naming without Broca's and Wernicke's area

Lexical and semantic retrieval was investigated in normal volunteers with PET by comparing picture confrontation naming and verb generation related to the same pictures. Conjunction analysis of the naming and verb generation uncovered a common network including the occipito-temporal ventral pathway for object recognition, and the bilateral anterior insula, SMA and precentral gyrus for coordination, planning and overt word production. Naming and verb generation highlighted two different patterns: verb generation showed specific implication of Broca and Wernicke's areas, whereas naming specifically relied on the primary visual areas, the right fusiform and parahippocampal gyri and the left anterior temporal region. These results indicate that speech does not necessarily involve the Wernicke-Broca's language network and testify that naming relies on an early developmental language network.

FMRI and PET of self-paced finger movement: comparison of intersubject stereotaxic averaged data

We compared the intersubject-averaged functional anatomy of self-paced right index finger movement as revealed by (15)O water positron emission tomography (PET) and blood oxygen level-dependent functional magnetic resonance imaging (FMRI) at 1.5 T. Image data sets were acquired with both techniques on a group of eight subjects, spatially normalized in the stereotaxic space and subsequently processed in order to get identical smoothness and degrees of freedom. Intersubject-averaged PET and FMRI activation maps were found congruent in the left primary sensorimotor area (PSM), bilateral supplementary motor area, bilateral supra marginalis gyri, left operculum, left inferior parietal lobule, right middle frontal gyrus, and right cerebellum. In those regions the mean distance between PET and FMRI local maxima was 7.4 mm. FMRI detected additional activations in the right precentral gyrus, right rolandic operculum, right inferior parietal lobule, and bilateral insula, whereas PET demonstrated a higher detection sensitivity at the deep nuclei level. PET and FMRI percentage signal variations were found linearly related by a factor around 10, both within the PSM and across a set of distributed local extrema. However, in most cases, FMRI was more sensitive than PET, as assessed by t values. Finally the pattern of deactivations was markedly dissimilar between the two techniques, possibly due to differences in the "Rest" control task.