Do Bone Scans Overstage Disease Compared with PSMA PET at Initial Staging? An International Multicenter Retrospective Study with Masked Independent Readers.

Prostate-specific membrane antigen (PSMA) PET has a higher accuracy than CT and bone scans to stage patients with prostate cancer. We do not understand how to apply clinical trial data based on conventional imaging to patients staged using PSMA PET. Therefore, we aimed to evaluate the ability of bone scans to detect osseous metastases using PSMA PET as a reference standard. Methods: In this multicenter retrospective diagnostic study, 167 patients with prostate cancer, who were imaged with bone scans and PSMA PET performed within 100 d, were included for analysis. Each study was interpreted by 3 masked readers, and the results of the PSMA PET were used as the reference standard. Endpoints were positive predictive value (PPV), negative predictive value (NPV), and specificity for bone scans. Additionally, interreader reproducibility, positivity rate, uptake on PSMA PET, and the number of lesions were evaluated. Results: In total, 167 patients were included, with 77 at initial staging, 60 in the biochemical recurrence and castration-sensitive prostate cancer setting, and 30 in the castration-resistant prostate cancer setting. In all patients, the PPV, NPV, and specificity for bone scans were 0.73 (95% CI, 0.61-0.82), 0.82 (95% CI, 0.74-0.88), and 0.82 (95% CI, 0.74-0.88), respectively. In patients at initial staging, the PPV, NPV, and specificity for bone scans were 0.43 (95% CI, 0.26-0.63), 0.94 (95% CI, 0.85-0.98), and 0.80 (95% CI, 0.68-0.88), respectively. Interreader agreement for bone disease was moderate for bone scans (Fleiss κ, 0.51) and substantial for the PSMA PET reference standard (Fleiss κ, 0.80). Conclusion: In this multicenter retrospective study, the PPV of bone scans was low in patients at initial staging, with 57% of positive bone scans being false positives. This suggests that a large proportion of patients considered low-volume metastatic by the bone scan actually had localized disease, which is critical when applying clinical data from trials such as the STAMPEDE M1 radiation therapy trial to patients being staged with PSMA PET.

Quantitative Assessment of Myocardial Ischemia With Positron Emission Tomography.

Recent advances in positron emission tomography (PET) technology and reconstruction techniques have now made quantitative assessment using cardiac PET readily available in most cardiac PET imaging centers. Multiple PET myocardial perfusion imaging (MPI) radiopharmaceuticals are available for quantitative examination of myocardial ischemia, with each having distinct convenience and accuracy profile. Important properties of these radiopharmaceuticals ( 15 O-water, 13 N-ammonia, 82 Rb, 11 C-acetate, and 18 F-flurpiridaz) including radionuclide half-life, mean positron range in tissue, and the relationship between kinetic parameters and myocardial blood flow (MBF) are presented. Absolute quantification of MBF requires PET MPI to be performed with protocols that allow the generation of dynamic multiframes of reconstructed data. Using a tissue compartment model, the rate constant that governs the rate of PET MPI radiopharmaceutical extraction from the blood plasma to myocardial tissue is calculated. Then, this rate constant ( K1 ) is converted to MBF using an established extraction formula for each radiopharmaceutical. As most of the modern PET scanners acquire the data only in list mode, techniques of processing the list-mode data into dynamic multiframes are also reviewed. Finally, the impact of modern PET technologies such as PET/CT, PET/MR, total-body PET, machine learning/deep learning on comprehensive and quantitative assessment of myocardial ischemia is briefly described in this review.

False positive pharmacologic myocardial perfusion SPECT study in the setting of a left bundle branch block.

We herein report a case of a false positive vasodilatory pharmacologic SPECT stress test in the setting of a left bundle branch block (LBBB). While this is more commonly seen with exercise stress testing, it can also occur with pharmacologic stress testing. In our SPECT exam, we illustrate the commonly mistaken septal/anteroseptal perfusion defects in those patients with a LBBB. PET stress testing may be more reliable for patients with LBBB.

Maximizing the use of batch production of 18F-FDOPA for imaging of brain tumors to increase availability of hybrid PET/MR imaging in clinical setting.

BACKGROUND: Amino acid PET imaging of brain tumors has been shown to play an important role in predicting tumor grade, delineation of tumor margins, and differentiating tumor recurrence from the background of postradiation changes, but is not commonly used in clinical practice because of high cost. We propose that PET/MRI imaging of patients grouped to the day of tracer radiosynthesis will significantly decrease the cost of PET imaging, which will improve patient access to PET. METHODS: Seventeen patients with either primary brain tumors or metastatic brain tumors were recruited for imaging on 3T PET/MRI and were scanned on 4 separate days in groups of 3 to 5 patients. The first group of consecutively imaged patients contained 3 patients, followed by 2 groups of 5 patients, and a last group of 4 patients. RESULTS: For each of the patients, standard of care gadolinium-enhanced MRI and dynamic PET imaging with 18F-FDOPA amino acid tracer was obtained. The total cost savings of scanning 17 patients in batches of 4 as opposed to individual radiosynthesis was 48.5% ($28 321). Semiquantitative analysis of tracer uptake in normal brain were performed with appropriate accumulation and expected subsequent washout. CONCLUSION: Amino acid PET tracers have been shown to play a critical role in the characterization of brain tumors but their adaptation to clinical practice has been limited because of the high cost of PET. Scheduling patient imaging to maximally use the radiosynthesis of imaging tracer significantly reduces the cost of PET and results in increased availability of PET tracer use in neuro-oncology.

124I-MIBG PET/CT to Monitor Metastatic Disease in Children with Relapsed Neuroblastoma.

The metaiodobenzylguanidine (MIBG) scan is one of the most sensitive noninvasive lesion detection modalities for neuroblastoma. Unlike 123I-MIBG, 124I-MIBG allows high-resolution PET. We evaluated 124I-MIBG PET/CT for its diagnostic performance as directly compared with paired 123I-MIBG scans. Methods: Before 131I-MIBG therapy, standard 123I-MIBG imaging (5.2 MBq/kg) was performed on 7 patients, including whole-body (anterior-posterior) planar imaging, focused-field-of-view SPECT/CT, and whole-body 124I-MIBG PET/CT (1.05 MBq/kg). After therapy, 2 of 7 patients also completed 124I-MIBG PET/CT as well as paired 123I-MIBG planar imaging and SPECT/CT. One patient underwent 124I-MIBG PET/CT only after therapy. We evaluated all 8 patients who showed at least 1 123I-MIBG-positive lesion with a total of 10 scans. In 8 pairs, 123I-MIBG and 124I-MIBG were performed within 1 mo of each other. The locations of identified lesions, the number of total lesions, and the curie scores were recorded for the 123I-MIBG and 124I-MIBG scans. Finally, for 5 patients who completed at least 3 PET/CT scans after administration of 124I-MIBG, we estimated the effective dose of 124I-MIBG. Results:123I-MIBG whole-body planar scans, focused-field-of-view SPECT/CT scans, and whole-body 124I-MIBG PET scans found 25, 32, and 87 total lesions, respectively. There was a statistically significant difference in lesion detection for 124I-MIBG PET/CT versus 123I-MIBG planar imaging (P < 0.0001) and 123I-MIBG SPECT/CT (P < 0.0001). The curie scores were also higher for 124I-MIBG PET/CT than for 123I-MIBG planar imaging and SPECT/CT in 6 of 10 patients. 124I-MIBG PET/CT demonstrated better detection of lesions throughout the body, including the chest, spine, head and neck, and extremities. The effective dose estimated for patient-specific 124I-MIBG was approximately 10 times that of 123I-MIBG; however, given that we administered a very low activity of 124I-MIBG (1.05 MBq/kg), the effective dose was only approximately twice that of 123I-MIBG despite the large difference in half-lives (100 vs. 13.2 h). Conclusion: The first-in-humans use of low-dose 124I-MIBG PET for monitoring disease burden demonstrated tumor detection capability superior to that of 123I-MIBG planar imaging and SPECT/CT.

Pediatric Cardiac PET/CT Imaging.

With the routine availability of PET/CT imaging for oncologic purposes, there has been renewed interest in and acceptance of cardiac and neurologic applications of PET/CT. As our understanding of the pathophysiology underlying various pediatric heart diseases has improved, there has been a parallel advance in imaging modalities. Cardiac MR imaging and cardiac PET continue to improve in the pediatric domain. Molecular imaging holds promise to provide a more robust assessment of the cardiac pathophysiology in a 1-stop setting with less radiation exposure to the patient, an important consideration for the pediatric patient population.

A Deep Learning Model to Predict a Diagnosis of Alzheimer Disease by Using 18F-FDG PET of the Brain.

Purpose To develop and validate a deep learning algorithm that predicts the final diagnosis of Alzheimer disease (AD), mild cognitive impairment, or neither at fluorine 18 (18F) fluorodeoxyglucose (FDG) PET of the brain and compare its performance to that of radiologic readers. Materials and Methods Prospective 18F-FDG PET brain images from the Alzheimer's Disease Neuroimaging Initiative (ADNI) (2109 imaging studies from 2005 to 2017, 1002 patients) and retrospective independent test set (40 imaging studies from 2006 to 2016, 40 patients) were collected. Final clinical diagnosis at follow-up was recorded. Convolutional neural network of InceptionV3 architecture was trained on 90% of ADNI data set and tested on the remaining 10%, as well as the independent test set, with performance compared to radiologic readers. Model was analyzed with sensitivity, specificity, receiver operating characteristic (ROC), saliency map, and t-distributed stochastic neighbor embedding. Results The algorithm achieved area under the ROC curve of 0.98 (95% confidence interval: 0.94, 1.00) when evaluated on predicting the final clinical diagnosis of AD in the independent test set (82% specificity at 100% sensitivity), an average of 75.8 months prior to the final diagnosis, which in ROC space outperformed reader performance (57% [four of seven] sensitivity, 91% [30 of 33] specificity; P < .05). Saliency map demonstrated attention to known areas of interest but with focus on the entire brain. Conclusion By using fluorine 18 fluorodeoxyglucose PET of the brain, a deep learning algorithm developed for early prediction of Alzheimer disease achieved 82% specificity at 100% sensitivity, an average of 75.8 months prior to the final diagnosis. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Larvie in this issue.

Detecting Pulmonary Nodules in Lung Cancer Patients Using Whole Body FDG PET/CT, High-resolution Lung Reformat of FDG PET/CT, or Diagnostic Breath Hold Chest CT.

RATIONALE AND OBJECTIVES: Pulmonary nodules can be missed on the non-breath hold computed tomography (CT) portion of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), and for this reason prior studies have advocated for routinely performing dedicated breath hold CT of the chest in addition to PET/CT for routine staging of malignancy. We evaluated the rate of pulmonary nodule detection on standard CT images from whole body PET/CT studies (WB-PET/CT), high-resolution lung reconstruction CT images from PET/CT studies (HR-PET/CT), and diagnostic breath hold chest CT (BH-CT). MATERIALS AND METHODS: A cohort of 25 patients was identified who had a history of lung cancer as well as a PET/CT staging or restaging scan and BH-CT within 30 days of each other. All PET/CTs included a set of CT images using a soft tissue algorithm filter and 3.75- to 5-mm slice thickness, as well as high-resolution reformats with a sharp reconstruction filter and 2-mm slice thickness. The CT images from WB-PET/CT, HR-PET/CT, and BH-CT were reviewed by three radiologists. Significance was analyzed by two-way repeated measures analysis of variance. RESULTS: There were 2.84 nodules found per patient with WB-PET/CT, 3.85 nodules with HR-PET/CT, and 3.91 nodules with BH-CT. When only nodules less than or equal to 8 mm in size were considered, WB-PET/CT also demonstrated significantly fewer nodules (1.98) compared to the HR-PET/CT (2.94) or a BH-CT (2.86) (P < 0.001). No difference in detection rate was noted between the two higher resolution modalities. CONCLUSIONS: More pulmonary nodules are detected on the CT portion of PET/CT studies when high-resolution reformatted images are created and reviewed. The ability to detect nodules with the reformatted images was indistinguishable from dedicated BH-CT. Overall, high-resolution reformats of PET/CT images of the lungs can increase the sensitivity for pulmonary nodule detection, approaching that of dedicated BH-CT. These data suggest that if HR-PET/CT reformats are used, additional dedicated BH-CT is unnecessary for routine staging of lung cancer.

Pitfalls in [¹8F]FDG PET imaging in gynecological malignancies.

Gynecologic malignancies are the leading causes of cancer in women and they represent about 10 to 20% of all solid tumors. During the past few decades, technological advancements in the detection and staging have gained a pivotal role in all oncological processes, including the gynecological ones. Beyond ultrasound, computed tomography (CT) and magnetic resonance (MR) imaging that are conventionally used for anatomical imaging, [18F]FDG imaging and its hybrid further development as PET/CT has become a crucial tool due of its ability to combine functional metabolic and anatomic information, and the ability to image the entire whole body in a single examination. Since the introduction of integrated hybrid PET/CT systems into clinical practice the accurate analysis of the images has detected a number of limitations and pitfalls. The purpose of this review was to describe in detail the different pitfalls related to the use of [18F]FDG PET/CT in the gynecological malignancies, providing imaging examples and discussing possible ways to avoid misinterpretations.

18F-fluorodeoxyglucose positron emission tomography-computed tomography imaging in the management of Merkel cell carcinoma: a single-institution retrospective study.

BACKGROUND: Merkel cell carcinoma (MCC) is among the deadliest of cutaneous malignancies. A lack of consensus evaluation and treatment guidelines has hindered management of this disease. The utility of simultaneous positron emission tomography and computed tomography (PET/CT) has been demonstrated for a variety of tumors yet remains underinvestigated for MCC. OBJECTIVES: To report the value of fluorodeoxyglucose PET/CT imaging in the initial staging and ongoing management of individuals with MCC and to determine whether any patient or tumor characteristics may predict when PET/CT is more likely to have greater influence on medical decision-making. MATERIALS AND METHODS: A single-institution retrospective chart review was conducted of all patients diagnosed with MCC who underwent FDG-PET/CT scanning from 2007 to 2010. The outcome of each of these studies was evaluated as to the influence on patient staging and management. Patient clinical information and information on gross and microscopic tumor characteristics were collected and analyzed. RESULTS: Twenty patients underwent 39 PET/CT scans. Results of PET/CT imaging revealed previously unknown information related to MCC in four (20%) patients, leading to changes in management in three of these four cases. Three previously unknown neoplasms were detected. CONCLUSION: Fluorodeoxyglucose-positron emission tomography and computed tomography is a valuable tool for initial staging and to assess response to therapy of patients diagnosed with MCC. Larger prospective studies would be required to establish the optimal timing for this imaging modality.

Heterogeneous 18F-FDG uptake in recurrent respiratory papillomatosis.

Recurrent respiratory papillomatosis (RRP) describes an infection of the upper aerodigestive tract by the human papilloma virus most commonly affecting the larynx with rare lung involvement in 1%-2% of affected patients. We describe an unusual case of a 28-year-old male patient with a longstanding history of RRP where a whole-body PET/CT obtained for disease staging revealed multiple cavitary pulmonary nodules in addition to the more typical tracheobronchial papillomas. In the case described herein, we report heterogeneous uptake of 18F-FDG among these RRP lesions, suggesting significant unexpected variability in the underlying metabolic behavior of these lesions.

Value of true whole-body FDG-PET/CT scanning protocol in oncology: optimization of its use based on primary diagnosis.

BACKGROUND: No standardized field of view (FOV) currently exists for whole-body (WB) positron emission tomography/computed tomography (PET/CT). Limited WB PET/CT FOV can exclude portions of the head, upper, and lower extremities, because there is little perceived clinical benefit to be gained from imaging these areas. PURPOSE: To determine how often utilizing WB PET/CT changes the clinical stage and management compared to each of the limited WB FOVs used for PET/CT. MATERIAL AND METHODS: We retrospectively identified 556 oncologic patients (804 PET/CT studies) who underwent staging or restaging PET/CT between November 2010 and November 2011. Abnormal hypermetabolic areas that were suspicious for malignancy in areas that are outside of some of the limited fields of view including in the brain, scalp, and calvarium (above the orbital ridge), in the proximal upper extremity (distal to the humeral neck), distal upper extremity (beyond the elbow), proximal lower extremity (distal to the lesser trochanter), and distal lower extremity (beyond the knees) were recorded. RESULTS: A total of 8.5% (47/556) of patients had abnormal findings outside the most limited FOV (skull base to upper thighs) used in PET/CT. More patients had abnormal hypermetabolic lesions in the lower extremity (5.9%) than in the upper extremity (2.3%). Similarly, more patients had abnormal lesions in the proximal (6.5%) compared to the distal (1.4%) upper and lower extremities. The stage was only changed in one patient (0.2%), however new lesions noted in the brain changed management in six patients (1.1%). Melanoma, lymphoma, multiple myeloma, sarcomas and stage IV lung, breast, prostate, bladder, testicular, and renal cancer were more likely to have findings outside the most limited FOV (skull base to upper thighs). CONCLUSION: WB FOV detects additional sites of disease compared to the limited WB FOV, and although these lesions rarely change stage, some of these lesions may change clinical management.

FDG PET/CT evaluation of pathologically proven pulmonary lesions in an area of high endemic granulomatous disease.

PURPOSE: The goal of this study is to assess how reliable the threshold maximum standardized uptake value (maxSUV) of 2.5 on positron emission tomography-computed tomography (PET/CT) is for evaluation of solitary pulmonary lesions in an area of endemic granulomatous disease and to consider other imaging findings that may increase the accuracy of PET/CT. MATERIALS AND METHODS: The staging PET/CT of 72 subjects with solitary pulmonary lesions (nodules (less than 3 cm) or masses (greater than 3 cm)) were retrospectively reviewed. Pathology proven diagnosis from tissue samples was used as the gold standard. Logistic regression was used to assess whether the subject's age, maxSUV, size of lesion, presence of emphysema, or evidence of granulomatous disease was predictive of malignancy. RESULTS: Malignant lesions were identified in 84.7 % (61/72) of the 72 subjects. A threshold maxSUV of 2.5 had a sensitivity of 95.1 % (58/61), specificity of 45.5 % (5/11), positive predictive value of 90.6 % (58/64), negative predictive value of 62.5 % (5/8) and an accuracy of 87.5 % (63/72). The false negative rate was 4.9 %, and the false positive rate was 54.5 %. All 3 false negatives were less than or equal to 1.0 cm; however, false positives ranged from 1.1 to 5.6 cm. The false negatives had a mean (SD) maxSUV of 2.0 (0.4), whereas the false positives had a mean (SD) maxSUV of 5.6 (3.0). Emphysema was associated with 1.1 higher odds of malignancy, and evidence of granulomatous disease was associated with 0.34 lower odds of benign disease, however, neither was statistically significant (p = 0.92 and p = 0.31, respectively). Higher maxSUV was significantly associated with increased risk of malignancy (p = 8.3 × 10(-3)). Older age and larger size of lesion were borderline associated with increased risk of malignancy (p = 0.05 and p = 0.07, respectively). CONCLUSION: In an area of high endemic granulomatous disease, the PET/CT threshold maxSUV of 2.5 retains a high sensitivity (95.1 %) and positive predictive value (90.6 %) for differentiating benign from malignant pulmonary lesions; however, the specificity (45.5) and negative predictive value (62.5) decrease due to increased false positives. The presence of emphysema and absence of evidence of granulomatous disease increases the probability that a pulmonary lesion is malignant; however, these were not statistically significant.

Tumor dosimetry using [124I]m-iodobenzylguanidine microPET/CT for [131I]m-iodobenzylguanidine treatment of neuroblastoma in a murine xenograft model.

PURPOSE: [(124)I]m-iodobenzylguanidine ((124)I-mIBG) provides a quantitative tool for pretherapy tumor imaging and dosimetry when performed before [(131)I]m-iodobenzylguanidine ((131)I-mIBG) targeted radionuclide therapy of neuroblastoma. (124)I (T (1/2) = 4.2 days) has a comparable half-life to that of (131)I (T (1/2) = 8.02 days) and can be imaged by positron emission tomography (PET) for accurate quantification of the radiotracer distribution. We estimated expected radiation dose in tumors from (131)I-mIBG therapy using (124)I-mIBG microPET/CT imaging data in a murine xenograft model of neuroblastoma transduced to express high levels of the human norepinephrine transporter (hNET). PROCEDURES: In order to enhance mIBG uptake for in vivo imaging and therapy, NB 1691-luciferase (NB1691) human neuroblastoma cells were engineered to express high levels of hNET protein by lentiviral transduction (NB1691-hNET). Both NB1691 and NB1691-hNET cells were implanted subcutaneously and into renal capsules in athymic mice. (124)I-mIBG (4.2-6.5 MBq) was administered intravenously for microPET/CT imaging at 5 time points over 95 h (0.5, 3-5, 24, 48, and 93-95 h median time points). In vivo biodistribution data in normal organs, tumors, and whole-body were collected from reconstructed PET images corrected for photon attenuation using the CT-based attenuation map. Organ and tumor dosimetry were determined for (124)I-mIBG. Dose estimates for (131)I-mIBG were made, assuming the same in vivo biodistribution as (124)I-mIBG. RESULTS: All NB1691-hNET tumors had significant uptake and retention of (124)I-mIBG, whereas unmodified NB1691 tumors did not demonstrate quantifiable mIBG uptake in vivo, despite in vitro uptake. (124)I-mIBG with microPET/CT provided an accurate three-dimensional tool for estimating the radiation dose that would be delivered with (131)I-mIBG therapy. For example, in our model system, we estimated that the administration of (131)I-mIBG in the range of 52.8-206 MBq would deliver 20 Gy to tumors. CONCLUSIONS: The overexpression of hNET was found to be critical for (124)I-mIBG uptake and retention in vivo. The quantitative (124)I-mIBG PET/CT is a promising new tool to predict tumor radiation doses with (131)I-mIBG therapy of neuroblastoma. This methodology may be applied to tumor dosimetry of (131)I-mIBG therapy in human subjects using (124)I-mIBG pretherapy PET/CT data.

Radiation dose estimation using preclinical imaging with 124I-metaiodobenzylguanidine (MIBG) PET.

PURPOSE: A pretherapy 124I-metaiodobenzylguanidine (MIBG) positron emission tomography (PET)/computed tomography (CT) provides a potential method to estimate radiation dose to normal organs, as well as tumors prior to 131I-MIBG treatment of neuroblastoma or pheochromocytoma. The aim of this work was to estimate human-equivalent internal radiation dose of 124I-MIBG using PET/CT data in a murine xenograft model. METHODS: Athymic mice subcutaneously implanted with NB1691 cells that express high levels of human norepinephrine transporter (n = 4) were imaged using small animal microPET/CT over 96 h (approximate imaging time points: 0.5, 2, 24, 52, and 96 h) after intravenous administration of 3.07-4.84 MBq of 124I-MIBG via tail vein. The tumors did not accumulate 124I-MIBG to a detectable level. All four animals were considered as control and organ radiation dosimetry was performed. Volumes of interest were drawn on the coregistered CT images for thyroid, heart, lung, liver, kidney, and bladder, and transferred to PET images to obtain pharmacokinetic data. Based on tabulated organ mass distributions for both mice and adult male human, preclinical pharmacokinetic data were extrapolated to their human-equivalent values. Radiation dose estimations for different age groups were performed using the OLINDA/EXM software with modified tissue weighting factors in the recent International Commission on Radiological Protection (ICRP) Publication 103. RESULTS: The mean effective dose from 124I-MIBG using weighting factors from ICRP 103 to the adult male was estimated at 0.25 mSv/MBq. In different age groups, effective doses using values from ICRP 103 were estimated as follows: Adult female: 0.34, 15-yr-old: 0.39 mSv/MBq, 10-yr-old: 0.58 mSv/MBq, 5-yr-old: 1.03 mSv/MBq, 1-yr-old: 1.92 mSv/MBq, and newborn: 3.75 mSv/ MBq. For comparison, the reported effective dose equivalent of 124I-NaI for adult male (25% thyroid uptake, MIRD Dose Estimate Report No. 5) was 6.5 mSv/MBq. CONCLUSIONS: The authors estimated human-equivalent internal radiation dose of 124I-MIBG using preclinical imaging data. As a reference, the effective dose estimation showed that 124I-MIBG would deliver less radiation dose than 124I-NaI, a radiotracer already being used in patients with thyroid cancer.

Pediatric Cardiac PET Imaging.

Cardiac PET imaging can play a significant role in assessing and managing children with congenital and acquired heart disorders but remains largely underused for multiple reasons, not related to the accuracy or usefulness of the modality. Current work focusing on evaluation of cardiac innervation, cardiac receptor function and noninvasive cardiac gene therapy assessment with PET imaging has tremendous potential to revolutionize cardiac evaluation. Awareness and widespread availability of PET systems is expected to increase use of cardiac PET applications in the pediatric population. The advent of integrated PET/CT systems with advanced CT technology and the possible integrated PET/MR imaging systems opens even more promising future possibilities for cardiac evaluation in a one-stop approach.

Accuracy of [18F]fluorodopa positron emission tomography for diagnosing and localizing focal congenital hyperinsulinism.

OBJECTIVES: Focal lesions in infants with congenital hyperinsulinism (HI) represent areas of adenomatosis that express a paternally derived ATP-sensitive potassium channel mutation due to embryonic loss of heterozygosity for the maternal 11p region. This study evaluated the accuracy of 18F-fluoro-l-dihydroxyphenylalanine ([18F]DOPA) positron emission tomography (PET) scans in diagnosing focal vs. diffuse disease and identifying the location of focal lesions. DESIGN: A total of 50 infants with HI unresponsive to medical therapy were studied. Patients were injected iv with [18F]DOPA, and PET scans were obtained for 50-60 min. Images were coregistered with abdominal computed tomography scans. PET scan interpretations were compared with histological diagnoses. RESULTS: The diagnosis of focal or diffuse HI was correct in 44 of the 50 cases (88%). [18F]DOPA PET identified focal areas of high uptake of radiopharmaceutical in 18 of 24 patients with focal disease. The locations of these lesions matched the areas of increased [18F]DOPA uptake on the PET scans in all of the cases. PET scan correctly located five lesions that could not be visualized at surgery. The positive predictive value of [18F]DOPA in diagnosing focal adenomatosis was 100%, and the negative predictive value was 81%. CONCLUSIONS: [18F]DOPA PET scans correctly diagnosed 75% of focal cases and were 100% accurate in identifying the location of the lesion. These results suggest that [18F]DOPA PET imaging provides a useful guide to surgical resection of focal adenomatosis and should be considered as a guide to surgery in all infants with congenital HI who have medically uncontrollable disease.

Age-related changes in the metabolic activity and distribution of the red marrow as demonstrated by 2-deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography.

OBJECTIVES: The objective of the study was to determine age-related changes occurring in red marrow with regard to its distribution and the degree of its metabolic activity by whole-body 2-deoxy-2-[F-18]fluoro-D-glucose (FDG)-positron emission tomography (PET). METHODS: This retrospective study included 112 patients (56 male, 56 female, mean age 40 years, range 2-85) who underwent whole-body FDG-PET scans for assessment of disorders that were determined not to affect red marrow activity. These patients were categorized into the following groups with equal gender distribution: 0-15 years (12 individuals), 16-25 years (20), 26-35 years (10), 36-45 years (20), 46-55 years (14), 56-65 years (16), 66-75 years (14), and 76-85 years (6). Whole-body FDG-PET images were performed at 60 min after the intravenous administration of 0.14 mCi/kg of FDG. By employing a dedicated whole-body PET scanner. Maximal standardized uptake value (SUV(max)) was calculated from three consecutive transverse sections of the upper thirds of the humeri and femora, manubrium of the sternum, 12th thoracic and 5th lumbar vertebra and anterior superior iliac crests of the pelvis. All available results from other imaging examinations [magnetic resonance imaging (MRI), computed tomography (CT), and conventional radiolography], laboratory data, biopsies, and the clinical course of these subjects were reviewed to make certain that the bone marrow sites examined were free of any known pathologies. RESULTS: SUV(max) in the extremities showed significant decline with aging (correlation coefficient of -0.60 to -0.67, p < 0.01). In contrast, a weak correlation was noted in the axial skeletal activity with advancing age (correlation coefficient of -0.28 to -0.48, p < 0.05). CONCLUSIONS: These data suggest that FDG metabolic activity of the red marrow in the extremities decline significantly with normal aging, while that of the axial skeleton show minimal decrease related to this biologic phenomenon. These findings are of value in assessing the effects of hematological and other disorders in the distribution and the metabolic activity of this important tissue and testing therapeutic interventions that are employed for treating such maladies.