Optimization of [18F]-FDOPA Brain PET Acquisition Times for Assessment of Parkinsonism in the Clinical Setting.

BACKGROUND AND PURPOSE: Fluorine 18-fluoro-L-dopa ([18F]-FDOPA) was approved by the FDA in 2019 and reimbursed by the Centers for Medicare & Medicaid Services in 2022 for use with PET to visualize dopaminergic nerve terminals in the striatum for evaluation of parkinsonism. We sought to determine the optimal image acquisition time for [18F]-FDOPA PET by evaluating rater-estimated FDOPA positivity and image quality across 4 time points. MATERIALS AND METHODS: Brain PET/CT was acquired 90 minutes following injection of 185 megabecquerel (5 mCi) of [18F]-FDOPA. PET was acquired in list mode for 20 minutes, and data were replayed to represent 15-, 10-, and 5-minute acquisitions. By means of MIMneuro, PET/MR imaging or PET/CT was independently graded for FDOPA positivity and image quality by 2 readers, blinded to the clinical report and diagnosis. Expert neuroradiologist clinical reads were used as the criterion standard. RESULTS: Twenty patients were included, average age 65.6 years, 55% women. Image-quality ratings decreased with shorter acquisition times for both readers (reader 1, ρ = 0.23, P = .044; reader 2, ρ = 0.24, P = .036), but there was no association between abnormality confidence scores and acquisition time (reader 1, ρ = -0.13, P = .250; reader 2, ρ = -0.19, P = .100). There was a high degree of consistency in intra- and interrater agreement and agreement with the expert reads when using acquisition times of ≥10 minutes (maximal confidence score consistency [ρ = 0.92] and interrater agreement [κ = 0.90] were observed at 15 minutes), while image quality was consistently rated as low and FDOPA positivity ratings were inconsistent when using a 5-minute acquisition time. CONCLUSIONS: Our study suggests that image-quality ratings were stable after 15 minutes and that between-subject abnormality detection rates were highly consistent between the 2 readers when acquired for at least 10 and up to 20 minutes but were inconsistent at 5 minutes. Shorter [18F]-FDOPA PET acquisition times may help maximize patient comfort while increasing throughput in the clinical setting.

Using 68 Ga-DOTATATE PET for Postoperative Radiosurgery and Radiotherapy Planning in Patients With Meningioma: A Case Series.

BACKGROUND: For patients with either an incompletely resected meningioma or recurrence after surgery, stereotactic radiosurgery is frequently used. MRI is typically used for stereotactic radiosurgery targeting, but differentiating tumor growth from postoperative change can be challenging. 68 Ga-DOTATATE, a positron emission tomography (PET) radiotracer targeting the somatostatin receptor type 2, has been shown to be a reliable meningioma biomarker. OBJECTIVE: To evaluate the impact of 68 Ga-DOTATATE on treatment planning in patients who had previously undergone meningioma resection. METHODS: We present a consecutive case series of 12 patients with pathology-proven meningioma who received a 68 Ga-DOTATATE PET between April 2019 and April 2021. Treatment planning was performed first using MRI. DOTATATE-PET images were then used to assess accurate tumor identification. RESULTS: Ten patients had WHO Grade 2 meningioma, and 2 patients had Grade 1 tumor. Eight patients had recurrent meningiomas, and 4 patients had newly diagnosed disease. Overall, 68 Ga-DOTATATE PET scans altered previously formulated treatment plans in 5 of 12 patients. In addition, 9 of 12 patients had disease foci not appreciated on MRI. CONCLUSION: In this series, incorporating 68 Ga-DOTATATE PET imaging had clinical utility for most patients in whom it was used. It proved particularly adept in demonstrating intraosseous meningiomas, differentiating recurrence from postoperative changes, and identifying subcentimeter disease foci. It is an imaging modality that our center will continue to use as a means of improving postoperative treatment plans after the surgical resection of meningiomas.

Myocardial hypoattenuation in cardiac sarcoidosis: CT correlation with CMR, PET and SPECT.

We report a marked abnormality in myocardial attenuation on non-gated contrast-enhanced CT in a patient with multiorgan sarcoidosis and correlate our findings with CMR, PET and SPECT. The noteworthy observation of myocardial hypoattenuation, in correspondence with the multimodality cardiovascular imaging findings, suggests that standard contrast-enhanced CT may provide information regarding tissue characterization. This report also demonstrates the independent clinical utility of CMR and PET in the evaluation and management of cardiac sarcoidosis.

Preoperative parathyroid scintigraphic lesion localization: accuracy of various types of readings.

PURPOSE: To retrospectively compare the accuracy of various parathyroid scintigraphy readings for single-gland disease (SGD) and multigland disease (MGD) in patients with primary hyperparathyroidism, with histologic analysis as the reference standard. MATERIALS AND METHODS: Institutional review board approval was obtained for this HIPAA-compliant study. Records of 462 patients with primary hyperparathyroidism who underwent preoperative imaging with a technetium 99m ((99m)Tc) sestamibi and (99m)TcO4- protocol that consisted of early and late pinhole (99m)Tc sestamibi, pinhole thyroid imaging, image subtraction, and single photon emission computed tomography (SPECT) were retrospectively reviewed. An experienced nuclear medicine physician without knowledge of other test results or of the final diagnoses graded images on a scale from 0 (definitely normal) to 4 (definitely abnormal). Early pinhole (99m)Tc sestamibi images, late pinhole (99m)Tc sestamibi images, subtraction images, SPECT images, early and late pinhole (99m)Tc sestamibi images, all planar images, and all images--including SPECT images--were read in seven sessions. Receiver operating characteristic curves were generated for each session and were used to calculate sensitivity, specificity, and accuracy. RESULTS: A total of 534 parathyroid lesions were excised. Of the 462 patients, 409 had one lesion, whereas 53 had multiple lesions. Reading all images together was more accurate (89%, P = .001) than was reading early (79%), late (85%), subtraction (86%), and SPECT (83%) images separately; however, it was not significantly more accurate than reading planar images (88%) or early and late images together (87%). Reading all images was significantly less sensitive in the detection of lesions with a median weight of 600 mg or less than in the detection of lesions with a median weight of more than 600 mg (86% vs 94%, P = .004). Per-lesion sensitivity for reading all images was significantly higher for SGD than for MGD (90% vs 66%, P < .001). Sensitivity of reading all images together in the identification of patients with MGD was 62%. CONCLUSION: Reviewing early, late, and subtraction pinhole images together with SPECT images maximizes parathyroid lesion detection accuracy. Test sensitivity is adversely affected by decreasing lesion weight and MGD.

Diagnosing prosthetic vascular graft infection with the antigranulocyte antibody 99mTc-fanolesomab.

AIM: The objectives of this retrospective investigation were to determine the accuracy of 99mTc-fanolesomab, an antigranulocyte antibody, for diagnosing prosthetic vascular graft infection, ascertain optimum imaging times for this indication, and assess safety of this agent. METHODS: Eighteen patients with 19 prosthetic vascular grafts were included. Indications for graft placement included peripheral vascular disease (8), haemodialysis (7), and aneurysm (4). Patients were imaged 2-5 h and 18-30 h after injection of 555-740 MBq (75-125 microg) 99mTc-fanolesomab. One experienced nuclear physician reviewed images in three separate sessions, early alone, late alone and early plus late images together. When early and late images were read alone, graft activity more intense than native blood pool activity was classified as positive for infection. When early and late images were interpreted together, graft activity which persisted or which increased in intensity over time was classified as positive for infection. Patient records were reviewed for adverse events up to 30 days after injection. RESULTS: Five (26%) prosthetic grafts were infected. Early, late and early plus late imaging were equally sensitive (1.00). Early images were significantly less specific (0.50), than late and early plus late images (0.93) (P<0.05, analysis of proportions). Accuracy of late imaging and early plus late imaging were the same: 0.93. No patient experienced adverse events following radiopharmaceutical injection. CONCLUSIONS: 99mTc-fanolesomab imaging, performed 18-30 h after injection, diagnosed prosthetic vascular graft infection safely and accurately (95%). (Although safety was not an issue in this investigation, following reports of serious, including two fatal, events after administration, 99mTc-fanolesomab was withdrawn from the United States market).

Phantom experiments to improve parathyroid lesion detection.

This investigation tested the hypothesis that visual analysis of iteratively reconstructed tomograms by ordered subset expectation maximization (OSEM) provides the highest accuracy for localizing parathyroid lesions using 99mTc-sestamibi SPECT data. From an Institutional Review Board approved retrospective review of 531 patients evaluated for parathyroid localization, image characteristics were determined for 85 99mTc-sestamibi SPECT studies originally read as equivocal (EQ). Seventy-two plexiglas phantoms using cylindrical simulated lesions were acquired for a clinically realistic range of counts (mean simulated lesion counts of 75 +/- 50 counts/pixel) and target-to-background (T:B) ratios (range = 2.0 to 8.0) to determine an optimal filter for OSEM. Two experienced nuclear physicians graded simulated lesions, blinded to whether chambers contained radioactivity or plain water, and two observers used the same scale to read all phantom and clinical SPECT studies, blinded to pathology findings and clinical information. For phantom data and all clinical data, T : B analyses were not statistically different for OSEM versus FB, but visual readings were significantly more accurate than T : B (88 +/- 6% versus 68 +/- 6%, p = 0.001) for OSEM processing, and OSEM was significantly more accurate than FB for visual readings (88 +/- 6% versus 58 +/- 6%, p < 0.0001). These data suggest that visual analysis of iteratively reconstructed MIBI tomograms should be incorporated into imaging protocols performed to localize parathyroid lesions.

Combined labeled leukocyte and technetium 99m sulfur colloid bone marrow imaging for diagnosing musculoskeletal infection.

The use of labeled leukocyte (white blood cell [WBC]) studies in the diagnosis of osteomyelitis can be problematic. A combined study consisting of WBC imaging and complementary bone marrow imaging performed with technetium 99m (99mTc) sulfur colloid is approximately 90% accurate and is especially useful for diagnosing osteomyelitis in situations involving altered marrow distribution. There are limitations and pitfalls associated with a combined study. If there is no labeled WBC activity in the region of interest, marrow imaging is not useful. The sulfur colloid image becomes photopenic within about 1 week after the onset of infection, so that the study should be interpreted cautiously in the acute setting. Labeled WBC accumulation in lymph nodes can also confound image interpretation, although nodal activity can usually be recognized because it is typically round, discrete, multifocal, linear in distribution, and often bilateral. Furthermore, 99mTc-sulfur colloid that is improperly prepared or is more than about 2 hours old degrades image quality, potentially causing erroneous conclusions. Nevertheless, WBC-marrow imaging is a very accurate technique for diagnosing osteomyelitis. Knowledge of the criteria for image interpretation and of the aforementioned limitations and pitfalls, combined with careful attention to imaging technique, will maximize the value of this study.

PET with FDG-labeled leukocytes versus scintigraphy with 111In-oxine-labeled leukocytes for detection of infection.

PURPOSE: To compare prospectively the accuracy of positron emission tomography (PET) with leukocytes labeled in vitro with (18)F fluorodeoxyglucose (FDG) versus that of conventional scintigraphy with leukocytes labeled in vitro with (111)In oxine in patients suspected of having infection. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval; informed consent was obtained from all patients. Patients were 25 men and 26 women aged 32-86 years. In vitro labeling of autologous human leukocytes with FDG and (111)In-oxine was performed according to published methods. Labeling efficiencies and cell viability were determined. Imaging was performed 2.5-5.8 hours after injection of 196-315 MBq of FDG-labeled leukocytes and approximately 24 hours after injection of 17-25 MBq of (111)In-oxine-labeled leukocytes. Forty-three (20 men, 23 women; mean age, 59 years; range, 32-86 years) patients could be successfully imaged with both tracers. Six patients were not injected with FDG-labeled leukocytes because of low labeling efficiency (<35%). Two patients were injected with FDG-labeled leukocytes but were not imaged. One reader interpreted all results as positive or negative for infection. Imaging results were compared with final diagnoses. Labeling efficiencies and cell viabilities were compared by using the paired t test. Differences between PET and scintigraphy were determined by using the McNemar test. RESULTS: For the 43 patients who were imaged with both tracers, labeling efficiency of FDG was lower than that of (111)In oxine (72% +/- 8 [standard deviation] vs 90% +/- 5, P < .001). Viability of FDG-labeled leukocytes was not different from that of (111)In-oxine-labeled leukocytes (98% +/- 1 vs 97% +/- 3). There were no differences between FDG PET and (111)In scintigraphy in terms of sensitivity (87% vs 73%), specificity (82% vs 86%), or accuracy (84% vs 81%). CONCLUSION: PET with FDG-labeled leukocytes was comparable to scintigraphy with (111)In-oxine-labeled leukocytes. Further investigation in a larger population with dedicated PET or PET/computed tomography seems warranted.

Coincidence-detection FDG-PET versus gallium in children and young adults with newly diagnosed Hodgkin's disease.

UNLABELLED: Coincidence-detection 18F-FDG-PET (PET) and 67Ga whole-body and SPECT (Ga) were compared in children and young adults with newly diagnosed Hodgkin's disease (HD). MATERIALS AND METHODS: Thirty patients with histologically confirmed HD underwent PET with attenuation correction 1 h after injection of 150-220 MBq 18F-FDG and whole-body and SPECT imaging 72 h after injection of 250-370 MBq 67Ga citrate. Two experienced readers retrospectively reviewed PET and Ga scans, grading 13 anatomic regions from one (normal) to five (abnormal). Numerical stages were assigned based on Ann Arbor classification. Comparison was made with disease sites (established by biopsy or two or more of the following: physical examination, conventional imaging studies, radionuclide studies, and follow-up studies) and clinical stages. Sensitivity, specificity, and accuracy were calculated and significance of differences determined using McNemar's test. RESULTS: PET detected 120/138 (87%) disease sites and Ga 109/138 (79%). PET and Ga were concordant for 103/138 (75%) sites. Accuracies were not significantly different for supradiaphragmatic disease. PET was more accurate than Ga for detecting splenic (0.91 vs 0.61, P = 0.012), infradiaphragmatic (0.89 vs 0.75, P = 0.042), and all disease sites combined (0.95 vs 0.91, P = 0.039). PET stage agreed with clinical stage in 79% of patients and Ga in 71%. CONCLUSION: PET was superior to Ga for evaluating children and young adults with newly diagnosed HD.

18F-FDG PET versus CT for evaluating the spleen during initial staging of lymphoma.

UNLABELLED: The purpose of this study was to compare (18)F-FDG PET to CT for evaluating the spleen during the initial staging of lymphoma. METHODS: Seven patients with newly diagnosed lymphoma underwent (18)F-FDG PET and CT. Splenic uptake of (18)F-FDG, diffuse or focal, greater than hepatic uptake was interpreted as consistent with tumor. CT demonstrating a positive splenic index or focal hypodensities was classified as positive for tumor. PET and CT results were compared with final diagnoses, which were confirmed surgically for 6 patients and at autopsy for 1 patient. RESULTS: Five of 7 patients had lymphomatous involvement of the spleen. (18)F-FDG PET was true-positive for all 5 patients with splenic disease and true-negative for both patients without splenic disease. CT, in contrast, was true-positive for 4 of the 5 patients with splenic disease and false-positive for the 2 patients without splenic disease. The accuracies of (18)F-FDG PET and CT for evaluating the spleen were 100% and 57%, respectively. CONCLUSION: (18)F-FDG PET correctly identified all patients with and without splenic disease and was superior to CT for this purpose.

F-18 FDG versus Ga-67 for detecting splenic involvement in Hodgkin's disease.

PURPOSE: The objectives of this investigation were to characterize splenic uptake patterns of F-18 fluorodeoxyglucose (FDG) and Ga-67 in newly diagnosed Hodgkin's disease, to correlate these uptake patterns with the presence or absence of splenic disease, and to compare the accuracy of these two studies for detecting splenic disease. METHODS: FDG positron emission tomography and Ga-67 whole-body and SPECT imaging were performed in 32 patients with previously untreated Hodgkin's disease. Two readers, blinded to clinical information and final diagnoses, independently reviewed the study results. For both FDG and Ga-67, the intensity of splenic uptake was compared with the intensity of hepatic uptake and graded as follows: 0, less than liver uptake; 1, equal to liver uptake; and 2, greater than liver uptake. Differences in interpretation were resolved by consensus. RESULTS: Twelve (38%) of 32 patients had splenic disease. Using splenic uptake greater than hepatic uptake as the criterion for a positive study, the sensitivity, specificity, and accuracy of FDG were 92%, 100%, and 97%, respectively. Using splenic uptake at least as intense as hepatic uptake as the criterion for a positive study, the sensitivity specificity, and accuracy of Ga-67 were 50%, 95%, and 78%, respectively. The differences in sensitivity and accuracy of FDG and Ga-67 were significant (P = 0.04, and 0.03, respectively). CONCLUSION: In newly diagnosed Hodgkin's disease, FDG accurately diagnoses splenic involvement and is significantly more sensitive and accurate than Ga-67 for this purpose.