Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

125 Aim: The aim of this study was to evaluate and compare the diagnostic performance of 68Ga-DOTA(0)-Tyr(3)-octreotate (68Ga-DOTATATE) positron emission tomography-computed tomography (PET/CT) to 18F-fluoro-2-deoxy-D-glucose (18F-FDG) PET/CT and magnetic resonance imaging (MRI) of cervical, thoracic, and lumbar spine for the detection of spinal bone metastases in metastatic pheochromocytoma and/or paraganglioma (PPGL). Methods: A total of 47 consecutive metastatic PPGL patients underwent MRI (sagittal T1w, sagittal STIR, axial T1w, and axial T2w) of the cervical, thoracic, and lumbar spine for the evaluation of spinal bone metastases between January 2014 and December 2019. Six patients were excluded (5 patients had incomplete MRI of the spine and 1 patient did not undergo 68Ga-DOTATATE PET/CT). A total of 41 patients (females: males, 19:22; mean age, 43±30 years; 26 patients harboring mutations in genes encoding subunits of succinate dehydrogenase enzyme, 10 patients tested negative for germline mutations in PPGL susceptibility genes, and in 5 patients genetic results are pending) were included in this study who also underwent 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT. The mean (±standard deviation) duration between 68Ga-DOTATATE and 18F-FDG was 21±46 days, between 18F-FDG and MRI 21±46, and between 68Ga-DOTATATE and MRI 27±40 days. Per patient and per lesion detection rates of 68Ga-DOTATATE PET/CT, 18F-FDG PET/CT, and MRI of the spine was calculated. A patient was considered as abnormal or “positive” regardless of the number of positive lesions present; counting of spinal bone metastases was limited to a maximum of one lesion per vertebrae. A composite of all the imaging studies served as an imaging comparator for the calculation of detection rates. A “positive” result on any of the imaging studies was counted as true positive for the presence of the disease. For statistical analysis, the McNemar test was used to compare detection rates between 68Ga-DOTATATE PET/CT and the other imaging modalities. Two-sided p values <0.05 were considered statistically significant. Results: All patients were positive for spinal bone metastases, with 484 lesions on the imaging comparator. 68Ga-DOTATATE PET/CT demonstrated a per lesion detection rate of 401/484 [82.9%, 95% confidence interval (CI): 79.2-86.1%]. 18F-FDG PET/CT and MRI of the spine, showed significantly lower per lesion detection rates of 262/484 (54.1%, 95% CI: 49.6-58.6%; p<0.0001) and 350/484 (72.3%, 95% CI: 68.1-76.3%; p=0.001), respectively. The per patient detection rates of 68Ga-DOTATATE was 41/41 (100%, 95% CI: 91.4-100%), and that of 18F-FDG PET/CT and MRI of the spine was 36/41 (87.8%, 95% CI: 73.8-95.9%) and 39/41 (95.1%, 83.5-99.4%), respectively. Further, 68Ga-DOTATATE PET/CT was found to detect greater (26/41, 63.4%) or equal (12/41, 29.2%) lesions compared to 18F-FDG PET/CT in 38/41 (92.7%) patients whereas 68Ga-DOTATATE PET/CT was found to detect greater (21/41, 51.2%) or equal (9/41, 22.0%) lesions compared to MRI of the spine in 30/41 (73.2%) patients. The detection rates for each of the imaging modalities are summarized in Table 1. Conclusions: 68Ga-DOTATATE PET/CT showed a significantly superior detection rate of spinal bone metastases compared to 18F-FDG PET/CT and MRI of the spine. Besides providing a three-dimensional analysis of the whole body, it maybe the imaging modality of choice to evaluate metastatic spine disease especially in the treatment planning and response assessment of the molecular radionuclide therapy (mRT: 223RaCl2, 177Lu/90Y DOTA-analogs, 131I-metaiodobenzylguanidine) in patients with bone only metastatic PPGL.

long term.However, novel approaches are required to minimize GC related organ damage and to improve asthma and ENT management.

305 Objectives: We have developed a new set of cardiac motion vector field (CMVF) estimation, analysis and display methods from 4D cardiac-gated (CG) myocardial perfusion (MP) PET images. The goal of this work is to evaluate the methods using 4D CG-MP PET images obtained from different reconstruction and analysis methods from patients with normal and known cardiac motion (CM) abnormalities. We acquired list-mode 4D CG-MP PET data from six patients with normal global ejection fractions (EF) and three patients with known CM abnormalities. The datasets were reconstructed using the standard image reconstruction provided by the vendor and with a new, in-house developed 4D image reconstruction method with respiratory motion (RM) and CM compensation. Specifically, the RM estimation and compensation were applied based on an equal count-based, data-driven gating method. The RM compensated data were reconstructed into CG PET images with a given number of equal time intervals, e.g., 8, 16 and 24, over each cardiac cycle. A reference frame PET image at the center of the heart cycle was then generated from the smoothed CG images using the Groupwise registration method, and the reference frame was transformed back to the individual CG images with the corresponding set of CMVF estimates. The final CM-compensated images showed significantly improved image resolution and lower image noise fluctuations as compared to the CG images obtained from the vendor method. The CMVF estimation is based on the traditional optical flow method for motion estimation and was applied to the 4D CG-MP PET images to estimate the CMVF between selected cardiac frames. The entire heart including both the left and right ventricles was used in the CM estimation. The radial, longitudinal and tangential components of the 3D CMVF over the left ventricle was grouped and displayed in a 13-segment and the standard 17-segment polar plots between each adjacent CG frames over the cardiac cycle. The data were further analyzed and the three components of the 3D CMVF in each segment were averaged and plotted as a function of time over the cardiac cycle. In general, the 3D CMVF estimates from the 4D CG-MP PET images with RM & CM motion compensation show more consistent patterns with less variations over time than those from the images without the compensations. The radial and longitudinal components also show more consistent changes between segments than the tangential component. Further, the 13-segment results show a general CM pattern and the 17-segment results show the CM in more detail, without the effect of noise variations. In patients with known CM abnormalities, the 3D CMVF shows asynchronized beating heart motion in certain segments, which is consistent with clinical findings. In typical normal patients, the components of the 3D CMVF demonstrate synchronized beating heart motion among all segments. In one patient with normal global EF, our results indicate a small but noticeable asynchronized motion among segments along the septal wall. A re-examination of the 4D CG-MP PET images confirms the finding. The developed 3D CMVF estimation, may hold promise for accurate characterization of CM and detection of CM abnormalities from 4D CG-MP PET images. The improved image quality obtained with RM and CM compensation provide more accurate estimations than quality obtained without compensation. The additional quantitative ‘cardiomics’ information of the left ventricular motion, in conjunction with perfusion information, from the same 4D CG-MP PET images may add additional important diagnostic information in subclinical and clinical manifest cardiac diseases.

1610 Background: Pulmonary embolism (PE) is a common disease and can be difficult to diagnose, owed to its variety of presenting clinical signs and symptoms. The incidence of PE in the United States is 1 in 1000 persons per year. Despite evaluation for PE, we have not changed morbidity and mortality in the past decade, suggesting limitations in how patients are evaluated or how the results of imaging tests are utilized clinically. We investigated a cohort of patients undergoing ventilation/perfusion (V/Q) scintigraphy for evaluation of acute pulmonary embolism and examined how pre-test probability and PIOPED-defined scan probability results impacted clinical decision-making as to whether patients were anticoagulated. Materials and Methods: We retrospectively reviewed the charts of 122 patients from a single tertiary care hospital (mean age 63.4) over a 1-year period from 2016-2017 who were referred for a V/Q scan to evaluate for acute PE. All patients underwent a V/Q scan, which utilized Xe-133 ventilation followed by intravenous Tc-99m MAA for perfusion imaging. If a documented Well’s score was available in the medical record, this was used to determine pre-test probability. For those patients in whom a Well’s score was unavailable, one was retrospectively assigned from best available clinical information in the char. Patients were scored as low, moderate and high pre-test probability. Result of the V/Q scans were scored in 5 different categories: normal, very low, low, intermediate and high. Anticoagulation management after V/Q scan results were noted. Results: A total of 33/122 (27%) patients were anticoagulated overall. Pre-test probability was low in 85/122 (69.7%) patients, moderate in 28/122 (22.9%) patients, and high in 9/122 (7.4%) patients. The break-down of V/Q scan results was: normal in 2/122 (1.6%) patients, very low in 9/122 (7.4%) patients, low in 76/122 (62.3%) patients, intermediate in 28/122 (22.9%) patients, and high in 7/122 (5.7%) patients. Pretest probability and V/Q scan results were combined to derive the number of patients in each of the following categories (see table) and corresponding clinical management in each. Of note, for patients with moderate pre-test probability and an intermediate probability V/Q scan result, 10/12 (83.3%) were anticoagulated. Conclusions: In this retrospective evaluation, a majority of patients undergoing V/Q scanning for suspicion of PE had low pre-test probability, raising the risk that patients in the study would have potential false positive findings that could lead to unnecessary anticoagulation. Furthermore, patients with moderate or high pre-test probability who were subsequently found to have intermediate probability V/Q scans were almost universally anticoagulated. While this is reasonable among the high pre-test probability population, the high number of patients with moderate pre-test probability and intermediate probability V/Q scan results that were anticoagulated (83.3%) suggests that this V/Q scan interpretive category is not well understood by clinicians. Nuclear medicine physicians should use caution in assigning intermediate probability reads to patients with moderate pre-test probability as this appears to be interpreted as “positive” for PE by treating clinicians in a disproportionate majority of cases.