Yu Iwabuchi

Diagnostic accuracy of lung subtraction iodine mapping CT for the evaluation of pulmonary perfusion in patients with chronic thromboembolic pulmonary hypertension: Correlation with perfusion SPECT/CT

BACKGROUND For treatment of chronic thromboembolic pulmonary hypertension (CTEPH), the evaluation of segmental pulmonary perfusion is important. There are no previous reports about lung subtraction iodine mapping (LSIM) computed tomography (CT) for evaluation of segmental pulmonary perfusion in patients with CTEPH, using lung perfusion SPECT/CT (LPS) as the reference. METHODS 50 patients (age, 60.7±16.7years) with known or suspected CTEPH were enrolled in this study. Non-contrast chest CT and CT pulmonary angiography (CTPA) were performed on a 320-detector row CT system. Then, based on a non-rigid registration followed by subtraction of non-contrast images from contrast-enhanced images, color-coded LSIM images were generated. LPS was performed using a SPECT/CT system within a period of 2months, and served as the reference standard. LSIM and CTPA images were evaluated in a blinded manner for the detection of pulmonary perfusion defects on a segment-by-segment basis. RESULTS The sensitivity, specificity, accuracy, and positive and negative predictive values of LSIM for the detection of segmental perfusion defects were 95% (734/773), 84% (107/127), 93% (841/900), 97% (734/754) and 73% (107/146), respectively, while the corresponding values for CTPA were 65% (505/773), 61% (78/127), 65% (583/900), 91% (505/554) and 23% (78/346). Generalized estimating equations analyses revealed a significantly better performance of LSIM than that of CTPA regarding the sensitivity, accuracy, and positive and negative predictive values (all P<0.0001). CONCLUSIONS LSIM is a feasible technique for segment-based evaluation of pulmonary perfusion in patients with CTEPH, and it provides a significantly higher diagnostic accuracy compared with CTPA.

Extremely Low Prevalence of Amyloid Positron Emission Tomography Positivity in Parkinson's Disease without Dementia

Background: Most cases of dementia with Lewy bodies (DLB) show Alzheimers disease pathology-like senile plaques and neurofibrillary tangles. Several studies have also revealed a high prevalence of positive amyloid imaging with positron emission tomography (PET) in DLB and moderate prevalence in Parkinsons disease (PD) with dementia. However, it remains unclear in PD without dementia as to when the brain β amyloid (Aβ) burden begins and progresses. Our study aimed to determine the prevalence of Aβ deposition in PD without dementia using amyloid PET. Methods: This was a cross-sectional study on 33 patients with PD without dementia, of whom 21 had normal cognition and 12 met the criteria for PD-mild cognitive impairment. All subjects underwent neuropsychological assessment and [18F] florbetaben (FBB) PET. Results: All subjects had Lewy body-related disorders, displaying a significantly reduced myocardial [123I] metaiodobenzylguanidine uptake. The cortical FBB-binding pattern in all subjects, including APOE e4 carriers, suggested negative Aβ deposition. Conclusion: Patients with PD without dementia exhibit an extremely low prevalence of Aβ positivity compared with those reported in cognitively normal elderly controls. Further longitudinal imaging studies and long-term follow-up are needed; however, our findings provide novel insights for understanding Aβ metabolism in PD.

Preclinical evaluation of heat-denatured [18F]FDG-labeled red blood cells for detecting splenic tissues with PET in rats

INTRODUCTION Heat-denatured 99mTc-labeled red blood cells (RBCs) are used for detecting splenic tissues with scintigraphy. The present study aimed to evaluate the feasibility of using heat-denatured [18F]fluorodeoxyglucose ([18F]FDG)-labeled RBCs in detecting splenic tissues using positron emission tomography (PET) in rats. METHODS RBCs were washed with phosphate buffered saline, labeled with [18F]FDG at 38°C, and heat-denatured at 50°C for 15 min. In vitro stability was assessed by measuring extracellular radioactivity during the 0-180 min incubation at 37°C. Thin layer chromatography (TLC) of the extracellular fluid was performed. The autologous RBCs were intravenously injected in four rats and PET scanning was simultaneously performed for 30 min. Time-activity curves of several organs, including the spleen, were analyzed on the PET images. RESULTS Labeling efficiency was 92%. Low levels of radioactivity were released from the labeled RBCs for 180 min. TLC revealed that 80% of the released radioactivity was due to [18F]FDG-6-phosphate. Whole body images showed strong uptake of heat-denatured [18F]FDG-labeled RBCs in the spleen soon after injection in all four rats. Time-activity curves revealed that the splenic uptake continued to increase for 30 min and the amount of radioactivity in the other organs, except the urinary bladder, decreased after the initial surge. CONCLUSIONS Heat-denatured [18F]FDG-labeled RBCs are suitable spleen-specific agents for PET. This method is clinically relevant as an alternative for heat-denatured 99mTc-labeled RBC scintigraphy.

Bilateral Adrenal Hyperplasia Due to Adrenocorticotropic Hormone-Secreting Esthesioneuroblastoma on FDG PET and 111In-Pentetreotide Scintigraphy

A 53-year-old woman with metastatic esthesioneuroblastoma was referred for FDG PET/CT imaging. FDG PET/CT showed symmetrical uptake in bilaterally enlarged adrenal glands, in addition to abnormal uptake in bone and lymph node metastases. In-pentetreotide scintigraphy was further performed and revealed the lack of adrenal uptake. The patients serum adrenocorticotropic hormone (ACTH) level was extremely high, suggesting that hyperplastic condition in the adrenal glands due to ACTH stimulation from the metastatic esthesioneuroblastoma was responsible for increased FDG uptake. The combination of FDG PET and In-pentetreotide scintigraphy was useful for the pathophysiological evaluation of ACTH-secreting esthesioneuroblastoma.

Quantitative evaluation of the tracer distribution in dopamine transporter SPECT for objective interpretation

PurposeQuantification of the tracer distribution would add objectivity to the visual assessments of dopamine transporter (DAT) single photon emission computed tomography (SPECT) data. Our study aimed to evaluate the diagnostic utility of fractal dimension (FD) as a quantitative indicator of tracer distribution and compared with the conventional quantitative value: specific binding ratio (SBR). We also evaluated the utility of the combined index SBR/FD (SBR divided by FD).Materials and methodsWe conducted both clinical and phantom studies. In the clinical study, 150 patients including 110 patients with Parkinsonian syndrome (PS) and 40 without PS were enrolled. In the phantom study, we used a striatal phantom with the striatum chamber divided into two spaces, representing the caudate nucleus and putamen. The SBR, FD, and SBR/FD were calculated and compared between datasets for evaluating the diagnostic utility. Mann–Whitney test and receiver-operating characteristics (ROC) analysis were used for analysis.ResultsROC analysis revealed that the FD value had high diagnostic performance [the areas under the curve (AUC) = 0.943] and the combined use of SBR and FD (SBR/FD) delivered better results than the SBR alone (AUC, 0.964 vs 0.899; p < 0.001). The sensitivity, specificity, and accuracy, respectively, were 79.1, 85.0, and 80.7% with SBR, 84.5, 97.5, and 88.0% with FD, and 92.7, 87.5, and 91.3% with SBR/FD.ConclusionOur results confirmed that the FD value is a useful diagnostic index, which reflects the tracer distribution in DAT SPECT images. The combined use of SBR and FD was more useful than either used alone.

RADIATION EXPOSURE TO OPERATORS PERFORMING PHARMACOLOGIC STRESS TESTING IN 99mTc MYOCARDIAL PERFUSION IMAGING: A PROSPECTIVE STUDY

This prospective study investigated radiation exposure dose (RED) to main operator (MO) and supervisory operator (SO) performing dypiridamole stress testing in a 1-d rest/stress 99mTc tetrofosmin single-photon emission computed tomography (SPECT) of consecutive 42 patients. MO was instructed to be close to the patients during the entire procedures including the vasodilator and radiotracer injection. SO mainly recorded the data on the procedures apart from the patients. RED, procedure time (PT) and internal radioactivity (IR) of patients were measured before and after a secondary tracer injection for stress SPECT, respectively. RED was significantly greater to MO than to SO (6.2 ± 2.7 vs 2.5 ± 2.1 μSV per stress procedure, p < 0.0001). Multivariate analyses revealed that IR and PT were significantly independent factors to predict RED to both operators. Operators performing pharmacologic stress procedure should be aware that IR and PT are independent factors for RED in 99mTc myocardial perfusion imaging.

Sternal uptake of 99mTc-MAA in thoracic outlet syndrome.

Tc-macroaggregated albumin (MAA) uptake in the vertebrae has been reported in central vein occlusion, although its sternal uptake is rarely seen. We present a case in which Tc-MAA SPECT/CT showed spotty uptake in the sternum. Contrast-enhanced CT revealed marked narrowing of the left subclavian vein at the thoracic outlet with a developed collateral vein running, in the left anterior chest subcutaneous tissue, between the sternum and left axilla. In this case, IV injection of Tc-MAA from the left forearm probably led to bone marrow uptake in the sternum due to retrograde venous flow through the collateral vein.