Detection of Functional Significance of Coronary Stenoses Using Dynamic 13N-Ammonia Stress-PET/CT with Absolute Values of Myocardial Blood Flow and Coronary Flow Reserve

Objectives. The aim of the study was to compare the values of myocardial blood flow (MBF) at stress, MBF at rest and coronary flow reserve (CFR) obtained by 13Nammonia stress-PET/CT in patients with various degrees of coronary stenosis and in healthy patients. And thus to estimate the possible contribution of the stress-PET/CT quantitative data to the detection of functionally significant coronary stenoses in patients with coronary artery disease (CAD). Materials and methods. 63 patients (mean age 64±9 years) with known CAD underwent dynamic 13N-ammonia stress-PET/CT followed by calculation of MBF both at stress and at rest in absolute units and CFR. We compared quantitative values in two groups of patients with coronary artery stenosis: 1) ≥75% (n = 36) and 2) <75% (n = 27) confirmed by invasive coronary angiography and in group of healthy patients (n = 11). Results. MBF at stress was significantly lower in group with ≥75% diameter stenoses (median 1,44 [1,21; 1,85] mL/min per g) compared with group with <75% diameter stenoses (2,42 [1,75; 2,89] mL/min/g) and the normal group (2,54 [2,31; 2,86] mL/min/g), (p <0,001). There was no reliable difference in MBF at rest between the three groups (p = NS). CFR was significantly lower in the group of patients with severe ≥75% stenoses (1,85 [1,54; 2,31]) in comparison with patients group with stenoses of intermediate <75% severity (2,73 [2,19; 3,21]), and also in comparison with the normal group (3,12 [2,75; 3,23]), (p <0,001). Conclusion. The values of MBF at stress and CFR are significantly lower in patients with severe coronary arteries stenoses comparing with the group of patients with mild and moderate stenoses. The value of MBF at rest used independently has no diagnostic utility for detection of functional significance of coronary artery stenoses. Keywords: myocardial blood flow, coronary flow reserve, PET/CT, 13N-ammonia, coronary stenosis

11C-Choline Pet/Ct in the Detection of Prostate Cancer Relapse in Patients After Radical Treatment With Psa Level < 10 Ng/Ml

Purpose: To evaluate the usefulness of 11C-Choline PET/CT in the detection of recurrent prostate cancer (PCa) in patients with biochemical relapse after radical treatment. Materials and methods: This retrospective study included 217 PCa patients who underwent 11C-Choline PET/CT in the Department of Nuclear Medicine of Bakoulev Scientific Centre. All patients had biochemical relapse 3±2 years after radical treatment for locally advanced PCa (T1–3 N0–1 M0): radical prostatectomy (n = 159) and radiation therapy (n = 58). The mean PSA value in the group was 2.1±2.5 (0.2–9.7) ng/ml, median – 1.9 ng/ml. Imaging was performed on PET/CT scanner (Biograph-64, Siemens) 10 min after injection of 11C-Choline (400–550 Mbq). Results: Overall, according to 11C-Choline PET/CT results PCa relapse was detected in 56% (121/217) of cases: in 50% (80/159) after radical prostatectomy and in 71% (41/58) after radiation therapy. The mean PSA value in PET-positive cases was 3.1±2.2 (0.2–9.7) ng/ml, while in PETnegative cases – 1.8±1.7 (0.2–4.6) ng/ml. The majority – 68% (65/96) patients with PET-negative scan had low PSA levels (&lt; 2 ng/ml). PET/CT results were positive in 43% (50/115) patients with PSA of &lt; 2 ng/ml, in 63% (45/72) with PSA of 2 to 5 ng/ml, and in 87% (26/30) with PSA of &gt; 5 ng/ml. Local relapse was detected in 51% (62/121) patients, distant metastases – in 28% (34/121) of cases, both local and distant metastases – in 21% (25/121) of cases. Lymph node metastases were detected in 38% (86/217) of all patients included in the analysis, of which 28% (24/86) had lesions in lymph node of normal size (median 7 mm). Of all PET-positive patients bone metastases were detected in 33% (40/121), of which 60% (24/40) had isolated skeletal involvement. Importantly, that 27% (11/40) of PETpositive patients with bone metastases had no structural abnormalities on CT images (CT-negative cases), corresponding to isolated involvement of bone marrow. And half of these CT-negative patients (5/11) had single lesions. The mean PSA value in patients with bone metastases was 5.0±3.7 (0.4–9.1) ng/ml, median – 3.8 ng/ml. According to 11C-Choline PET/CT results oligometastatic PCa recurrence was revealed in 38% (82/217) of all patients, of which 62% (51/82) had local relapse only. Distant oligometastatic lesions were detected in 38% (31/82), of which 13% (4/31) were presented by normal-size lymph nodes and 19% (6/31) – by early bone marrow metastases. 48% (58/121) of PET-positive results were confirmed by data of repeated PET/CT examinations. Conclusion: 11C-Choline PET/CT has been shown to be a single noninvasive accurate technique for detection of recurrent PCa in patients with rising PSA after radical treatment, which allows to differentiate patients with local and distant metastases in one study, as well as identify oligometastatic process, and therefore was useful in determining the further personalized therapeutic approach. Keywords: prostate cancer, PET/CT, 11C-Choline, biochemical recurrence, PSA

Analysis of factors affecting the accuracy of 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography in case of suspected prosthetic valve infective endocarditis

Aim. To analyze the factors affecting the accuracy of 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography (PET/CT) in case of suspected prosthetic valve endocarditis (PVE).Material and methods. The results of PET/CT performed in 66 patients after heart valve replacement were analyzed: 55 patients with suspected PVE (≥3 months after surgery) and 11 comparison groups without PVE (2 months after surgery). In the group with suspected PVE (n=55) at the time of the study, 27% (15/55) had a normal body temperature, 85% (47/55) — no leukocytosis. In 16% (9/55), the examination was performed from 3 to 6 months after surgery and in 67% (37/55)  — against the background of long-term antibiotic therapy (ABT). The final diagnosis of PVE was made on the basis of clinical (including 6±3 followup), laboratory, instrumental, and intraoperative (n=40) data: confirmed  — in 37 patients; ruled out — in 29 patients. In order to determine the influence of factors on obtaining false PET/CT results, the odds ratio was calculated.Results. In the group with suspected PVE (n=55), the PET/CT results made it possible to establish and rule out PVE in 92% (34/37) and 67% (12/18) of patients, respectively. In 16% (9/55) of patients, false positive (n=6) and false negative (n=3) results. Thus, the sensitivity, specificity and diagnostic accuracy of PET/CT in the diagnosis of PVE were 92%, 67% and 84%, respectively; positive and negative predictive values — 85% and 80%. The analysis of the odds ratio did not reveal the relationship of low inflammatory activity, the interval between surgery and PET/CT from 3 to 6 months, and long-term ABT before PET/CT with false PET/CT results (p&gt;0,05). In the comparison group without PVE (n=11), 91% (10/11) received false positive PET/CT results, and one patient received a true negative result.Conclusion. The data obtained indicate the high informative value of PET/CT in the diagnosis of PVE. Interval &gt;2 months between surgery and PET/CT significantly reduces the accuracy of PET/CT results. Other factors analyzed in the presented group did not affect the accuracy of PET/CT results