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BACKGROUND: Positron emission tomography (PET) is now an established diagnostic method for myocardial perfusion imaging (MPI) in coronary artery disease, which is the main cause of death globally. The available tracers show several limitations, therefore, the 18F-labelled tracer is in high demand nowadays. The preclinical studies on normal Wistar rats aimed to characterise two potential, novel radiotracers, [18F]SYN1 and [18F]SYN2, to evaluate which is a better candidate for PET MPI cardiotracer. RESULTS: The dynamic microPET images showed rapid myocardial uptake for both tracers. However, the uptake was higher and also stable for [18F]SYN2, with an average standardized uptake value of 3.8. The biodistribution studies confirmed that [18F]SYN2 uptake in the cardiac muscle was high and stable (3.02%ID/g at 15 min and 2.79%ID/g at 6 h) compared to [18F]SYN1 (1.84%ID/g at 15 min and 0.32%ID/g at 6 h). The critical organs determined in dosimetry studies were the small intestine and the kidneys. The estimated effective dose for humans was 0.00714 mSv/MBq for [18F]SYN1 and 0.0109 mSv/MBq for [18F]SYN2. The tested dose level of 2 mg/kg was considered to be the No Observed Adverse Effect Level (NOAEL) for both candidates. The better results were achieved for [18F]SYN2, therefore, further preclinical studies were conducted only for this tracer. Radioligand binding assays showed significant responses in 3 from 68 assays: muscarinic acetylcholine M1 and M2 receptors and potassium channel hERG. The compound was mostly metabolised via an oxidative N-dealkylation, while the fluor substituent was not separated from the molecule. CONCLUSION: [18F]SYN2 showed a favourable pharmacodynamic and pharmacokinetic profile, which enabled a clear visualization of the heart in microPET. The compound was well-tolerated in studies in normal rats with moderate radiation exposure. The results encourage further exploration of [18F]SYN2 in clinical studies.

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BACKGROUND: We aimed to find the minimum feasible activity of fluorodeoxyglucose ([18F]FDG) in positron emission tomography/computed tomography (PET/CT) of Hodgkin lymphoma patients performed on a camera with bismuth germanate (BGO) crystals. MATERIAL AND METHODS: Ninety-one [18F]FDG PET/CT scans (each in seven Bayesian Penalized Likelihood [BPL] reconstructions with varying acquisition time per bed position - 2 min, 1.5 min, 1 min, 50 s, 40 s, 30 s, and 20 s) were independently assessed by three physicians to evaluate image quality. Mean administered activity was 3.0 ± 0.1 MBq/kg and mean uptake time was 54.0 ± 8.7 min. The series quality was subjectively marked on a 1-10 scale and then ranked 1-7 based on the mean mark. Interobserver rank correlation and intraclass correlation within each series for the three observers were calculated. Phantom studies were also performed to determine if reduced acquisition time can be directly translated into a reduced activity. RESULTS: Time series were marked and ranked unanimously - the longer the time of acquisition the higher the mark and rank. The interobserver agreement in the ranking was excellent (100%) with a kappa coefficient of 1.00 (95% CI [0.83-1.0]). The general intraclass correlation coefficient (agreement between the marks observers gave each time series) was very high (0.945, 95% CI [0.936-0.952]) and was higher the shorter the time per bed. According to all three observers only the series with 2 min and 1.5 min acquisition time were appropriate for assessment (mean mark ≥ 7). In phantom studies there was a linear correlation between time per bed, administered activity, and number of total prompts detected by a scanner. Hence, a reduction of acquisition time of 25% (from 2 min to 1.5 min) could be directly translated into a 25% activity reduction (from 3.0 to 2.25 MBq/kg). CONCLUSIONS: In patients with HL, [18F]FDG activity can be reduced by up to 25% when using a BGO crystal camera, without substantial impact on image quality.

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INTRODUCTION: The aim of the study was to estimate the sensitivity of ¹8F-FCH PET/CT in preoperative localisation of hyperfunctioning parathyroid glands in patients with primary hyperparathyroidism (PHPT). MATERIAL AND METHODS: Sixty-five consecutive patients with PHPT, who underwent neck ultrasound (US) and 99mTc/99mTc-MIBI dual-phase parathyroid scintigraphy, were prospectively enrolled. Twenty-two patients had unsuccessful parathyroid surgery prior to the study. PET/CT scans were performed 65.0 ± 13.3 min after injection of 218.5 ± 31.9 MBq of 18F-fluorocholine (FCH). Three experienced nuclear medicine physicians assessed the detection rate of hyperfunctioning parathyroid tissue. Response to parathyroidectomy and clinical follow-up served as a reference test. Per-patient sensitivity and positive predictive value (PPV) were calculated for patients who underwent surgery. RESULTS: ¹8F-FCH PET/CT was positive in 61 patients, and negative in 4. US and parathyroid scintigraphy showed positive and negative results in 20, 45 and 17, 48, respectively. US showed nodular goitre in 31 patients and chronic thyroiditis in 9 patients. Parathyroid surgery was performed in 43 (66%) patients. ¹8F-FCH PET/CT yielded a sensitivity of 100% (95% CI: 87.99-100) and PPV of 85.7% (95% CI: 70.77-94.06). Similar values were observed in patients with chronic thyroiditis, nodular goitre, and patients after an unsuccessful parathyroid surgery. PET/CT identified hyperparathyroidism complications (kidney stones, osteoporotic bone fractures, and brown tumours) in 11 patients. CONCLUSIONS: ¹8F-FCH PET/CT effectively detected hyperfunctioning parathyroid tissue and its complications. The method showed excellent sensitivity and positive predictive value, including patients with nodular goitre, chronic thyroiditis, and prior unsuccessful parathyroidectomy. PET/CT performance was superior to neck ultrasound and parathyroid scintigraphy.

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BACKGROUND Tuberous sclerosis complex (TSC; Bourneville-Pringle disease) is a multisystem genetic disorder manifesting as benign tumors that can affect any system. Malignant neoplasm may coexist in patients with TSC. In such cases, there are diagnostic difficulties in distinguishing between metastatic lesions and benign changes. We show the usefulness of positron emission tomography (PET) in resolving these difficulties. CASE REPORT The purpose of this article is to present the usefulness of metabolic imaging using 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in distinguishing benign from neoplastic lesions in a patient with TSC. A 17-year-old female patient with TSC was referred for 18F-FDG PET/CT with suspected lung and bone metastases. The patient underwent a bilateral nephrectomy because of multiple cysts and angiomyolipomas. A colonoscopy - performed in preparation for kidney transplantation - revealed sevearal colon polyps, one of which was found to be cancerous upon histopathologic examination. A diagnosis of adenocarcinoma G3 was made and a CT scan of the chest and abdomen performed afterwards showed multiple pulmonary nodules and sclerotic bone lesions suggestive of metastases. Two 18F-FDG PET/CT scans (performed within 6 months) showed multiple nodules of 7-15 mm in diameter and changes typical of multifocal micronodular pneumocyte hyperplasia in both lungs. In the bones, we found multiple sclerotic lesions. All of the above findings showed FDG uptake at the level of the background activity which contradicted the lesions' metastatic origin. CONCLUSIONS Using the example of a 17-year-old patient with TSC, we present the usefulness of metabolic imaging using 18F-FDG PET/CT in distinguishing benign from neoplastic lesions.

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BACKGROUND: The aim of the study was to compare widely used ordered subset expectation maximisation (OSEM) algorithm with a new Bayesian penalised likelihood (BPL) Q.Clear algorithm in 18F-PSMA-1007 PET/CT. METHODS: We retrospectively assessed 25 18F-PSMA-1007 PET/CT scans with both OSEM and Q.Clear reconstructions available. Each scan was independently reported by two physicians both in OSEM and Q.Clear. SUVmax, SUVmean and tumour-to-background ratio (TBR) of each lesion were measured. Reports were also compared for their final conclusions and the number and localisation of lesions. RESULTS: In both reconstructions the same 87 lesions were reported. Mean SUVmax, SUVmean and TBR were higher for Q.Clear than OSEM (7.01 vs 6.53 [p = 0.052], 4.16 vs 3.84 [p = 0.036] and 20.2 vs 16.8 [p < 0.00001], respectively). Small lesions (< 10 mm) had statistically significant higher SUVmax, SUVmean and TBR in Q.Clear than OSEM (5.37 vs 4.79 [p = 0.032], 3.08 vs 2.70 [p = 0.04] and 15.5 vs 12.5 [p = 0.00214], respectively). For lesions ≥ 10 mm, no significant differences were observed. Findings with higher tracer avidity (SUVmax ≥ 5) tended to have higher SUVmax, SUVmean and TBR values in Q.Clear (11.6 vs 10.3 [p = 0.00278], 7.0 vs 6.7 [p = 0.077] and 33.9 vs 26.7 [p < 0.00001, respectively). Mean background uptake did not differ significantly between Q.Clear and OSEM (0.42 vs 0.39, p = 0.07). CONCLUSIONS: In 18F-PSMA-1007 PET/CT, Q.Clear SUVs and TBR tend to be higher (regardless of lesion localisation), especially for small and highly avid lesions. Increase in SUVs is also higher for lesions with high tracer uptake. Still, Q.Clear does not affect 18F-PSMA-1007 PET/CT specificity and sensitivity.

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BACKGROUND: The aim of the study was to prospectively evaluate diagnostic performance of 18F-PSMA-1007 PET/CT in patients with prostate cancer (PCa) after radical treatment and low but rising prostate-specific antigen (PSA) levels. METHODS: We prospectively enrolled 40 consecutive patients after radical treatment (80%-radical prostatectomy, 20%-radiation beam therapy) of PCa and low (0.008 to ≤2.0 ng/ml), rising PSA. Skull to mid-thigh PET/CT imaging was performed 95 (±12) min after injection of 295.5 (±14.1) MBq 18F-PSMA-1007. Detection rate was correlated with PSA levels, Gleason score (GS) and T stage ≥ 3. PET/CT results were verified during 10.3 (±4.7) months follow-up to calculate sensitivity, specificity, negative predictive values (NPV) and positive predictive values (PPV). RESULTS: 18F-PSMA-1007 PET/CT was positive in 24/40 patients, which yielded overall detection rate of 60%. Detection rate was 39%, 55% and 100% for PSA < 0.5, 0.5 to <1.0 and 1.0 to ≤2.0 ng/ml, respectively. PET/CT showed metastases in locoregional lymph nodes in 55% of patients, bones in 36% of patients and local recurrence in 9% of patients. Detection rate was correlated with PSA-a 0.1 ng/ml rise in PSA level increased odds for positive PET/CT by ~30%. PET/CT positivity was independent of GS and T stage. Verification of 40 lesions yielded sensitivity, specificity, PPV and NPV of 100%, 94.4%, 66.7% and 100%, respectively. CONCLUSIONS: 18F-PSMA-1007 PET/CT shows relatively high detection rate in patients with PCa after radical treatment and low, rising PSA levels. Like other PSMA-targeting radiotracers, its detection rate is dependent on PSA levels. 18F-PSMA-1007 also presents excellent sensitivity, specificity and NPV.

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PURPOSE OF THE REPORT: The aim of the study was to prospectively compare performance of F-fluorocholine (FCH) and F-prostate-specific membrane antigen (PSMA)-1007 PET/CT in patients with biochemical relapse (BCR) of prostate cancer and low prostate-specific antigen levels. METHODS: We prospectively enrolled 40 BCR patients after radical treatment and prostate-specific antigen levels 2.0 ng/mL or less. F-FCH and F-PSMA-1007 PET/CT imaging was performed within a mean interval of 54 ± 21 days. Scans were done 87 ± 10 and 95 ± 12 minutes after injecting 248 ± 35 and 295 ± 14 MBq of F-FCH and F-PSMA-1007, respectively. Rates of negative, equivocal, and positive scan results were compared per patient. Per lesion, findings were grouped as equivocal or highly suggestive of malignancy and then compared for their number, localization (local relapse, lymph nodes, bones), and SUVmax values. RESULTS: Positive, equivocal, and negative results were reported in 60%, 27.5%, and 12.5% of F-PSMA-1007 and in 5%, 37.5%, and 57.5% of F-FCH scans, respectively. In 70% of scans, F-PSMA-1007 PET/CT upgraded F-FCH PET/CT results. F-PSMA-1007 scans also showed significantly more lesions (184 vs 63, P = 0.0006). Local relapse, lymph node, and bone lesions accounted, respectively, for 9%, 58%, and 33% of F-PSMA-1007 and 5%, 89%, and 6% F-FCH of PET/CT findings. Highly suspicious lesions accounted for 74% of F-PSMA-1007 and 11% of F-FCH PET/CT findings. In F-PSMA-1007 PET/CT SUVmax values of highly suggestive lesions were significantly higher than in equivocal lesions (median, 3.6 vs 2.5; P < 0.00001). CONCLUSIONS: In early BCR patients F-PSMA-1007 showed a higher detection rate than F-FCH PET/CT. The former also showed more lesions in total, more highly suggestive lesions and less equivocal lesions.

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F-prostate-specific membrane antigen (PSMA) 1007 is one of the most promising radiotracers for PET imaging of relapsing prostate cancer. Minimal urinary clearance seems to be its most valuable and outstanding feature. We present images of biochemically relapsed prostate cancer where F-PSMA-1007 PET/CT (performed to verify an ambiguous finding adjacent to the urinary bladder found in F-FCH PET/CT) proved superior to radiocholine and precisely visualized site of local recurrence.

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BACKGROUND: Myocardial perfusion scintigraphy remains one of the substantial noninvasive diagnostic methods in coronary artery disease. Recent technological advancement allowed to create novel semiconductor, dedicated cardiac gamma camera with better spatial resolution and higher energy resolution, resulting in the reduction of radiation burden and acquisition time. The aim of this study was to evaluate the efficacy and safety of stress-only supine and prone MPS with a cardiac gamma camera in patients with suspected or known coronary artery disease. MATERIAL AND METHODS: A total number of 203 consecutive patients with suspected or known coronary artery disease, who underwent MPS were enrolled in the study. The patients without perfusion abnormalities on stress supine and prone MPS scans had no rest MPS, in the remaining patients two-day stress-rest imaging was performed. The group of 160 patients with one-year follow up was subjected to final analysis. RESULTS: Stress-only protocol of myocardial perfusion imaging was performed in 72 patients, 88 patients underwent two-day stress and rest myocardial perfusion scintigraphy. In 46 out of 72 stress-only group of patients, prone study did not affect further proceedings. However, in over 1/3 of cases (26/72), prone scans resulted in abstaining from rest imaging. One year follow-up revealed no sudden cardiac deaths or myocardial infarctions in both (stress-only and stress-rest) groups. Revascularization was performed most often in the double-positive group - patients with significant ischaemia on myocardial perfusion images and chest pain or electrocardiographic changes or both during the stress test. In this double-positive group, all 11 patients had coronary angiography (two of them prior to myocardial perfusion scintigraphy), nine of them had subsequent revascularization. CONCLUSIONS: In patients with no significant perfusion abnormalities on stress scans omitting rest study is safe with very good one-year risk prognosis of acute cardiac events and allows to limit the radiation exposure and procedure duration. Additional prone acquisitions are valuable supplements in determining the decision of safe early completion of myocardial perfusion imaging.

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INTRODUCTION: Prostate cancer (PCa) is a major health concern worldwide with up to 60% of patients experiencing biochemical relapse after radical treatment. Early diagnosis of PCa recurrence is of high importance for successful salvage therapy. The need for accurate imaging has prompted the introduction of prostate-specific membrane antigen (PSMA)-based radiotracers for positron emission tomography (PET). MATERIAL AND METHODS: In this review we summarized and discussed the results of the studies analyzing the utility of 68Ga-PSMA PET/CT in patients who experienced a biochemical relapse of prostate cancer. RESULTS: PSMA-based PET scans have been proved to provide a superior diagnostic performance over other modalities for localization of the site of early PCa recurrence. 68Ga-PSMA has been also shown to have a higher sensitivity and specificity than other established PET radiotracers such as radiocholines. CONCLUSIONS: The early studies show promising results and support the use of 68Ga-PSMA for PCa restaging. However, the number of studies concerning the utility of 68Ga-PSMA PET in the context of secondary PCa staging is limited and there is still a considerable scope for further research in this field.

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OBJECTIVES: Sentinel lymph node (SLN) mapping is currently a routine technique in breast cancer management and preoperative scintigraphic imaging plays a crucial role in the process of SLN detection. The guidelines recommend performing planar acquisition and optional single-photon emission tomography/computed tomography (SPECT/CT) imaging. The aim of this study was to verify whether routine performing of SPECT/CT in addition to planar imaging increases the sensitivity of SLN detection in patients with early-stage breast cancer. The secondary aims were to compare radionuclide SLN imaging with intraoperative SLN detection and identify clinical and histopathological factors affecting the SLN detection rate. MATERIALS AND METHODS: A total of 153 early-stage breast cancer patients underwent lymph node scintigraphy in the years 2007-2013. Breast cancer patients with staging T1-2N0M0 were included. Planar and SPECT/CT lymphoscintigraphy were performed on the day before the surgery. The data on presence or absence of SLN, their number and localization were recorded for both methods and compared with each other as well as with intraoperative blue dye staining and histopathological findings. RESULTS: SPECT/CT identified SLN in 119/153 and planar scintigraphy in 114/153 patients. Identification rates were 77.7 and 74.5%, respectively. Intraoperative lymph node assessment identified SLN in 76/126 cases with an identification rate of 60.3%. Identification rates for second echelon lymph node were 34.6% for hybrid imaging and 21.2% for planar scintigraphy. Statistical analysis did not yield a significant difference in diagnostic accuracy between these methods; however, the Wilcoxon signed-rank test showed that SPECT/CT significantly increases SLN identification rate compared with planar scintigraphy and intraoperative detection. Histopathological examination of excised SLN showed that 22 nodes were metastatic. SPECT/CT visualized all of these, whereas planar imaging and intraoperative lymph node detection procedure visualized 19 and 18, respectively. No clinical and histopathological factors affecting SLN detection rate were identified. CONCLUSION: Hybrid SPECT/CT lymphatic mapping yields a high SLN detection rate in patients with early-stage breast cancer and provides lymph node localization details. It identifies more SLN than planar imaging and intraoperative SLN detection. However, its limited superiority over the remaining two methods does not support its routine use for SLN localization. We suggest using SPECT/CT for SLN detection in case of equivocal planar imaging results.

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A 29-year-old patient after blunt chest trauma with right lung atelectasis and pulmonary empyema was referred for lung ventilation and perfusion scintigraphy before right-sided pneumonectomy. Radionuclide imaging revealed severely reduced perfusion and lack of ventilation in the collapsed right lung. Additionally, it showed a matching lobar perfusion-ventilation defect in the lower left lobe, which, apart from consolidation area in posterior basal segment, appeared normal in computed tomography. A normal perfusion and ventilation pattern was observed in the upper left lobe. Since it was found to be the only functioning lobe, pneumonectomy was excluded from possible treatment options.

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BACKGROUND: Pulmonary embolism (PE) is diagnosed either by ventilation/perfusion (V/Q) scintigraphy or pulmonary CT angiography. One of the imaging methods used in nuclear medicine is hybrid SPECT/CT scintigraphy. OBJECTIVES: The aim of this study was to evaluate the utility of SPECT/CT(Q) scintigraphy in the diagnosis of PE and to compare SPECT/CT(Q) with planar(Q) and SPECT(Q) methods. METHODS: The study group consisted of 109 consecutive patients suspected of having PE referred for performing lung scintigraphy. The inclusion criteria were: performance of perfusion planar, SPECT and SPECT/CT scans; availability of clinical data covering a 6-month follow-up period, and D-dimer level testing. The number of eligible patients was 84. PE was reported in patients with at least 1 segmental or 2 subsegmental perfusion defects without parenchymal abnormalities on CT scans. PE was excluded when there was a normal perfusion pattern or perfusion defects were caused by lung parenchymal abnormalities or were not arranged in accordance with the pulmonary vasculature. RESULTS: Twenty-six patients (31%) had a final diagnosis of PE. The sensitivity and specificity values of each method were as follows: planar(Q) 73 and 43%, SPECT(Q) 88 and 47% and SPECT/CT(Q) 100 and 83%. SPECT/CT(Q) yielded a significantly higher diagnostic accuracy than planar(Q) (p < 0.001) and SPECT(Q) (p < 0.001) scans. CONCLUSIONS: We conclude that hybrid SPECT/CT(Q) imaging has a high diagnostic efficacy in the diagnosis of PE. Lung perfusion scintigraphy performed with a hybrid SPECT/CT device has a significantly higher sensitivity and specificity than scanning performed with the planar or SPECT technique.

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BACKGROUND: The aim of this study was to assess the prevalence of long bone metastases in renal cancer patients and to evaluate their utility as predictors of survival in this group. MATERIAL AND METHODS: This retrospective study included 20 patients with metastatic renal cancer and bone metastases. The patients were referred for regular bone scintigraphy in order to assess disease spread in the skeleton. The patients were divided into two groups: those with 1) metastases in the skeleton (including long bones) and those with 2) metastases in the axial skeleton only. RESULTS: Bone scintigraphy imaging was performed regularly up to 81 months from the first positive bone scan. During that time 11 deaths (8 among patients with long bone lesions) were recorded. Kaplan-Meyer curves showed that patients with long bone metastases tend to have lower survival probability in comparison to the ones with metastases in other bones. CONCLUSIONS: Bone metastases localization seems to influence survival in patients with renal cancer. Long bone-involving spread of the disease is associated with worse survival probability than the spread to the other bones.

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Brain metastases are a rare complication of prostate cancer. They are usually diagnosed in an end-stage disease when the tumor has already spread to the other organs and tissues. We present a case of a male with castration-resistant prostate cancer with bone metastases visualized in ¹8F-fluorocholine PET/CT scan.

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