Iranian Journal of Nuclear Medicine
Volume:28 Issue: 2, Summer-Autumn 2020

Quantitative evaluation is recommended to improve diagnostic ability and serial assessment of dopamine transporter (DAT) density scans. We decided to compare the ordered subsets expectation-maximization (OSEM) with filtered back-projection (FBP), and to investigate the impact of different iteration and cut-off frequencies on SBR values.

We retrospectively examined 27 consecutive patients. SPECT reconstruction was performed using OSEM and FBP with Chang’s attenuation correction (AC). Iterative reconstruction parameters were used with different iterations ranging from 2, 4, 6, 8, and 10 with fixed 10 subsets and different subsets including 5, 10 and 15 with fixed 6 iterations. Reconstruction with FBP were performed with different critical cut-off frequencies of 0.3, 0.4 and 0.5.

Comparing SBR derived by OSEM reconstruction with 10 subsets but different iterations revealed statistically significant intraclass correlation (ICC) in both right and left side. There is also no significant difference between different OSEM reconstruction with different subsets and ICC was excellent in all patients. ICC for FBP reconstruction with different cut-off frequency revealed good ICC in all patients. However, lower degree of SBR showed higher decrease in ICC with insignificant and poor correlation in patients with SBR

Our study showed that change in FBP reconstruction parameters can greatly impact the SBR value of 99mTc-TRODAT-1, especially in patients with more severe disease. However, OSEM reconstruction revealed better reproducibility for SBR using different iterations.

18F-FDG PET/CT provides very effective results in detecting metastases of breast cancer. In our study, we investigated the relationship between maximum standard uptake value (SUVmax) and prognostic pathologic factors in breast cancer cases with isolated bone metastasis and whether there was any difference in terms of prognostic pathologic factors between the group with and without bone metastasis. Between 2013 and 2016, isolated bone metastases (55 female; 56±12 years; 32-87), and non-metastatic (46 female; 55±13 years; 30-81) patients who were referred to department of nuclear medicine and underwent 18F-FDG PET/CT for staging were included in the study. PET/CT images of patients and pathologic prognostic factors were evaluated retrospectively. SUVmax value of the most intense activity from metastatic bone lesions was calculated. In the metastatic group, there was no statistically significant relationship between measured SUVmax value of bone metastasis and pathologic prognostic factors. A statistically significant difference was found between the metastatic group and the non-metastatic group in terms of lymph node stage, lymphovascular/perineural invasion. The lymph node stage in the metastatic group was higher than the non-metastatic group. The presence of lymphovascular/perineural invasion in bone metastasis cases was more than in the non-metastatic group. In our study, it was determined that there was a relationship between the lymph node stage, lymphovascular/ perineural invasion and formation of bone metastasis in breast cancer. Between SUVmax values and other factors in the metastatic group, no significant relationship was detected.

Prostate-specific membrane antigen (PSMA) has been demonstrated as a promising tool for specific imaging of prostate cancer (PCa) via positron emission tomography-computed tomography (PET/CT) scanning. Radiation treatment planning (RTP) based on 68Ga-PSMA PET/CT scanning can also lead to some decision modifications.  The specific goal of this comparative study is to show how 68Ga-PSMA PET/CT images can influence the target volume delineation (TVD) and normal tissue radiation dose for PCa RTP, and to compare gross tumor volumes (GTVs) delineated using various strategies for 68Ga-PSMA PET-based image segmentation techniques. This study consisted of eleven 68Ga-PSMA PET/CT images related to patients affected with locally advanced PCa. Four strategies also included manual segmentation techniques, a 2.5 standardized uptake value (SUV) cutoff (SUV=2.5), as well as a fixed threshold of 40% and 50% of the maximum signal intensity (SUV=%40 SUVmax and SUV=%50 SUVmax) for 68Ga-PSMA PET-based segmentation techniques to delineate GTVPET. Two treatment planning were accordingly generated for each patient based on manual GTVPET and CT-only. The GTV was statistically and significantly smaller for PET/CT-derived volumes (9.39 vs. 77.98 cm3 for CT alone) (p<0.002). There was no significant difference in volumes of GTV2.5 and GTV40% with GTVman (p=0.11) although we observed a significant difference in volumes of GTV50% with GTVman (p=0.02). Mean bladder dose (MBD), V50 of rectum, and mean femoral dose (MFD) for PET/CT plans were significantly lower than CT-only (22.36 vs. 46.55 Gy; p=0.004), (33% vs. 67.82%; p=0.000), and (28.01 vs. 37.12Gy; p=0.013); respectively. The contribution of hybrid modalities of PSMA-PET/CT can be useful for detailed target volume planning and reduce radiation exposure to organs at risk. Using molecular images in RTP also demonstrates the biological volume of GTV so that it will not be left out of the field to cause recurrent tumor.

Pulmonary embolism (PE) is a preventable cause of morbidity and mortality which needs prompt recognition. Ventilation-perfusion (V/Q) scan is a well-established diagnostic test for evaluation of suspected PE. We report a 32-year-old woman with history of rheumatologic disease and acute dyspnea, who was referred for V/Q scintigraphy. The planar images revealed multiple mismatched defects throughout both lungs. SPECT images showed that only one of the defects was real, the others were caused by patient’s elevated right arm. Our case showed a V/Q pitfall with emphasis on importance of SPECT imaging in V/Q scintigraphy.

A 50-year-old man with postprandial abdominal pain, weight loss, and generalized body ache was referred to Nuclear medicine department for a whole body bone scan to look for any malignancy. Clinical examination did not reveal any specific positive findings. He underwent aTechnetium-99m Methylene Diphosphonate (99mTc-MDP) bone scan which showed no obvious bone pathology. But there was abnormal increased MDP uptake in the entire transverse colon, splenic flexure, and sigmoid colon prompting further evaluation. Contrast-enhanced computed tomography (CECT) was performed and it suggested superior mesenteric vein thrombosis. Thus MDP uptake in bowel loops reflects the extra osseous tracer uptake at the cellular and tissue level due to chronic inflammation and plasma protein binding due to edema. Colonoscopy and segmental biopsy were non-contributory.

A 68-year-old male, known case of abdominal aortic dissection and recent aortic stent insertion, presented with gross hematuria. The urologists suspected aoro-ureteric fistula and performed open surgery (ureterolysis). Tc-99m labeled red blood cell (99mTc-RBC) scintigraphy was ordered to confirm the diagnosis and localize the possible aorto-ureteric fisula, Considering sustained gross hematuria and ongoing anemia, and the fact that the patient had some degrees of renal insufficiency consequently not a candidate for contrast Computed Tomography (CT) angiography, a 99mTc-RBC blood pool study was requested instead. The dynamic planar images showed a zone of abnormal radiotracer accumulation in the left side of the aorta, which remained till the end of study. SPECT images revealed a left aorto-ureteric fistula approximately 8cm above the aortic bifurcation.

Parotid metastasis originated from papillary thyroid carcinoma is extremely rare, especially as the first presentation of the disease. We present a 70-year-old man with a history of painless swelling in the right side of the neck. He was evaluated for parotid tumor and histopathologic examination revealed a poorly differentiated carcinoma in the parotid gland with suspicion of thyroid origin. The thyroid was examined and a small nodule was palpable in the right lobe of the thyroid that was found to be dedifferentiated papillary thyroid carcinoma upon total thyroidectomy. He received 5.5GBq of 131I and post-ablation whole body iodine scan showed thyroid remnant, cervical lymph node metastasis, lung and pericardial metastases and pleural effusion. He succumbed to his disease 8 months after diagnosis despite further treatments efforts including chemoradiation.