Asia Oceania Journal of Nuclear Medicine & Biology
Volume:8 Issue: 1, Spring 2020

99mTc-PSMA SPECT/CT is a cost effective alternative for 68Ga-PSMA PET/CT. The aim of this study was to directly compare these two techniques in patients with prostate cancer. 28 man with prostate cancer were studied using 99mTc-PSMA SPECT/CT and 68Ga-PSMA PET/CT in a short time period (68Ga-PSMA. 99mTc-PSMA kit (PSMA I+S) was used for SPECT/CT and whole body imaging was performed 4 hours after IV injection of 740 MBq of 99mTc-PSMA.  Images were interpreted independently and the results of each imaging were recorded. The mean age of the patients was 64.7±9.6 years old and the mean time difference between two sets of images was 16.6±13.5 days. Abnormal uptake was seen in 25 (89.2%) patients by 68Ga-PSMA PET/CT and 20 (71.4%) patients with 99mTc-PSMA SPECT/CT. No patients with positive 99mTc-PSMA SPECT/CT had negative 68Ga-PSMA PET/CT. The mean number of detected lesions was 26.07±27.5 by 68Ga-PSMA PET/CT and 10.52±10.99 by 99mTc-PSMA SPECT/CT (P<0.001). Detection of lymph nodes and bone metastases were not significantly different between two sets of imaging (P>0.05), however 68Ga-PSMA PET/CT were more successful in detection of prostate bed lesions compared to 99mTc-PSMA scan. Interestingly, no patient with PSA level of >2.1 ng/ml had discordant result between two sets of images. 99mTc-PSMA SPECT/CT is as accurate as  68Ga-PSMA PET/CT in M staging, however 68Ga-PSMA PET/CT detected more lesions compared to 99mTc-PSMA SPECT/CT. Detection rate was not significantly different between two techniques in patients with PSA levels>2.1 ng/ml.

68Ga-DOTATATE positron emission tomography (PET)/computed tomography (CT) has shown promising results in imaging of neural crest tumors (NCT). Herein, we compared the performance of 68Ga-DOTATATE PET/CT and 131I-MIBG single photon emission computed tomography (SPECT)/CT in the initial diagnosis, staging and follow-up of patients with NCTs.

Twenty-five patients (males:females=8:17; age range=2–71 years) with clinically proven or suspicious neuroblastoma, pheochromocytoma (PCC) or paraganglioma (PGL) were enrolled in this prospective study and underwent both 68Ga-DOTATATE PET/CT and 131I-MIBG SPECT/CT. A composite reference standard derived from histopathological information, together with anatomical and functional imaging findings, was used to validate the results. Imaging findings were assessed on a per-patient and on a per-lesion basis. Sensitivity and accuracy were assessed using McNemar’s test.

Referring to radiological imaging and histopathological findings as reference standard, 68Ga-DOTATATE and 131I-MIBG scans showed a sensitivity and accuracy of (100%, 96%) and (86.7%, 88%), respectively, on a per-patient basis. In PCC/PGL patients, on a per-patient basis, the sensitivity of 68Ga-DOTATATE was 100% and that of 131I-MIBG was 77.8%. In neuroblastoma patients, on a per-patient basis, the sensitivities of both 68Ga-DOTATATE and 131I-MIBG were 100%. Overall, in this patient cohort, 68Ga-DOTATATE PET/CT identified 52 lesions and 131I-MIBG SPECT/CT identified only 30 lesions. On a per-lesion analysis, 68Ga-DOTATATE was found to be superior to 131I-MIBG in detecting lesions in all anatomical locations, particularly osseous lesions. According to the McNemar test results, differences were not statistically significant.

This relatively small patient cohort suggests 68Ga-DOTATATE PET/CT be superior to 131I-MIBG SPECT/CT in providing particularly valuable information for both primary staging and follow-up in patients with NCT.

Cardiovascular disease is a leading cause of morbimortality with over half cardiovascular events occurring in the asymptomatic population by traditional risk stratification. This preliminary study aimed to evaluate systemic plaque vulnerability in patients with prior Coronary Artery Disease (CAD) with a single Whole Body [FDG] PET-CT scan in terms of plaque inflammation and calcifications. Twenty-two patients referred for oncological evaluation and with prior history of advanced CAD or age and gender matched controls without cardiovascular disease, underwent a Whole Body PET-CT scan 90 min after injection of 18F-FDG. A total of 975 transaxial PET images were retrospectively analysed to assess plaque inflammation using a standardized method of analysis with averaged Target-to-Background Ratios (TBRs) at different levels, in the thoracic and abdominal aorta, carotids, LAD, common iliac and femoral arteries, and were correlated with calcium scores from the CT images. TBRs from the thoracic aorta were higher in male patients than controls (1.49±0.11, p<0.05) and a gradient was observed (ascending > descending > aortic arch), and were also higher in the carotids in female patients (1.43±0.07) versus controls (p<0.05). A tendency for higher levels of plaque inflammation in the abdominal aorta was noted in all groups, but no significant FDG uptake was found either in the iliac or femoral arteries in any group. Plaque inflammation was also higher in the LAD in males but with large variations. Higher levels of calcifications were noted in the LAD, infra-renal abdominal aorta and common iliac arteries, but without significant correlation with plaque inflammation except sporadic overlapping.  Patients with advanced CAD are at risk for vulnerable inflamed atheromas in other territories such as the thoracic aorta and carotid arteries, underpinning the systemic nature of the atherosclerotic disease. Coexistence with calcifications is rare, suggesting a different functional status of the plaques and different stages of the disease. Evaluation of subclinical systemic plaque vulnerability in CAD with a Whole Body [FDG] PET-CT scan is feasible and a potentially useful biomarker to assess subclinical vascular risk for risk stratification and treatment optimization, but further studies are needed.

Studies have reported that invasive ductal carcinoma (IDC) with coexisting ductal carcinoma in situ (DCIS) show lower metastatic potential and recurrence and better overall survival than pure IDC. In this study, we assessed F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imagesof patients with newly diagnosed IDC to determine if there is any difference in PET findings in IDC-DCIS and pure IDC cases.
FDG PET/CT images of patients with newly diagnosed IDC of the breast who subsequently   underwent breast surgery and had histopathology result in our records were further evaluated. Tumor grade, pathological staging, and presence of DCIS were noted from the histopathology results. Standardized uptake value (SUV) of the primary tumor (SUVmax and SULmax), other hypermetabolic foci in the breast, and   ipsilateral normal breast were measured. Presence of axillary and distant metastases was noted.  
Fifty seven (57) patients with IDC were included. Coexisting DCIS was present in 44 (IDC-DCIS) and not present in 13 (pure IDC) cases.  Per histopathology, the primary tumor was unifocal in 33 IDC-DCIS (75%) and 12 pure IDC (92.3%) cases, and multifocal in 11 IDC-DCIS cases (25%), and 1 pure IDC case (7.7%). FDG uptake was multifocal in 20 IDC-DCIS cases (45.5%) and 1 pure IDC case (7.7%), and unifocal in 24 IDC-DCIS (54.5%), and 12 pure IDC (92.3%) cases. There was no significant difference in patient age, size of the primary tumor, SUVmax and SULmax of the primary tumor and SUVmax of the normal breast in IDC-DCIS and pure IDC cases (p>0.05). Pathology showed axillary metastasis in all 13 pure IDC (100%), and 27 IDC-DCIS (61.4%) cases. PET showed axillary uptake in 25 IDC-DCIS (56.8%), and 8 pure IDC (61.5%) cases, and abnormal/questionable distant uptake in 12 IDC-DCIS cases and 1 pure IDC case.
In our preliminary findings,multifocal breast FDG uptake and multifocal tumor appear to be more common inIDC-DCIS than pure IDC. There is no significant difference in SUV and size of the primary tumor in IDC-DCIS and pure IDC cases. Axillary metastases appear to be more common in pure IDC than IDC-DCIS cases.

We aimed to assess the association between blood pressure and LV myocardial uptake of FDG, hypothesizing that subjects with raised blood pressure would have higher FDG uptake.

We analyzed 86 healthy controls who underwent PET/CT imaging 180 minutes following FDG (4 MBq/Kg) administration. LV myocardial analysis was performed on axial sections using standard operator guided computer software (OsiriX MD). The average LV myocardial SUVmean (MSUVmean) was calculated for each subject. Subjects were assessed according to the 2017 ACC/AHA guidelines for high blood pressure in adults. Mean arterial blood pressure (MABP) was calculated for each patient. Regression models were employed for statistical analysis. 

The association of MSUVmean was more pronounced with DP (r=0.32, p=0.003) than SP (r=0.28, p=0.010); MABP was comparable (r=0.33, p=0.002). Correlations of MSUVmean with categorized BPs were: normal SP (r=0.27, p=0.010), elevated SP (r=0.28, p=0.009), stage 1 SP (r=0.27, p=0.010), stage 2 SP (r=0.28, p=0.008); normal DP (r=0.33, p=0.001), stage 1 DP (r=0.34, p=0.001), stage 2 DP (r=0.35, p=0.001). Multivariate analysis demonstrated DP (p=0.006), MABP (p=0.007), and SP (0.026).

LV myocardial FDG uptake was higher in subjects with elevated blood pressure and correlated positively with SBP and in particular DBP and MABP.

Studies have mainly assessed the effect of hyperglycemia on18F-fluorodeoxyglucose (FDG) uptake in the brain. In this study, we assessed the FDG uptake of the brain not only in normo- and hyperglycemia but also in hypoglycemia to compare the effect of various blood glucose levels on regional FDG uptake in the brain. This retrospective study was conducted on whole-body FDG positron emission tomography/computed tomography (PET/CT) images including the brain. The inclusion criteria included adult patients with no known history of diseases or symptoms affecting the brain, lack of abnormal brain findings on both PET and CT images, no image artifacts, and lack of any factors affecting brain FDG uptake. Maximum standardized uptake values (SUVmax) were measured in the lateral and medial frontal, temporal, parietal, and occipital cortices, lateral cerebellar cortex, posterior cingulate cortex, caudate nucleus, putamen, thalamus, brain stem (BS), and scalp in patients with normal (91-100 mg/dl), low (61-70 mg/dl), and high (171-200 mg/dl) blood glucose (BG) levels. Mean SUVmax of the brain regions for each BG range was calculated and statistically analyzed. In all BG levels, FDG uptake was at the highest level in the lateral frontal cortex and lowest level in the medial temporal cortex (MTC) and BS. The SUVmax in all assessed brain regions was significantly lower in hyperglycemia (P<0.001). However, this value was not significantly different in hypoglycemia (P>0.05) as compared to that in normoglycemia. At the BG range of 171-200 mg/dl, hyperglycemia-induced reduction in regional SUVmax had a range of 55.9-63.7% (60%±2.4%). This reduction was below 60% in the MTC, cerebellum, and BS and above 60% in other regions. Scalp activity was lower in hyperglycemia (P<0.001) and not different in hypoglycemia (P>0.05) as compared to normoglycemia. The FDG uptake appears to be at the highest level in the lateral frontal cortex and the lowest level in the MTC and BS in normo-, hypo-, and hyperglycemia. Hyperglycemia-induced reduction in FDG uptake was approximately the same as that in various regions of the brain. However, the MTC, cerebellum, and BS may be slightly less affected than the other regions. Hypoglycemia does not seem to have a significant effect on FDG uptake in the brain.

The aim of this study was to determine whether technetium (99mTc) uptake is a relevant method for the differential diagnosis of Graves disease and subacute thyroiditis and calculate its cutoff value in case of its relevancy.

A total of 69 patients, who were followed up (>3 months) in our hospital for thyrotoxicosis within 2015-2019 were enrolled in the study. Out of these 69 subjects, 39 patients had been diagnosed with Graves disease, and 30 of them had subacute thyroiditis. Biochemical parameters, thyroid scintigraphy, and 99mTc uptake test results were evaluated.

99mTc uptake was significantly higher in the patients with Graves disease than in the patients with subacute thyroiditis (P<0.001). Based on the ROC analysis the 99mTc uptake cutoff value of 1.55% had an accuracy of 92.9%, with the sensitivity and specificity of 92% and 87%, respectively.

In conclusion, the results of our study suggested that 99mTc uptake test could be used in the differential diagnosis of Graves disease and subacute thyroiditis. The cutoff value of 1.55% for 99mTc uptake test may guide in establishing a differential diagnosis between the two diseases.

Size specific dose estimate (SSDE) is a new parameter that includes patient size factor in its calculation. Recent studies have produced mixed results on the utility of SSDE, especially when automatic exposure control (AEC) was used. The objective of the study was to find out if there is a relationship between patient size and each of the parameters, SSDE and CTDIvol, when AEC is used.
CT data of consecutively selected 111 patients were included for analysis. CTDIvol values of the CT scans were extracted for each patient. Effective diameter of each patient was calculated as geometric mean of anteroposterior and lateral diameters measured on axial CT images. Corresponding conversion factors for effective diameters were obtained from American Association of Physicists in Medicine (AAPM) report 204. SSDE was obtained as the product of CTDIvol and conversion factor values. Linear regression model was used to evaluate the relationship between patient size and the parameters SSDE and CTDIvol.
Mean weight was 62 (11.5) and range was 34 - 103 kg. Median CTDIvol (mGy) on AEC mode was 7.27(IQ range 7.27, 7.65) and mean effective diameter was 26.2 cm (2.4). Mean SSDE (mGy) was 10.6 (0.84). Good positive correlation was obtained between CTDIvol and effective diameter (r=0.536; p<0.0005). Strong inverse correlation was noted between SSDE and effective diameter (r=-0.777; p<0.0005). Linear regression model for establishing relationship between CTDIvol and effective diameter showed slope of 0.314mGy/cm (R=0.561; R2=0.314; P<0.0005) whereas between effective diameter and SSDE slope was -0.23mGy/cm (R=0.676; R2=0.457; P< 0.0005).
The study shows that CTDIvol and SSDE vary but divergently, with patient size. SSDE is a better estimate of patient radiation dose from CT of MPI SPECT/CT than CTDIvol in systems that use automated exposure control.

Functional imaging presents a non-invasive process that may capture the hyper-metabolic nature of red bone marrow in myeloproliferative neoplasms, such as polycythemia vera (PV).

This study analyzed the FDG-PET/CT scans (n=12) of six patients diagnosed with PV and six age-sex matched controls using a quantitative global analysis methodology.

All PV patients had elevated activities in the bone marrow of each skeletal structure as compared to matched controls with respect to mean standardized uptake value (femoral neck p=0.01, lumbar spine p=0.02, pelvis p=0.002, sternum p=0.04). Notable variations in splenic uptake were observed among the treated and untreated PV patients.  

Our study exemplifies the potential utility of PET in reflecting hyperactive bone marrow activity related to PV. Future studies may further substantiate and elaborate on the use of PET-derived metabolic data in PV.

Technetium-99m-pyrophosphate (99mTc-PYP) has been used, in combination with thallium-201, to estimate the site and extent of myocardial infarcts. We report a case of acute myocardial infarction with severe coronary disease in which the distribution of 99mTc-PYP was extensive. A 78-year-old man presented with dyspnea, and a diagnosis of non-ST-segment elevation acute myocardial infarction was made. Emergency coronary angiography revealed total occlusion of the proximal portion of the right coronary artery and left circumflex coronary artery with collateral flow from the left anterior descending coronary artery, which also had severe stenoses. Given his comorbidities and preferences, subsequent angioplasty was waived. Dual myocardial scintigraphic imaging, which was performed four days after admission, demonstrated slightly reduced thallium-201 uptake in the inferior wall and apex, whereas 99mTc-PYP was positive in the entire left ventricular subendocardial region and the free wall of the right ventricle. His clinical course was uneventful with conservative treatment and the patient was discharged 20 days after admission in a stable condition.

Pyrexia of unknown origin (PUO) is a common problem in day-to-day practice. FDG PET CT is an established investigation that aids in identifying the cause of PUO. Due to its high sensitivity PET detects an occult hypermetabolic focus in the body where CT helps in anatomical localization, vascularity, enhancement characteristics of the lesion detected on PET. It helps to differentiate benign versus malignant cause and target biopsy. Tuberculosis, lymphoma, pyelonephritis, thyroiditis appear hypermetabolic on FDG PET CT. Pericardial sarcoidosis is rare and not reported in literature as a cause of PUO. Presented here is a case of PUO secondary to pericardial granulomatosis diagnosed on PET CT. Cardiac MRI also helps in better tissue characterization and associated myocardial involvement of sarcoidosis. Histology confirmed the diagnosis of pericardial sarcoidosis in this case.

Acute pyelonephritis presents with high-grade fever, dysuria, flank pain, leukocytosis, and microscopic hematuria. Urine culture aids in the diagnosis of this infection. It can be complicated or uncomplicated. Complicated pyelonephritis includes uncontrolled diabetes, transplant, pregnancy, acute or chronic renal failure, structural abnormality of the urinary tract, immunocompromised state, and hospital-acquired infections. Gram-negative bacteria commonly involved are Escherichia, Klebsiella, Proteus, and Enterobacter. TheFDG PET/CT helps detect occult causes of fever, such as skeletal tuberculosis, thyroiditis, and lymphoma, when other investigations are inconclusive. We present three cases of pyrexia of unknown origin (PUO) in whom FDG PET/CT helped localize the focus of infection in the kidneys.

The18F-FDG PET/CT was performed on all three cases and images were acquired using the Biograph Horizon PET/CT system.

A cortical-based focus of FDG uptake was localized in the kidneys. The focus of abnormality was persistent following diuretic administration at 1-hour delayed regional image. Two cases had supportive evidence of pyelonephritis on DMSA scan. One case also had frank pus drained after DJ stenting of the affected side. All of them responded to treatment.

Physiologic excretion of FDG in the urinary tract may interfere with the detection of the focus of infection in the kidneys on FDG PET/CT. However, occult infection in the kidneys may be detected with adequate precautions, such as the use of diuretics and delayed imaging, as illustrated in this case report. Routine investigations were noncontributory in all three cases presenting with PUO. However, FDG PET provided a diagnostic clue for pyelonephritis.

Ewing Sarcoma is the second most common type of bone cancer in children. The dominant features of this malignant bone tumor are the tendency for rapid growth and metastasis.  In addition, Ewing sarcoma of the mandible is extremely rare and can be mistaken for odontogenic infection. We report a 14-year-old girl who had had swelling, pain, and hypoesthesia in the left cheek for three weeks.  She was diagnosed with pericoronitis initially, and then referred toour hospital due to worsening symptoms.  CT and MRI revealed an expanding and destructive mass mainly in the left mandible.  18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and fused PET/CT demonstratedincreased uptake in the mandibular lesion.  Whole-body 18F-FDG PET images showed no abnormal activity except for the mandibular lesion.  Histologic examination confirmed Ewing sarcoma.  Although this tumor has an aggressive clinical behavior and rapid growth, early diagnosis can reduce patient’s morbidity, mortality and thus it is important to distinguish it from periodontal inflammation.

In this series a pictorial quiz pertaining to identification of normal anatomical structures and landmarks at a given level on the computed tomography (CT) is presented. An image depicting normal anatomy is followed by a series of images showing different pathologies. Readers are expected to identify and appreciate variation and changes in the normal anatomy in presence of a given pathology. The series is intended to enhance understanding of sectional anatomy thus aiding interpretation of the CT component of the single photon emission computed tomography (SPECT) and positron emission tomography (PET) studies.