Purpose of the Study: Our study purpose was to compare the epicardial fat volume (EFV) in myocardial perfusion imaging single photon emission computed tomography/computed tomography (MPI SPECT/CT) with normal and abnormal perfusion in patients with known or suspected coronary artery disease (CAD). Materials and Methods: one hundred and seventy-six patients (88 records with normal and 88 with reversible perfusion defects) underwent physical or adenosine stress with Tc-99m MIBI followed by SPECT and low-dose CT for attenuation correction. Rest MPI was done in patients showing perfusion defects on stress imaging. Software-based quantification of EFV was done by manually delineating pericardial contours with epicardial fat threshold set between −30 HU and −190 HU. Results: Median EFV in scans with normal perfusion was found to be 74.46 ml (32.92–211.51), and with reversible ischemia was 92.94 ml (43.70–207.53) with a median-summed difference score (SDS) of 5.00 (1.0–27). In 15 scans with reversible perfusion defects associated with infarcts in other segments, median EFV was 101.71 ml (63.03–156.46) with mean - SDS of 7.50 (standard deviation = 6.20). Scans with reversible perfusion defects demonstrated an increased EFV (median - 92.94 ml) when compared to scans with a normal perfusion (median = 74.64 ml) (P < 0.001). Conclusion: Our results demonstrated an increased EFV in scans with presence of active reversible ischemia compared to that of normal perfusion on MPI (P < 0.001) suggesting potential role of cardiac SPECT/CT to evaluate EFV for risk stratification of suspected CAD.

Purpose: Incorporating ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG-PET/CT) for gross tumor volume (GTV) delineation is challenging due to varying tumor edge based on the set threshold of the standardized uptake value (SUV). This study aims to determine an optimal SUV threshold that correlates best with the pathological tumor size. Materials and Methods: From January 2013 to July 2014, 25 consecutive patients of operable nonsmall-cell lung cancer (NSCLC) who underwent staging¹⁸F-FDG-PET/CT before surgical resection were included in the test cohort and 12 patients in the validation cohort. GTVs were delineated on the staging PET/CT by automatic delineation using various percentage threshold of maximum SUV (SUVmax) and absolute SUV. The maximum pathological tumor diameter was then matched with the maximum auto-delineated tumor diameter with varying SUV thresholds. First-order linear regression and Bland–Altman plots were used to obtain an optimal SUV threshold for each patient. Three radiation oncologists with varying degrees of experiences also delineated GTVs with the visual aid of PET/CT to assess interobserver variation in delineation. Results: In the test set, the mean optimal percentage threshold for GTV was SUVmax of 35.6%±18.6% and absolute SUV of 4.35 ± 1.7. In the validation set, the mean optimal percentage threshold SUV and absolute SUV were 36.9 ± 16.9 and 4.1 ± 1.6, respectively. After a combined analysis of all 37 patients, the mean optimal threshold was 36% ± 17.9% and 4.27 ± 1.7, respectively. Using Bland–Altman plots, auto-contouring with 40% SUVmax and SUV 4 was in greater agreement with the pathological tumor diameter. Conclusion: Automatic GTV delineation on PETCT in NSCLC with percentage threshold SUV of 40% and absolute SUV of 4 correlated best with pathological tumor size. Auto-contouring using these thresholds will increase the precision of radiotherapy contouring of GTV and will save time.

Purpose of the Study: To establish the most appropriate ordered subset expectation maximization (OSEM) parameters for image reconstruction in Tc-99m methoxyisobutylisonitrile (MIBI) myocardial perfusion SPECT (MPS) and comparison with corresponding filtered back projection (FBP)-reconstructed images. Methods: A total of 99 stress–rest MPS studies (47 normal and 52 abnormal) were retrospectively analyzed using 16 different combinations of iterations and subsets. Images were reconstructed both with and without postreconstruction Butterworth filter (cutoff frequency and order for stress: 0.4 and 10 and for rest: 0.52 and 5, respectively) for each combination. A total of 3168 images were evaluated qualitatively by two nuclear medicine physicians on a scoring scale of 1–4. Best visual quality image iteration–subset combination was determined for each patient both with and without Butterworth filter and was further compared with FBP-reconstructed image. The interobserver agreement was obtained using kappa statistics. Results: The best quality images were obtained using a combination of four iterations and six subsets for both with and without Butterworth filter. The value of kappa for interobserver agreement for OSEM images with Butterworth filter was 0.570 and for OSEM images without Butterworth filter was 0.857. On comparison, FBP images were better than OSEM-reconstructed images without Butterworth filter (P < 0.0001 calculated using Fisher's exact test) with substantial agreement (kappa = 0.628). However, OSEM-reconstructed images with Butterworth filter were better than FBP images and showed moderate agreement (kappa = 0.486). Conclusion: The most appropriate OSEM reconstruction parameter in Tc-99m MIBI MPS is 4-iteration and 6-subset combination. FBP-reconstructed images were better than the images reconstructed with OSEM without postreconstruction Butterworth filter. However, OSEM-reconstructed image with Butterworth filter was better than FBP images.

Purpose of the Study: The aim of our study was to compare the technetium-99m (Tc-99m)-ethylenedicysteine (EC) renography calculation of differential renal function (DRF) with this measurement using Tc-99m-dimercaptosuccinic acid (DMSA) scintigraphy. Materials and Methods: Patients referred to our department were included in our study, and both DMSA and EC scans were performed for each patient according to the standard imaging protocols. A checklist was filled for each patient. Statistical analysis was performed using correlation and regression methods. Results: Forty-two patients (mean age: 3.6 ± 3.4 years), including 32 boys and 10 girls, participated in our study. The results of EC scintigraphy were significantly correlated with the values of DMSA scintigraphy (P < 0.001). Performing linear regression, EC renography significantly (P < 0.001) predicted the DRF as it was calculated by DMSA scintigraphy (R² = 0.92, P < 0.001). This test was significant in both male and female subgroups (P < 0.001). Conclusions: Overall, our study findings were similar to the reported results in the other reviewed studies, showing that Tc-99m-EC can be considered as an alternative for DMSA scintigraphy, providing interchangeable results.

Purpose of the Study: Radioiodine (I-131) is used as an effective noninvasive treatment for thyroid malignancies. Salivary gland is one of the most affected nontarget organs. The present study aims to perform early quantification of salivary gland function after I-131 therapy (RIT) for thyroid cancer considering I-131 down-scatter in the Tc-99m window. Materials and Methods: A total of 20 patients (6 males and 14 females) with differentiated thyroid carcinoma were enrolled in the study. Baseline dynamic salivary scintigraphy was performed in all patients using 185–370 MBq (5–10 mCi) Tc-99m pertechnetate. Posttherapy, salivary scintigraphy was performed 10–25 days after RIT in the range of 1.85–7.4 GBq (50–200 mCi). Time–activity curves obtained from the pre- and posttherapy dynamic salivary scintigraphy were used for semi-quantitative analysis. Uptake ratio (UR), ejection fraction (EF%), and maximum accumulation (MA%) were calculated by drawing regions of interest of individual parotid and submandibular glands over a composite image, after correcting for down-scatter from I-131 in the Tc-99m window. A paired t-test was used for comparison of the parameters obtained. Results: Significant changes were observed in UR and EF% of both parotid and submandibular glands (P < 0.05). No significant changes were found in the value of MA% of left parotid gland and both submandibular glands in the posttherapy scans in comparison to pretherapy scans (P > 0.05). However, significant difference was observed in the MA% of the right parotid gland (P = 0.025). Conclusion: Salivary gland function was found to deteriorate after RIT, with the parotid glands affected more than the submandibular glands.

Purpose of Study: The purpose of the study was to evaluate the effect of patient characteristics and equipment-related factors on the computed tomography (CT) dose received by patients from positron emission tomography-CT (PET-CT) using system-generated dose-length product (DLP) values and also to check the effective dose (ED) received from various CT protocols at our institute. Materials and Methods: This retrospective study included 78 adult patients who underwent F-18 fluorodeoxyglucose whole-body PET-CT and were divided into three groups based on the area of primary cancerous lesion. In Group A, we had 44 patients who underwent PET-CT (head-and-neck protocol), in Group B, we had 24 patients who underwent PET-CT (whole body with brain protocol), and in Group C, we had 10 patients who underwent PET-CT (pelvis protocol). All of the patients under the study are of South Asian ethnicity. A majority of patients 53.85% were males and remaining 46.15% were females. The product of conversion factor (k-coefficient), as described in “American Association of Physicists in Medicine Report No. 96” and DLP value generated by the scanner, was used to calculate the ED. Moreover, we also performed regression analysis to check relation between body weight, height, scan range, tube current, Volume computed tomography dose index (CTDIvol), DLP, and ED. Results: The regression analysis shows that scan range, patient height, weight, tube current, and DLP were significantly correlated with ED (P < 0.05 for all). Moreover, the DLP and conversion factor method estimated the ED from various groups. Patients under Group A (head-and-neck protocol), Group B (whole body with brain protocol), Group C (pelvis protocol) received an average ED of 22.45 mSv, 22.40 mSv, and 21.24 mSv, respectively. Conclusion: ED from CT component of PET-CT can be assessed as the product of scanner-generated DLP and conversion factor for selected range. Moreover, body weight, scan range, and tube current had an independent significant effect on ED received from CT.

Metastatic lesions to thyroid cartilage are very rare and can be often missed on conventional imaging. Anatomical and functional fused positron emission tomography/computed tomography (PET/CT) imaging has higher sensitivity as compared to conventional CT imaging and can thus identify such atypical sites of metastasis. Here, we present four cases of thyroid cartilage metastases detected on ¹⁸fluorodeoxyglucose PET/CT scan from carcinoma lung, breast, stomach and urinary bladder.

Fever of unknown origin (FUO) is a convoluted clinical dilemma. It can be caused by infective, inflammatory, malignant, and other pathologies. The identification of etiopathogenesis is essential for instituting definitive management. ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography-computed tomography (PET-CT) is now an integral part of FUO management. We present the case of a 60-year-old female with autosomal dominant polycystic kidney disease (ADPKD), where the infected renal cyst was detected as the cause of FUO on¹⁸F-FDG PET-CT.

Isolated cardiac sarcoidosis (ICS) accounts for 5%–10% of patients with sarcoidosis. It can involve atrioventricular node causing heart block, as well as the basal septum, papillary muscles, focal regions in the free wall, and the myocardium being more commonly involved. The diagnosis is achieved on magnetic resonance imaging (MRI) and endomyocardial biopsy. Recently, Fluorine-18 fluorodeoxyglucose positron emission tomography and computed tomography (F-18 FDG PET) has been incorporated in the diagnosis as well as management algorithm. We describe an interesting case of ICS detected on F-18 FDG PET and MRI and discuss its role in the management of this rare presentation.

Conventionally, multiparametric magnetic resonance imaging (mpMRI) incorporating T2-weighted, diffusion-weighted, and dynamic contrast-enhanced sequences is considered the standard for detection and staging of clinically important prostate cancer (PCa).^[1] The ⁶⁸gallium (⁶⁸Ga)-labeled positron emission tomography (PET) tracer targeting prostate-specific membrane antigen (PSMA), ⁶⁸Ga-PSMA PET, is a promising tool for detection, localization, and staging carcinoma prostate.^[2] Here, we present a case of PCa, showing incongruence between ⁶⁸Ga-PSMA PET and the corresponding mpMRI findings. Moreover, the final histopathology revealed a surprise, which exemplifies the complementary nature of combining ⁶⁸Ga-PSMA PET and mpMRI in the diagnosis and staging of carcinoma prostate.

Detection of recurrence of a brain tumor after treatment is one of the most important and challenging diagnostic problems in neuro-oncological practice. In spite of technical advances in imaging modalities, sometimes, certain clinical presentations and manifestations can lead to a diagnostic dilemma even with the best of the technical know-how. We present a case of recurrence of anaplastic oligoastrocytoma (World Health Organization Grade III), where the patient's initial clinical presentation and the F-18 flourodeoxyglucose positron emission tomography (PET) magnetic resonance imaging findings were suggestive of stroke-like migraine attacks after radiation therapy syndrome. Due to a seizure episode before PET image acquisition, intense gyral uptake was noted in the left parietal lobe which made it difficult to ascertain the presence of a tumor recurrence. However, Tc-99m glucohepatonate single-photon emission computed tomography done after 1 week revealed radiotracer uptake within the site corresponding to the primary tumor, and a diagnosis of recurrence was made.

Rhabdoid tumor commonly occurs in the kidney and has an aggressive clinical course with high mortality. Extrarenal rhabdoid tumours can involve a number of organs, but poorly differentiated follicular carcinoma with rhabdoid phenotype is an extremely rare clinical entity. The 18F-FDG PET feature of this thyroid malignancy is not available in the literature to the best of our knowledge. But, this feature has significant clinical relevance in management of such patients. We present such a case.

Melioidosis, caused by the soil saprophyte Burkholderia pseudomallei, is a great mimicker. With its wide variety of presentations which are often nonspecific, a good clinical suspicion is required for the timely diagnosis of the disease. F-18 fludeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) has a well-established role in the diagnosis and management of various infective diseases. Given the multifocal nature of this disease, we believe that F-18 FDG PET/CT has a definite role in improving the management of melioidosis. Here, we discuss a case of melioidosis presenting as septic arthritis and the role of F-18 FDG PET/CT in the management of the disease.

Postpartum methicillin-resistant Staphylococcus aureus (MRSA) infection occurs in patients with complicated vaginal delivery or cesarean section. The infection can manifest as mastitis, endometritis, and if untreated may lead to toxic shock syndrome. We report a case of postpartum MRSA osteomyelitis diagnosed by 99mtechnetium-methylene diphosphonate skeletal scintigraphy and single-photon emission computed tomography–computed tomography (CT) that was further confirmed by magnetic resonance imaging and CT-guided biopsy. This multimodal imaging approach helped reach the diagnosis and in further management of the patient.

We report the case of a young male who gradually developed a subacute demyelinating polyradiculoneuropathy. Routine examination and extensive biochemical investigations revealed demyelinating neuropathy, M-Band in electrophoresis. The patient referred for the whole-body ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography to look for skeletal and bone marrow lesions. The patient was found to have rib plasmacytoma. The case is rare because of infrequent association with the site, age, and symptoms.

Following a moving hot spot in the projections of raw images and profound perfusion defects in myocardial perfusion single-photon emission computed tomography (SPECT) imaging of a patient, a hypothesis was postulated that the perfusion defects were artifactual, and the high activity concentration of the gallbladder may be a culprit for this phenomenon, owing to flawed event positioning function of the gamma camera due to a malfunctioning digital event processor electronics board. To depict the characteristics of this artifact, a point source containing an activity of 3 mCi of pertechnetate is placed on the scanning table with the detector facing the table (at a distance of 30 cm), and then, in other detector positions and 1-min static images are acquired accordingly. The ratio is calculated as follows: count of the artifactual focus: 1860, count of the index focus: 705,727, and artifactual-to-index focus ratio: 0.003. In testing the uniformity of gamma camera based on the National Electrical Manufacturers Association protocol, a nonuniform response was detected, seemingly, a smaller field of view (FOV) is reproduced in the main FOV causing nonuniformity more than the acceptable level. The smaller flood image lies in the upper right corner of the main flood image. In essence, the extremely bright gallbladder was the source of error, and its image was reproduced in the FOV, which was superimposed on the left ventricular myocardium in some of the projections and was propagated to SPECT images.

Seroma can occur as a complication following nephroureterectomy. We report a case of squamous cell carcinoma of the kidney, postnephroureterectomy where serial fluorodeoxyglucose positron emission tomography-computed tomography images helped in distinguishing the diagnostic dilemma between lymph node recurrence and infected seroma.

Tumoral calcinosis is a rare entity presenting with periarticular calcium deposits, leading to multiple swellings and biochemical hyperphosphatemia and normocalcemia. Skeletal scintigraphy in these cases is helpful by providing a whole-body survey and delineating the common multifocality of this entity. We present the case of a 16-year-old boy with multiple swellings around the knee and elbow joints, having developed over 4 years and diagnosed as tumor calcinosis.

Osteogenic sarcoma is an aggressive malignant bone tumor arising from primitive mesenchymal bone-forming cells. Ossification is the characteristic feature of the metastases in osteosarcoma which aids their detection on ^99mTc-MDP bone scintigraphy. Although lung is the most common site of metastasis in osteogenic sarcoma, pleural involvement with effusion and skip metastases are rare. Herein, we report a case of osteogenic sarcoma of distal femur with diffuse calcified pleural thickening leading to malignant pleural effusion, calcified lung, lymph node, and bone metastases illustrated on bone scan.

Emergency pathologies often accompany malignancies. We herein report a case of pulmonary abscess in a patient with esophageal cancer which was depicted during the F-18-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) staging study. The patient's history of recent dilatation of the cancer stenosis in adjunct to the previous CT lung imaging, which was normal, made evident the diagnosis of the pulmonary abscess due to the perforation of the esophageal neoplasm. This life-threatening condition was promptly referred and successfully managed.

Ovarian carcinoma is associated with many cutaneous and paraneoplastic manifestations. We present a case of 52-year-old female who underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy for epithelial origin ovarian carcinoma. She presented with skin rashes over the face and neck region after 2 years. ¹⁸F-fluoro-D-glucose positron emission tomography-computed tomography scan revealed recurrent metastatic retroperitoneal lymph nodes.

A 50-year-old man with carcinoma of the right buccal mucosa underwent staging whole-body 18F-fluorodeoxyglucose positron emission tomography–computed tomography, which revealed a hypermetabolic heterogeneously enhancing lobulated primary lesion in the right buccal region and an incidental finding of subacute stroke. The case highlights the importance of discriminating brain neoplasms mimicking stroke from true ischemic stroke, which is crucial for appropriate management of patients in an oncology setting.

We describe the metabolic phenotype on F-18 fluorodeoxyglucose positron emission tomography (PET) in a 13-year-old female with myelin oligodendrocyte glycoprotein (MOG) antibody–positive encephalitis. Unilateral hemispheric hypometabolism on PET may be the metabolic phenotype of autoimmune epilepsy associated with MOG antibody.

⁶⁸Ga-prostate-specific membrane antigen (⁶⁸Ga-PSMA) is expressed in the endothelium of tumor-associated neovasculature of various solid malignancies possibly due to tumor-associated angiogenic factors and endothelial cell sprouting. We report a case of a 45-year-old man with known colorectal cancer, cirrhosis, and hepatitis C. Contrast-enhanced computed tomography (CT) showed a hypervascular lesion in the liver, and ¹⁸F-fluorodeoxyglucose positron emission tomography (PET) did not show any suspicious hepatic uptake. ⁶⁸Ga-PSMA PET-CT showed predominantly heterogeneous perilesional uptake in a configuration similar to the arterial enhancement pattern on the diagnostic CT. ⁶⁸Ga-PSMA uptake in hepatocellular carcinoma appears to be primarily neoangiogenesis driven, and its morphological and functional characterization can subsequently influence the selection of anti-neoangiogenic chemotherapy agents as well as guiding radionuclide ligand therapy.

An elderly male on androgen deprivation therapy for prostatic adenocarcinoma presented with obstructive jaundice. Since biopsy from the head of the pancreas showed neuroendocrine carcinoma (NEC), he was diagnosed with second primary pancreatic NEC. Ga-68 DOTANOC positron emission tomography/computed tomography (PET/CT) done subsequently showed enlarged mildly DOTANOC-avid retroperitoneal nodes infiltrating the pancreas. These nodes were found to be progression of prostate-specific membrane antigen (PSMA) nonavid retroperitoneal nodes visualized in his Ga-68 PSMA PET/CT performed at another institution before 4 months, when there was no lesion in the pancreas. This observation revised the diagnosis from second primary pancreatic NEC to progression of neuroendocrine differentiation in preexisting prostatic adenocarcinoma.

We report a case of an 81-year-old male evaluated for a liver space-occupying lesion. US-guided biopsy and immunohistochemistry were suggestive of hepatocellular adenoma (HCA)-inflammatory (with telangiectasia). Serial 18-F fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography scans revealed a heterogeneously enhancing hypermetabolic mass in the right lobe of the liver, remaining stable for a span of 3 years. This case highlights that benign rare tumors of the liver such as HCA can be intensely FDG avid and that uptake cannot conclude its malignant transformation.

Here, we report a case of a 54-year-old woman affected by thyrotoxicosis, with scintigraphic evidence of a diffuse hyperfunctioning goiter and a large ectopic thyroid tissue in the thyroglossal duct remnant. The latter was apparently more active than the two lobes at ^99mTc-pertechnetate scintigraphy, mimicking a condition of preexisting increased sensitivity to thyroid-stimulating hormone stimulation. On the other hand, single-photon emission computed tomography/computed tomography has proven to be a very useful tool in demonstrating this activity to be similar to the thyroid lobes and in defining extension and anatomical relationships of the mass.

¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) scan is the imaging modality of choice in the management of lymphoma. However, 18F-FDG is a nonspecific tracer for tumoral metabolic activity and infective pathology, thus posing a challenge in accurate response assessment. Here, we present a case of Hodgkin's lymphoma, referred for staging PET/CT scan which showed FDG-avid disease in the mediastinum, and on interim ¹⁸F-FDG PET/CT in addition to the mediastinal mass lesion, a FDG-avid lesion was also noted in the spleen suggestive of disease progression. The biopsy report of the lesion was tuberculosis, which was masquerading as disease progression on interim ¹⁸F-FDG PET/CT.

Diffuse extranodal cutaneous lymphomatous involvement is a unique presentation in a case of adult T-cell lymphoma. We present the case of a 26-year-old female who presented with erythematous rashes with subsequent evaluation with 18F fluorodeoxyglucose positron-emission tomography–computed tomography showing enlarged inguinal and axillary lymph nodes, and biopsy findings from the inguinal lymph nodes were suggestive of adult T-cell lymphoma.