Abhinav Singhal

Evaluation of thymic tumors with 18F-FDG PET-CT: A pictorial review:

Thymic tumors represent a broad spectrum of neoplastic disorders and pose considerable diagnostic difficulties. A non-invasive imaging study to determine the nature of thymic lesions can have significant impact on management of such tumors. 18F-flurorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET-CT) has shown promising results in characterization of thymic tumors. The objective of this article is to provide an illustrative tutorial highlighting the clinical utility of 18F-FDG PET-CT imaging in patients with thymic tumors. We have pictorially depicted the 18F-FDG PET-CT salient imaging characteristics of various thymic tumors, both epithelial and non-epithelial. Also discussed is the dynamic physiology of thymus gland which is to be kept in mind when evaluating thymic pathology on 18F-FDG PET-CT, as it can lead to interpretative pitfalls.

In Vivo Demonstration of PSMA Expression in Adenocarcinoma Urinary Bladder Using 68Ga-PSMA 11 PET/CT

In vitro and in vivo studies have demonstrated prostate-specific membrane antigen (PSMA) expression in various malignant and benign tumors. Based on the recent immunohistochemical study showing PSMA expression in adenocarcinoma of urinary bladder, we hypothesized that PSMA expression in adenocarcinoma of urinary bladder can be demonstrated in vivo using Ga-PSMA 11 PET/CT. We present a man with exstrophy bladder, presenting with adenocarcinoma urinary bladder referred for staging PET/CT. Both F-FDG and Ga-PSMA-11 PET/CT were done, which showed PSMA expression in the primary tumor as well as metastatic lymph nodes.

Role of 99m Tc-MDP bone scan in the diagnosis of Erdheim-Chester disease

Erdheim–Chester disease (ECD) is a rare systemic non-Langerhans cell histiocytosis. It is a progressive disease of unknown etiology. The 99mtechnetium-methylene diphosphonate (99mTc-MDP) bone scan is useful in finding the sites of involvement in the skeleton and is helpful in excluding other causes of bony pain. Also a scintigraphic pattern consistent with ECD should alert the physician to evaluate the patient for visceral sites of involvement using fludeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), as this is known to be fatal at times.

Discordance in 68Ga-DOTANOC and 177Lu-DOTATATE uptake in diagnostic and post-therapy scans in patients with medullary thyroid cancer-likely reasons

Sir, We qualitatively studied the discordance between pre-therapy 68Ga-DOTANOC scans and post-therapy 177Lu-DOTATATE scans in patients with medullary thyroid cancer (MTC). Patients with metastatic/recurrent, inoperable MTC showing good uptake of Ga-DOTANOC on positron emission tomography (PET)/computed tomography (CT); >18 years of age with serum creatinine ≤1.3 mg%, bilirubin ≤1 mg%, SGOT, SGPT ≤50 IU; baseline normalized GFR (2 sample method-Tc-DTPA) ≥70 ml/min/1.73 mr, Hb ≥9 gms%, TLC ≥4000/μl, platelets ≥1,50,000/μl were included in this study.

Detection of recurrent cutaneous angiosarcoma of lower extremity with (18)f-fluorodeoxyglucose positron emission tomography-computed tomography: report of three cases.

Cutaneous angiosarcomas (CAS) are uncommon, aggressive tumours. Very rarely, they arise from the lower extremity. Such tumours are usually associated with chronic lymphedema, a phenomenon known as Stewart-Treves Syndrome. Treatment is usually radical surgery with adjuvant therapy (radiotherapy/chemotherapy). Recurrence rate after primary treatment is high. Because of post therapy changes, conventional imaging has limited specificity for diagnosing recurrence. 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET-CT) might be useful in such patients. It can demonstrate local recurrence along with distant metastasis, if any and can have significant impact on patient management. We here present three cases of recurrent CAS of lower extremity diagnosed with 18F-FDG PET-CT.

68Ga DOTANOC PET/CT for accurate delineation of disease extent in a case of sinonasal small cell neuroendocrine carcinoma.

Neuroendocrine tumors constitute a heterogeneous group of neoplasms arising from the cells of the neural crest. We present a rare case of primary sinonasal neuroendocrine carcinoma in a 61-year-old male patient where somatostatin receptor PET/CT with 68Ga-DOTANOC correctly delineated the extent of primary tumor as compared to contrast-enhanced CT, thereby changing patient management.

13N-Ammonia PET/CT for detection of recurrent glioma: a prospective comparison with contrast-enhanced MRI.

PurposeWe assessed the value of 13N-ammonia PET-computed tomography (PET/CT) in recurrent glioma and compared the results with those of contrast-enhanced MRI (CE MRI). Materials and methodsFifty-two (mean age, 39.8±11.6 years; male, 33; female, 19) histopathologically proven and previously treated glioma patients with clinical suspicion of recurrence were evaluated with 13N-ammonia PET/CT and CE MRI. PET/CT images were evaluated qualitatively and quantitatively (maximum standardized uptake value). Tumour to white matter (T/W), tumour to grey matter (T/G) and tumour to pituitary (T/P) ratios were calculated and cutoff levels were derived with receiver operating characteristic curve analysis. Sensitivity, specificity and predictive values were compared. A combination of clinical follow-up, repeat imaging and biopsy (when available) was taken as the reference standard. ResultsOn the basis of the reference standard, 23 out of 52 patients were seen to have recurrence. Overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 13N-ammonia PET/CT were 82.6, 86.2, 82.6, 86.2 and 84.6%, respectively, whereas those of CE MRI were 96.7, 48.3, 59.5, 93.3 and 69.2%, respectively. Overall, 13N-ammonia PET/CT was statistically superior to CE MRI (P=0.001). In low-grade tumours, 13N-ammonia PET/CT performed better than MRI with an accuracy of 86.8 versus 68.4% (P=0.003). In high-grade tumours, both the modalities had comparable performances with accuracies of 78.6% for 13N-ammonia PET/CT and 71.4% for CE MRI (P=0.250). Among the ratios, T/P was the most useful, with the largest area under the curve (0.825; P=0.0001). Conclusion13N-Ammonia PET/CT shows higher accuracy compared with contrast-enhanced MRI for detecting recurrent gliomas, particularly in low-grade tumours.

Ictal PET in Ohtahara Syndrome With Hemimegalencephaly

Ohtahara syndrome is one of the causes of infantile epilepsies, which presents with refractory seizures and characteristic EEG changes. It is often associated with structural anomalies in the brain. We report a case of 5-month-old girl with Ohtahara syndrome with hemimegalencephaly who presented with refractory seizures and ictal FDG PET/CT helped in localizing the seizure focus.

68Ga-DOTANOC PET-CT demonstrating in vivo somatostatin receptor expression in idiopathic gynecomastia.

Gynecomastia is abnormal enlargement of the male breasts due to the excess growth of glandular component. A 65-year-old man with medullary carcinoma of thyroid underwent (68)Ga-DOTANOC PET-CT for somatostatin receptor (SSTR) scintigraphy. Extensive nodal, bone, and bone marrow disease was seen. Interestingly, increased (68)Ga-DOTANOC uptake was also noted in bilateral enlarged mammary glands (gynecomastia). Although SSTR types 1 and 3 have been identified in the normal female breast, no report exists regarding SSTR expression in gynecomastia.

Peritoneal super scan on 18F - FDG PET-CT in a patient of burkitt's lymphoma

Peritoneal lymphomatosis is seen less frequently, but when seen, it is mostly associated with aggressive variants of malignancies. FDG uptake has been reported in peritoneal lymphomatosis both in DLBCL and Burkitts lymphoma. We report a case of Burkitts lymphoma with involvement of entire peritoneum, which looks like a “peritoneal super scan” on FDG PET-CT.