Chandrasekhar Bal

Solid variant of papillary carcinoma thyroid in a child with no history of radiation exposure

Solid variant is a rare and poorly characterized variant of papillary thyroid carcinoma (PTC) and comprises approximately 3% of PTCs. It is more common in children and has high propensity for extrathyroidal metastasis. It is seen in higher proportion in post-radiation PTCs and has been seen in more than one-third of post Chernobyl radiation induced PTCs in some studies. It usually presents with differential diagnosis of poorly differentiated carcinoma versus anaplastic versus medullary thyroid carcinoma versus metastasis from extrathyroidal malignancy on fine needle aspiration cytology. This report describes a case of solid variant of PTC in a child who had no history of radiation exposure and shows the importance to be given to histopathology when the pre-operative diagnosis is not clear.

Divergent Role of 68 Ga-Labeled Somatostatin Analogs in the Workup of Patients with NETs: AIIMS Experience

Neuroendocrine tumors (NETs) encompass a wide range of rare and heterogeneous neoplasms arising from the neural crest. Diagnosis of NETs is conventionally done by a combination of common clinical symptoms and biochemical evidence of hormonal excess, which these tumors are known to secrete. After a diagnosis of NET is established, a search for its localization is carried out using common morphologic imaging methods such as ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI). The main problem with structural imaging is, however, its inability to distinguish between endocrine and exocrine lesions. Functional imaging of NETs started with use of iodine-131-meta-iodobenzylguanidine ((131)I-MIBG) and has come a long way since. From accurate demonstration of functioning tumors to detection of small and occult lesions, functional imaging has penetrated almost every aspect of NET management. Procedures such as (131/123)I-MIBG, (111)In-Octreoscan and others are rapidly giving way to use of PET/CT based on the superior resolution of the system and the availability of target-specific positron-emitting radiotracers. The availability of (68)Ga from generator-based radionuclide systems, namely (68)Ge/(68)Ga generators, opened up a new era of molecular imaging for NETs. A multitude of somatostatin analogs can be easily radioliganded with (68)Ga using heterocyclic macromolecular bifunctional chelating systems for targeted diagnosis of somatostatin receptor-expressing tumors, used most effectively to date for detection of NETs. This chapter focuses on our experience at the All India Institute of Medical Sciences, New Delhi regarding the divergent roles of (68)Ga-labeled somatostatin analogs in the workup of patients with NETs.

Utility of 18F-choline photon emission tomography/computed tomography in the diagnosis of parathyroid adenoma

Recently, the role of 18F-choline in the detection of parathyroid adenomas has been reported. At our institution, we are currently studying the role of this tracer in comparison to the standard methoxy-isobutyl-isonitrile.(MIBI) scan with single photon emission tomography/computed tomography. Our initial results show that 18F-choline is at least as good as 99mTc-MIBI scan. We present here a representative case of a 45-year-old woman with multiple skeletal lytic lesions and a high parathyroid hormone.(PTH) who underwent both these imaging techniques with concordant results, further confirmed by histopathology and postoperative fall in serum PTH levels.

Inguinal node metastasis from follicular thyroid cancer.

A 58‐year‐old female patient presented to the nuclear medicine department our institute with history of tender inguinal swelling since 1 month. She was a known case of follicular thyroid carcinoma. She underwent total thyroidectomy 9 years ago but no radioiodine ablation and was only on suppressive thyroxine therapy. Six months later she developed a left parietal skull swelling which was excised and histopathology showed metastatic follicular carcinoma. Three months later she developed pain in the back and left side of chest. A dorsolumbar spine MRI showed involvement of D7 to L2 vertebrae. She was referred to our center for further management 1 year after surgery. She underwent 131I whole body scan (WBS) which showed remnant uptake of 4.8% at 48 hrs in the thyroid bed and uptake in mediastinal nodes, left chest wall and dorsolumbar vertebrae and was treated with 200 mCi 131I. A further dose of 200 mCi radioiodine was given 8 months after the first dose. She was lost to follow‐up for 4 years after which she again presented to us with right gluteal pain. She received the 3rd dose of 200 mCi 131I. The post‐therapy scan revealed a metastatic lesion in the right ilium [Figure 1]. She received further three doses of 150 mCi 131I each over a period of next 2 years with good uptake in the metastatic deposits on the post therapy scan. Six months after the sixth dose she presented with a tender right inguinal lymphadenopathy which had not responded to antibiotics. She underwent a fine needle aspiration cytology which revealed features compatible with metastatic follicular carcinoma [Figure 2].

Demonstration of 68Ga-prostate-specific membrane antigen uptake in metastatic pancreatic neuroendocrine tumor

We present the case of a 47-year-old female with metastatic pancreatic neuroendocrine tumor (NET). The patient was treated with long-acting octreotide which failed to halt disease progression. The patient was being considered for 177Lu-peptide receptor radionuclide therapy, and a 68Ga-DOTANOC positron emission tomography-computed tomography (PET-CT) was acquired initially, which showed good uptake in the primary and metastatic lesions. Metastatic pancreatic NETs have limited treatment options, and given the background that these tumors are highly vascular and prostate-specific membrane antigen (PSMA) expression is known in the endothelium of tumor neovasculature, we decided to perform a 68Ga-PSMA-HBED-CC PET-CT scan. It revealed radiotracer uptake in the metastatic liver lesions although not as high as 68Ga-DOTANOC-PET-CT. PSMA expression needs to be researched further, especially in high-grade NETs where somatostatin expression may be poor.

Prostate-specific membrane antigen imaging in recurrent medullary thyroid cancer: A new theranostic tracer in the offing?

Prostate-specific membrane antigen (PSMA) expression has been shown in neovasculature of various malignancies. Recurrent medullary thyroid cancer (MTC) is difficult to treat. We present the findings on PSMA-positron emission tomography/computed tomography (PET/CT) of a 68-year-old man with MTC, who presented with a recurrent left paratracheal mass and rising calcitonin. The scan revealed significant uptake on PSMA imaging but not on 68Ga-DOTANOC PET/CT. 177Lu-PRRT is one of the therapeutic options in patients with recurrent MTC, but in this case was not possible due to lack of somatostatin receptor expression. Imaging evidence of PSMA expression alerts us to the potential use of 177Lu-DKFZ-PSMA-617 therapy in such patients.

Can early dynamic positron emission tomography/computed tomography obviate the need for postdiuresis image in 68Ga-PSMA-HBED-CC scan for evaluation of prostate adenocarcinoma?

Introduction: Forced diuresis technique is often adopted to wash out the high amount of urinary radioactivity that masks the foci of abnormal uptake in the pelvic region on 68Ga-PSMA-HBED-CC positron emission tomography/computed tomography (PET/CT) scan in prostate cancer (PC) patients. However, this method is time-consuming, makes the patient non/less compliant, and is not feasible in patients with renal dysfunction. We hypothesized that early dynamic imaging can obviate the need for a postdiuresis view as the urinary activity is expected to be low at the time. Materials and Methods: A total of 20 biopsy-proven PC patients who were referred to our department for a 68Ga-PSMA PET/CT for staging/restaging were prospectively studied. Dynamic PET/CT was done with on table intravenous (i.v.) injection of 2–3 mCi (74–111 MBq) of the radiotracer. Dynamic images were acquired over the pelvis with a frame time of 1 min for 10 min. Static images of 2 min/bed position were acquired between 45 and 60 min p.i. The patients were then administered i.v. furosemide and encouraged water intake and frequent urination. A static view of pelvic region was acquired at 5 min/bed at 120 min p.i. A three-dimensional volume of interest (3D-VOI) was plotted on the primary lesion, bladder, involved nodes if any, pelvic bones at involved and uninvolved sites, gluteal muscles, and artery. The sentence seems fine. This was to generate the Time activity curve for analysis. Results: Nine patients were referred for staging and 11 for restaging. Mean age of 20 patients was 64.6 years, and median prostate-specific antigen level was 21.4 ng/ml (range: 0.05–2180). Prostatic lesion was present in 20 patients, nodal involvement in 8, and bone involvement in 10 patients. Median maximum standardized uptake value (SUVmax) of the prostatic lesion (P) showed an ascending trend: 5.31 at 5 min, 10.65 at 60 min, and 10.52 at 120 min p.i. At the same time, median SUVmax of the bladder (B) also progressed steeply and then decreased postdiuresis: 1.01 at 5 min, 24.6 at 60 min, and 6.88 at 120 min. Despite forced diuresis, the bladder activity remained higher than that during early dynamic imaging. Median prostate-to-bladder (P/B) ratio was highest during early dynamic imaging at 5 min p.i. was 5.17, while at 60 min, P/B ratio was 0.42 (P = 0.002) and, at 120 min, it was 1.27 (P = 0.009). Further, all the nodal and bone lesions were clearly visualized on early dynamic images. Conclusion: The study results suggest that early dynamic imaging performs better than a postdiuresis view in terms of delineation of prostatic and regional lesions on 68Ga-PSMA scan. Further, it saves time and the patients are more compliant to this technique.

Occurrence of symptomatic meningioma as a second neoplasm in patients with differentiated thyroid cancer treated with radioiodine

Occurrence of second tumors has been seen in patients with papillary and follicular thyroid cancer. We studied the occurrence of meningioma as a second neoplasm in patients with differentiated thyroid cancer treated with radioiodine at our institution.