Gaurav Malhotra

Functional imaging in primary tumour-induced osteomalacia: relative performance of FDG PET/CT vs somatostatin receptor-based functional scans: a series of nine patients.

Localization of phosphatonin‐producing mesenchymal tumours in patients with primary tumour‐induced osteomalacia (pTIO) is challenging. Functional imaging plays an important role in the localization of these tumours.

Can carbonated lime drink intake prior to myocardial perfusion imaging with Tc-99m MIBI reduce the extracardiac activity that degrades the image quality and leads to fallacies in interpretation?

Background: During myocardial perfusion imaging with Tc-99m sestamibi, intestinal and hepatic radiotracer activity commonly interfere with visualization of the inferior wall of the myocardium leading to difficulties in interpretation. This study was undertaken to assess if carbonated lime drink ingestion prior to imaging prevents the said interference and improves the quality of images. Materials and Methods: The study group comprised 33 consecutive patients including 26 males (age range: 30–80 years) and 7 females (42–62 years) who were referred for myocardial perfusion imaging. Of 33 patients, 21 (18 males, 3 females) were imaged at rest, 5 patients (3 males, 2 females) underwent physical stress, and 7 patients (5 males, 2 females) had pharmacological stress with adenosine. Five to 10 minutes after intravenous injection of 296 to 444 MBq (8–12 mCi) Tc-99m MIBI, anterior, and left anterior oblique (LAO) 45 degree planar views were acquired with a gamma camera using LEHR collimator. Each view was acquired for 100 seconds in a 256 × 256 matrix in all patients. Thereafter each patient was administered about 250 mL of a carbonated lime drink and repeat views were acquired within 5 minutes with the same parameters. Quantitative assessment of counts in the inferior wall of myocardium (M) to those in adjacent abdomen (A) was performed on both pre- and postintervention studies by drawing an ROI of about 50 ± 5 pixels. M/A ratios were recorded for each patient in both the groups. The student t test was performed to evaluate the significance of difference between pre- and postintervention images. P < 0.05 was considered significant. All patients underwent myocardial perfusion single photon emission computed tomography. Results: It was found that the inferior wall of the myocardium was better visualized, and there was no interference from gut or hepatic tracer activity in postintervention planar and single photon emission computed tomography reconstructed views as compared with preintervention images in all patients. The M/A ratio expressed as mean ± SD was significantly higher in the postintervention group, viz. 2.19 ± 0.71 in the anterior and 2.07 ± 0.70 in the LAO45 views as compared with those of preintervention values of 1.50 ± 0.59 in the anterior and 1.41 ± 0.49 in the LAO 45 views, respectively (P < 0.001). Conclusion: We conclude that intake of carbonated lime drink is a simple and an effective technique to improve the image quality of the inferior wall of the myocardium on myocardial perfusion imaging with Tc-99m MIBI. This technique may also help in reducing the time interval between injection of radiotracer and imaging, which is otherwise delayed in routine practice.

Unilateral proptosis due to orbital metastasis as a presenting clinical manifestation of carcinoma of the thyroid.

Differentiated thyroid cancers commonly present with thyroid swelling with or without regional nodal involvement and usually have an indolent clinical course. We report a rare case of unilateral proptosis due to orbital metastasis as a primary manifestation of differentiated thyroid carcinoma. A 55-year-old woman presented with protrusion of the left eye for 6 months and progressively diminishing vision for 7 days duration. She had an anterolateral orbitotomy with radical excision of the tumor that had shown enhancement with osteolytic destruction on contrast-enhanced CT scan. Histopathological examination of the orbital mass revealed a metastatic follicular carcinoma of the thyroid. She then had a total thyroidectomy with lymph node dissection, final histopathology of which revealed widely invasive follicular carcinoma of the thyroid. A diagnostic radioiodine scan after thyroid hormone withdrawal showed residual tumor in the thyroid bed, left orbital, and multiple bony metastases for which she underwent high-dose radioiodine therapy. The case is important due to its unusual clinical presentation that was also the primary manifestation. Even though orbital metastasis of carcinoma of the thyroid is rare, thyroid carcinoma should be considered as a potential primary tumor in such presentations.

Renal metastases from thyroid carcinoma.

We are writing regarding a recent article entitled ‘‘Renal Metastasis from Hurthle Cell Thyroid Carcinoma and Its Evaluation with Hybrid Imaging’’ by Djekidel et al. (1). We agree with the authors’ point regarding the rarity of renal involvement from primary cancers of the thyroid. In our recently accepted article, however, a literature search revealed that renal metastases from a primary thyroid cancer have been reported in about 20 patients to date (2). This is contrary to the authors’ claim that these metastases have been reported in only 10 patients. Another pertinent reference describing single photon emission computed tomography-computed tomography evidence for renal metastasis from follicular thyroid cancer should also be noted (3). Second, Marino et al. (4) have reported a rare case of renal metastasis from thyroid carcinoma that started as Hurthle cell adenoma and transformed into a carcinoma with a follicular appearance after 26 years. Hence, this may not be the first case of Hurthle cell cancer with renal metastases. Third, we were surprised to find that multiple lesions that showed F-18 fluorodeoxyglucose uptake were not thought to show iodine concentration. Perhaps, a small amount of abnormal uptake could have been missed on the radioiodine scan. In the literature and from our institutional experience of treating advance metastatic thyroid cancer, we find that many such lesions show both fluorodeoxyglucose and iodine avidity. Hence, they are amenable to administration of radioiodine therapy, in high doses of 200–250 mCi, with intent to palliate. Many such patients have dramatic symptomatic relief and good quality of life despite harboring multiple metastases.

F 18 fluorodeoxyglucose positron emission tomography "super scan" in a patient of metastatic primitive neuroectodermal tumor of the kidney

We report F-18 fluorodeoxyglucose (FDG) “positron emission tomography (PET) super scan” akin to “super scan” of conventional skeletal scintigraphy, in a rare case of primitive neuroectodermal tumor (PNET) of the kidney. A twelve year old male patient of metastatic PNET of the kidney was subjected to a “true” whole body F-18 FDG PET scan including lower limbs and skull region as per the institution protocol. The images revealed extensive hypermetabolic areas corresponding to the computed tomography described renal, hepatic, and pancreatic lesions along with intense and non-uniform uptake in the marrows of axial and appendicular skeletal system. Interestingly, low background tracer concentration was observed along with very low F-18 FDG uptake in the brain, skeletal muscles of limb, mediastinum, and bowel. In view of these findings, the scan can be interpreted as “PET super scan” due to its resemblance with the super scan of skeletal scintigraphy. A repeat F-18 FDG PET scan after chemotherapy revealed marked treatment response with disappearance of “super scan”-like pattern, reduction in number, size, metabolic activity of the lesions, and stimulated marrow sans the previously diseased portion. Though uncommon, the reporting physician should be aware of “PET super scan” and its implications as described in this case.

Cancer of Unknown Primary: Role of FDG PET/CT

Cancer of unknown primary (CUP) represents a heterogeneous group of metastatic malignancies for which no primary site of the tumour is found despite extensive diagnostic workup. The patients have malignancy which appears to derive from epithelial cells. CUP accounts for approximately 5% of all cancer diagnoses and is characterised by early dissemination and uncommon metastatic sites and usually carries a poor prognosis [1]. Appropriate treatment strategy is still lacking in this subgroup of patients. Detection of primary tumour in CUP patients may help optimise treatment and thereby improve prognosis.

Pictorial Atlas: Cancer of Unknown Primary

A 62-year-old male presented with left-sided neck lump and weight loss. FNAC of the enlarged cervical lymph node was proven to be an adenocarcinoma. Other routine investigations failed to identify the primary tumour. A PET-CT study was performed to search for the unknown primary.

Genetic status determines 18F-FDG uptake in pheochromocytoma/paraganglioma

Although few studies have demonstrated utility of 18F‐ fluoro‐2‐deoxy‐d‐glucose positron emission tomography/computerised tomography (18F‐FDG PET/CT) in benign pheochromocytoma/paragangliomas (PCC/PGLs), there limited data on factors predicting the FDG uptake in PCC/PGL.

Meckel scan findings in an infant with ileocolic intussusception.

A 7-month-old male infant who presented with bleeding per rectum was evaluated and diagnosed to have ileocolic intussusception on ultrasonography. Despite ultrasonography-guided saline reduction, there was persistence of bleeding per rectum. He was given blood transfusion and referred for Tc-99m pertechnetate scan to rule out ectopic gastric mucosa. The scan was done as per the standard institution protocol and the images revealed a focus of progressively increasing tracer uptake in the right lower abdominal quadrant suggesting the presence of ectopic gastric mucosa. An exploratory laparotomy revealed ileocolic intussusception secondary to Meckel diverticulum acting as a pathologic lead point (PLP). A wedge resection of the intestinal wall containing the diverticulum with suture closure was performed. The presence of Meckel diverticulum and ectopic gastric mucosa was confirmed on subsequent histopathological examination of the specimen. The patient rapidly improved postoperatively and was discharged 9 days after surgery. Bleeding per rectum can be seen in both intussusception and in Meckel diverticulum with ectopic gastric mucosa. Intussusception originating from a Meckel diverticulum as PLP remains a diagnostic challenge because of the overlapping symptoms.The Meckel scan findings, in this case, avoided the further CT scan, angiography, and endoscopy for the diagnosis of the cause of symptoms, sparing not only the time but cost of investigations and unnecessary radiation exposure to the patient.

Pathological extracardiac uptake of Tc-99m sestamibi (MIBI) leading to a false impression of reduced wall thickening in a region of apparent hyperperfusion on gated myocardial perfusion single photon emission computed tomography (G-SPECT).

Myocardial perfusion studies with Tc-99m sestamibi (MIBI) are routinely performed to evaluate patients with ischaemic heart disease. However, this tracer is not specific for myocardium and is known to concentrate in tumours and inflamed tissue. A 55-year-old male patient without known coronary risk factors was subjected to gated myocardial perfusion single photon emission computed tomography (G-SPECT) imaging in view of baseline ECG changes to rule out inducible ischaemia. The final output in the form of a bull’s eye display of perfusion …