Sneha Shah

Therapeutic Response to Radiofrequency Ablation of Neoplastic Lesions: FDG PET/CT Findings

Ablation of neoplastic lesions by using radiofrequency energy is gaining popularity in clinical practice because of the minimally invasive nature of radiofrequency ablation (RFA). Primary and secondary tumors of the liver and lung are treated with RFA when surgery is precluded because of comorbidity. Benign bone tumors are also treated with RFA to relieve pain and prevent further tumor growth. Differentiation between postablation tissue changes and residual disease is difficult with morphologic imaging modalities such as ultrasonography, computed tomography (CT), and magnetic resonance (MR) imaging, thus limiting the use of these modalities to detection of residual disease early after RFA. Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is a functional imaging modality that can be used to study the effects and efficacy of RFA. Lesions that show increased FDG uptake at PET become completely photopenic immediately after RFA, a finding that is suggestive of the completeness of ablation. Focal areas of increased FDG uptake within the ablated zone are suggestive of residual disease. Reactive tissue changes such as inflammation are depicted in the periphery of the ablated lesion and show a uniform low-grade FDG uptake, which can be differentiated from the focal, nodular intense uptake in areas of residual disease. Use of combined FDG PET/CT to detect residual disease early after RFA allows ablation to be repeated, if necessary, to obtain the maximum therapeutic benefit. Note that FDG uptake in the complications sometimes associated with RFA can be a cause of potential false-positive PET results.

Integrated PET/CT in evaluating sarcomatous transformation in osteochondromas.

Aim: To study the role of PET-CT in evaluating sarcomatous transformation in osteochondromas. Materials and Methods: This was a retrospective analysis of a prospective data base of 12 patients from 2005 to 2007 with a clinical diagnosis of an osteocartilaginous lesion who were referred for a FDG PET-CT study to evaluate for possible malignant transformation. Imaging was performed on a GE Discovery ST PET-CT system after intravenous injection of 370 MBq (10 mCi) of F-18 FDG. Results: Seven patients with histopathological evidence of a sarcomatous transformation to grade II chondrosarcoma showed moderate to high FDG uptake (SUV 3.3–6.9), whereas 1 patient with a dedifferentiated chondrosarcoma showed a focus of very intense uptake (SUV 11.4). Four patients with histopathological and/or clinical or follow-up diagnosis of a benign osteocartilaginous lesion showed low grade FDG uptake (SUV 0.8–1.3). FDG uptake was also noted in an asymptomatic osteochondroma which on histopathology revealed a grade II chondrosarcoma. Conclusions: Whole body FDG PET-CT is an important adjunct to conventional morphologic imaging in evaluating suspected malignant transformation in osteochondromas. Increased glucose metabolism can help diagnose sarcomatous transformation at the suspected sites as well as detect early malignant change at clinically unsuspected sites. Moreover, its ability to detect a focus of dedifferentiation can be useful for prognostication and to plan adjuvant treatment. A small cohort limits statistically sound conclusions to be drawn from this study, however further prospective trials based on these findings can help explore the potential application of FDG PET-CT in this clinical condition.

18F-FDG PET/CT-directed biopsy: does it offer incremental benefit?

PurposeTo study whether the metabolic information provided by a prior PET/computed tomography (CT) scan can add valuable information and an incremental benefit while performing image-guided biopsies. MethodsFluorine-18 fluorodeoxyglucose (18F-FDG) PET/CT findings of 112 patients were available before biopsy and were considered for analysis. Biopsies were performed using standard techniques only after the needle tip was confirmed to be in the portion of the lesion corresponding to the hypermetabolic area seen on PET. This was achieved by visual coregistration and also by software registration algorithms that registered the intraprocedural CT images with the preselected PET/CT data. Only those biopsies for which a definitive histopathological diagnosis could be made were considered ‘diagnostic’. Cases in which PET/CT added an incremental value were divided into three categories. ResultsA total of 112 patients (66 male and 46 female, age range 16–74 years) underwent a biopsy based on PET findings. The biopsy sites were as follows: lung, 54; lymph nodes, 27; bone, 12; and soft-tissue masses/deposits, 19. Out of the 112 biopsies, an incremental benefit was seen overall in 53 patients (47.3%): in 40.7% (22/54) of patients who underwent lung biopsies, 44.4% (12/27) of those who underwent lymph node biopsies, 66.6% (8/12) of those who underwent bone biopsies and 57.8% (11/19) of those who underwent soft-tissue biopsies. Out of the cases that showed an incremental benefit, the highest number (30) belonged to the category in which the biopsy sample was obtained from the focal hypermetabolic portion of the apparently larger morphological lesion seen on CT. ConclusionPET/CT data coregistered with intraprocedural CT images can guide needle placement in the viable portion of the lesion, thus increasing the chances of achieving a definitive diagnosis. This approach can offer a significant incremental benefit while performing image-guided biopsies.

Isolated asymptomatic skeletal muscle metastasis in a potentially resectable non-small cell lung cancer: detection with FDG PET-CT scanning.

Abstract Asymptomatic skeletal muscle metastasis in non-small cell lung cancer is a rare event particularly when it is detected at initial staging. This report describes how whole body imaging with [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET)-computed tomography (CT) detected a solitary asymptomatic metastasis to the gluteus maximus muscle in a potentially resectable case of non-small cell lung cancer, thereby changing the treatment plan from surgical resection to systemic chemotherapy.

90Y microsphere therapy: does 90Y PET/CT imaging obviate the need for 90Y Bremsstrahlung SPECT/CT imaging?

BackgroundTransarterial radioembolization using 90Y microspheres is a novel therapeutic option for inoperable hepatic malignancies. As these spheres are radiolucent, real-time assessment of their distribution during the infusion process under fluoroscopic guidance is not possible. Bremsstrahlung radiations arising from 90Y have conventionally been used for imaging its biodistribution. Recent studies have proved that sources of 90Y also emit positrons, which can further be used for PET/computed tomography (CT) imaging. This study aimed to assess the feasibility of 90Y PET/CT imaging in evaluating microsphere distributions and to compare its findings with those of Bremsstrahlung imaging. Materials and methodsThirty-five sessions of 90Y microsphere transarterial radioembolization were performed on 30 patients with hepatic malignancies. 90Y PET/CT imaging was performed within 3 h of therapy. Bremsstrahlung imaging was also performed for each patient. The imaging findings were compared for concordance in the distribution of microspheres. ResultsExact one-to-one correspondence between 90Y PET/CT imaging and 90Y Bremsstrahlung imaging was observed in 97.14% of cases (i.e. in 34/35 cases). Discordance was observed only in one case in which 90Y PET/CT imaging resolved the microsphere uptake in the inferior vena cava tumor thrombus, which was, however, not visualized on Bremsstrahlung imaging. ConclusionThere is good concordance in the imaging findings of 90Y PET/CT and 90Y Bremsstrahlung imaging. 90Y PET/CT imaging scores over the conventionally used Bremsstrahlung imaging in terms of better resolution, ease of technique, and comparable image acquisition time. This makes it a preferred imaging modality for assessment of the distribution of 90Y microspheres.

Etiology and significance of incidentally detected focal colonic uptake on FDG PET/CT.

Background: Incidental colonic uptake of 18F-flurodeoxyglucose (FDG) is not an infrequent finding encountered during whole body positron emission tomography (PET) imaging. Almost all studies on this topic are in Western populations, which have a markedly different epidemiological profile for colorectal premalignant and malignant conditions as compared to that of the Indian subcontinent. Aim: The purpose of this study was to assess the etiology of incidentally detected focal FDG uptake in the colon by comparing it with colonoscopy and histopathology. Materials and Methods: Electronic medical records of patients who underwent FDG PET/computed tomography (CT) at our institution for a 2½-year period from January 2009 to July 2011 were reviewed. There were 32 out of 9000 (0.35%) patients whose PET/CT reports mentioned incidental focal colonic FDG uptake, of which 24 patients subsequently underwent colonoscopy. Lesions which appeared neoplastic on colonoscopy were confirmed with histopathology obtained after biopsy or surgery. Colonoscopy and pathology findings were considered as gold standard. Results: Among the 24 patients who underwent a colonoscopy, 3 patients had normal findings (12.5%). A positive colonoscopy was noted in 21 patients (87.5%) with the lesion coinciding with the location described in the PET/CT report. Adenomatous polyps were detected in 12 patients (37.5%), whereas in 8 patients (25%) malignant lesions were confirmed [adenocarcinoma n = 5, non-Hodgkins lymphoma (NHL) n = 2, malignant melanoma n = 1]. In one patient, colonic uptake was diagnosed as inflammatory. The mean standardized uptake valuemax (SUVmax) for the 12 premalignant lesions was 16.9 ± 9.6 (range 7.5-37.4) and the mean SUVmax for the 8 malignant lesions was 12.9 ± 5.5 (range 6.7-21.6). The difference in SUVmax between the premalignant adenomatous polyps and the malignant lesions was not statistically significant (P = 0.316). Conclusions: Our study shows that a significant proportion of patients (62.5%, 20/32) showing an incidental focal FDG uptake will harbor premalignant (adenomatous polyps) or malignant lesions, and further evaluation with colonoscopy and biopsy is warranted in such cases.

Imaging findings in a rare case of extra-articular chondrocalcinosis.

We report the imaging findings in extra-articular chondrocalcinosis in a 53-year-old man with swelling and pain in right scapular area for 1 year. Plain radiography showed a right scapular area calcific mass. The clinical suspicion was of a soft tissue sarcoma. As a part of diagnostic workup, a bone scan and a PET/CT scan were done. Bone scan revealed intense MDP uptake in the right scapular area. FDG PET/CT revealed intense FDG uptake in the mass. The biopsy revealed chondrocalcinosis. This is an addition to our long list of causes of extraosseous uptake of MDP.

18F-FDG uptakes in leptomeningeal metastases from carcinoma of the breast on a positron emission tomography/ computerized tomography study

Leptomeningeal metastases (LM) are most commonly observed in hematological malignancies. With prolonged survival in solid tumors, an increased frequency of metastases is noted in these tumors too. Early diagnosis, when the patient has minimal neurological disability, is associated with prolonged survival and improved functional outcome although the therapy is palliative. The diagnosis of LM is difficult, and the demonstration of tumor cells in the cerebrospinal fluid remains the gold standard. This can also be done by definitive neuroimaging. MRI is routinely used in this aspect. We discuss here a case where 18F-FDG PET/CT (Fluoro-de-oxy glucose positron emission tomography/computerized tomography) study helped us in the diagnosis of LM. Whole-body PET/CT imaging could be a useful tool in identifying the possibility of metastases of breast carcinoma in the usual sites and the not-so-usual sites of metastases.

Incremental value of 18F-FDG PET/CT in therapeutic decision-making of potentially curable esophageal adenocarcinoma.

Aims and objectivesThe aim of the study was to estimate the incremental value of fluorine-18 fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) in aiding treatment decisions in a specific cohort of patients with lower esophageal and gastroesophageal junction adenocarcinoma who were considered for potentially curative treatment on the basis of conventional imaging. Materials and methodsThe study included patients referred for a staging 18F-FDG PET/CT who were considered for potentially curative treatment (neoadjuvant therapy followed by surgery or definitive chemoradiotherapy) by a multidisciplinary tumor board. The proportion of patients with M1b disease (American Joint Committee on Cancer, 6th ed.) detected on 18F-FDG PET/CT was calculated. The sensitivity, specificity, positive and negative predictive values, and accuracy of 18F-FDG PET/CT for M1b disease were calculated. PET/CT findings were verified with histopathological analysis; when it was not possible to obtain pathological confirmation, correlative imaging or follow-up imaging studies were used for validation. ResultsA total of 156 patients who fulfilled the inclusion criteria were analyzed. 18F-FDG PET/CT detected M1b disease in 25 patients (16%), changing the intent of treatment from potentially curative to palliative. In five patients, PET/CT failed to detect distant metastases. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 18F-FDG PET/CT for detecting M1b disease were 83.3, 98.4, 92.5, 96.1, and 95.3%, respectively. Additional surgical procedures (hemicolectomy and polypectomy) were performed in three patients because of the detection of a second primary cancer in the colon in two patients and a colonic dysplastic polyp in one patient. ConclusionIn patients who are considered to be potentially curable after conventional imaging, 18F-FDG PET/CT can detect unsuspected sites of distant metastases (M1b) in a significant number of cases and thus contribute to the clinical decision-making process. PET/CT should be an integral part of the staging workup of patients with esophageal adenocarcinoma.

Positron emission tomography / computerized tomography evaluation of primary Hodgkin's disease of liver

Occurrence of primary Hodgkins lymphoma (PHL) of the liver is extremely rare. We report on a case of a 60-year-old male who presented with liver mass and B-symptomatology. Hepatoma or hepatic metastasis from a gastrointestinal primary was initially suspected. Tumor markers like AFP, CEA, Total PSA, and CA-19.9 were within normal limits. Positron Emission Tomography / Computerized Tomography (PET/CT) revealed a large hepatic lesion and a nodal mass in the porta hepatis. A liver biopsy was consistent with Hodgkins lymphoma. There was complete regression of the hepatic lesion and evidence of shrinkage of the nodal mass following four cycles of chemotherapy. 18F Fluro -de-oxy Glucose (FDG) PET / CT in this case helped in establishing a primary hepatic lymphoma by demonstrating the absence of pathologically hypermetabolic foci in any other nodes or organs. PET / CT scan is a useful adjunct to conventional imaging and histopathology, not only to establish the initial diagnosis, but also to monitor treatment response in PHL.