Ameya D Puranik

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.

Role of FDG PET/CT in assessing response to targeted therapy in metastatic lung cancers: Morphological versus metabolic criteria

Introduction: Targeted therapeutic agents are indicated in metastatic lung cancers. These being receptor specific therapies, manifestation of response can be best assessed by estimating the metabolic activity of tumor, rather than the size. This retrospective analysis studied metabolic and morphological response on Positron Emission Tomography (PET) and Computed Tomography (CT), respectively to these agents. Materials and Methods: Thirty-one patients (23 males, 8 females with an age range of 42–77 years) with Epidermal Growth Factor Receptor (EGFR) positive metastatic lung cancer on Gefitinib, who underwent PET/CT, at baseline and at 4–6 weeks, were assessed by Response Evaluation Criteria In Solid Tumors [RECIST] 1.1 and European Organization for Research and Treatment of Cancer (EORTC) criteria. Results: Concordance between RECIST 1.1 and EORTC was seen in 26 (83.7%) patients. Discordance was seen in 5 (16.3%) patients. In patients with discordance, the results were confirmed by follow-up imaging. Metabolic EORTC criteria changed the disease status from stable disease to partial response (3 out of 5) and progressive disease (2 out of 5) in these five patients. Conclusions: Metabolic criteria using PET/CT could accurately predict response as well as disease progression early in the course of targeted therapy, compared to morphologic criteria. In addition, early metabolic response assessment can predict refractoriness of therapy.

Imaging spectrum of peritoneal carcinomatosis on FDG PET/CT.

Recognition of patterns has always been extremely important in cross-sectional imaging. Peritoneal involvement, both primary and as dissemination from abdominopelvic malignancies, is manifested in different forms, purely because of anatomical complexity. We studied series of peritoneal involvement by 18F-fluorodeoxyglucose positron-emission tomography/computed tomography fusion imaging and derived patterns of tracer uptake on maximum intensity projection and cross-sectional fusion images.

Common malignant brain tumors: can 18F-FDG PET/CT aid in differentiation?

Objectives The objectives of this study were to evalute the metabolic characteristics of common malignant space-occupying lesions (SOL) of the brain and to determine the utility of fluorine-18-fluorodeoxyglucose (18F-FDG) PET/CT in differentiating between the common types of malignant brain SOL. Patients and methods All patients with brain SOL who were referred for an 18F-FDG PET/CT scan by a multidisciplinary team were included in this retrospective study. The metabolic characteristics of the brain lesions in the form of maximum standardized uptake value (SUVmax) along with tumor-to-background activity ratios were determined and differences were compared using nonparametric statistical tests. Histopathological confirmation was used as the gold standard in all patients. Receiver operating characteristic curve analysis was used to find the optimal SUVmax cutoff to differentiate the tumor types. Results Glioblastoma multiforme (GBM; n=30), lymphoma (n=25), and metastases (n=46) accounted for most malignant tumors (95.2%). Lymphomas showed a significantly high metabolic uptake (median SUVmax=20.3, range: 8.1–46.3) compared with GBM ( median SUVmax=10.3, range: 2.6–21.7) and metastases (median SUVmax=11.5, range: 2.9–19.6) (P=0.00). The tumor-to-background activity ratios for lymphomas were also significantly higher. There was an overlap in the metabolic uptake of GBM and metastases, with no significant difference between their SUVmax values (P=0.245). A SUVmax more than 15.5 showed an 84% sensitivity and an 80% specificity to diagnose lymphomas (area under the curve=0.876, P=0.00). Four patients with brain lymphoma had extracranial disease on 18F-FDG PET. Lung cancer was the most common primary malignancy in patients with brain metastases. Conclusion Central nervous system lymphomas can be differentiated from GBM and metastases by their higher metabolic activity. In addition, 18F-FDG PET/CT can potentially impact therapeutic decisions by detecting primary malignancy in patients with metastatic brain lesions and extracranial disease sites in patients with brain lymphoma.

Post-treatment appearances, pitfalls, and patterns of failure in head and neck cancer on FDG PET/CT imaging

Majority of patients with head and neck cancer are treated with combined treatment regimes such as surgery, radiation therapy, and chemotherapy. The loss of structural symmetry and imaging landmarks as a result of therapy makes post-treatment imaging a daunting task on conventional modalities like computed tomography (CT) scan and magnetic resonance imaging (MRI) as well as on 18 Fluorine-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F FDG PET/CT). Combined multimodality treatment approach causes various tissue changes that give rise to a spectrum of findings on FDG PET/CT imaging, which are depicted in this atlas along with a few commonly encountered imaging pitfalls. The incremental value of FDG PET/CT in detecting locoregional recurrences in the neck as well as distant failures has also been demonstrated.

Response assessment in metronomic chemotherapy: RECIST or PERCIST?

Introduction: Metronomic chemotherapy (MC) is a novel therapeutic variation for resistant cancers, wherein chemotherapeutic drugs are administrated in low doses with no prolonged drug-free break. It lessens the level of toxicity, is better tolerated and enhances the quality of life. This retrospective analysis was undertaken to evaluate whether anatomical (computed tomography [CT]) or functional (positron emission tomography [PET]) imaging be used for response assessment in patients on MC. Materials and Methods: A total of 16 males and 27 females with age range of 12-83 years on MC who underwent PET/CT were assessed by new response evaluation criteria in solid tumors (RECIST 1.1) and PET response criteria in solid tumors (PERCIST 1.0). Results: Concordance between RECIST 1.1 and PERCIST was seen in 32 (75%) patients. There was discordance in 11 (25%) patients. In patients with discordance, the results were confirmed by follow-up imaging. PET upstaged the disease in 81% of patients (9/11) and down-staged the disease in 19% of patients (2/11). Conclusions: Metabolic response accurately identified the disease status as assessed by clinical or imaging follow-up. Alteration in morphology takes time to manifest, which is demonstrated by CT or magnetic resonance; whereas in MC which brings about tumor dormancy, assessing metabolic response by PET would be more appropriate. MC is usually given in palliative setting but in few cases complete metabolic response was demonstrated in our study. In such a scenario this form of treatment has the potential to become an adjunct mode of treatment in some tumors. This needs to be evaluated with larger, homogenous patient population in a prospective mode.

Isolated mandibular condylar metastases: an uncommon manifestation of recurrent cervical cancer.

Bone metastases from recurrent cervical cancer is a rare scenario, with commonly involved sites being lumbar spine and pelvic bones report an extremely rare manifestation of cervical cancer recurrence presenting as a painful jaw swelling due to metastasis to the mandibular condyle.

Rare solitary focal tuberculous involvement of liver masquerading as hepatic metastasis on FDG PET/CT in a case of fibular round cell tumor

Finding of focal 18F-fluoro-deoxyglucose (FDG) uptake in liver on FDG positron emission tomography/computed tomography (FDG PET/CT) in a known case of malignancy is often considered to be metastases. We report a similar finding on FDG PET/CT in a case of Ewings sarcoma of thigh, which turned out to be of tuberculous etiology, an unusual cause of false positive FDG uptake in the liver.

Asymptomatic myocardial metastasis from cancers of upper aero-digestive tract detected on FDG PET/CT: a series of 4 cases

Metastatic involvement of the heart is a rare occurrence and remains undiagnosed until autopsy. In some instances, patients may have cardiac symptoms, leading to ante-mortem diagnosis. Although most primary cancers have been documented to metastasize to heart, the existing literature on cancers of upper aero-digestive tract is an exception, with only a few reports. We report four cases of upper aero-digestive tract cancers, three of which arise from oral cavity, one from lower esophagus, metastasising to the myocardium, detected on 18 F – Fluoro-deoxy-glucose Positron Emission Tomography/Computed Tomography (FDG PET/CT) study , in the absence of related symptoms.

Intense focal Fluoro-deoxyglucose uptake in the lungs with no corresponding computed tomography abnormality

Scenario such as uptake of Fluoro-deoxyglucose (FDG) with no corresponding abnormality on computed tomography (CT) is encountered in case of brown fat uptake. However, it is rarely encountered in the lung parenchyma. We report one such case of a focal FDG uptake in the lung parenchyma with no corresponding CT abnormality, in a treated case of hypopharyngeal cancer.