Rathan M. Subramaniam

Clinical Significance of Diffusely Increased 18F-FDG Uptake in the Thyroid Gland

Our purpose was to determine the clinical significance of diffusely increased 18F-FDG uptake in the thyroid gland as an incidental finding on PET/CT. Methods: All patients who were found to have diffuse thyroid uptake on 18F-FDG PET/CT in our institution between November 2004 and June 2006 were investigated and compared with an age- and sex-matched control group. The 18F-FDG uptake in the thyroid was semiquantified using maximum standardized uptake value and correlated to the available serum thyroid-stimulating hormone (TSH) and thyroid peroxidase (TPO) antibody levels using regression analysis. Results: Of the 4,732 patients, 138 (2.9%) had diffuse thyroid uptake. Clinical information was available for 133 of the 138 patients. Sixty-three (47.4%) had a prior diagnosis of hypothyroidism or autoimmune thyroiditis, of whom 56 were receiving thyroxine therapy. In the control group, consisting of 133 patients with no thyroid uptake, there were 13 (9.8%) with a prior diagnosis of hypothyroidism, 11 of whom were receiving thyroxine therapy. In the study group, 38 (28.6%) of 133 patients did not undergo any further investigation for thyroid disease, whereas 32 (24.1%) of 133 patients were examined for thyroid disease after PET. Nineteen were found with autoimmune thyroiditis or hypothyroidism, and replacement therapy was initiated in 12. No significant correlation was found between maximum standardized uptake value and TSH (P = 0.09) or TPO antibody (P = 0.68) levels. Conclusion: The incidental finding of increased 18F-FDG uptake in the thyroid gland is associated with chronic lymphocytic (Hashimotos) thyroiditis and does not seem to be affected by thyroid hormone therapy. SUV correlated neither with the degree of hypothyroidism nor with the titer of TPO antibodies.

The Value of [18F]Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Extranodal Natural Killer/T—Cell Lymphoma

PURPOSEnTo our knowledge, there are no published data pertinent to the use of [(18F)]fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in patients with natural killer (NK)/T-cell lymphoma. The purpose of this study was to assess the value of FDG PET/CT in this aggressive type of non-Hodgkin lymphoma.nnnPATIENTS AND METHODSnAll patients with NK/T-cell lymphoma referred for FDG PET/CT at our institution from July 2001 to July 2006 were retrospectively studied. PET/CT examinations were blindly reviewed by 2 experienced readers. The results were compared with the status of the disease, which was determined after evaluation of biopsy, laboratory, clinical and conventional imaging examination, and follow-up results. PET/CT results were thereby classified as true-positive, true-negative, false-positive, or false-negative. The degree of FDG uptake in the positive lesions was semiquantified using maximum standard uptake value (SUV(max)).nnnRESULTSnTwenty-one PET/CT examinations were performed in 10 patients with NK/T-cell lymphoma. For nasal disease, PET/CT was true-positive in 5 cases, true-negative in 15 cases, and positive but unconfirmed in 1 case. For extranasal disease, PET/CT was true-positive in 3 cases, true-negative in 16 cases, and false-negative in 2 cases. The mean SUV(max) in PET-positive lesions in nasal cavities or paranasal sinuses was 16 gm/mL (range, 5-25 gm/mL; median, 19.3 gm/mL). In extranasal disease, the mean SUV(max) was 10.9 gm/mL (range, 4.6-34.1 gm/mL; median, 5.6 gm/mL).nnnCONCLUSIONnViable NK/T-cell lymphoma is intensely FDG hypermetabolic. PET/CT appears to be sensitive for the detection of disease in the nasopharynx and, to a lesser extent, in extranasal sites.

Utility of Integrated Computed Tomography—Positron Emission Tomography for Selection of Operable Malignant Pleural Mesothelioma

BACKGROUNDnMalignant pleural mesothelioma (MPM) is a primary malignancy characterized by local invasion of the pleura and metastasis. Despite advances in computed tomography (CT) and magnetic resonance imaging (MRI), accurately staging patients remains challenging. Recent studies have examined the use of integrated CT-positron emission tomography (PET) for staging patients.nnnMATERIALS AND METHODSnMayo Clinic databases were queried to identify cases with a histologic diagnosis of MPM from 2000 to 2006. Inclusion criteria were a diagnosis of MPM, an available CT scan, and an initial staging integrated CT-PET scan. A total of 35 patients were identified who met the inclusion criteria. Computed tomography and integrated CT-PET scans were reviewed by experienced radiologists. Laboratory parameters were reviewed. The Mayo Clinic tumor registry and Social Security database were queried for survival data in patients in which no follow-up was available.nnnRESULTSnFindings on integrated CT-PET excluded 14 of 35 patients from surgical intervention. Extrapleural pneumonectomies (EPPs) were performed in 8 patients, and partial pleurectomies were performed in 2 patients. Upstaging from integrated CT-PET occurred in 70% of the patients when surgical pathology was available, 2 cases to an inoperable stage. Although not statistically significant, median survival was 20 months for patients undergoing an EPP and 12 months for patients excluded from surgical intervention by integrated CT-PET.nnnCONCLUSIONnMalignant pleural mesothelioma is a difficult disease to accurately stage. The most common reason for upstaging in our series was an increase in T (tumor; tumor-node-metastasis staging system) disease. Our data suggest that integrated CT-PET is excellent for detecting nodal and distant metastases. However, the ability of this imaging modality to correctly stage locoregional disease is not superior to the combination of CT and MRI as reported in the literature.

Pulmonary Embolism Outcome: A Prospective Evaluation of CT Pulmonary Angiographic Clot Burden Score and ECG Score

OBJECTIVEnThe purpose of this study was to establish whether a correlation exists between the CT pulmonary angiographic clot burden score, the ECG score at diagnosis, and the 12-month mortality rate among patients diagnosed with pulmonary embolism.nnnSUBJECTS AND METHODSnA total of 523 consecutive patients who underwent CT pulmonary angiography for a suspected moderate to high pretest probability of pulmonary embolism were recruited from March 2003 to October 2004. There were 105 patients with positive CT pulmonary angiography examinations. Two consultant respiratory physicians and two consultant radiologists independently and prospectively calculated an ECG score and a quantified pulmonary artery clot burden, respectively. Twelve-month follow-up was completed in all patients.nnnRESULTSnThe mean ECG score was 2.36 (SD, 2.84) and the mean clot burden score percentage was 23.74% (16.8%). Poor correlation (r = 0.09) was seen between the average ECG score and the average clot burden score percentage (p = 0.39) at diagnosis. Thirteen patients had died at the 12-month follow-up. The mean ECG score for those patients who were alive was 2.4 (2.91) and for those who had died was 2.03 (2.34) at 12 months (p = 0.65). The mean clot burden score percentage for those patients who were alive was 24% (17%) and for those who had died was 22.1% (15.7%) at 12 months (p < 0.73).nnnCONCLUSIONnNo statistically significant association was seen between ECG score and CT pulmonary angiographic clot burden at diagnosis and the 12-month all-cause mortality rate of patients diagnosed with pulmonary embolism.

18F-FDG PET/CT in primary central nervous system lymphoma in HIV-negative patients

ObjectiveTo determine the value of 18F-FDG PET/CT in the different manifestations of primary central nervous system lymphoma (PCNSL) in HIV-negative patients. MethodsAll PCNSL and HIV-negative patients referred for PET/CT in our institution from July 2001 to June 2006 were retrospectively studied. PET/CT examinations were reviewed by two experienced readers and evaluated for each possible anatomical site of nervous system involvement: cerebral, spinal/nerve and ocular. PET/CT results were characterized as true positive or negative and false positive or negative according to the status of the disease, which was determined after the evaluation of biopsies, laboratory, clinical and imaging examinations, and follow-up. ResultsForty-two PET/CT examinations were carried out in 25 PCNSL patients. For intracerebral disease, PET/CT was true positive in 13 cases, true negative in 27 and false negative in two. For disease involving spinal cord and/or nerves, PET/CT was true positive in four cases, true negative in 37 and false negative in one. For ocular disease, PET was true positive in only one case and false negative in four. The sensitivity of PET/CT in detecting active disease in the brain was 87% (13/15), in the spine/nerves 80% (4/5), and in the eyes only 20% (1/5). ConclusionPET/CT seems to be sensitive for the detection of viable intracerebral as well as for spinal and peripheral nerve disease, but not for the detection of ocular involvement.

Occult Malignancy in Patients With Suspected Paraneoplastic Neurologic Syndromes: Value of Positron Emission Tomography in Diagnosis

OBJECTIVEnTo determine the value of positron emission tomography (PET) in diagnosing occult malignancies in patients with paraneoplastic neurologic syndromes (PNSs) at Mayo Clinics site in Rochester, MN.nnnPATIENTS AND METHODSnWe retrospectively reviewed the medical charts of all 107 patients who underwent PET from January 1, 2000, to July 31, 2006, for the indication of suspected PNS. Three patients did not meet inclusion criteria. PET results were considered positive if increased fludeoxyglucose F 18 uptake indicated malignancy (24 patients). Results from computed tomography were interpreted as positive if any suspect lesion was consistent with malignancy (26 patients).nnnRESULTSnOne hundred four patients with PNS were identified from the PET central database; 73 patients had at least 1 positive result for paraneoplastic antibody, and 31 had antibody-negative PNS. Malignancy was confirmed pathologically in 10 patients, of whom 8 had positive PET results. There were 2 cases of confirmed malignancy (fallopian tube adenocarcinoma and spindle cell uterine carcinoma) for which PET results were negative. Two patients with positive PET results declined biopsy. Computed tomography was able to identify 3 of the 10 malignancies detected. Five cases of malignancy were detected only by PET. All patients with confirmed malignancy had positive results for at least 1 paraneoplastic antibody. One patient with positive results for PNS antibody and negative PET results was diagnosed as having small cell carcinoma on a follow-up PET scan after 27 months. PET had sensitivity, specificity, positive predictive value, and negative predictive value of 80%, 67%, 53%, and 88%, respectively.nnnCONCLUSIONnPET scan was shown to be more sensitive than computed tomography for detecting occult malignancy (confirmed by positive test results for autoantibody) among patients with suspected PNS. The greatest clinical utility of PET could be in its high negative predictive value.

Contribution of F-18 FDG PET-CT in the detection of systemic spread of primary central nervous system lymphoma

Purpose: Primary central nervous system lymphoma (PCNSL) accounts for ∼3% of all primary brain tumors and 1% of all non-Hodgkin lymphomas. Detection of systemic spread of PCNSL, although rare (4%), is very important since therapy is usually modified. Contrast-enhanced computed tomography (CT) is commonly used for systemic staging of PCNSL. No previous case report is available in the published literature elaborating the potential contribution of F-18 FDG PET in systemic staging of PCNSL. The purpose of this case report was to document the potential usefulness of F-18 FDG-PET in the detection of occult systemic involvement in PCNSL. Materials and Methods: A 50-year-old, immunocompetent, male patient completed successful treatment of PCNSL. As part of a routine pretransplant evaluation he had an F-18 FDG PET coregistered with CT (PET-CT). The PET-CT results were then compared with those of contrast-enhanced CT of the chest, abdomen, and pelvis. Results: The PET-CT examination detected multiple sites of extranodal systemic disease that were not seen in the contrast-enhanced CT of the chest, abdomen, and pelvis (both studies were performed within 24 hours of each other). Percutaneous ultrasound guided biopsy confirmed the presence of systemic spread of PCNSL. The patients subsequent therapy was modified to include rituximab with cyclophosphamide, doxorubicin, vincristine, prednisone (R-CHOP). A follow up PET-CT confirmed resolution of systemic spread. Conclusion: F-18 FDG PET coregistered to CT may be a useful examination in the detection and monitoring for systemic spread of the disease in PCNSL patients.

Focal F-18 fluoro-deoxy-glucose accumulation in the lung parenchyma in the absence of CT abnormality in PET/CT

Objective: To demonstrate 3 cases of artifactual focal F-18 fluoro-deoxy-glucose accumulation in the lung parenchyma in the absence of any computed tomographic (CT) abnormality. Materials and Methods: Three patients were examined: a 30-year-old man who had a positron emission tomography (PET)/computed tomography for restaging a biopsy-proven recurrence of head and neck cancer, a 68-year-old woman who was referred for initial staging of esophageal carcinoma, and a 57-year-old man who had a PET/computed tomography for initial staging of melanoma. In each case, there was intense focal activity in the lung parenchyma with no corresponding CT abnormality. Each patient was further evaluated with a repeat PET scan in days 1 and 3 in the first 2 cases and with a delayed repeat acquisition in the third case. Patients were followed for 24, 10, and 1 month, respectively. Results: In the first 2 cases, the abnormal focal activity in the lungs had resolved in the repeat study. In the third case, the focus of increased activity in the lung had moved more peripherally in the delayed acquisition. Clinical follow-up was negative for disease in the corresponding pulmonary parenchymal sites. Conclusions: The finding of significant focal accumulation of fluoro-deoxy-glucose in the lung parenchyma in the absence of corresponding CT abnormality was artifactual. This was likely due to injection technique and the creation of particulate embolus. Positron emission tomography/Computed tomographic readers should be aware of this type of artifact to avoid misinterpretation.

[18F]fluoro-L-DOPA PET/CT in congenital hyperinsulinism

Abstract Congenital hyperinsulinism can be divided into diffuse or focal form. The treatment and outcome depend on distinguishing between the 2 forms. Pancreatic venous sampling was the only method available to localize the insulin secretion. [18F]Fluoro-levodopa, 3,4-dihydroxy-L-phenylalanine positron emission tomography/computed tomography is a noninvasive imaging investigation and increasingly used to determine the type of hyperinsulinism preoperatively. We present a case of diffuse form of congenital hyperinsulinism demonstrated by the [18F]levodopa, 3,4-dihydroxy-L-phenylalanine positron emission tomography/computed tomography preoperatively and review the literature.

F-18 fluorodeoxyglocose positron emission tomography/computed tomography in the diagnosis of chronic myopathic sarcoidosis

Muscle involvement is a frequent histopathological feature of sarcoidosis, occurring in 50% to 80% of patients, but it is rarely symptomatic, and often, underreported. Although computed tomography and magnetic resonance imaging findings of muscular sarcoidosis have been described, the fluorodeoxyglucose positron emission tomography imaging characteristics have only recently been reported in a case of localized uptake in the lower extremities. We present a case of diffuse uptake within the most common clinical variant of symptomatic muscular sarcoidosis, chronic myopathy, showing significant uptake of F-18 fluorodeoxyglocose on a positron emission tomography/computed tomography fusion examination.