No abstract

The combined metabolic and morphological information of FDG PET/CT imaging allows high sensitivity for the detection of various sarcomas and accurate discrimination between newly diagnosed low-grade and high-grade sarcomas.

The purpose of this study was to determine the actual standardized uptake value (SUV) by using the lesion size from computer tomography (CT) scan to correct for resolution and partial volume effects in positron emission tomography (PET) imaging. This retrospective study included 47 patients with lung lesions seen on CT scan whose diagnoses were confirmed by biopsy or by follow up CT scan when the PET result was considered negative for malignancy. Each lesion's FDG uptake was quantified by the SUV using two methods: by measuring the maximum voxel SUV (maxSUV) and by using the lesion's size on CT to calculate the actual SUV (corSUV). Among small lesions (2.0 cm or smaller on CT scan), ten were benign and 17 were malignant. The average maxSUV was 1.43+/-0.77 and 3.02+/-1.74 for benign and malignant lesions respectively. When using an SUV of 2.0 as the cutoff to differentiate benignity and malignancy, the sensitivity, specificity, and accuracy were 65%, 70%, and 67% respectively. When an SUV of 2.5 was used for cutoff, the sensitivity, specificity, and accuracy were 47%, 80%, and 59% respectively. The average corSUV was 1.65+/-1.09 and 5.28+/-2.71 for benign and malignant lesions respectively. Whether an SUV of either 2.0 or 2.5 was used for cutoff, the sensitivity, specificity, and accuracy remained 94%, 70%, and 85% respectively. The only malignant lesion that was falsely considered benign with both methods was a bronchioalveolar carcinoma which did not reveal any elevated uptake of fluorine-18 fluorodeoxyglucose (FDG). Of the large lesions (more than 2.0 cm and less than 6.0 cm), one was benign and 19 were malignant and the corSUV technique did not significantly change the accuracy. It is concluded that measuring the SUV by using the CT size to correct for resolution and partial volume effects offers potential value in differentiating malignant from benign lesions in this population. This approach appears to improve the accuracy of FDG-PET for optimal characterization of small lung nodules.

Hip arthroplasty is a common surgical procedure, but the diagnosis of infection associated with hip arthroplasty remains challenging. Fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) has been shown to be a promising imaging modality in settings where infection is suspected. However, inflammatory reaction to surgery can result in increased FDG uptake at various anatomic locations, which may erroneously be interpreted as sites of infection. The purpose of this study was to assess the patterns and time course of FDG accumulation following total hip replacement over an extended period of time. Firstly, in a prospective study nine patients with total hip replacement were investigated to determine the patterns of FDG uptake over time. Three FDG-PET scans were performed in each patient at about 3, 6 and 12 months post arthroplasty. Secondly, in a retrospective analysis, the medical and surgical history and FDG-PET imaging results of 710 patients who had undergone whole-body scans for the evaluation of possible malignant disorders were reviewed. The history of arthroplasty and FDG-PET findings in the hip region were reviewed for this study. Patients with symptomatic arthroplasties or related complaints during FDG-PET scanning were excluded from the analysis. During the entire study period, all nine patients enrolled in the prospective study were demonstrated to have increased FDG uptake around the femoral head or neck portion of the prosthesis that extended to the soft tissues surrounding the femur. Among the patients reviewed in the retrospective study, 18 patients with a history of 21 hip arthroplasties who were asymptomatic at the time of FDG-PET scan met the criteria for inclusion. The time interval between the hip arthroplasty and the FDG-PET study ranged from 3 months to 288 months (mean+/-SD: 80.4+/-86.2 months). In 81% (17 of 21) of these prostheses, increased FDG uptake could be noted around the femoral head or neck portion of the prosthesis. The average time interval between arthroplasty and FDG-PET scan in these patients was 71.3 months. In only four prostheses (19%, 4 of 21) was no abnormally increased FDG uptake seen around the prostheses or adjacent sites. The average time interval in these patients was 114.8 months. It is concluded that following hip arthroplasty, non-specifically increased FDG uptake around the head or neck of the prosthesis persists for many years, even in patients without any complications. Therefore, to minimize the number of false-positive results for infection with PET studies obtained to evaluate a painful hip prosthesis, caution should be exercised when interpreting FDG uptake around the head or neck portion of the prosthesis.

Perioperative DCF is a tolerable and highly effective regimen for the treatment of esophagogastric ADC.

It is known that following a traumatic fracture or surgical intervention, bone scintigraphy reveals positive results for an extended period of time, posing a challenge when evaluating patients for possible malignancy or superimposed osteomyelitis. Previous reports indicate that acute fractures can also result in increased fluorine-18 fluorodeoxyglucose (FDG) accumulation and therefore cause difficulties when patients are evaluated for other indications by FDG-PET. The purpose of this study was to assess the pattern and time course of abnormal FDG uptake following traumatic or surgical fracture. A total of 1,517 consecutive patients who underwent whole-body FDG-PET imaging were retrospectively studied. A history of fractures or orthopedic intervention was obtained from an interview prior to scanning. The FDG-PET results were compared with the results of other imaging studies, including bone scans, radiographs, CT, and MRI, as well as surgical pathology reports. Thirty-seven patients with a known date of traumatic or surgical fracture were identified. Among these, 14 had fractures or surgery within 3 months prior to FDG-PET, while 23 had fractures or surgical intervention greater than 3 months prior to FDG-PET. FDG-PET showed no abnormally increased uptake at the known fracture or surgical sites in 30 of these patients. Notably, in the 23 patients with fractures more than 3 months old, all but one showed no abnormally increased uptake. Furthermore, the positive FDG uptake in this exception was a result of complicating osteomyelitis. In the 14 patients with a history of fracture less than 3 months old, only six had abnormally increased FDG uptake. Following traumatic or surgical fractures, FDG uptake is expected to be normal within 3 months unless the process is complicated by infection or malignancy.

Soft-tissue sarcomas spread predominantly to the lung and it is unclear how often FDG-PET scans will detect metastases not already obvious by chest CT scan or clinical examination. Adult limb and body wall soft-tissue sarcoma cases were identified retrospectively. Ewing's sarcoma, rhabdomyosarcoma, GIST, desmoid tumors, visceral tumors, bone tumors, and retroperitoneal sarcomas were excluded as were patients imaged for followup, response assessment, or recurrence. All patients had a diagnostic chest CT scan. 109 patients met these criteria, 87% of which had intermediate or high-grade tumors. The most common pathological diagnoses were leiomyosarcoma (17%), liposarcoma (17%), and undifferentiated or pleomorphic sarcoma (16%). 98% of previously unresected primary tumors were FDG avid. PET scans were negative for distant disease in 91/109 cases. The negative predictive value was 89%. Fourteen PET scans were positive. Of these, 6 patients were already known to have metastases, 3 were false positives, and 5 represented new findings of metastasis (positive predictive value 79%). In total, 5 patients were upstaged by FDG-PET (4.5%). Although PET scans may be of use in specific circumstances, routine use of FDG PET imaging as part of the initial staging of soft-tissue sarcomas was unlikely to alter management in our series.

There was a statistically significant correlation between the mitotic count and the SUV(max) as well as between the presence of tumor necrosis and the SUV(max). Although a correlation between the presence of a myxoid component and SUV(max) was shown, it was not found to be statistically significant. These findings improve on the current information in the literature regarding the use of PET/CT for guidance in sarcoma biopsy. Correlating the SUV(max) with histologic markers that also feature prominently in major sarcoma grading systems may help improve the accuracy of grading and of prognostication by allowing the SUV(max) to potentially serve as a surrogate marker in these grading systems, particularly in cases in which there is interobserver disagreement in the pathologic diagnosis or in cases in which the sarcoma cannot be properly classified on the basis of histopathologic evaluation alone.