Reproducibility of FDG PET/CT image-based cancer staging and standardized uptake values with simulated reduction of injected FDG dose or acquisition time.

18F-fluorodeoxyglucose (FDG) PET/CT is widely used for oncologic imaging. This study aimed to evaluate, using data simulation, if reduction of injected FDG dose or PET acquisition time could be technically feasible when utilizing a sensitive commercial PET/CT imaging system, without sacrificing image quality, image-based staging accuracy, or standardized uptake value (SUV) accuracy. De-identified, standard of care oncologic FDG PET/CT datasets from 83 adults with lymphoma, lung carcinoma or breast carcinoma were retrospectively analyzed. All images had been acquired using clinical standard dose and acquisition time on a single PET/CT system. The list mode datasets were retrospectively software reprocessed to achieve undersampling of counts, thus simulating the effect of shorter PET acquisition time or lower injected FDG dose. The simulated reduced-count images were reviewed and compared with full-count images to assess and compare qualitative (subjective image quality, stage stability) and semi-quantitative (image noise, SUVmax stability, signal-to-noise and contrast-to-noise ratios within index lesions driving cancer stage) parameters. While simulated reduced-count images had measurably greater noise, there appeared to be no significant loss of image-based staging accuracy nor SUVmax reproducibility down to simulated FDG dose of 0.05 mCi/kg at continuous bed motion rate of 1.1 mm/sec. This retrospective simulation study suggests that a modest reduction of either injected FDG dose or emission scan time might be feasible in this limited oncologic population scanned on a single PET/CT system. Verification of these results with prospectively acquired images using actual low injected FDG activity and/or short imaging time is recommended.

Uncommon causes of thyrotoxicosis.

Apart from the common causes of thyrotoxicosis, such as Graves' disease and functioning nodular goiters, there are more than 20 less common causes of elevated free thyroid hormones that produce the symptoms and signs of thyrotoxicosis. This review describes these rarer conditions and includes 14 illustrative patients. Thyrotropin and free thyroxine should be measured and, when the latter is normal, the free triiodothyronine level should be obtained. Measurement of the uptake of (123)I is recommended for most patients.

Update 2018: 18F-FDG PET/CT and PET/MRI in Head and Neck Cancer.

There are recent advances, namely, a standardized method for reporting therapy response (Hopkins criteria), a multicenter prospective cohort study with excellent negative predictive value of F-FDG PET/CT for N0 clinical neck, a phase III multicenter randomized controlled study establishing the value of a negative posttherapy F-FDG PET/CT for patient management, a phase II randomized controlled study demonstrating radiation dose reduction strategies for human papilloma virus-related disease, and Food and Drug Administration approval of nivolumab for treatment of recurrent head and neck squamous cell carcinoma.

A Bayesian analysis of the true sensitivity of a temporal artery biopsy.

PURPOSE: The temporal artery biopsy (TAB) has long been the standard for diagnosing temporal arteritis (TA), but in practice this test is less than 100% sensitive; false-negative biopsy results are known to occur. The true sensitivity of a single TAB cannot be directly observed, because there is no true gold standard for comparison. The authors propose a mathematical method for calculating the true sensitivity of the TAB, using data from published bilateral TAB RESULTS: METHODS: Based on Bayesian methodology, this statistical technique can be used to calculate the true sensitivity of a single TAB with data from studies reporting the results of bilateral simultaneous TABs. This technique also allows for calculation of the true prevalence of TA in a study population. Bootstrap techniques are used to provide confidence intervals. This technique is applied to data derived from four studies in the literature. results. With this methodology, the sensitivity of a single TAB is calculated to be 87.1% (95% confidence interval, 81.8%-91.7%). CONCLUSIONS: Knowledge of the true sensitivity of any imperfect test is necessary for an accurate decision analysis, because it can affect the optimal diagnostic-therapeutic pathway. Although few studies report results of bilateral simultaneous TABs, such data are important because they permit the calculation of the true TAB sensitivity. The authors believe that this mathematical method is superior to observational methods (e.g., clinical criteria) for estimating the true sensitivity of a TAB.

Clinical value of including the head and lower extremities in 18F-FDG PET/CT imaging for patients with malignant melanoma.

OBJECTIVE: To assess the added benefit of scanning lower extremities and skull in addition to 'skull base to upper thigh' images in PET/CT evaluation of metastatic melanoma. SUBJECTS/METHODS: Reports of consecutive whole-body PET/CT scans from January 2003 to March 2006 in patients with melanoma were retrospectively reviewed. PET abnormalities in the brain/scalp and lower extremities were tabulated by location and whether they were 'anticipated' or 'unanticipated' based on previously available data. Findings were correlated with pathology, other imaging studies, and clinical follow-up. RESULTS: Two hundred and ninety-six PET/CT examinations in 173 patients with melanoma were included. Twenty-five of the 296 (8.4%) scans showed brain/scalp abnormalities. Of these, only four (1.4% of all scans) showed unanticipated abnormalities: two were false positive findings, and two (0.7% of all scans) represented metastases in addition to multiple other metastases in the usual field of view. Fifty-nine of the 296 (19.9%) scans showed lower extremity abnormalities. Of these, 13 (4.4% of all scans) showed unanticipated abnormalities which were equivocal or suggestive of malignancy: eight (2.7% of all scans) represented metastases in addition to multiple other metastases in the usual field of view, and five represented false positive findings. In no case was an unanticipated isolated malignant lesion identified in the brain/scalp or lower extremities. CONCLUSIONS: In patients with no known or suspected primary or metastatic melanoma involving the head or extremities, inclusion of these regions on PET/CT is of low yield and appears to offer little significant additional benefit, as detection of additional metastases in these patients is unlikely to change clinical management. Routine skull base to upper thigh images may be adequate for this subset of patients with melanoma.

Incidental gallbladder visualization on nonhepatobiliary nuclear medicine studies: case series and review of the literature.

Gallbladder uptake is occasionally encountered with commonly used nonhepatobiliary radiopharmaceuticals. Identification of the biliary tract by a nonhepatobiliary agent can identify disease, such as uptake of labeled white blood cells. However, in most cases, gallbladder uptake of nonhepatobiliary tracers is not due to pathology in these cases. It is important to avoid attributing gallbladder uptake to disease in the gallbladder or adjacent anatomic structures. We present 3 cases of unexpected gallbladder tracer uptake and provide a review of the literature describing incidental gallbladder uptake on nonhepatobiliary nuclear medicine studies. The potential for misdiagnosis and the steps taken to avoid this are discussed.

Management of the patient with suspected temporal arteritis a decision-analytic approach.

OBJECTIVE: To perform a decision analysis of temporal arteritis (TA) to guide clinicians in the interpretation of diagnostic testing and choice of therapy. DESIGN: Computer-based decision analytic model. METHODS: A 785-node decision tree was created that reflects common testing and therapeutic options for a patient with suspected TA. A comprehensive literature search was then performed. From this search, point estimates and distributions for pooled probabilities and utilities were derived using inverse variance weighting and random effects techniques. Employing utility analysis, this decision model selects the diagnostic/therapeutic pathway resulting in the greatest utility for any user-defined set of patient characteristics on presentation. MAIN OUTCOME MEASURE: Using utility analysis, the diagnostic/therapeutic pathway that results in the least expected disutility is selected as the optimal course of action. RESULTS: The choice of diagnostic testing depends on several factors, including patient age, symptoms, and clinical findings. These factors can be used to calculate the pretest probability of TA being present. The optimal selection of diagnostic tests (laboratory or biopsy) depends on the pretest probability of disease. A temporal artery biopsy is recommended under most circumstances, with the choice of a unilateral versus bilateral biopsy depending upon blood test results and calculated pretest probability. A few scenarios exist in which blood tests alone can rule in or rule out TA without the need for biopsy. Empiric steroid therapy is almost never recommended. CONCLUSIONS: In TA, both the disease and its treatment are hazardous for the patient. Clinicians should have a very low threshold to initiate a diagnostic workup for TA. Physicians are often uncertain when a temporal artery biopsy is indicated and whether to perform a unilateral or bilateral biopsy. Often, the pathway chosen is not evidence based. Although the biopsy has long been considered the gold standard for diagnosis, it is invasive and less than 100% sensitive. The decision whether to undertake unilateral or bilateral biopsies is difficult, and our decision model delineates a method for choosing.

99mTc-oxidronate uptake within urothelial carcinoma confirmed with SPECT/CT imaging.

A 63-year-old woman with recurrent urothelial carcinoma was referred for skeletal scintigraphy to evaluate for osseous metastatic disease. The bone scan showed no osseous metastatic disease, but did show intense focal radiotracer accumulation along the left aspect of the urinary bladder. SPECT/CT images localized this uptake to a calcified bladder wall mass corresponding with the biopsy-proven (via cystoscopy) recurrent tumor. This case demonstrates that (a) some tumors may accumulate radionuclide bone tracer, emphasizing the need for careful evaluation of nonosseous structures during bone scan interpretation; (b) SPECT/CT is useful for clarifying potentially confusing findings and preventing misdiagnosis.

Reporting guidance for oncologic 18F-FDG PET/CT imaging.

The written report (or its electronic counterpart) is the primary mode of communication between the physician interpreting an imaging study and the referring physician. The content of this report not only influences patient management and clinical outcomes but also serves as legal documentation of services provided and can be used to justify medical necessity, billing accuracy, and regulatory compliance. Generating a high-quality PET/CT report is perhaps more challenging than generating a report for other imaging studies because of the complexity of this hybrid imaging modality. This article discusses the essential elements of a concise and complete oncologic (18)F-FDG PET/CT report and illustrates these elements through examples taken from routine clinical practice.

(153)Sm-EDTMP appears to accumulate only trivially within peritoneal ascites.

UNLABELLED: (153)Sm-lexidronam (EDTMP) is a therapeutic radiopharmaceutical used for palliation of pain resulting from osseous metastatic disease. METHODS: We recently treated with (153)Sm-EDTMP a patient who had extensive osseous metastases and malignant ascites requiring intermittent drainage from an indwelling catheter. Because we could find no useful data regarding quantification of accumulation of this agent within ascites, we opted to assay the fluid after treatment. RESULTS: The measured ratio of (153)Sm-EDTMP activity in peritoneal fluid (1.71 L) relative to injected dose was 0.01% (i.e., trivially above background level). CONCLUSION: To our knowledge, this represents the first published measurement of (153)Sm-EDTMP accumulation within peritoneal fluid. This information may be useful to the nuclear medicine community since malignant ascites is not uncommon in patients with widely metastatic carcinoma and such patients may be referred for (153)Sm-EDTMP therapy.