The Evaluation of Cardiac Sarcoidosis with 18F-FDG PET.

Cardiac involvement in sarcoidosis is associated with poor prognosis. (18)F-FDG PET can detect the presence of cardiac sarcoidosis, assess disease activity, and serve as a means to monitor treatment response in patients with cardiac sarcoidosis.

Detection of Aberrant Right Subclavian Artery by PET/CT.

An aberrant right subclavian artery can be diagnosed by PET/CT, as demonstrated in this case of a 70-y-old man undergoing PET/CT for staging of squamous cell carcinoma of the right lung. It is important to report this finding during the evaluation of oncologic patients, to prevent severe complications that may arise from various oncologic interventions.

Glucose metabolism gene expression patterns and tumor uptake of ¹8F-fluorodeoxyglucose after radiation treatment.

PURPOSE: To investigate whether radiation treatment influences the expression of glucose metabolism genes and compromises the potential use of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) as a tool to monitor the early response of head and neck cancer xenografts to radiation therapy (RT). METHODS AND MATERIALS: Low passage head and neck squamous cancer cells (UT14) were injected to the flanks of female nu/nu mice to generate xenografts. After tumors reached a size of 500 mm(3) they were treated with either sham RT or 15 Gy in 1 fraction. At different time points, days 3, 9, and 16 for controls and days 4, 7, 12, 21, 30, and 40 after irradiation, 2 to 3 mice were assessed with dynamic FDG-PET acquisition over 2 hours. Immediately after the FDG-PET the tumors were harvested for global gene expression analysis and immunohistochemical evaluation of GLUT1 and HK2. Different analytic parameters were used to process the dynamic PET data. RESULTS: Radiation had no effect on key genes involved in FDG uptake and metabolism but did alter other genes in the HIF1α and glucose transport-related pathways. In contrast to the lack of effect on gene expression, changes in the protein expression patterns of the key genes GLUT1/SLC2A1 and HK2 were observed after radiation treatment. The changes in GLUT1 protein expression showed some correlation with dynamic FDG-PET parameters, such as the kinetic index. CONCLUSION: (18)F-fluorodeoxyglucose positron emission tomography changes after RT would seem to represent an altered metabolic state and not a direct effect on the key genes regulating FDG uptake and metabolism.

Time sensitivity factor of single pulmonary nodule: a new cancer characteristic metabolic parameter by (18) F-FDG PET.

OBJECTIVE: To calculate the time sensitivity factor (S) for discriminating the solitary pulmonary nodule (SPN) by FDG PET at different time points. METHODS: The multiple time-point FDG PET images from 41 patients for evaluating SPN seen on chest X-ray or CT were prospectively analyzed to calculate and evaluate S against the gold standard of tissue histology (n = 38) or long term clinicoradiographic follow-up (n = 3). The maximal standardized uptake values (SUV) at the 3 hourly time points were measured. The S was calculated using S = d{ln⁡(SUV)}/d{ln⁡(t)} at 3 different time intervals. ROC analysis of the S parameters was performed to evaluate the optimal cut-off value and their accuracy in classifying the SPN. RESULTS: The SUV in malignant SPN was higher than the corresponding value in benign lesions at all 3 hourly time points (P < 0.003). The S parameters using 3 different time intervals all significantly separated the two groups (P < 0.0005) with an optimal cut-off point near the theoretical value of zero with a high sensitivity of 100% and specificity of 86%. CONCLUSION. The S can be calculated for SPNs using multiple time-point FDG PET, providing a tumor characteristic metabolic parameter with high discrimination power using a simple positive value representing malignancy.

Use of SPECT/CT with 99mTc-MDP bone scintigraphy to diagnose sacral insufficiency fracture.

Bone SPECT/CT offers additional information on pelvic insufficiency fractures, especially when there is incomplete formation of the H-sign on planar bone scanning.

Early treatment response monitoring using 2-deoxy-2-[ 18F]fluoro-D-glucose positron emission tomography imaging during fractionated radiotherapy of head neck cancer xenografts.

BACKGROUND: To determine the optimal timing and analytic method of 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography (PET) imaging during fractionated radiotherapy (RT) to predict tumor control. METHODS: Ten head neck squamous cell carcinoma xenografts derived from the UT-14-SCC cell line were irradiated with 50 Gy at 2 Gy per day over 5 weeks. Dynamic PET scans were acquired over 70 minutes at baseline (week 0) and weekly for seven weeks. PET data were analyzed using standard uptake value (SUV), retention index (RI), sensitivity factor (SF), and kinetic index (Ki). RESULTS: Four xenografts had local failure (LF) and 6 had local control. Eighty scans from week 0 to week 7 were analyzed. RI and SF after 10 Gy appeared to be the optimal predictors for LF. In contrast, SUV and Ki during RT were not significant predictors for LF. CONCLUSION: RI and SF of PET obtained after the first week of fractionated RT were the optimal methods and timing to predict tumor control.

MicroPET/CT imaging of an orthotopic model of human glioblastoma multiforme and evaluation of pulsed low-dose irradiation.

PURPOSE: Glioblastoma multiforme (GBM) is an aggressive tumor that typically causes death due to local progression. To assess a novel low-dose radiotherapy regimen for treating GBM, we developed an orthotopic murine model of human GBM and evaluated in vivo treatment efficacy using micro-positron-emission tomography/computed tomography (microPET/CT) tumor imaging. METHODS: Orthotopic GBM xenografts were established in nude mice and treated with standard 2-Gy fractionation or 10 0.2-Gy pulses with 3-min interpulse intervals, for 7 consecutive days, for a total dose of 14 Gy. Tumor growth was quantified weekly using the Flex Triumph (GE Healthcare/Gamma Medica-Ideas, Waukesha, WI) combined PET-single-photon emission CT (SPECT)-CT imaging system and necropsy histopathology. Normal tissue damage was assessed by counting dead neural cells in tissue sections from irradiated fields. RESULTS: Tumor engraftment efficiency for U87MG cells was 86%. Implanting 0.5 × 10(6) cells produced a 50- to 70-mm(3) tumor in 10 to 14 days. A significant correlation was seen between CT-derived tumor volume and histopathology-measured volume (p = 0.018). The low-dose 0.2-Gy pulsed regimen produced a significantly longer tumor growth delay than standard 2-Gy fractionation (p = 0.045). Less normal neuronal cell death was observed after the pulsed delivery method (p = 0.004). CONCLUSION: This study successfully demonstrated the feasibility of in vivo brain tumor imaging and longitudinal assessment of tumor growth and treatment response with microPET/CT. Pulsed radiation treatment was more efficacious than the standard fractionated treatment and was associated with less normal tissue damage.

Model-based radiation dose correction for yttrium-90 microsphere treatment of liver tumors with central necrosis.

PURPOSE: The objectives of this study were to model and calculate the absorbed fraction ϕ of energy emitted from yttrium-90 ((90)Y) microsphere treatment of necrotic liver tumors. METHODS AND MATERIALS: The tumor necrosis model was proposed for the calculation of ϕ over the spherical shell region. Two approaches, the semianalytic method and the probabilistic method, were adopted. In the former method, the range--energy relationship and the sampling of electron paths were applied to calculate the energy deposition within the target region, using the straight-ahead and continuous-slowing-down approximation (CSDA) method. In the latter method, the Monte Carlo PENELOPE code was used to verify results from the first method. RESULTS: The fraction of energy, ϕ, absorbed from (90)Y by 1-cm thickness of tumor shell from microsphere distribution by CSDA with complete beta spectrum was 0.832 ± 0.001 and 0.833 ± 0.001 for smaller (r(T) = 5 cm) and larger (r(T) = 10 cm) tumors (where r is the radii of the tumor [T] and necrosis [N]). The fraction absorbed depended mainly on the thickness of the tumor necrosis configuration, rather than on tumor necrosis size. The maximal absorbed fraction φ that occurred in tumors without central necrosis for each size of tumor was different: 0.950 ± 0.000, and 0.975 ± 0.000 for smaller (r(T) = 5 cm) and larger (r(T) = 10 cm) tumors, respectively (p < 0.0001). CONCLUSIONS: The tumor necrosis model was developed for dose calculation of (90)Y microsphere treatment of hepatic tumors with central necrosis. With this model, important information is provided regarding the absorbed fraction applicable to clinical (90)Y microsphere treatment.

Incremental value of integrated FDG-PET/CT in evaluating indeterminate solitary pulmonary nodule for malignancy.

OBJECTIVES: The objective of this study was to evaluate the increased diagnostic benefit of integrated positron emission tomography/computed tomography (PET/CT) interpretation in evaluating solitary pulmonary nodules for malignancy. METHODS: One hundred seventeen patients (67 men and 50 women; mean age +/- SD, 61.7 +/- 13.6 years, range, 31-86 years) with indeterminate solitary pulmonary nodules and no previous history of malignancy were analyzed. PET/CT was performed with an integrated PET/CT scanner (Siemens Biograph BGO duo) 1 h after an intravenous injection of 370 MBq (10 mCi) (18)F-fluorodeoxyglucose. Patients fasted for 6 h before imaging. PET was interpreted alone or combined with CT and was graded according to a five-point scale. A malignant diagnosis was based on histological findings or a clinical and radiological follow-up after at least 24 months. The diagnostic performances of PET alone and integrated PET/CT interpretation were evaluated using discriminant analysis. RESULTS: PET alone correctly classified 85% of nodules and integrated PET/CT interpretation increased the correct classification to 89%, with similar sensitivity and specificity of 88% and 89%, respectively. False-positive PET results mainly resulted from granulomatous disorders. Four (50%) of the eight cases deemed indeterminate on PET alone were resolved with combined PET/CT interpretation. CONCLUSIONS: Although the benefit attributable to the CT component was limited when integrated PET/CT was used, PET and CT acted synergistically to significantly increase the diagnostic veracity for PET-indeterminate nodules.

FDG positron emission tomography/computed tomography scan may identify mantle cell lymphoma patients with unusually favorable outcome.

OBJECTIVE: Patients diagnosed with mantle cell lymphoma (MCL) have generally poor prognosis, but a minority have a longer survival. There are no markers to identify this group and no generally established prognostic index for MCL. Our objective was to assess the prognostic value of the staging FDG PET/computed tomography (CT) scan. METHODS: We retrospectively analyzed initial scans performed at three institutions on biopsy-proven, cyclin D (+) MCL patients. The association of the SUVmax of the 'hottest focus' with overall survival (OS) and failure-free survival (FFS) was evaluated. Receiver operating characteristic analysis of SUVmax versus survival was used to establish a cut-off point of 4.83. In addition, PET findings were compared with contrast-enhanced CT performed within 3 weeks in patients from one institution. RESULTS: Both the OS and FFS for patients with SUVmax greater than 5 were significantly decreased (P<0.01 and <0.001, respectively) as compared with the patients with SUV < or = 5. The 5-year OS for group with SUVmax < or = 5 was 87.7% and for SUVmax greater than 5 it was 34%. For SUVmax < or = 5, the median FFS was 45.3 months as compared with 10.6 months for SUVmax greater than 5. PET changed the stage as compared with CT alone in 45% of patients. CONCLUSION: Staging FDG PET/CT is superior to CT and may be used in the future for identification of a subset of MCL patients with a better outcome than otherwise expected.