Calibration of the EBT3 Gafchromic Film Using HNN Deep Learning.

To achieve a dose distribution conformal to the target volume while sparing normal tissues, intensity modulation with steep dose gradient is used for treatment planning. To successfully deliver such treatment, high spatial and dosimetric accuracy are crucial and need to be verified. With high 2D dosimetry resolution and a self-development property, the Ashland Inc. product EBT3 Gafchromic film is a widely used quality assurance tool designed especially for this. However, the film should be recalibrated each quarter due to the "aging effect," and calibration uncertainties always exist between individual films even in the same lot. Recently, artificial neural networks (ANN) are applied to many fields. If a physicist can collect the calibration data, it could be accumulated to be a substantial ANN data input used for film calibration. We therefore use the Keras functional Application Program Interface to build a hierarchical neural network (HNN), with the inputs of net optical densities, pixel values, and inverse transmittances to reveal the delivered dose and train the neural network with deep learning. For comparison, the film dose calculated using red-channel net optical density with power function fitting was performed and taken as a conventional method. The results show that the percentage error of the film dose using the HNN method is less than 4% for the aging effect verification test and less than 4.5% for the intralot variation test; in contrast, the conventional method could yield errors higher than 10% and 7%, respectively. This HNN method to calibrate the EBT film could be further improved by adding training data or adjusting the HNN structure. The model could help physicists spend less calibration time and reduce film usage.

Calibration of Gafchromic EBT Film Using the Microtek ScanMaker 9800XL Plus Flatbed Scanner with a Modified One Red-Channel after Three-Channel Method.

PURPOSE: Using the Microtek ScanMaker 9800XL Plus (9800XL+) flatbed scanner, a method is presented to accurately calibrate EBT film, which cannot be calibrated simply using a general three-channel method because of the nonhomogeneous scanning. MATERIALS AND METHODS: Through the percentage-depth-dose method, 6-MV photon beams with two different monitor units were delivered to eight EBT2 films, each of which was tightly sandwiched in a 30-cm cubic polystyrene phantom and positioned parallel to the central axis of the beam. Before and after irradiation, all films were scanned using the Microtek 9800XL+ scanner and the pixel values (PVs) were measured along the central axis of the beam on the film and fitted to the corresponding depth doses. Before calibration, the irradiated film image was first modified using a template matrix, which was generated using the prescanned background images. Then, a modified one red-channel after three-channel method was used to calibrate the film. RESULTS: Without a template matrix, the three-channel method cannot be used because the PVs do not correspond to a rational fitting form. Using the proposed method, the difference between the fitted dose and the delivered dose is <2%. The green channel, and not the red, is found to have the largest dynamic range. CONCLUSION: The proposed technique allows the use of the three-channel method to calibrate film using a Microtek 9800XL+ scanner.

Investigated geometrical characteristics and image density of left ventricle of multi-detector computed tomography in early coronary artery disease patients.

BACKGROUND: Coronary artery disease (CAD) remains the leading cause of death worldwide. Currently, cardiac multi-detector computed tomography (MDCT) is widely used to diagnose CAD. The purpose in this study is to identify informative and useful predictors from left ventricular (LV) in the early CAD patients using cardiac MDCT images. MATERIALS AND METHODS: Study groups comprised 42 subjects who underwent a screening health examination, including laboratory testing and cardiac angiography by 64-slice MDCT angiography. Two geometrical characteristics and one image density were defined as shape, size and stiffness on MDCT image. The t-test, logistic regression, and receiver operating characteristic curve were applied to assess and identify the significant predictors. The Kappa statistics was used to exam the agreements with physician's judgments (i.e., Golden of True, GOT). RESULTS: The proposed three characteristics of LV MDCT images are important predictors and risk factors for the early CAD patients. These predictors present over 80% of AUC and higher odds ratio. The Kappa statistics was 0.68 for the combinations of shape and stiffness into logistic regression. CONCLUSIONS: The shape, size and stiffness of the left ventricular on MDCT can be used to be the effective indicators in the early CAD patients. Besides, the combinations of shape and stiffness into logistic regression could provide substantial agreement with physician's judgments.

Ir-192 Calibration in Air with Farmer Chamber for HDR Brachytherapy.

A comprehensive review for the in-air calibration of an Ir-192 high-dose-rate brachytherapy source in terms of air kerma strength (AKS) and reference air kerma rate (RAKR) using the Farmer chamber was conducted. The reviewed calibration methods include the National Physical Laboratory (NPL) calibration standard in the UK, the 7-distance technique with the standard calibration of the National Institute of Standards and Technology and Accredited Dosimetry Calibration Laboratory in the US, the calibration conducted in Australia following recommendations of the International Atomic Energy Agency with the chamber primarily calibrated by the Australian Radiation Protection and Nuclear Safety Agency, the calibration conducted in India following the Deutsche Gesellschaft fur Medizinische Physik recommendation, and the convenient empirical method used in Taiwan. The calibrated AKS (or RAKR) and uncertainty obtained using Farmer chambers are similar to those obtained using well chambers. All reported differences (between measurements obtained using Farmer and well chambers, respectively) and uncertainties (k = 2) were generally less than 1.5 and 2.5 %, respectively. The standard uncertainty of the NPL calibration is approximately half that of all the other proposed approaches, and may become the gold standard calibration procedure. Almost all techniques follow the 7-distance technique basis; however, the services at NPL can calibrate the source with lower uncertainty. Users can calibrate the Ir-192 source more conveniently using the empirical method with only one source-chamber distance.

Calibration of EBT2 film using a red-channel PDD method in combination with a modified three-channel technique.

PURPOSE: Ashland Inc. EBT2 and EBT3 films are widely used in quality assurance for radiation therapy; however, there remains a relatively high degree of uncertainty [B. Hartmann, M. Martisikova, and O. Jakel, "Homogeneity of Gafchromic EBT2 film," Med. Phys. 37, 1753-1756 (2010)]. Micke et al. (2011) recently improved the spatial homogeneity using all color channels of a flatbed scanner; however, van Hoof et al. (2012) pointed out that the corrected nonuniformity still requires further investigation for larger fields. To reduce the calibration errors and the uncertainty, the authors propose a new red-channel percentage-depth-dose method in combination with a modified three-channel technique. METHODS: For the ease of comparison, the EBT2 film image used in the authors' previous study (2012) was reanalyzed using different approaches. Photon beams of 6-MV were delivered to two different films at two different beam on times, resulting in the absorption doses of ranging from approximately 30 to 300 cGy at the vertical midline of the film, which was set to be coincident with the central axis of the beam. The film was tightly sandwiched in a 30(3)-cm(3) polystyrene phantom, and the pixel values for red, green, and blue channels were extracted from 234 points on the central axis of the beam and compared with the corresponding depth doses. The film was first calibrated using the multichannel method proposed by Micke et al. (2010), accounting for nonuniformities in the scanner. After eliminating the scanner and dose-independent nonuniformities, the film was recalibrated via the dose-dependent optical density of the red channel and fitted to a power function. This calibration was verified via comparisons of the dose profiles extracted from the films, where three were exposed to a 60° physical wedge field and three were exposed to composite fields, and all of which were measured in a water phantom. A correction for optical attenuation was implemented, and treatment plans of intensity modulated radiation therapy and volumetric modulated arc therapy were evaluated. RESULTS: The method described here demonstrated improved accuracy with reduced uncertainty. The relative error compared with the measurements of a water phantom was less than 1%, and the overall calibration uncertainty was less than 2%. Verification tests revealed that the results were close to those of the authors' previous study, and all differences were within 3%, except those with a high-dose gradient. The gamma pass rates (2%/2 mm) of the treatment plan evaluated using the method described here were greater than 99%, and no obvious stripe patterns were observed in the dose-difference maps. CONCLUSIONS: Spatial homogeneity was significantly improved via the calibration method described here. This technique is both convenient and time-efficient because it does not require cutting the film, and only two exposures are necessary.

Using [¹8F]FBAU for imaging brain tumor progression in an F98/tk-luc glioma-bearing rat model.

1-(2-Deoxy-2-[18F]fluoro-ß-D-arabinofuranosyl)-5-bromouracil ([18F]FBAU), a substitute for thymine, has been reported as an effective reporter probe by which to trace cellular metabolism with its positron emission. In the present study, a rat xenograft model bearing F98 glioma transfected with dual reporter genes, herpes simplex virus type 1 thymidine kinase (HSV1-tk) and firefly luciferase (luc) was used for monitoring tumor progression by multimodalities of molecular imaging using [18F]FBAU and D-luciferase as probes. Rat F98 glioma cells were transfected with the pC1-tk-IRES-luc vectors. The selected stable clone was renamed as the F98/tk-luc cell line. Fischer 344 male rats bearing orthotropic F98/tk-luc gliomas in the left brain were used. On day 13 post tumor inoculation, biodistribution, positron emission tomography (PET), magnetic resonance imaging (MRI) and ex vivo autoradiography were performed. The surviving fraction of F98/tk-luc cells treated with 15 µM ganciclovir (GCV) was 15.9%, and the uptake of [131I]FIAU in these cells was significantly enhanced when compared with F98 cells. The correlation coefficient of tumor volume vs. the bioluminescence in the F98/tk-luc glioma-bearing rats was 0.90. The biodistribution showed that the accumulation ratios of [18F]FBAU for glioma-to-normal brain were 9.16, 14.24, 5.7 and 13.7 at 30, 60, 90 and 120 min post i.v. injection, respectively. Consistent tumor enhancement of [18F]FBAU/PET imaging was also noted from 30-90 min post injection. Ex vivo autoradiography also confirmed significant [18F]FBAU uptake in tumors. In conclusion, [18F]FBAU may be used as a PET probe for monitoring glioma progression in animal models and may have potential for clinical use as well.

Dependency of EBT2 film calibration curve on postirradiation time.

PURPOSE: The Ashland Inc. product EBT2 film model is a widely used quality assurance tool, especially for verification of 2-dimensional dose distributions. In general, the calibration film and the dose measurement film are irradiated, scanned, and calibrated at the same postirradiation time (PIT), 1-2 days after the films are irradiated. However, for a busy clinic or in some special situations, the PIT for the dose measurement film may be different from that of the calibration film. In this case, the measured dose will be incorrect. This paper proposed a film calibration method that includes the effect of PIT. METHODS: The dose versus film optical density was fitted to a power function with three parameters. One of these parameters was PIT dependent, while the other two were found to be almost constant with a standard deviation of the mean less than 4%. The PIT-dependent parameter was fitted to another power function of PIT. The EBT2 film model was calibrated using the PDD method with 14 different PITs ranging from 1 h to 2 months. Ten of the fourteen PITs were used for finding the fitting parameters, and the other four were used for testing the model. RESULTS: The verification test shows that the differences between the delivered doses and the film doses calculated with this modeling were mainly within 2% for delivered doses above 60 cGy, and the total uncertainties were generally under 5%. The errors and total uncertainties of film dose calculation were independent of the PIT using the proposed calibration procedure. However, the fitting uncertainty increased with decreasing dose or PIT, but stayed below 1.3% for this study. CONCLUSIONS: The EBT2 film dose can be modeled as a function of PIT. For the ease of routine calibration, five PITs were suggested to be used. It is recommended that two PITs be located in the fast developing period (1 ∼ 6 h), one in 1 ∼ 2 days, one around a week, and one around a month.

Pretreatment metabolic tumor volumes to predict the short-term outcome of unresectable locally advanced squamous cell carcinoma of the esophagus treated with definitive chemoradiotherapy.

PURPOSE: The aim of the study was to investigate the predictive role of pretreatment metabolic tumor volume (MTV) in patients with squamous cell carcinoma of locally advanced esophageal cancer treated with definitive chemoradiotherapy. PATIENTS AND METHODS: Ninety patients received pretreatment with (18)F-fluorodeoxyglucose ((18)F-FDG) PET/CT, and two types of MTVs were measured on the basis of either a maximal standardized uptake value (SUVmax) of 2.5 (MTV2.5) or a fixed threshold of 20% (MTV20%). Overall survival (OS) and disease-free survival (DFS) were examined, and independent prognosticators were identified by Cox regression analysis. RESULTS: On a median follow-up of 15 months, 51 patients were seen to have died because of tumor recurrence or other illnesses. Multivariate analysis of OS revealed that MTV20%>40 ml was the only predictor of outcome with a lower 1-year OS [P=0.003, hazard ratio (HR)=2.29, 95% confidence interval (CI) 1.36-3.91]. Two independent predictors of DFS were MTV20%>40 ml (P=0.02, HR=1.78, 95% CI 1.09-2.91) and stage IV disease (P=0.01, HR=1.84, 95% CI 1.12-3.03). CONCLUSION: Pretreatment MTV20% is a novel marker for OS and DFS in patients with unresectable locally advanced esophageal cancer treated with definitive chemoradiotherapy. Treatment intensification must be considered for patients with higher MTVs.

FDG PET or PET/CT in evaluation of renal angiomyolipoma.

OBJECTIVE: Angiomyolipoma is the most common benign kidney tumor. However, literature describing FDG PET findings on renal angiomyolipoma (AML) is limited. This study reports the FDG PET and PET/CT findings of 21 cases of renal AML. MATERIALS AND METHODS: The study reviews FDG PET and PET/CT images of 21 patients diagnosed with renal AML. The diagnosis is based on the classical appearance of an AML on CT scan with active surveillance for 6 months. The study is focused on the observation of clinical and radiographic features. RESULTS: Six men and 15 women were included in our study. The mean age of the patients was 57.14 ± 9.67 years old. The mean diameter of 21 renal AML on CT scans was 1.76 ± 1.00 cm (Min: 0.6 cm; Max: 4.4 cm). CT scans illustrated renal masses typical of AMLs, and the corresponding FDG PET scans showed minimal FDG activities in the area of the tumors. None of the 21 AMLs showed a maximum standardized uptake value (SUV(max)) greater than 1.98. No statistically significant correlation was present between SUV(max) and tumor size. CONCLUSION: Renal AMLs demonstrate very low to low uptake on FDG PET and PET/CT imaging in this study. When a fat-containing tumor in the kidney is found on a CT scan, it is critical to differentiate an AML from a malignant tumor including an RCC, liposarcoma, and Wilms tumor. This study suggests that FDG PET or PET/CT imaging is useful for differentiating a renal AML from a fat-containing malignant tumor.

Meta-analysis of the diagnostic performance of [18F]FDG-PET and PET/CT in renal cell carcinoma.

OBJECTIVES: Positron emission tomography (PET) using fluorodeoxyglucose (FDG) is useful for restaging renal cell carcinoma (RCC) and detecting metastatic diseases but is less satisfactory for detecting primary disease. We evaluated whether the integration of computed tomography (CT) scans with the PET system could increase the applicability of FDG-PET for RCC. METHODS: The MEDLINE databases were searched for relevant studies published since 2001. Two reviewers independently assessed the methodological quality of each study identified. We then performed a meta-analysis of the sensitivity and specificity of FDG-PET findings as reported in all the selected studies. RESULTS: Fourteen studies were eligible for inclusion. The pooled sensitivity and specificity of FDG-PET were 62% and 88% respectively, for renal lesions. For detecting extra-renal lesions, the pooled sensitivity and specificity of FDG-PET were 79% and 90%, respectively, based on the scans, and 84% and 91% based on the lesions. The use of a hybrid FDG-PET/CT to detect extra-renal lesions increased the pooled sensitivity and specificity to 91% and 88%, respectively, with good consistency. CONCLUSIONS: For RCC, combining the FDG-PET and CT systems is helpful for detecting extra-renal metastasis rather than renal lesions. The hybrid PET/CT system has comparable sensitivity and specificity with PET in detecting extra-renal lesions of RCC. ADVANCES IN KNOWLEDGE: The FDG-PET and PET/CT systems are both useful for detecting extra-renal metastasis in renal cell carcinoma.

Use of pretreatment metabolic tumor volumes on PET-CT to predict the survival of patients with squamous cell carcinoma of esophagus treated by curative surgery.

AIM: To investigate the prognostic role of the pretreatment metabolic tumor volume (MTV) as determined by Positron emission tomography--computed tomography (PET-CT) in patients with esophageal cancer undergoing curative surgery. PATIENTS AND METHODS: We retrospectively reviewed the data of 26 patients with squamous cell carcinoma of the esophagus, who underwent 18F-Fluorodeoxyglucose PET-CT before surgery. MTVs were defined as the volumes with FDG uptake above a standardized uptake value (SUV) of 2.5 (MTV2.5), or a fixed threshold of 20% (MTV20%) of the maximum intratumoral activity. Overall survival (OS) and disease-free survival (DFS) were examined by the Kaplan-Meier method and the log-rank test. RESULTS: In a median follow-up of 15 months, 13 patients had died. The mean MTV2.5 was 18.9 ± 15.4 ml (median, 16.0), whereas the mean MTV20% was 21.7 ± 15.0 ml (median, 19.1). Patients who had tumors of an MTV2.5 >16.0 ml had an inferior one-year OS compared with patients with a lower MTV2.5 (70% vs. 84%, p=0.018). Similarly, patients with an MTV20% >19.1 ml had poorer outcomes compared with patients who had small tumors, with one-year OS of 69% and 85%, respectively (p=0.016). No statistical significance was found in DFS for both MTV approaches. The SUVp-max had no impact on the OS and the DFS when using a median value of 8.3. CONCLUSION: Pretreatment MTV is a novel marker for OS of patients with esophageal cancer treated with curative surgery. For those with higher MTVs, more aggressive adjuvant treatments should be considered.

Calibration of EBT2 film by the PDD method with scanner non-uniformity correction.

The EBT2 film together with a flatbed scanner is a convenient dosimetry QA tool for verification of clinical radiotherapy treatments. However, it suffers from a relatively high degree of uncertainty and a tedious film calibration process for every new lot of films, including cutting the films into several small pieces, exposing with different doses, restoring them back and selecting the proper region of interest (ROI) for each piece for curve fitting. In this work, we present a percentage depth dose (PDD) method that can accurately calibrate the EBT2 film together with the scanner non-uniformity correction and provide an easy way to perform film dosimetry. All films were scanned before and after the irradiation in one of the two homemade 2 mm thick acrylic frames (one portrait and the other landscape), which was located at a fixed position on the scan bed of an Epson 10 000XL scanner. After the pre-irradiated scan, the film was placed parallel to the beam central axis and sandwiched between six polystyrene plates (5 cm thick each), followed by irradiation of a 20 × 20 cm² 6 MV photon beam. Two different beams on times were used on two different films to deliver a dose to the film ranging from 32 to 320 cGy. After the post-irradiated scan, the net optical densities for a total of 235 points on the beam central axis on the films were auto-extracted and compared with the corresponding depth doses that were calculated through the measurement of a 0.6 cc farmer chamber and the related PDD table to perform the curve fitting. The portrait film location was selected for routine calibration, since the central beam axis on the film is parallel to the scanning direction, where non-uniformity correction is not needed (Ferreira et al 2009 Phys. Med. Biol. 54 1073-85). To perform the scanner non-uniformity calibration, the cross-beam profiles of the film were analysed by referencing the measured profiles from a Profiler™. Finally, to verify our method, the films were exposed to 60° physical wedge fields and the compositive fields, and their relative dose profiles were compared with those from the water phantom measurement. The fitting uncertainty was less than 0.5% due to the many calibration points, and the overall calibration uncertainty was within 3% for doses above 50 cGy, when the average of four films were used for the calibration. According to our study, the non-uniformity calibration factor was found to be independent of the given dose for the EBT2 film and the relative dose differences between the profiles measured by the film and the Profiler were within 1.5% after applying the non-uniformity correction. For the verification tests, the relative dose differences between the measurements by films and in the water phantom, when the average of three films were used, were generally within 3% for the 60° wedge fields and compositive fields, respectively. In conclusion, our method is convenient, time-saving and cost-effective, since no film cutting is needed and only two films with two exposures are needed.

A systematic review and meta-analysis of pretherapeutic lymph node staging of colorectal cancer by 18F-FDG PET or PET/CT.

The purpose of the present study was to conduct a systematic review and meta-analysis of the published literature to evaluate the diagnostic performance of fluorine-18 2-fluoro-2-deoxy-D-glucose (18F-FDG) PET in the pretherapeutic assessment of nodal staging in patients with colorectal cancer (CRC). We conducted a systematic MEDLINE search of articles in the published literature (last update, February 2012). Two reviewers independently assessed the methodological quality of each study. We estimated pooled sensitivity, specificity, summary receiver operating characteristic curves, and summary likelihood ratios. A total of 409 patients from 10 studies were analyzed. The pooled estimates of sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 18F-FDG PET [PET/computed tomography (CT)] in the detection of pretherapeutic lymph node involvement in patients with CRC were 42.9% [95% confidence interval (CI): 36.0-50.0%], 87.9% (95% CI: 82.6-92.0%), 2.82 (95% CI: 1.96-4.07), and 0.69 (95% CI: 0.62-0.78), respectively. There is no solid evidence to support the routine clinical application of 18F-FDG PET (PET/CT) in the pretherapeutic evaluation of lymph node status in patients with CRC. However, 18F-FDG PET (PET/CT) could be used to strengthen the possibility of suspected metastatic lymph nodes detected by other imaging modalities.

Detection of gastroesophageal reflux esophagitis using 2-fluoro-2-deoxy-d-glucose positron emission tomography.

BACKGROUND: Gastroesophageal reflux disease (GERD) is a common disease and a major upper gastrointestinal problem. The purpose of the present study is to evaluate the use of noninvasive 2-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) to detect gastroesophageal reflux esophagitis. MATERIALS AND METHODS: This is a retrospective study reviewing 408 healthy check-up subjects (169 females and 239 men), who underwent both FDG-PET and upper gastrointestinal endoscopy during September 2008 to December 2009. Quantitative analysis of FDG uptake in the distal part of the esophagus was performed by calculating the maximum standard uptake value (SUVmax). This indicated the degree of esophagitis. FDG-PET findings were compared with endoscopic (modified version of the Los Angeles classification) diagnoses as the gold standard. RESULTS: The SUVmax ranged from 1.30 to 3.40 in normal subjects and from 1.30 to 4.00 in subjects with gastroesophageal reflux esophagitis. In the esophagitis group, the SUVmax was 2.13 ± 0.42 in subjects with modified LA grade M, 2.21 ± 0.45 in subjects with LA grade A, and 2.48 ± 0.44 in subjects with LA grade B and C gastroesophageal reflux esophagitis. One-way ANOVA and post-hoc comparison with Bonferroni correction (P value = 0.003) identified statistical differences between the three groups. CONCLUSION: Noninvasive FDG-PET may be useful in the detection and evaluation of various degrees of gastroesophageal reflux esophagitis.

Potential value of dual-time-point ¹8F-FDG PET compared with initial single-time-point imaging in differentiating malignant from benign pulmonary nodules: a systematic review and meta-analysis.

We performed a meta-analysis to assess the potential value of dual-time-point (DTP) imaging as compared with initial single-time-point (STP) scanning with 18F-fluorodeoxyglucose (18F-FDG) PET in differentiating malignant from benign single pulmonary nodules. Data on the performance of DTP 18F-FDG PET imaging in assessing lung nodules were extracted from articles of prospective or retrospective original research published between January 2001 and April 2010. The Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool was used to assess the quality of study methodology. Heterogeneity in the results of the studies was assessed, and summary receiver operating characteristic (SROC) curves were constructed. Eleven studies comprising a total of 788 patients who underwent initial scanning, 778 of whom also underwent DTP imaging, were included in the final analysis. The quality of study methodology was judged to be moderate. Substantial heterogeneity in the results of the studies, with inconsistency (I2) index values above 85%, reflected important differences in study methods and populations, including varying lesion sizes, 18F-FDG avidity, uptake interval for delayed imaging, and threshold for positive result on DTP imaging. SROC curve analysis revealed a statistically nonsignificant trend toward higher sensitivity with DTP imaging, at moderate levels of specificity, when compared with initial STP scanning. The area under the curve (SE) values for DTP and initial STP imaging were 0.839 (0.079) and 0.757 (0.074), respectively. Although the results of our analysis do not support the routine use of DTP imaging with 18F-FDG PET in the differential diagnosis of pulmonary nodules, this technique may provide additional information in selected cases with equivocal results from initial scanning. Further prospective research is required to better define the potential benefits of DTP 18F-FDG PET imaging.

Analyzing coronary artery disease in patients with low CAC scores by 64-slice MDCT.

PURPOSE: Coronary artery calcification (CAC) scores are widely used to determine risk for Coronary Artery Disease (CAD). A CAC score does not have the diagnostic accuracy needed for CAD. This work uses a novel efficient approach to predict CAD in patients with low CAC scores. MATERIALS AND METHODS: The study group comprised 86 subjects who underwent a screening health examination, including laboratory testing, CAC scanning, and cardiac angiography by 64-slice multidetector computed tomographic angiography. Eleven physiological variables and three personal parameters were investigated in proposed model. Logistic regression was applied to assess the sensitivity, specificity, and accuracy of when using individual variables and CAC score. Meta-analysis combined physiological and personal parameters by logistic regression. RESULTS: The diagnostic sensitivity of the CAC score was 14.3% when the CAC score was ≤30. Sensitivity increased to 57.13% using the proposed model. The statistically significant variables, based on beta values and P values, were family history, LDL-c, blood pressure, HDL-c, age, triglyceride, and cholesterol. CONCLUSIONS: The CAC score has low negative predictive value for CAD. This work applied a novel prediction method that uses patient information, including physiological and society parameters. The proposed method increases the accuracy of CAC score for predicting CAD.

Sex- and age-related differences in brain FDG metabolism of healthy adults: an SPM analysis.

BACKGROUND AND PURPOSE: The purpose of our study was aimed to analyze the sex- and age-related differences of brain metabolism in healthy individuals. METHODS: Consecutive 100 healthy subjects, 50 males and 50 females, undergoing routine 2-[(18)F]-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) for health checkup in our hospital were retrospectively enrolled in this study. Statistical parametric mapping (SPM) was used for analyses of the FDG PET images to disclose the possible effects of age on brain metabolism in males and females as well as the differences of brain metabolism between male and female groups. RESULTS: In males and females, decreased brain metabolism with aging is found in bilateral lateral orbital prefrontal and right anterior cingulate cortices. In comparisons between sexes, males are found to have more brain metabolism than females in bilateral visual cortices and cerebellum. CONCLUSIONS: Our report discloses different sex- and age-related brain metabolism. Decreased brain metabolism with aging in males and females is similar to findings reported in previous literatures. However, whether declined brain function or volume with aging causing metabolic changes is unknown and should be further evaluated. Nevertheless, the sex-related differences are possibly compatible with the historical observation of better performance in visual-spatial tasks in males than females.

Clinically unrecognized pulmonary aspiration during gastrointestinal endoscopy with sedation: a potential pitfall interfering the performance of 18F-FDG PET for cancer screening.

PURPOSE: We found several cases with unexpected pulmonary abnormalities on the 18F-FDG PET scan after the gastrointestinal endoscopy with sedation during a compact health check-up course, interfering the interpretations of 18F-FDG PET scan for cancer screening. The current studies aimed to analyze the incidence and the clinical relevance of this pulmonary finding. MATERIALS AND METHODS: From June to December 2009, 127 subjects undergoing the sequential gastrointestinal endoscopy with sedation and 18F-FDG PET scan within 48 h as part of routine health check-up were retrospectively enrolled in this study. The incidence of abnormal pulmonary findings and their SUVmax of FDG were calculated and correlated with the clinical manifestations. RESULTS: Five subjects had abnormal 18F-FDG PET findings but pulmonary symptoms were only found in 2. The SUVmax did not seem to reflect the severity of pulmonary symptoms or the need of intervention. Although the incidence of unrecognized pulmonary aspiration featuring inflammation detected by the 18F-FDG PET scan was high (3.94%, 5/127), the incidence of events needed intervention remained low (0.79%, 1/127), similar to those previously reported literatures. CONCLUSIONS: Although higher incidence of pulmonary aspiration in this study, it probably reflects the better sensitivity of 18F-FDG PET for inflammation. The low incidence of clinical events needed intervention may still reflect the safety of sedation used for gastrointestinal endoscopy. Proper arrangement of the sequential examinations if subjects need both gastrointestinal endoscopy with sedation and 18F-FDG PET is important to reduce the interference degrading the performance of 18F-FDG PET in cancer screening, diagnosis or staging.

Utility of TL-201 SPECT in clarifying false-positive FDG-PET findings due to osteoradionecrosis in head and neck cancer.

BACKGROUND: This study aimed to determine whether Tl-201 single photon emission CT (SPECT) is potentially useful in differentiating false-positive fluorodeoxyglucose positron emission tomography (FDG-PET) findings caused by osteoradionecrosis (ORN) from recurrent head and neck cancer after radiotherapy. METHODS: Five patients were recruited. Dual-phase FDG-PET and dual-phase Tl-201 SPECT were performed for each patient. RESULTS: All 5 patients proved to have ORN without recurrent cancer. By visual interpretation, the results were 4 positive versus 1 negative for PET, and 4 negative versus 1 positive for Tl-201 SPECT. The Tl-201 SPECT clarified 3 of the 4 false-positive PETs to be ORN. Dual-phase semiquantitative studies showed decreased standardized uptake value (SUV) over time in 3 of the 4 false-positive PETs and decreased lesion/background ratio over time in the false-positive Tl-201 SPECT. CONCLUSION: The Tl-201 SPECT may help clarify suspected false-positive FDG uptake caused by ORN. Dual-phase FDG-PET and dual-phase Tl-201 SPECT may also have some value.

Impact of age on FDG uptake in the liver on PET scan.

PURPOSE: The intensity of physiological 18F-2-deoxy-D-glucose (FDG) uptake in the liver varies. It is important to be familiar with the varying degree of FDG accumulation in the liver that represents normal distribution and physiological changes, before attempting to interpret whole-body positron emission tomography (PET) imaging for malignancy detection. The aim of this study is to evaluate the possible factors influencing the intensity of physiological FDG uptake in the liver on FDG PET imaging. MATERIALS AND METHODS: From 2005 to 2007, a total of 339 consecutive healthy subjects, referred from the Department of Community Medicine and Health Examination Center of our hospital for health screening, were retrospectively recruited for analysis. Demographic data were collected from chart records. Whole body FDG PET imaging and serologic determination of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection status were performed on all subjects. The mean and maximum standard uptake values (SUVs) of the liver were calculated. The relationships between sex, age, HBV and HCV infection status, and SUVmax and SUVmean of the liver on FDG PET imaging were evaluated. RESULTS: There was no statistically significant relationship between sex, HBV and HCV infection status and maximum standard uptake value (SUVmax) or mean standard uptake value (SUVmean) of the liver. After adjusting for covariables, age was a statistically significant predictor of SUVmax (B=0.18; P= .001) and SUVmean (B=0.16; P= .004) of the liver on FDG PET imaging. CONCLUSION: Age has a significant and positive impact on both maximum and mean standard uptake values of the liver on FDG PET imaging. High physiological background FDG uptake will reduce diagnostic sensitivity and accuracy for malignancy detection in the liver.