Single CT Scan Research Articles

SU‐FF‐T‐431: 4D Monte Carlo Dose Calculations for Particle Therapy Combined with a Computational Biomechanical Model of Lung Motion

Purpose: To evaluate the impact of respiratory motion on particle therapy and to realize 4D planning while keeping CT exposure as low as possible. To accomplish this, we develop a Monte Carlo dose calculation system combined with a computational biomechanical model of lung motion. Method and Materials: The human lung was CT scanned for a single phase of a respiratory motion. The CT images were transformed into tetrahedral elements by automated segmentation. Then, the respiratory motion was simulated using a computational biomechanical model called the spring network model, and the calculated 3D shape of the lung for a given phase was transformed to a voxel data set. For each phase, assuming carbon‐ion beam irradiation, biological dose distribution was calculated using the Monte Carlo particle and heavy ion transport code PHITS coupled with a microdosimetric kinetic model. The dose was mapped onto the reference data set to obtain the accumulated dose. Results: We have developed the first version of the 4D dose calculation system. The lung motion is realistically reproduced. The Monte Carlo module can successfully read the data set for each phase and calculate the accumulated dose. How many phases to use and their weights can be set arbitrarily, without need of additional CT scanning. Our first simulations for a 70 MeV/u carbon ion beam with a diameter of 2 cm indicate that the dose distribution can significantly change with phase and that many data sets may be needed to accurately evaluate the dose to the surrounding normal tissue. Conclusion: The impact of the system we developed is two‐fold: in the short term, it can be used to investigate different issues of 4D treatment planning; our goal is an entirely simulation‐based 4D planning from a single CT scanning. The system is being developed further.

WE‐C‐BRB‐02: A Support Vector Machine (SVM) Classifier Identifies From Prone CT Simulation the Optimal Set Up for Breast Radiotherapy

Purpose: To determine optimal (prone vs. supine) treatment positions for breast radiotherapy by classifying geometric features extracted from prone CT scans. Method and Materials: CT scans from patients enrolled in NYU 05‐181 Protocol were studied to discern predicting factors for optimizing treatment positions for breast radiotherapy. Each of the 400 patients accrued for this protocol underwent CT simulation and planning in both supine and prone positions. The treatment set up was chosen based on maximum sparing of heart and lung. Since the results demonstrated that most patients were best treated prone, we studied whether a support vector machine (SVM) classifier could successfully predict optimal position based on a single prone CT scan and limit a second supine CT only to the minority of women best treated supine. To build this classifier, prone CT scans of NYU 05‐181 were de‐identified and exported in DICOM RT format. Three‐dimensional shape and distance features were computed from organs at risk and the planning target volume in the CT scans. We used a k‐fold cross validation procedure to test the performance of the SVM classifier. Results: Images of 36 patients (23 prone‐treated and 13 supine‐treated) were used. Preliminary results indicate that breast volume, heart and lung involvement in the treatment field are significant predicting factors. A weighting of 1:5 (prone‐treated: supine‐treated) was used when determining the soft margin hyper plane of the SVM classifier. The purpose is to increase the specificity [true‐supine/ (true‐supine+false‐prone)] of the classifier since patients classified as prone will not receive a validation supine CT scan. A sensitivity [true‐prone/(true‐prone+false‐supine)] of 87% and a specificity of 92% was achieved using 11 geometric features and the SVM classifier. Conclusion: Preliminary data support the use of a feature‐based classification to predict the optimal treatment position from prone CT scans.

Can abdominal bioelectrical impedance refine the determination of visceral fat from waist circumference?

Ryo et al (2005 Diabetes Care 28 451–3) reported a new method for measuring the visceral fat area (VFA) by combining abdominal bioelectrical impedance analysis (BIA) with measurement of waist circumference (WC), but very few methodological details were provided. Furthermore, the study did not test the use of WC alone as an indicator of VFA even though others had previously reported a strong correlation. We sought to determine the optimal measurement technique and analysis for measuring VFA by abdominal BIA and WC. 18 volunteers (age 23–64 years) underwent measurement of WC, abdominal impedance (Bodystat 500 four-electrode system) and a single cross-sectional CT scan at the umbilicus. VFA derived using WC3 and measurements of abdominal impedance from electrode pairs sited at the flank predicted the value of VFA measured by CT with correlation r = 0.904 (p < 0.0001); the optimizing power of WC was 3.3 (r = 0.905). However, the use of WC1.9 alone, without involving BIA at all, provided a similar correlation (r = 0.923). Our small preliminary study shows that abdominal BIA is potentially a practicable non-invasive technique for measurement of VFA but casts doubt on whether it adds any value to the use of WC alone. Larger studies are now required to test this finding.

Lower radiation dose coronary CT angiography with new imaging technologies

Developments in multidetector computed tomography (MDCT) are largely driven by the goal of high quality, reproducible, and accurate coronary CT angiography that is simple to perform and simple to interpret. Until recently, 64-slice CT was considered state-of-the-art; the 64 slices per gantry rotation were achieved with either 64-detector rows, or 32-detector rows and a strategy to double the slice number by alternating the focal spot of the X-ray source. These ‘‘64-generation’’ scanners offered considerable advantages over earlier technology such as superior spatial resolution and volume coverage. Temporal resolution was dramatically improved with the introduction of dual source CT. All four CT vendors have released new products for cardiac CT since November 2007 at the annual meeting of the Radiological Society of North America (RSNA). Many developments have focused on lowering the patient radiation dose and applications for lower dose imaging. Some of these features were available for ‘‘64-generation’’ scanners, although doses using these technologies varied [1]. The group of new technologies can be called the ‘‘post-64’’ era [2] of coronary CT angiography (CTA). This collection of advances is difficult to name more descriptively because, unlike the evolution from 4 to 64 detector row coronary CTA, current CT releases are far from uniform, reflecting different approaches to image acquisition in the post-64 era. No single CT scanner offers the full portfolio of newest features. However, each offers coronary CTA with radiation doses reported (or marketed, for those new technologies that do not have peer-review publications to date) as comparable to, or lower than, conventional coronary angiography. This Special Edition compiles peer-review low dose imaging articles from authors who use all major CT platforms. Below is a brief summary of new cardiac CT technologies as of February 2009. The descriptions are far from complete, but additional detail will be found in the pages to follow, including an overview of dose reduction techniques from Dr. Halliburton. Most cardiovascular imagers primarily use only one CT platform. This potentially introduces bias. Under normal circumstances, such bias could be considered detrimental. However, in this Special Issue the editorial staff has purposely solicited input from users of each vendor. The most recent strategy (US approval in October 2008) for cardiac CT imaging features a scanner with two 4 cm detectors (dual source), each with 64 detector rows (128 slices each with an alternating focal spot) and a 285 ms gantry rotation time (Somatom Definition Flash, Siemens Medical Systems, F. J. Rybicki (&) Applied Imaging Science Laboratory, Department of Radiology, Noninvasive Cardiovascular Imaging Program, Brigham and Women’s Hospital & Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA e-mail: frybicki@partners.org

Meta-Analysis of Cranial CT Scans in Children

Objective: We aimed to estimate the risks of radiation exposure from a single head CT scan to children of different ages. Materials and Methods: We constructed a multistate time-dependent Markov model to simulate the course of children exposed to a head CT. The relevant literature was reviewed for probabilities, which were used to calculate tumor types, latencies after exposure and outcomes in the model. Where multiple approximations of the same probability had been reported, meta-analytic techniques were employed to compute pooled estimates. The model was then used to calculate the effect of the radiation exposure on life expectancy and quality of life for children following head CT at different ages. Results: The tumors likely to be induced by low-level cranial irradiation include thyroid carcinoma (47%), meningioma (34%) and glioma (19%). According to the model, a single head CT is likely to cause one of these tumors in 0.22% of 1-year-olds, 30% of whom will consequently die. The exposure will shorten the life expectancy of all exposed 1-year-olds by an average of 0.04 years and their expected quality of life by 0.02 quality-adjusted life years. The risks of radiation exposure diminish for older children. Conclusions: The model predicts that the effective radiation dose from a single head CT is capable of inducing a thyroid or brain tumor in an infant or child. These tumors can severely impact both quality of life and life expectancy. Care should be taken before ordering CT scans in children, particularly in infants and toddlers.

Abstract 4181: Dual-Energy CT of the Heart for Diagnosing Coronary Artery Stenosis and Myocardial Ischemia - Comparison with SPECT

A single dual-energy CT (DECT) scan can assess coronary anatomy and detect myocardial perfusion defects (PD) seen on SPECT. 28 patients underwent SPECT myocardial perfusion imaging, invasive coronary angiography (ICA), and a single contrast medium-enhanced, retrospectively ECG-gated DECT scan using a dual-source CT system with simultaneous acquisition of high and low x-ray spectra. Scan data was used to reconstruct anatomic coronary CT angiographic (cCTA) images and to map the myocardial iodine distribution on virtually non-contrast enhanced long- and short-axis views of the left ventricle. Two independent observers analyzed all DECT studies for coronary artery stenosis and myocardial blood-pool deficits. Segmental comparison was performed between DECT, ICA, and SPECT. Data were analyzed using the Bayesian model. 484 myocardial segments were evaluated. 135 segments in 21 patients showed blood-pool deficits on DECT. In all territories where DECT showed blood-pool deficits, SPECT or catheter angiography confirmed PD or critical stenosis. Overall, DECT had 94.4% sensitivity and 95.2% specificity with 95% accuracy for detecting PD seen on SPECT. In patients without significant stenosis and negative SPECT (n=7), DECT showed no sign of blood-pool deficits. Interobserver agreement was very good (weighted kappa = 0.87). Compared with ICA, cCTA reconstructions had 98% sensitivity, 88% specificity and 92% accuracy for detection of &gt;50% stenosis. Initial experience suggests that DECT may be promising for the comprehensive analysis of coronary artery morphology and the myocardial blood pool in good agreement with ICA and SPECT.

WE‐E‐332‐06: Estimated Cumulative Effective Dose From PET/CT in Pediatric Patients with Malignancies

Purpose: To estimate the cumulative effective dose to pediatric patients with malignancy from regularly PET/CT scans. Method and Materials: We retrospectively reviewed 248 PET/CT studies performed on 78 pediatric patients with malignancies who were being periodically scanned for evaluation of disease progression. To estimate the effective dose from the CT portion of the exam, we used the ImPACT CT Patient Dosimetry Calculator software package which provides estimates based on patient specific scan parameters (scanner, kVp, mAs, collimation, scan coverage and so on). To estimate effective dose from the PET portion of the study, OLINDA software (Vanderbilt University) was used which provides estimates based on patient specific FDG doses. Since estimations from both parts were based on adult models, effective doses were adjusted for patient age according to published values. Results: The average effective dose from a single CT scan was 20.3mSv, ranging from 2.7 to 54.2 mSv. For the PET study the average effective dose was 4.6mSv, ranging from 0.4 to 7.7mSv. For a combined PET/CT study the average was 24.8 mSv, ranging from 6.2 to 60.7mSv. The average cumulative effective dose per patient from combined PET/CT studies was 78.9mSv, ranging from 6.2 to 399 mSv. Radiation doses varied significantly depending on the number of studies as well as the number of additional CT scans performed. Conclusion: Effective doses from combined PET/CT studies for pediatric patients with malignancies may be significant. While some of these patients will go on to radiation therapy, many will not. While PET/CT remains an important non‐invasive diagnostic, staging, and surveillance modality, the decision to use PET/CT should be made with particular awareness to the cumulative radiation dose, potential dose reduction options (such as further reducing tube currents) and the overall benefit of this exam.

A neural network-based diagnostic method for solitary pulmonary nodules

Several computer-aided diagnostic (CAD) methods for solitary pulmonary nodules (SPNs) have been proposed, which can be divided into two major categories: (1) the morphometric CT method, depending on high-resolution morphometric characteristics from single CT scan and (2) the perfusion CT method, depending on properties of the post-contrast enhancement dynamics obtained from repeated CT scans at predefined time points. The goal of this work is to introduce a neural network-based CAD method of lung nodule diagnosis by combining morphometry and perfusion characteristics by perfusion CT. Compared with previous methods, the proposed approach has the following distinctive features. Firstly, this work develops a very efficient semi-automatic procedure to segment entire nodules. Secondly, reliable nodule classification can be achieved by using only two time-point perfusion CT feature measures (precontrast and 90 s). This greatly reduces the amount of radiation exposure to patients and the data processing time. The effectiveness of the proposed approach is compared with those of several previously developed CAD methods.

Cine CT for Attenuation Correction in Cardiac PET/CT

In dual-modality PET/CT systems, the CT scan provides the attenuation map for PET attenuation correction. The current clinical practice of obtaining a single helical CT scan provides only a snapshot of the respiratory cycle, whereas PET occurs over multiple respiratory cycles. Misalignment of the attenuation map and emission image because of respiratory motion causes errors in the attenuation correction factors and artifacts in the attenuation-corrected PET image. To rectify this problem, we evaluated the use of cine CT, which acquires multiple low-dose CT images during a respiratory cycle. We evaluated the average and the intensity-maximum image of cine CT for cardiac PET attenuation correction. Cine CT data and cardiac PET data were acquired from a cardiac phantom and from multiple patient studies. The conventional helical CT, cine CT, and PET data of an axially translating phantom were evaluated with and without respiratory motion. For the patient studies, we acquired 2 cine CT studies for each PET acquisition in a rest-stress (13)N-ammonia protocol. Three readers visually evaluated the alignment of 74 attenuation image sets versus the corresponding emission image and determined whether the alignment provided acceptable or unacceptable attenuation-corrected PET images. In the phantom study, the attenuation correction from helical CT caused a major artifactual defect in the lateral wall on the PET image. The attenuation correction from the average and from the intensity-maximum cine CT images reduced the defect by 20% and 60%, respectively. In the patient studies, 77% of the cases using the average of the cine CT images had acceptable alignment and 88% of the cases using the intensity maximum of the cine CT images had acceptable alignment. Cine CT offers an alternative to helical CT for compensating for respiratory motion in the attenuation correction of cardiac PET studies. Phantom studies suggest that the average and the intensity maximum of the cine CT images can reduce potential respiration-induced misalignment errors in attenuation correction. Patient studies reveal that cine CT provides acceptable alignment in most cases and suggest that the intensity-maximum cine image offers a more robust alternative to the average cine image.

Segementation of X-Ray Microtomography Data of Porous Scaffold

Computerized X-ray micro tomography (micro CT) is a powerful technique for studying the structure and properties of porous scaffold. A variety of sample parameters can be studied using a single micro CT scan [1]. In general a segmented data set is a required for most quantitative analysis. However, segmentation of CT data can be difficult due to the artifacts in micro CT images such as blurred interfaces due to the machine contrast transfer function and the partial volume effect. Therefore the segmentation can be biased and prone to errors. Many methods have been developed to improve segmentation, however the interface problem has not been solved perfectly [2]. Porous scaffolds suffer from these effects because of their high surface to volume ratio and hence large interface. In this paper we discuss the interface problem in detail and demonstrate the effect of voxel size on the histograms of CT images of porous scaffold as well as a thresholding method based on 2 dimensional histogram is also presented. The potential of this method in more complicated scenarios such as 3-phase system is currently being investigated [3].

ASSESSMENT OF LOWER EXTREMITY VENOUS ENHANCEMENT AFTER LOW- (CONTRAST) DOSE COMPUTED TOMOGRAPHIC PULMONARY ANGIOGRAPHY.

Background Computed tomographic pulmonary angiography (CTA) combined with computed tomographic venography (CTV) of the lower extremities has been shown to have a higher diagnostic sensitivity than does CTA alone in patients with suspected pulmonary embolism. Most published studies of CTV following CTA have used 130 to 150 mL of nonionic intravenous contrast, the standard dose of contrast used with single detector CT scanning. The amount of intravenous contrast used for multidetector CT scanners is usually 100 mL or less. The objective of this study is to determine if 100 mL of intravenous contrast provides adequate opacification of the pelvic and lower extremity veins. Methods Venous phase images were acquired in patients undergoing CTA for pulmonary embolism using a 16-row multidetector CT scanner. Three 5 mm single axial CT slices were taken: one at the level of the anterior inferior iliac spine, one at the level of the midfemoral heads, and one 5 cm below the lesser trochanter. Images were obtained 21/2 minutes after completion of the pulmonary angiogram. Hounsfield units (HU) were measured of the external iliac vein, common femoral vein, and superficial femoral vein and compared to the adjacent artery. Results Preliminary data from 9 patients and 50 vein cross sections show an opacification average of 89.39 HU with a standard deviation of 19.5 HU. External iliac veins show an average of 93.13 HU with a standard deviation of 20.03 HU. Common femoral veins show an average of 89.82 HU with a standard deviation of 19.21 HU. Superficial femoral veins show an average of 85.16 HU with a standard deviation of 19.72 HU. The patient9s average creatinine was 0.87, and the average weight was 91.25 kg. Conclusions In patients with suspected pulmonary embolism, 100 mL of intravenous contrast appears to provide adequate opacification of the pelvic and lower extremity veins. Veins measuring 60 HU are considered adequately opacified. This suggests that using the current dose of contrast will permit concurrent testing for venous thrombosis and pulmonary embolism using multidetector CTA-CTV, but additional testing is necessary to compare weights and creatinine clearances and their effect on venous opacification.

SU‐DD‐A2‐04: A Simple Method to Reconstruct a Representative Mid‐Ventilation CT Scan From 4D Respiration Correlated CT Scans for Radiotherapy Treatment Planning of Lung Cancer Patients

Purpose: Four‐dimensional (4D) imaging techniques can be used to obtain (respiration) artifact‐free CT images of the thorax. However, its use in radiotherapy is limited since clinical treatment planning systems are currently not able to use the full 4D data. The purpose of this study was to reconstruct a representative single 3D CT scan from the 4D data set (with tumor closest to the mean position) for use in radiotherapy planning of lung tumors to enable reduction of treatment error margins. Method and Materials: After acquisition of the 4D CT scan (10 frames), the tumor is manually segmented (roughly) in the first frame and automatically (gray‐value) registered to the tumor in the subsequent frames. This gives the motion of the tumor during the respiratory cycle in 3D. Subsequently, from the cranio‐caudal (CC) tumor motion curve, the mean tumor position and its corresponding mid‐ventilation (MV) time‐percentage are calculated. The CT scan for planning is reconstructed at this time‐percentage. As indication of the merit of this concept, its effect on margins from CTV to PTV and on the PTV volume was calculated covering respiratory motion, respiratory baseline variation and setup errors (systematic and random). Results: Based on 13 patients, the worst tumor position accuracy (with respect to the mean tumor position) in the mid‐ventilation CT scan occurred in the anterior‐posterior direction: −0.7±0.8 mm (due to hysteresis). For these patients, the errors in conventional free‐breathing CT were estimated to be 0±3.4 mm (CC) and 0±1.4 mm (AP). The mid‐ventilation concept resulted in margin reduction up to 45% and a PTV volume reduction up to 35%. Conclusion: The mid‐ventilation concept, based on tumor motion, is a simple method to obtain an artifact‐free CT scan with smaller systematic errors compared to conventional CT scans. Significant reduction of the PTV volume can be achieved.

Preliminary study on the use of nonrigid registration for thoraco‐abdominal radiosurgery

The inclusion of organ deformation and movement in radiosurgery treatment planning is of increasing importance as research and clinical applications begin to take into consideration the effects of physiological processes, like breathing, on the shape and position of lesions. In this scenario, the challenge is to localize the target in toto (not only by means of marker sampling) and to calculate the dose distribution as the sum of all the contributions from the positions assumed by the target during the respiratory cycle. The aim of this work is to investigate the use of nonrigid registration for target tracking and dynamic treatment planning, i.e., treatment planning based not on one single CT scan but on multiple CT scans representative of the respiration. Twenty patients were CT scanned at end-inhale and end-exhale. An expert radiation oncologist identified the PTV in both examinations. The two CT data sets per patient were nonrigidly registered using a free-form deformation algorithm based on B-splines. The optimized objective function consisted of a weighted sum of a similarity criterion (Mutual Information) and a regularization factor which constrains the transformation to be locally rigid. Once the transformation was obtained and the registration validated, its parameters were applied to the target only. Finally, the deformed target was compared to the PTV delineated by the radiation oncologist in the other study. The results of this procedure show an agreement between the center of mass as well as volume of the target identified automatically by deformable registration and manually by the radiation oncologist. Moreover, obtained displacements were in agreement with body structure constraints and considerations usually accepted in radiation therapy practice. No significant influence of initial target volume on displacements was found. In conclusion, the proposed method seems to offer the possibility of using nonrigid registrations in radiosurgery treatment planning, even if more cases need to be investigated in order to give a statistical consistency to parameter setup and proposed considerations.

The value of contrast-enhanced helical CT scan with rectal contrast enema in the diagnosis of acute appendicitis

Background: The aim of this retrospective study is to assess the accuracy of single slice helical CT scan with intravenous, and rectal contrast (CTRC) in the diagnosis of acute appendicitis (AA) in patients with suspected AA, with particular analysis of the diagnostic signs. Participants and methods: Abdomino–pelvic helical CTRC was performed on 75 consecutive patients with suspicion of AA. Radiologic diagnosis was compared with surgical/pathologic results and clinical follow-up. In addition, the CTRC examinations were retrospectively reviewed independently by two experienced radiologists using predefined diagnostic criteria. The sensitivity, specificity, and frequency of each diagnostic sign were calculated. The interobserver agreement and the statistical significance of the frequency for each diagnostic criterion were assessed using the Kappa and Fisher tests, respectively. Results: The accuracy of helical CTRC in the diagnosis of AA was 94.7%, sensitivity 100%, specificity 90%, PPV 89.7%, and the NPV 100%. Wall enhancement and nonopacification of the appendix recorded the highest sensitivity and specificity (97% and 100%, 94% and 95%, respectively). Appendiceal thickness greater than 6 mm was present in 100% of true-positive cases. However, 26.5% of true-negative cases had also an appendiceal diameter exceeding 6 mm, a value used as a cut-off for normal appendiceal diameter. The highest interobserver agreement was recorded for appendiceal wall enhancement and for nonopacification of the appendix ( K=0.97 and 0.88, respectively). Conclusions: CTRC is an accurate and relatively fast technique for investigation of patients with suspected AA. A negative CTRC can exclude completely the diagnosis of AA. Nonopacification of the appendix and appendiceal wall enhancement are highly sensitive, specific, and reproducible, signs representing major criteria for the diagnosis of AA.

WE-E-J-6C-05: Variability of Four Dimensional CT Patient Models

Purpose: Several studies address the use of 4D CT to increase the geometrical accuracy of radiotherapy for lung cancer patients. A single 4D CT scan, however, gives a ‘snapshot’ movie loop of the patient's respiratory motion. In this study, we investigated the variability of respiratory motion over the course of radiotherapy using repeated 4D cone beam CT (4DCBCT) scans. Method and Materials: 4DCBCT scans of 10 lung cancer patients were acquired on the linac just prior to irradiation for 7–13 fractions. The diaphragm motion, extracted automatically from the projection images, was analyzed in terms of period and phase-histogram (relative time spend in [exhale, exhale-to-inhale, inhale and inhale-to-exhale]). Tumor motion was determined by registering a region of interest from the planning CT to each phase of the 4DCBCT. Results: The average breathing period ranged from 2.1 s to 5.6 s for different patients, with an inter- and intra-fraction variation of 0.8 s SD. The average phase histogram was [0.3 0.23 0.2 0.27] with little variation between fractions and patients, i.e., patients generally spend more time at exhale than inhale. The mean (over all patients) intra-fraction variation (SD) of the average tumor position relative to the bony anatomy was 1.6 mm LR, 2.7 mm SI and 2.3 mm AP, reflecting baseline breathing variation. The peak-to-peak tumor motion ranged from 0.4 to 2.0 cm, with an inter-fraction variability of 16% (1SD). Conclusion: Substantial variation in respiratory frequency, mean tumor position and peak-to-peak amplitude was found. These uncertainties can be taken into account by adapting the CTV-to-PTV margin accordingly. 4D-patient models should be regularly updated, e.g., by acquiring 4DCBCT prior to treatment, for safe implementation of precision 4D radiotherapy techniques like gating and tracking. Conflict of Interest: This research was sponsored by Elekta Oncology Systems Ltd.

Effects Of Strength Training On Visceral And Total Fat Among Women

PURPOSE The SHE study (Strong Healthy and Empowered) seeks to determine the effects of twice-weekly strength training on abdominal and total body fat among overweight and obese (BMI 25–35), generally healthy premenopausal women aged 25–44 at study entry. METHODS Participants were randomized into strength training (n=82) or 'standard care' (n=82) groups. The randomization was stratified by baseline body fat % and age (25–34 vs 35–44). The 'standard care ' group received brochures with the current public health guidelines to be regularly physically active. The strength training group received supervision and instruction for 16 weeks, followed by ongoing behavioral support from certified fitness professionals over 1 year of twice weekly strength training. Participants were asked to avoid dietary changes that would lead to weight changes over the course of the study. All participants underwent measures at baseline and 1 year later, including body composition by DEXA scan and visceral and subcutaneous abdominal adiposity by single slice CT scan at the L2-L3 disk space. RESULTS Attendance to strength training sessions averaged 73% over 1 year of training. Measures revealed no between group differences at baseline. Significant between group differences were noted for 1 year changes in lean mass (p=0.03) and %fat (p=0.04). The between group difference for visceral abdominal fat changes was marginally significant (p =0.07). The treatment group showed a decrease of 3% in total fat and a 4% decrease in visceral abdominal fat stores. CONCLUSIONS Twice weekly strength training is behaviorally feasible. Fat may be lost equally or preferentially from visceral abdominal stores (versus total fat stores) as a result of strength training. Preferential loss of fat from visceral abdominal stores as a result of strength training may have implications for reducing risk for chronic diseases, including diabetes, hypertension, metabolic syndrome, heart disease, and some forms of cancer.Table

105 poster workshop Target volume definition for stage I NSCLC: single 4D CT scan vs. one standard vs. six standard CT scans

105 poster workshop Target volume definition for stage I NSCLC: single 4D CT scan vs. one standard vs. six standard CT scans

Defining target volumes for stage I NSCLC using a single 4D CT scan (versus a single standard CT and 6 standard CT scans)

Defining target volumes for stage I NSCLC using a single 4D CT scan (versus a single standard CT and 6 standard CT scans)

可視シンチレーション光によるX線CTの性能評価

We proposed a new method of performance evaluation for X-ray CT using visible scintillation light and examined its usefulness in this study. When we scanned a plastic scintillator disk in a gantry opening of the X-ray CT, we could observe visible scintillation light. The rotation of the light-emitting area of the disk corresponded to that of the X-ray tube. We were able to record the scintillation light by digital video camera. By analyzing the area of visible scintillation light, the rotation speed of the X-ray tube, angular spread of the X-ray beam, uniformity of the incident X-rays, and change in X-ray energy were measured. No other method is available to obtain the above parameters of X-ray CT during a single CT scan. In the measurements of the uniformity of incident X-rays and change of X-ray energy, our method showed good accuracy in detecting the attenuation caused by the couch between the X-ray tube and the plastic scintillator disc. The proposed method is inexpensive and easy-to-use. We conclude that the method is a useful tool for performance evaluation as well as a maintenance tool for X-ray CT.

The Cost-Effectiveness of Low-Dose CT Screening for Lung Cancer : Preliminary Results of Baseline Screening

Low-dose CT scan screening greatly improves the likelihood of detecting small nodules and, thus, of detecting lung cancer at a potentially more curable stage. To evaluate the cost-effectiveness of a single baseline low-dose CT scan for lung cancer screening in high-risk individuals, data from the Early Lung Cancer Action Project (ELCAP) was incorporated into a decision analysis model comparing low-dose CT scan screening of high-risk individuals (ie, those > or = 60 years with at least 10 pack-years of cigarette smoking and no other malignancies) to observation without screening. Cost-effectiveness was expressed as the incremental cost per year of life saved. The analysis adopted the perspectives of the health-care system. The probability of the different outcomes following the decision either to screen or not to screen an individual at risk was based on data from ELCAP and the Surveillance, Epidemiology, and End Results Registry or published data, respectively. The cost of the screening and treatment of patients with lung cancer was established based on data from the New York Presbyterian Hospital's financial system. The base-case analysis was conducted under the assumption of similar aggressiveness of screen-detected and incidentally discovered lung cancers and then was followed by multiple sensitivity analyses to relax these assumptions. The incremental cost-effectiveness ratio of a single baseline low-dose CT scan was 2,500 US dollars per year of life saved. The base-case analysis showed that screening would be expected to increase survival by 0.1 year at an incremental cost of approximately 230 US dollars. Only when the likelihood of overdiagnosis was > 50% did the cost effectiveness ratio exceed 50,000 US dollars per year of life saved. The cost-effectiveness ratios were also relatively insensitive to estimates of the potential lead-time bias. A baseline low-dose CT scan for lung cancer screening is potentially highly cost-effective and compares favorably to the cost-effectiveness ratios of other screening programs.