Establishing Protocol-based Dose Metrics for Common Abdomen and Pelvis Computed Tomography Protocols

BACKGROUND AND AIM: The majority of the existing diagnostic reference levels (DRLs) that have been established for computed tomography (CT) are based on various anatomical locations, such as the head, chest, abdomen, etc. However, DRLs are initiated to improve radiation protection by conducting a comparison of similar examinations with similar objectives. The aim of this study was to explore the feasibility of establishing dose baselines based on common CT protocols for patients who underwent enhanced CT abdomen and pelvis exams. METHODS: Dose length product total (tDLPs), volumetric CT dose index (CTDIvol), size-specific dose estimate (SSDE), effective dose (E), and scan acquisition parameters for a total of 216 adult patients, who underwent an enhanced CT abdomen and pelvis exams over a one-year period, were obtained and retrospectively analyzed. Spearman coefficient and one-way ANOVA tests were used to check significant differences between dose metrics and the different CT protocols. RESULTS: The data exhibited 9 different CT protocols to acquire an enhanced CT abdomen and pelvis exam at our institute. Out of these, 4 were found more common, i.e., CT protocols were acquired for a minimum of 10 cases. Triphasic liver demonstrated the highest mean and median tDLPs across all 4 CT protocols. Triphasic liver protocol registered the highest E followed by gastric sleeve protocol with a mean of 28.7 and 24.7 mSv, respectively. Significant differences (p < 0.0001) were found between the tDLPs of anatomical location and the CT protocol. CONCLUSION: Evidently, wide variability exists across CT dose indices and patient dose metrics relying on anatomical-based dose baseline, i.e., DRLs. Patient dose optimizations require establishing dose baselines based on CT protocols rather than the anatomical location.

Challenges Associated with Effective Implementation of CT Dose Check Standards and Radiation Monitoring Index in Computed Tomography: Healthcare Sector Experience.

Computed tomography (CT) radiation dose management tools should be used whenever possible, particularly with the increasing demand for acquiring CT studies. Herein, we aim to assess the advantages and challenges faced with implementing two CT dose management tools. A second aim was to highlight CT examinations exceeding dose notification values (NVs) and define the common set of causes. A total of 13,037 CT examinations collected over a six-month period, were evaluated, using two independent CT dose management tools, a CT Dose Notification prospective-view tool (PVT) following CT Dose Check standards and a retrospective statistical-based view tool (RSVT). Dose NVs were set to twice the Local Diagnostic Reference Levels. There was a significant discrepancy between dose NV counts registered with prospective (4.15%) and retrospective (7.98%) tools using T-Test. A core difference is the dose configuration setup, with PVT and RSVT being dose per series and whole study, respectively. Both prospective and retrospective dose management tools were equally useful despite their technical difference. Configuring the CT prospective dose notification check tool using NVs that is based on DRLs has limitations, and one needs to establish dose NVs per series to overcome this technical hurdle. Technical challenges make the implementation of CT Dose Check standards puzzling.

Regression Analysis between the Different Breast Dose Quantities Reported in Digital Mammography and Patient Age, Breast Thickness, and Acquisition Parameters.

Breast cancer is the leading cause of cancer death among women worldwide. Screening mammography is considered the primary imaging modality for the early detection of breast cancer. The radiation dose from mammography increases the patients' risk of radiation-induced cancer. The mean glandular dose (MGD), or the average glandular dose (AGD), provides an estimate of the absorbed dose of radiation by the glandular tissues of a breast. In this paper, MGD is estimated for the craniocaudal (CC) and mediolateral-oblique (MLO) views using entrance skin dose (ESD), X-ray spectrum information, patient age, breast glandularity, and breast thickness. Moreover, a regression analysis is performed to evaluate the impact of mammography acquisition parameters, age, and breast thickness on the estimated MGD and other machine-produced dose quantities, namely, ESD and organ dose (OD). Furthermore, a correlation study is conducted to evaluate the correlation between the ESD and OD, and the estimated MGD per image view. This retrospective study was applied to a dataset of 2035 mammograms corresponding to a cohort of 486 subjects with an age range of 28-86 years who underwent screening mammography examinations. Linear regression metrics were calculated to evaluate the strength of the correlations. The mean (and range) MGD for the CC view was 0.832 (0.110-3.491) mGy and for the MLO view was 0.995 (0.256-2.949) mGy. All the mammography dose quantities strongly correlated with tube exposure (mAs): ESD (R2 = 0.938 for the CC view and R2 = 0.945 for the MLO view), OD (R2 = 0.969 for the CC view and R2 = 0.983 for the MLO view), and MGD (R2 = 0.980 for the CC view and R2 = 0.972 for the MLO view). Breast thickness showed a better correlation with all the mammography dose quantities than patient age, which showed a poor correlation. Moreover, a strong correlation was found between the calculated MGD and both the ESD (R2 = 0.929 for the CC view and R2 = 0.914 for the MLO view) and OD (R2 = 0.971 for the CC view and R2 = 0.972 for the MLO view). Furthermore, it was found that the MLO scan views yield a slightly higher dose compared to CC scan views. It was also found that the glandular absorbed dose is more dependent on glandularity than size. Despite being more reflective of the dose absorbed by the glandular tissue than OD and ESD, MGD is considered labor-intensive and time-consuming to estimate.

Gender based lung cancer risks for symptomatic coronary artery disease patients undergone cardiac CT.

We estimate the lifetime attributable risk (LAR) of lung cancer incidence in symptomatic Coronary Artery Disease (CAD) patients receiving enhanced Coronary Computed Tomography Angiography (CCTA) and the unenhanced Computed Tomography Calcium Scoring (CTCS) examination. Retrospective analysis has been made of CCTA and CTCS data collected for 87 confirmed CAD adult patients. Patient effective dose (E) and organ doses (ODs) were calculated using CT-EXPO. Statistical correlation and the differences between E and ODs in enhanced CCTA and unenhanced CTCS were calculated using the Pearson coefficient and Wilcoxon unpaired t-test. Following BEIR VII report guidance, organ-specific LARs for the cohort were estimated using the organ-equivalent dose-to-risk conversion factor for numbers of cases per 100,000 patients exposed to low doses of 0.1 Gy. Significant statistical difference (p<0.0001) is found between E obtained for CTCS and that of CCTA. The scan length was found to be greater in CCTA (17.5 ± 2.9 cm) compared to that for CTCS (15 ± 2 cm). More elevated values of dose were noted for the esophagus (4.2 ± 2.15 mSv) and thymus (9.6 ± 2.54 mSv) for both CTCS and CCTA. CTCS organ doses were lower than that of CCTA. Per 100,000 patients, female cumulative doses are seen to give rise to greater lung cancer LARs compared to that for males, albeit with risk varying significantly, noticeably greater for females, younger patients and combined CCTA and CTCS scans. While scan parameters and tube-modulation methods clearly contribute to patient dose, mAs offers by far the greater contribution.

Challenges experienced in establishing clinical indication based diagnostic reference levels: Pilot study.

PURPOSE: The objective of this study is to establish clinical-indication based Diagnostic Reference Levels (DRLs) for the Computed Tomography (CT) examinations of Head, Abdomen & Pelvis + Contrast, and Kidney Ureter Bladder (KUB). Further, is to investigate the cases that register high-end doses to enable dose optimization. MATERIAL AND METHODS: Dose length product total (tDLPs) and scan acquisition parameters of a total of 715 patients who underwent CT Head, CT Abdomen & Pelvis + Contrast, and CT KUB studies were obtained and retrospectively examined. An electronic patient radiation dose monitoring system DOSE-TQM linked with the existing PACS was used to randomly generate patient dose information. Patient's demographics, clinical indications and scan acquisitions were also collected. ANOVA and Tukey's multiple comparison tests were used to check statistical differences between tDLPs per clinical indications. RESULTS: The data exhibited 341 CT Head, 109 patients for CT Abdomen & Pelvis + Contrast, and 265 CT KUB examinations. The DRLs proposed using total DLP (mGy.cm) for clinical indications; abdominal pain for both CT Abdomen & Pelvis + Contrast and CT KUB (441 and 311 mGy.cm, respectively), appendicitis /acute appendicitis (484 mGy.cm), head trauma (544 mGy.cm), stroke (544 mGy.cm) and renal colic (308 mGy.cm). These values were concluded to be below or in close proximity with the total DLP based indication reported internationally. Patient weight is a significant dose contributor. CONCLUSION: DLP differences exists not only between the same anatomical based CT studies but also across the same clinical indications. DLPs based on clinical indications provide a tool for CT dose optimisation that is better adapted to clinical practices and to the variability of patient's morphology.

Assessing visceral and subcutaneous adiposity using segmented T2-MRI and multi-frequency segmental bioelectrical impedance: A sex-based comparative study.

BACKGROUND AND AIM: This study aims to quantify abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) using T2-weighted magnetic resonance imaging (MRI), and assess the extent of its concordance with VAT surface-area measured by a state-of-the-art segmental multi-frequency bioelectrical impedance analysis (BIA) device. A comparison between manual and semi-automated segmentation was conducted. Further, abdominal VAT and SAT sex-based comparison in healthy Arab adults was piloted. METHODS: A cross-sectional design was followed to recruit subjects. Abdominal VAT and SAT were determined on T2-weighted MRI manually and semi-automatically. Body composition was assessed using a BIA machine. Statistical differences between the abdominal VAT areas defined by BIA, manual, and semi-automated MRI were compared. Correlation between all methods was assessed, and statistical differences between sex abdominal VAT/SAT defined areas were compared. RESULTS: A total of 165 abdominal T2-weighted MR images taken for 55 overweight/obese adult subjects were analyzed Differences between manual and semi-automated MRI-obtained abdominal VAT and SAT were found statistically significant (P<0.001) for all subjects. Mean abdominal VAT using the BIA technique was found to correlate significantly with manually and semi-automated T2-weighted MRI defined VAT (r=0.7436; P<0.001 and r=0.8275; P<0.001, respectively). Abdominal VAT was significantly (P<0.001) different between male and female subjects accumulating at different abdominal levels. CONCLUSION: Semi-automatic segmentation showed a stronger significant correlation with BIA compared to manual segmentation, implying a more reliable quantification of abdominal VAT/SAT. Segmental BIA technique may serve as a feasible and convenient assessment tool for the visceral adiposity in obese subjects.

Utilizing neutron generators in boron neutron capture therapy.

Neutron capture therapy (NCT) is a radiotherapeutic technique that is designed to utilize the neutron capture reaction and damage the tumor cells through the energy release from the reaction. Nuclear reactors are typically utilized in this therapy because of the high neutron fluence rate that can be achieved. There has been minimal work to evaluate the effectiveness of neutron generators in NCT. This work presents the preliminary simulation results of utilizing of a deuterium-deuterium generator in boron neutron capture therapy. MCNP 6.1 was used to model the detailed geometry of the neutron generator and the phantom. Neutron moderators and photon shielding were used to optimize the neutron fluence rate in the tumor and decrease the photon dose in the phantom respectively. The study showed that a good localization of the neutron dose can be achieved in the tumor area with a reduction of the photon dose in the surrounding areas.

Challenges estimating patient organs doses undergoing enhanced chest CT examination: exploratory study.

Purpose: Estimate organs doses (ODs) of patients subjected to unenhanced (S1) and enhanced (S2) chest CT studies relying on image parameters such as Hounsfield Units (HUs).Materials and Methods: CT scans and images of a total of 16 patients who underwent two series of chest CT studies were obtained and retrospectively examined. OD increments of liver and pancreas for both series (S1 & S2) were estimated using two different independent methods, namely simulation approach using CT-EXPO and Amato's phantom-based fitting model (APFM). HUs were quantified for each organ by manually drawing fixed area-sized regions of interest (ROIs). The mean HUs were collected to obtain the ODs increments following APFM. Regression analysis was applied to find and assess the relationship between the HUs and the OD increments estimated using APFM and that using CT-EXPO. Spearman Coefficient and Wilcoxon Matched Pairedt-testwere conducted to show statistical correlation and difference between ODs increments using the two methods.Results:A strong significant difference was depicted between S1 and S2 scan series of liver and pancreas using CT-EXPO simulation. Mean HU values for S1 were lower than S2, resulting in statistically significant (p < 0.0001) HU changes. CT-EXPO simulation yielded significantly higher difference in ODs compared to the APFM for liver (p = 0.0455) and pancreas (p = 0.0031). Regression analysis revealed a strong relationship between HU of S1 and S2 and ODs increments using APFM in both organs (R2 = 0.99), dissimilar to CT-EXPO (R2 = 0.39 in liver andR2 = 0.05 in pancreas).Conclusions: Although CT-EXPO allows for estimating ODs accounting for major acquisition scan parameters, it is not a reliable tool to evaluate the impact of contrast enhancement on ODs. On the other hand, the APFM accounts for contrast enhancement accumulation yet only provides relative OD increments, an information of limited clinical use.

Age-dependent effective ingestion dose estimations and lifetime risk assessment for selected radionuclides (40K and 3H) in bottled waters marketed in United Arab Emirates.

Monitoring drinking water, including bottled water, is imperative to safeguarding public health especially where bottled water consumption is high like in the United Arab Emirates (UAE). In this study, radionuclide activity levels of Tritium (3H) and Potassium (40K) were assessed in various brands of bottled water marketed in UAE. Activity level data was used to calculate the annual effective doses (Ed) for different age groups, and the excess lifetime cancer risk (ELCR) for adult males and females in the UAE population. Activity levels for both radionuclides were below the allowable maximum guideline values specified by local and international standards. Calculated total age dependent ingestion doses revealed that adults and lactation age groups received the highest effective ingestion doses. Adult males exhibited a higher ELCR for both isotopes, compared to females. Nonetheless, total radioactive dose for each water brand (0.91-1.47 µSv/yr) as well as for each population group were well below the recommended annual reference dose level of 100 µSv set by World Health Organization. Therefore, bottled water in the UAE is safe from the radiological aspect for investigated radionuclides, and poses no significant radiological exposure and health risk to the public.

Effect of Ramadan diurnal fasting on visceral adiposity and serum adipokines in overweight and obese individuals.

AIM: Excessive visceral adiposity is a major risk factor for developing insulin resistance and systemic low-grade inflammation. Ramadan diurnal fasting (RDF) is a religious ritual practiced by more than one billion Muslim throughout the world. It has been considered as one of the most common types of complementary and integrative health practices. The aim of this study is to examine the impact of RDF on visceral adiposity, circulating adipokines and glucoregulatory markers in patients with overweight or obesity. METHODS: Overweight and obese subjects (n = 61; 23 men and 38 women) were included in the study. Body weight, visceral fat tissue area (measured by 3D-MRI), glucoregulatory factors, serum adipokines concentrations, dietary intake, and physical activity were assessed one week before and at the end of the lunar month of Ramadan. RESULTS: From baseline, body weight and visceral fat tissue area serum total cholesterol, triglycerides, HDL-cholesterol, and systolic blood pressure significantly decreased (P < 0.05 for each) at the end of Ramadan. The serum levels of adiponectin, IL-6, TNF-α, and IGF-1 significantly decreased (P < 0.05 for each), but serum visfatin, leptin, apelin, IL-10, and IL-10/IL-6 ratio significantly increased (P < 0.05 for each) at the end of Ramadan. Changes in visceral adiposity significantly correlated with changes in plasma glucose (r = 0.4, P < 0.5) and resistin (r = 0.44, P < 0.001) at the end of Ramadan. CONCLUSION: RDF lowers visceral adiposity, body weight and variably affects adipokines without adversely affecting markers of glucose homeostasis in individuals with overweight or obesity.

ESTIMATE OF UAE COMMERCIAL AIRCREW EFFECTIVE DOSES USING CARI-6, EPCARD AND SIEVERT CODES.

The aim of this study is to calculate total cruising route effective doses using three commonly used algorithm codes CARI-6, EPCARD and SIEVERT. Further, the impact of flight cruising duration, altitude and latitude on the estimated effective doses will also be investigated. A total of 24 commercial UAE flight data were collected and retrospectively analysed. CARI-6, EPCARD and SIEVERT codes were used to estimate the total route effective doses per single trip of different destinations including USA, Europe, South Africa, Asia and Australia. Aircraft crew effective doses were shown to significantly increase with flying altitude. A strong significant correlation (0.6469; p < 0.05) was obtained between flight duration and the estimated effective doses, while a moderate insignificant correlation (0.3899; p > 0.05) was obtained with flying altitude for all 24 flights using CARI-6. For flights with the same latitude and duration, all codes gave total effective doses within experimental uncertainties.

PET-based Treatment Response Assessment for Neoadjuvant Chemoradiation in Pancreatic Adenocarcinoma: An Exploratory Study.

PURPOSE: Performance of anatomical metrics of Response Evaluation Criteria in Solid Tumors (RECIST1.1) versus Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST1.0) for neoadjuvant chemoradiation (nCR) of pancreatic adenocarcinoma was evaluated based on the pathological treatment response (PTR) data. METHODS AND MATERIALS: The pre- and post-nCR CT and PET data for 14 patients with resectable or borderline resectable pancreatic head adenocarcinoma treated with nCR followed by surgery were retrospectively analyzed. These data were compared with the PTR which were graded according to tumor cell destruction (cellularity), with Grade 0, 1, 2 or 3 (G0, G1, G2 or G3) for complete, moderate, minimal and poor responses, respectively. Maximum standardized uptake value (SUVmax) was defined using body-weight (SUVbw). PERCIST1.0 was defined using lean-body mass normalized SUV (SUVlb or SUL). RECIST1.1 was defined by contouring the whole pancreas head on the CT image. Pre- and post-SUL-peak and SUVmax, RECIST1.1 and PETRECIST1.0 were correlated with PTR using Pearson's correlation coefficient test. RESULTS: The average mean and SD in SUL-peak for all patients analyzed were lower in post-nCR (3.63±1.06) compared to those at pre-nCR (4.29±0.89). Using PERCIST1.0, 62% of patients showed stable metabolic disease (SMD), 23% partial metabolic response (PMR), and 15% progressive metabolic disease (PMD). Using RECIST1.1, 85% of patients showed stable disease (SD), 8% partial response (PR), and 7% progressive diseases (PD). A poor insignificant correlation was established between PRT and PERECIST1.0 (r=0.121), whereas no correlation was seen with RECIST1.1. CONCLUSIONS: PERCIST1.0 appears to increase the chance of detecting patients with progressive disease compared to the conventional anatomical-based assessment of RECIST1.1. The integration of these additional radiographic metrics in assessing treatment response to nCR for pancreatic adenocarcinoma may provide a promising strategy to better select patients that are most suitable for therapeutic intensification.

Correlation of ADC With Pathological Treatment Response for Radiation Therapy of Pancreatic Cancer.

PURPOSE: To investigate the feasibility of using apparent diffusion coefficient (ADC) to assesspathological treatment response in pancreatic ductal adenocarcinoma (PDAC) following neoadjuvant chemoradiation (nCR). MATERIALS/METHODS: MRI and pathological data collected for 25patients with resectable and borderline resectable PDAC following nCR were retrospectively analyzed. Pre- and post-nCR mean ADC values in the tumors were compared using Wilcoxon matched pairs test. Correlation of pathological treatment response and ADC values was assessed using Pearson's correlation coefficient test and receiver-operating-curve (ROC) analysis. RESULTS: The average mean and standard deviation (SD) of the ADC values for all the patients analyzed were significantly higher in post-nCR (1.667±0.161×10-3) compared with those prior to nCR (1.395±0.136×10-3 mm2/sec), (P<0.05). The mean ADC values after nCR were significantly correlated with the pathological responses (r=-0.5172); P=0.02. The area under the curve (AUC) of the ADC values for differentiating G1, G2 and G3 pathological responses, using ROC analysis, was found to be 0.6310 and P=0.03. CONCLUSION: Changes of pre- and post-treatment ADC values significantly correlated with pathological treatment response for PDAC patients treated with chemoradiation therapy, indicating that the ADC could be used to assesstreatment response for PDAC.

Early Assessment of Treatment Responses During Radiation Therapy for Lung Cancer Using Quantitative Analysis of Daily Computed Tomography.

PURPOSE: To investigate early tumor and normal tissue responses during the course of radiation therapy (RT) for lung cancer using quantitative analysis of daily computed tomography (CT) scans. METHODS AND MATERIALS: Daily diagnostic-quality CT scans acquired using CT-on-rails during CT-guided RT for 20 lung cancer patients were quantitatively analyzed. On each daily CT set, the contours of the gross tumor volume (GTV) and lungs were generated and the radiation dose delivered was reconstructed. The changes in CT image intensity (Hounsfield unit [HU]) features in the GTV and the multiple normal lung tissue shells around the GTV were extracted from the daily CT scans. The associations between the changes in the mean HUs, GTV, accumulated dose during RT delivery, and patient survival rate were analyzed. RESULTS: During the RT course, radiation can induce substantial changes in the HU histogram features on the daily CT scans, with reductions in the GTV mean HUs (dH) observed in the range of 11 to 48 HU (median 30). The dH is statistically related to the accumulated GTV dose (R2 > 0.99) and correlates weakly with the change in GTV (R2 = 0.3481). Statistically significant increases in patient survival rates (P=.038) were observed for patients with a higher dH in the GTV. In the normal lung, the 4 regions proximal to the GTV showed statistically significant (P<.001) HU reductions from the first to last fraction. CONCLUSION: Quantitative analysis of the daily CT scans indicated that the mean HUs in lung tumor and surrounding normal tissue were reduced during RT delivery. This reduction was observed in the early phase of the treatment, is patient specific, and correlated with the delivered dose. A larger HU reduction in the GTV correlated significantly with greater patient survival. The changes in daily CT features, such as the mean HU, can be used for early assessment of the radiation response during RT delivery for lung cancer.

Variability of target and normal structure delineation using multimodality imaging for radiation therapy of pancreatic cancer.

PURPOSE: To explore the potential of multimodality imaging (dynamic contrast-enhanced magnetic resonance imaging [DCE-MRI], apparent diffusion-coefficient diffusion-weighted imaging [ADC-DWI], fluorodeoxyglucose positron emission tomography [FDG-PET], and computed tomography) to define the gross tumor volume (GTV) and organs at risk in radiation therapy planning for pancreatic cancer. Delineated volumetric changes of DCE-MRI, ADC-DWI, and FDG-PET were assessed in comparison with the finding on 3-dimensional/4-dimensional CT with and without intravenous contrast, and with pathology specimens for resectable and borderline resectable cases of pancreatic cancer. METHODS AND MATERIALS: We studied a total of 19 representative patients, whose DCE-MRI, ADC-DWI, and FDG-PET data were reviewed. Gross tumor volume and tumor burden/active region inside pancreatic head/neck or body were delineated on MRI (denoted GTVDCE, and GTVADC), a standardized uptake value (SUV) of 2.5, 40%SUVmax, and 50%SUVmax on FDG-PET (GTV2.5, GTV40%, and GTV50%). Volumes of the pancreas, duodenum, stomach, liver, and kidneys were contoured according to CT (VCT), T1-weighted MRI (VT1), and T2-weighted MRI (VT2) for 7 patients. RESULTS: Significant statistical differences were found between the GTVs from DCE-MRI, ADC-DW, and FDG-PET, with a mean and range of 4.73 (1.00-9.79), 14.52 (3.21-25.49), 22.04 (1.00-45.69), 19.10 (4.84-45.59), and 9.80 (0.32-35.21) cm(3) for GTVDCE, GTVADC, GTV2.5, GTV40%, and GTV50%, respectively. The mean difference and range in the measurements of maximum dimension of tumor on DCE-MRI, ADC-DW, SUV2.5, 40%SUVmax, and 50%SUVmax compared with pathologic specimens were -0.84 (-2.24 to 0.9), 0.41 (-0.15 to 2.3), 0.58 (-1.41 to 3.69), 0.66 (-0.67 to 1.32), and 0.15 (-1.53 to 2.38) cm, respectively. The T1- and T2-based volumes for pancreas, duodenum, stomach, and liver were generally smaller compared with those from CT, except for the kidneys. CONCLUSIONS: Differences exists between DCE-, ADC-, and FDG-PET-defined target volumes for RT of pancreatic cancer. Organ at risk volumes based on MRI are generally smaller than those based on CT. Further studies combined with pathologic specimens are required to identify the optimal imaging modality or sequence to define GTV.

Effect of window level on target volume delineation in treatment planning.

In radiotherapy the efficacy of medical imaging is central to the selection and delineation of target volume. Of note is that target volume is intended to be larger than tumour volume, including a geometric margin that accounts for the possible uncertainties in patient set-up. However this reduces potential tissue sparing, irradiating not only the target but also normal tissue. Additionally, features of the object that appear in the 2D image display may be influenced by the appropriate window level selection. This is especially critical for target volume delineation in radiotherapy. The present work seeks to assess the effect of window level selection on feature size in CT, MR and PET images, use being made of a NEMA body phantom and ProSoma 3D simulation software. In general, the window level produced discrepancies of up to +/-2 mm in all imaging modalities.

Evaluating commercial image registration packages for radiotherapy treatment planning.

Multi-modality imaging is involved in almost all oncology applications from diagnosis through treatment planning and follow-up. Commercial image fusion software packages are becoming available but require comprehensive evaluation to ensure reliability of fusion and the underpinning registration algorithm. This is especially critical for target volume delineation in radiotherapy. The present work seeks to assess such accuracy for a number of available registration methods. A National Electrical Manufacturers Association (NEMA) body phantom was used in evaluating computer tomography (CT), magnetic resonance (MR) and PET images. In addition, discussion is provided concerning the choice and geometry of fiducial markers in phantom studies and the effect of window level on target size, in particular in regard to the application of multimodality imaging in treatment planning. In general, the accuracy of fusion of multi-modality images was within 0.5-1.5mm of actual feature diameters and <2 ml volume of actual values, particularly in CT images.