bluuebunny/crossref_metadata_2025 huggingface dataset:
Exposure to hexachlorobenzene during pregnancy increases the risk of overweight in children aged 6 years
Authors: Smink Agnes , Ribas‐Fito Nuria , Garcia Raquel , Torrent Maties , Mendez Michelle A , Grimalt Joan O , Sunyer Jordi
Published: July 2008

Aim: To determine whether prenatal exposure to hexachlorobenzene (HCB) has potential adverse effects on child's weight and body mass index (BMI) in a general population with no local pollution sources.

Methods: Starting from mid 1997, all mothers presenting for antenatal exposure in Menorca were recruited. Subsequently, 482 children were enrolled. HCB was measured in cord blood. Weight and height were measured at birth and at age 6.5 years.

Results: Children with HCB levels higher than 1.03 ng/mL in cord blood were 1.14 kg (0.38) heavier and had a higher BMI (β= 0.80 (0.34)) than children with HCB levels lower than 0.46 ng/mL. No statistically significant associations were found in height. Children in the higher exposure group of HCB had an increased risk of 2.5 and 3.0 of being overweight and obese. Children from normalweight mothers also presented an increased risk of having higher BMI with increasing concentrations of HCB in cord serum.

Conclusion: Prenatal exposure to HCB is associated with an increase in BMI and weight at age 6.5 years. Further studies with larger samples and longer follow‐up are needed to confirm these results.
THE EFFECT OF NISIN AND BOVINE LACTOFERRIN ON THE MICROBIOLOGICAL QUALITY OF TURKISH‐STYLE MEATBALL (TEKIRDAĞ KÖFTE)
Authors: COLAK HILAL , HAMPIKYAN HAMPARSUN , BINGOL ENVER BARIS , AKSU HARUN
Published: July 2008

Tekirdağ köfte, a Turkish‐style meatball, is one of the most popular ground meat products in Turkey. The aim of this study was to evaluate the effect of different nisin and lactoferrin (Lf) concentrations and their combinations on the microbiological quality of Turkish‐style meatball (Tekirdağ köfte). For this purpose, the meatball dough was divided into six equal groups, and each of the groups was treated separately with different nisin and/or Lf concentrations (0, 100 and 200 µg/g). Analyses were performed on each meatball group at 0, 1, 3, 5, 7, 10 and 12 days for microbiological parameters (total mesophilic aerobic bacteria, lactic acid bacteria, coliforms, Escherichia coli, total staphylococcae, Staphylococcus aureus, total psychrophilic bacteria, Pseudomonas spp., sulfite‐reducing anaerobic bacteria, and yeast and mold) and physicochemical analyses (pH, water activity and moisture). Treatment with Lf alone and its combination with nisin significantly reduced (P < 0.05) the total aerobic bacteria, coliform, E. coli, total psychrophilic bacteria, Pseudomonas spp., and yeast and mold counts in meatballs. The largest reduction in these counts occurred on the meatballs treated with a mixture of Lf (200 µg/g) and nisin (100 µg/g). This combination prolonged the refrigerated shelf life of naturally contaminated Turkish‐style meatballs to 10 days compared to 3 days for nontreated control.

PRACTICAL APPLICATIONS

Meatballs are prepared from ground meat in Turkey. Studies have shown that total bacteria, coliform, and yeast and mold counts were usually high in meatball samples in Turkey, and these products were also usually contaminated with pathogenic bacteria. Therefore, this product mostly poses a risk to consumer health and has a short shelf life (about 3–4 days). In order to control the growth of spoilage microorganisms, the use of natural antimicrobial preservatives has been preferred in the food industry. For this purpose, nisin and lactoferrin were preferred in this study. Although there are many reports on the use of nisin to inhibit pathogenic bacteria, especially Listeria monocytogenes and Staphylococcus aureus in food, research on the antimicrobial activity of lactoferrin in food systems is limited.

According to the results of our study, treatment with lactoferrin alone and its combination with nisin significantly reduced spoilage bacteria counts and extended the refrigerated shelf life of Turkish‐style meatballs. Therefore, the use of these natural compounds in meatballs may be useful for consumer health, and may also be a practical application for the producer because of the short shelf life of this product.
CHEMICAL COMPOSITION AND MICROBIOLOGICAL QUALITY OF THE BONAB KEBABS SOLD IN TABRIZ MARKET
Authors: NEMATI M. , GHORBANPOUR H. , RAZAVIEH S.V. , HOSEINI M.
Published: July 2008

The objective of this research was to determine chemical composition and microbiological quality of the Bonab kebabs sold in the Tabriz market. In the chemical analysis, pH, moisture, protein, fat and salt contents, as well as some minerals such as Na, K, Fe and Cu were determined both for raw and cooked samples. The samples were examined for aerobic plate count (APC), coliforms, mold and yeast, Clostridium perfringens and Salmonella spp. to observe the hygienic quality of the Bonab kebabs.

The results of the chemical analysis showed 5.99–6.45 pH, 66.23–56.94% of moisture, 14.3–19.59% of protein, 14.05–18.58% of fat, 2.06–2.72% of ash and 1.27–1.96% of salt values for the raw–cooked samples, respectively. The results for minerals were (mg/100 g): 0.72–1.06 Fe, 0.21–0.27 Cu, 573–745 Na and 616–913 K. The microbiological analysis showed 6.75–3.22 cfu/g APC, 5.30–1.69 cfu/g coliforms, 3.36–0 cfu/g Clostridium and 4.53–3.39 cfu/g mold and yeast for the raw–cooked samples, respectively. In conclusion, it could be proposed from the data that the Bonab kebabs sold in Tabriz market had acceptable nutritional value and hygienic quality, but future inspections are necessary for the hygenic quality of places which prepare these foods.

PRACTICAL APPLICATIONS

A wide range of ready‐to‐eat foods have been reported as a source of foodborne diseases in different countries. Because of lack of information on the incidence of foodborne diseases related to Bonab kebabs and absence of microbiological standards for this food product, the survey reported here was undertaken to explore populations and profiles of microorganisms on raw and cooked kebabs. Data reported for the first time from this study could be used to inform kebab producers and consumers of the potentially associated microbial hazards and adequate means for food protection.
Epidemiological factors associated with treated incidence of first‐episode non‐affective psychosis in Cantabria: insights from the Clinical Programme on Early Phases of Psychosis
Authors: Pelayo‐Terán José M. , Pérez‐Iglesias Rocío , Ramírez‐Bonilla MariLuz , González‐Blanch César , Martínez‐García Obdulia , Pardo‐García Gema , Rodríguez‐Sánchez José M. , Roiz‐Santiáñez Roberto , Tordesillas‐Gutiérrez Diana , Mata Ignacio , Vázquez‐Barquero José Luis , Crespo‐Facorro Benedicto
Published: July 2008

Aim: The aim of the study was to analyse the treated incidence of schizophrenia in Cantabria (Northern Spain) and the sociodemographic risk factors associated with the illness onset.

Methods: Data were obtained from patients included in the Cantabria's Clinical Programme on First‐Episode Psychosis (schizophrenia spectrum DSM‐IV diagnosis) from 2001 to 2005, from the Cantabria first‐episode schizophrenia study (carried out between 1988 and 1989) and from the 2001 Spanish census.

Results: Annual incidence was 1.38 per 10 000 inhabitants in the risk‐ageperiod. Identified risk factors were male gender (relative risk (RR): 1.61), age 15–25 years (RR: 3.48), unemployment (RR: 2.82), single status (RR: 5.88), low educational level (RR: 4.38), urban environment (RR: 1.62) and cannabis consumption (odds ratio: 12.83). The incidence in females was significantly lower than the one obtained 15 years ago.

Conclusions: The reported factors suggest that underlying biological and social factors modulate the risk of psychosis. This balance operates differently in males and females.
SU‐AA‐350‐01: Student Meeting
Authors: O'Daniel J
Published: July 2008

The annual AAPM student meeting welcomes current and prospective trainees in medical physics. Speakers will address issues of importance to trainees, including the impact of the 2012/2014 residency requirement for the ABR, and what the AAPM is doing to increase the number of residency positions. Breakfast will be provided. Come and meet your fellow students, and have a great start to the AAPM meeting!
SU‐DD‐A1‐01: IMRT Monitor Unit Efficiency Comparison of Treatment Planning/delivery Systems
Authors: Doemer A , Cao J , Harrison A , Perera H , Xiao Y
Published: July 2008

Purpose: Treatment planning system/delivery system combinations affect IMRT optimization. Delivery method (step and shoot vs. dynamic), leakage radiation variations (lack of secondary collimators on the Elekta SL‐S MLC head), hardware constraints and leaf edge shape all factor in when a radiation treatment planning system (RTPS) optimizes MLC segments. Different optimization algorithms within treatment planning systems influence IMRT planning results as well. In our study we evaluated delivery efficiencies from Elekta, Varian and Siemens machines coupling with two different treatment planning systems. Method and Materials: 16 IMRT plans were created for prostate and headneck (HN) sites (5 and 6 co‐planar beams respectively) using CMS Xio and Philips ADAC Pinnacle. Plans were optimized using the same dose and DVH objectives and modulated using clinical thresholds. The monitor units needed to deliver the weight point dose for each field were tabulated for each site and machine source data. Results: All plans have similar quality meeting the objectives. HN plans have an average MU efficiency of 5.02 +/− 1.09 MU/cGy. The plans created on the Pinnacle RTPS had a lower mean efficiency but was not statistically significant due to the high standard deviation. Prostate plans were more efficient than the HN plans with an average value of 2.19 +/− 0.47 MU/cGy. Pinnacle prostate plans had a mean MU efficiency of 1.69 +/− 0.18 MU/cGy compared to 2.51 +/− 0.22 MU/cGy from Xio. Conclusion: There is no statistical difference in MU efficiency for HN plans from different planning/delivery system combinations. Prostate plans have higher delivery MU efficiencies than those from HN plans, most likely due to less modulation. For the prostate plans there exist slight differences in MU efficiencies with unknown clinical significance between different planning/delivery systems.
SU‐DD‐A1‐05: Treatment Planning of Prone Position Accelerated Partial Breast Irradiation Customized for Magnetic Resonance Imaging Guidance
Authors: Ahn K , Dieterich S , Luxton G , Horst K , Hristov D
Published: July 2008

Purpose: It is important to deliver an optimized dose distribution to an accurately delineated target volume for a successful accelerated partial breast irradiation (APBI) treatment. Breast magnetic resonance imaging (MRI) could improve lumpectomy delineation. We investigated treatment plans for CyberKnife and conventional C‐arm LINAC delivery of MRI‐guided APBI in prone position. Method and Materials: We acquired a CT scan of a patient positioned on a mechanical assembly with the same geometry as the dedicated MR coil to simulate the position during breast MRI acquisition. Ellipsoidal virtual PTV's of 4 cm were defined in the anterior part and in the lower outer quadrant of the right breast. Treatment plans were generated by inverse planning techniques for each system. For CyberKnife, we minimized beam directions from posterior to anterior to protect critical normal tissues (heart, lung and contralateral breast) and normalized the maximum dose to 120% of the prescription dose (38.5 Gy). For the conventional LINAC, we excluded any beams directed towards the critical normal tissues and normalized the plan to achieve 99% of the prescription coverage for 99% of PTV. Results: LINAC‐based plans resulted in maximum doses of 41.6 Gy in PTV and ⩽ 0.5 Gy in the critical normal structures. CyberKnife‐based plans led to 90% of the prescription dose coverage for 95% of PTV. Maximum doses were ⩽ 0.5 Gy in contralateral breast, ⩽ 1.9 Gy in heart, and ⩽ 4.2 Gy in both lungs. The fraction of normal ipsilateral breast tissue receiving ⩾ 37 Gy was 1% and 5% for CyberKnife and LINAC plans respectively. Conclusion: CyberKnife and LINAC generate treatment plans for MRI‐guided prone position APBI with acceptable dose distributions. The standard LINAC requires careful beam configuration to secure clearances between equipments. CyberKnife results in better conformity and slightly higher doses in the critical normal tissues.
SU‐DD‐A3‐06: The Impact of Probe Angle and Tissue Elastic Module in Ultrasound‐Guided Prostate IMRT
Authors: Ding C , Li X , Yang Y , Smith R , Deutsch M , Beriwal S , Heron D , Huq M
Published: July 2008

Purpose: An integrated ultrasound and CT‐Sim system can be used to assist the daily setup of prostate IMRT patient. The purpose of this study is to investigate the influence of probe angle and the tissue elastic module on the displacement of prostate during ultrasound localization using Finite Element Method (FEM). Method and Materials: An ultrasound localization system (Resonant Medical System, Montreal, Canada) integrated with a CT‐Sim was used to obtain a full set of 3‐D ultrasound (US)‐CT images. The patients' anatomical structures, such bone, bladder, and prostate, were contoured on the CT images by radiation oncologists. The ultrasound probe was positioned at 1cm inferior to bladder superior boundary. A 3D finite element model was generated for each of the patient. The corresponding displacement of prostate during ultrasound localization was calculated by FEM software (Ansys). Results: Under normal tissue elastic module (body (E=15kPa), bone (E=10GPa), bladder wall (E=300kPa), prostate (E=100kPa), and probe (E=3GPa)), when the angle of ultrasound probe increased from 10 to 60 degree to vertical plane with 2cm compression of ultrasound probe, the total displacement of prostate was 0.46∼0.6mm (0.43∼0.54mm inferior, 0.15∼0.25mm posterior). When the elastic module of bladder wall changed from 50kPa to 1MPa with the probe angle of 45 degree, the total displacement of prostate was increased from 0.26mm to 0.76mm (0.23 to 0.68mm inferior, 0.1 to 0.32mm posterior). There was almost no left and right displacement during compression. Conclusion: For the displacement of prostate, there was no significant dependent on the probe angle and limited dependent on the tissue elastic module. With proper controlled compression, the total prostate displacement can be limited within 2mm. This displacement can be corrected by FEM calculation.
SU‐DD‐A4‐02: Assessment of PET Estimated Tumor Volume by Four‐Dimensional Computed Tomography Measurements
Authors: ElNaqa I , Nofal A , Trovo M , Apte A , Yang D , Bradley J , Deasy J , Low D
Published: July 2008

Purpose: PET imaging is increasingly playing a key role in tumor detection, staging, and radiotherapy target definition of different cancer sites. However, the use of PET delineation in treatment planning of lung cancer is hindered by breathing motion blur artifacts. These artifacts complicate the evaluation of segmentation algorithms accuracy for PET. In this work, we propose to assess PET estimated tumor volume by comparing with four‐dimensional computed tomography measurements under different motion conditions. Method and Materials: We analyzed six NSCLC patients' datasets who underwent pre‐treatment FDG‐PET/CT scanning and 4D‐CT simulations. The 4D‐CT were acquired according to a ciné‐mode 4D protocol; 25 scans were collected at each couch position while the patient underwent simultaneous bellows and spirometry measurements. Volumetric datasets were rebinned to the following phases: end‐of exhalation, beginning‐of‐exhalation, mid‐exhalation, mid‐inhalation, and end‐of‐inhalation, in addition to computing average CT and MIP datasets. The tumor volume was manually contoured on nine PET and CT datasets by two physicians for each patient to provide a gold standard for comparison. Different PET segmentation algorithms based on SUV thresholding and active contours were evaluated. Motion artifacts were mitigated using a deconvolution‐based deblurring approach. Results: Our preliminary analysis indicates that manual contouring on 4D‐CT datasets produced relatively consistent results across the different phases by the two observers. Motion deblurring had varying effects on the evaluated algorithms; it increased the estimated volume by the 40% maximum SUV thresholding and reduced it when applying an SUV cutoff of 2.5. The active contour model produced robust results independent of the blurring effect. Conclusion: We have investigated a 4DCT approach for assessing the performance of PET segmentation methods in lung cancer. Our preliminary results indicate high sensitivity of thresholding methods and better robustness by active contouring models. Further investigation is required to improve accuracy relative to the 4DCT gold standard.
SU‐EE‐A1‐03: A Study On the Use of Full‐Field Non‐Flat Beams for IMRT Treatment
Authors: Gupta N , Weldon M , Kong X , Wang J , Zhang H , Li K
Published: July 2008

Purpose: The purpose of this study was to investigate the adequacy of full‐field non‐flat megavoltage beams for planning and delivery of step‐and‐shoot Intensity Modulated Radiation Therapy for different body sites. Method and Materials: IMRT treatment optimization creates non‐flat fluence maps to accomplish prescribed treatment objectives. With “Stereotactic” mode available in commercial linacs with the flattening filter removed, non‐flat beams are now available that produce dose rates much higher than the flattened beam modes in current clinical use, thus offering the potential of delivering treatments much faster. We have recently installed and commissioned such a photon beam. This beam is currently restricted in its clinical use to 5×5cm2. Full field beam data was acquired for this beam in research mode. The full‐field stereotactic mode beam data was modeled in Eclipse TPS. IMRT plans previously delivered for different target sizes and complexities ranging from prostate, head and neck and abdomen were re‐planned using the same target and normal tissue constraints. Plans comparable to the clinically accepted treatment plans were obtained. These plans were compared using several plan comparison parameters, along with the total number of MU's and segments required to deliver a comparable plan, and correlated to the size of the target. Results: Our results show that clinically acceptable treatment plans are easily accomplished with the non‐flat beams, with comparable MU's for smaller targets, but proportionally larger MU's for larger targets. The number of segments required to deliver comparable plans with the non‐flat beam were very similar, but slightly higher. Conclusion: Our study indicates that treatment delivery with highly modulated fields do not require flattened beams for clinical treatment delivery. The benefit of three times higher dose rates than the flattened beam will make treatment delivery significantly faster for non‐flat beams. This benefit will be much more significant for hypofractionated treatments.
SU‐EE‐A2‐01: A General Formula Predicting Near‐Target Dose Fall‐Off Characteristics for Different Isocentric and Non‐Isocentric Delivery Modalities
Authors: Ma L , Hossain S , Descovich M , Chuang C , Verhey L , Shrieve D , Larson D
Published: July 2008

Purpose: To investigate whether a common relationship exists governing the near‐target dose fall‐off for Gamma Knife, Cyberknife and MLC‐based Novalis linac systems. Method and Materials: Three groups of intracranial patient cases treated with Gamma Knife, Cyberknife, Novalis MLC‐based system were selected for the study. Each group contains 10–20 delivered treatment plans. In each case, the target was covered conformally by a peripheral isodose line ranging from 45% (Gamma Knife) to 95% (Novalis) of the maximum dose inside the target. Based on the divergence theorem, the dose fall‐off near the target was derived as , where V0 is volume of the prescribed isodose line covering at least 99% of the target volume, γ is a constant fitting parameter, which measures the steepness of the dose fall‐off near the target. The goodness of the fit and the average γ‐values were obtained for all cases of each modality. Results: The formula fitted excellently for all cases with the linear correlation coefficient R2 exceeded 0.99 in the log‐log plot for each case. No obvious dependence was found for the size of the targets, the number of the beams or the isocenters used for each group. An average γ‐value of 1.49± 0.13 was obtained for Gamma Knife, 1.48± 0.41 for Cyberknife, and 1.46 ± 0.19 for Novalis group of cases. No statistical significance was found in the mean value differences among the groups. However, Gamma Knife exhibited the smallest range of deviations in the mean value while Cyberknife exhibited the largest range of deviations in the mean value. Conclusion: A general formula and a common parameter was demonstrated for relating the average dose fall‐off near the target for Gamma Knife, Cyberknife and Novalis MLC‐based Linac systems. Despite large physical differences, nearly identical dose fall‐off was found for these modalities for treating intracranial lesions.
SU‐EE‐A2‐06: An Integrated Software Platform for Treatment Documentation and Outcome Analysis for Stereotactic Radiosurgery and Hypo‐Fractionated Stereotactic Body Radiotherapy
Authors: Liu D , Jin J , Ryu S , Siddiqui F , Movsas B , Chetty I
Published: July 2008

Purpose: Outcome analysis is an important and challenging task in radiation oncology. We have developed an integrated software platform that facilitates evaluation of outcomes for patients treated with stereotactic radiosurgery (SRS) and hypo‐fractionated stereotactic body radiotherapy (SBRT). Method and Materials: An outcomes‐study database was designed, under IRB‐approval, to store medical information of patients who undergo SRS or SBRT. The outcomes‐study database is integrated with a record‐and‐verify system (ARIA, Varian Medical Systems) and with an in‐house developed hospital database. A software package with GUI was developed using Visual Studio. Net (Microsoft, USA) to evaluate treatment plans. Biological dose models including TCP, EUD (Niemierko's model), NTCP (Lyman, Fdam, relative seriality models, etc.) as well as biologically effective doses are determined from dose distributions and DVHs, automatically imported from the treatment planning systems. Patient clinical data (from physician on‐treatment and followup visits) and image data (including planning CT scans and followup CT scans) are imported for outcomes analysis. Results: Thus far approximately 700 SRS/SBRT patients medical records have been populated into the outcomes database. The database contains all medical information, including demographic, social, diagnostic, treatment and follow‐up information. As it is linked to the hospital database, treatment information encompasses multi‐disciplinary‐based treatments including surgery and chemotherapy. The web‐based interface enables access and information management remotely. The calculation of biological dose indices provides useful means to correlate dose distributions with clinical outcome with respect to tumor control and healthy tissue complications assessed from followup physical examinations as well as image data used to inspect possible recurrent disease or radiation‐induced damage. Conclusion: The goal of the database is to study the various factors of significance related to the outcomes of patients treated with SRS and SBRT, using non‐standard, hypo‐fractionated RT doses. Parameters specific to biological dose models will be updated using maximum likelihood analysis.

Acknowledgement: NIH‐R01CA106770.
SU‐GG‐I‐01: Improving the Utility of In‐Room Video Camera Systems for Continuous Surveillance of Patient Motion During Radiation Treatment
Authors: Kut C , Chen C , Wong J , Taylor R
Published: July 2008

Purpose: To improve the utility of in‐room video‐based system for continuous quantitative monitoring of patient motion independent of environmental changes in lighting and geometry. Method and Materials: A video‐based tracking system was developed using a webcam with 600 by 450 pixels and Microsoft Visual C++. It is mounted at the end of the treatment couch to constantly view a specified region on the patient's torso of 50 cm by 30 cm at 55 degrees viewing angle. Small high contrast “sticky” markers are placed within the viewing region for easy detection. Environmental disturbances such as changes in machine positions and lightings are minimized through appropriate real‐time image subtraction and processing techniques. An alarm is activated when the patient movement is deemed out‐of‐tolerance. For validation, a lead ball phantom and a flat “sticky” marker of 1 cm diameter each were used to determine detectable target displacements. Each tracking session was automatically recorded for further data analysis. Pre‐clinical evaluations were performed on two subjects. Results: Target displacements of (2, 2, 5) mm for the lead ball phantom and (4,4,7) mm for the flat phantom are readily detected in the lateral, superior‐inferior and vertical directions respectively. Most importantly, the system detects these changes in the presence of environmental disturbances which include large changes in room lighting, and couch and gantry positions. The system fails when the camera's view is obstructed. Conclusion: Our system provides an effective approach to track and monitor patient position after highly accurate setup, such as using cone‐beam CT. It is considerably lower in cost relative to existing commercial tracking systems. The use of more optimal markers and 2 cameras are under investigation to improve detection resolution. With further refinement, the system can be adapted for routine clinical use that is superior to present in‐room video‐monitoring systems.
SU‐GG‐I‐06: Characterization of True and False Positive Locations of Spiculated Lesions On Mammography
Authors: Jahanbin R , Muralidhar G , Sampat M , Whitman G , Bovik A , Markey M
Published: July 2008

Purpose: We are developing a model‐based framework for the detection of spiculated masses on mammography, the current performance of which is 88% sensitivity with 2.7 false positives per image. The goal of this study is to identify features that uniquely characterize the true positive (TP) and false positive (FP) detections from this system. Method and Materials: A two alternative‐forced‐choice observer experiment was used. For each of the 47 cases of spiculated masses, the true lesion location and the highest‐ranked FP from the CAD were shown to the observer (radiologist). The observer was not told if he/she was looking at the true lesion location or FP and the order in which these were shown was random. The radiologist visually inspected these images to pick the one that corresponds to the true lesion location. We then compared this decision to the ground truth to analyze the TP and FP detections that were incorrectly determined by the radiologist. Results: The radiologist correctly identified the true lesion location and false positive for all 47 cases. These data suggest that the radiologist could easily dismiss the false positives marked by the CAD algorithm. Conclusion: While false positive detections remain a challenge with the current version of our model‐based framework for the detection of spiculated masses on mammography, this study implies that those false positives may be recognizable as such by the radiologists and suggests future directions for reducing the number of false positive marks.
SU‐GG‐I‐07: Evaluation of Cine‐CT for Quantifying Respiratory Displacement of Lung Tumors Without a Respiratory Surrogate
Authors: Ahmad Moiz , Riegel Adam C , Pan Tinsu
Published: July 2008

Purpose: The conventional approach to measuring tumor displacement, the net movement of its geometric center, is to use 4D‐CT with a respiratory surrogate. We propose using the MIP, average CT and new Max‐Min projection CT images from cine‐CT without a respiratory surrogate as a method of evaluating respiratory displacement of lung tumors. We evaluate the reliability of this method in producing accurate displacement quantification. Method and Materials: We design a new Max‐Min projection CT image, which is the pixel‐by‐pixel average of the maximum intensity projection (MIP) and minimum intensity projection (mip.) The Max‐Min directly shows the displacement volume of a tumor. A simple distance measurement on Max‐Min yields the tumor displacement. Max‐Min, cine‐MIP and cine‐ACT are obtained on a scanner with the cine‐CT capability without using a respiratory surrogate. The average CT (ACT) images are derived from averaging the cine CT images at the same slice location. All cine‐CT images are acquired on a GE 8‐slice CT. We use Max‐Min, cine‐MIP and cine‐ACT images to measure the tumor displacement for 38 4D‐CT simulation patients with lung tumors. For comparison, the 4D‐CT scan of each patient is also used to measure displacement. Results: The Max‐Min images show a clear displacement volume and yield a measurable displacement in 76.3% of cases. The Max‐Min method works best for tumors with reasonably smooth boundaries and displacements less than the tumor size. With 4D‐CT as a gold standard, Max‐Min measures displacement accurately to within one CT voxel (2.5 mm). In the other 23.7% of cases, cine‐MIP and cine‐ACT are used to quantify the displacement with 5 mm accuracy (2 CT voxels). Conclusion: Use of the Max‐Min, cine‐MIP and cine‐ACT images is a reliable method of quickly quantifying tumor respiratory displacement without a respiratory surrogate.
SU‐GG‐I‐11: Dose and Image Quality Evaluation of a Mobile CT Scanner for Head and Neck Imaging
Authors: Gingold E , Dave J
Published: July 2008

Purpose: To evaluate the radiation dose delivered to patients and personnel by a mobile x‐ray CT scanner designed for bedside imaging of the head and neck, and to examine image quality under clinical conditions. Method and Materials: Computed Tomography Dose Index (CTDI) was measured using a 100 mm pencil ionization chamber and 16 cm diameter acrylic phantom over a range of acquisition parameters on a mobile CT scanner (Neurologica Ceretom, Danvers, MA). Scatter radiation was measured using the same phantom. Image quality was evaluated using the manufacturer's QA phantom and the common CATPHAN phantom. Results: At 120 kVp, CTDI‐100 measured 44.8, 83.5, and 122 mGy at 7 mA and 2, 4, and 6 seconds per rotation, respectively. At 140 kVp, commonly used for head scanning, the CTDI‐100 measured 65.3, 126.8, and 176.3 mGy at 7 mA and 2, 4, and 6 seconds per rotation, respectively. All measured doses were within 10% of the CTDI values indicated to the operator on the scanner's console. Using protective lead curtains provided with the scanner, scatter radiation was well within ALARA standards. CATPHAN images demonstrated acceptable alignment, slice width and incrementation accuracy, geometric accuracy, low contrast resolution, high contrast spatial resolution, image uniformity and CT number linearity at clinical techniques. Conclusion: When operated in “low dose” (2 seconds/rotation) mode, the radiation dose delivered by the mobile CT scanner is below or comparable to the ACR's diagnostic Reference Value (RV) for head CT dose. The “standard” (4 seconds/rotation) and “high‐quality” (6 seconds/rotation) modes deliver more radiation, with a corresponding increase in image quality. Assessment using an industry‐standard phantom produced acceptable image quality performance under clinical conditions. With proper precautions, the scanner can be safely used in most intensive care environments without additional shielding, with minimal occupational exposure.
SU‐GG‐I‐17: A Technique for Removing Motion Related Image Artifacts in KV Cone‐Beam CT From On‐Board Imager: 4D‐CBCT Implications
Authors: Ali I , Ahmad S
Published: July 2008

Purpose: To correct motion related image artifacts in kV cone‐beam CT (CBCT) by tracking a seed marker in cone‐beam projections obtained from an on‐board imager (OBI). Method and Materials: The motion of metal markers attached to the CATPHAN phantom mounted on a moving platform was measured by tracking the marker positions in kV cone‐beam projections. The motion tracking algorithm is based on a normalized cross‐correlation algorithm that determines the position of the marker in each projection. The position of the marker was determined from 650 projections (0°–360°) acquired for about a minute in a single CBCT scan. The motion cycle of the moving platform was set at 15cycles/min, with 1.75 cm amplitude, in order to mimic respiratory motion. The marker motion track was used to map cone‐beam projections to eliminate motion shifts. Pre‐processed projections were used to reconstruct CBCT using Feldkamp back‐projection. The CATPHAN was used to evaluate image quality parameters such as contrast, position resolution, uniformity and linearity of CBCT reconstructed before and after motion correction. Results: A new technique was developed and tested to track the motion of seed markers in cone‐beam projections acquired in a kV CBCT scan with no additional dose other than that for imaging. We were able to successfully remove motion related image artifacts such as blurring, spatial distortion and improve contrast and position resolution from CBCT reconstructed from motion‐corrected projections. Besides motion correction, this technique also allows to extract information about seed marker motion that can be used to correlate internal and external marker motion providing possible usage for beam gating implications. Conclusion: This technique eliminates motion artifacts in CBCT. Combining 3D volumetric CBCT with motion tracks of one or more markers may provide a method to perform four‐dimensional CBCT where anatomical information and dynamic positioning of the tumor can be utilized.
SU‐GG‐I‐18: An Image‐Domain Based Cone Beam CT Scatter Correction Method
Authors: Li X , Li T , Yang Y , Heron D , Huq M
Published: July 2008

Purpose: Due to a large cone angle, scatter contribution significantly degrades the image quality of cone beam computed tomography (CBCT) by introducing the cupping effect. The objective of this study is to develop a new CBCT scatter correction method in image domain. Method and Materials: The hypotheses of the proposed method are that the image intensity of different kind of materials in CBCT image is globally uniform and the cupping effect can be described as a bias field, a low frequency signal across the whole 3‐D images. Based on above assumptions, we proposed a maximum a posteriori probability (MAP) framework to estimate the bias field contribution. The well‐known fuzzy C‐mean model is extended to define the likelihood function of the CBCT image. A markov random field model is used to describe the prior probability of the mixture defined in FCM model. The bias field is characterized by a zero mean Gaussian prior probability. An iterated conditional mode‐like approach is utilized to maximize the objective function. The corrected CBCT image can be obtained by subtracting the bias field from original CBCT image. Results: The performance of correcting the cupping effect of CBCT image with the proposed MAP framework was tested using both digital phantoms and clinical CBCT images. In the phantom studies the intensity of higher density material in the simulated CBCT images of contrast phantoms is even lower that that of lower density material due to cupping effect. The corrected CBCT image showed almost same intensity distribution as the original contrast phantom images. For real patient study, compared to the original brain CBCT image, the corrected CBCT image significantly improved the uniformity of intensity distribution of brain soft tissue. Conclusion: The proposed image‐based scatter correction method showed a promising result to reduce the cupping effect commonly encountered in CBCT image.
SU‐GG‐I‐23: A Comparison of Adaptive Radiotherapy Treatment Planning Between Planning CT and KVCBCT
Authors: Juh R , Back G , Ahn S , Kim J , Suh T
Published: July 2008

Purpose: The recent integration of kilo‐voltage cone beam computed tomography (kV‐CBCT) imaging systems into linear accelerators makes it possible to image and treat a patient on a single machine. The goal of this study is to investigate the feasibility and usefulness of acquiring kV‐CBCT for adaptive radiotherapy for patients with lung and phantom study with significant target position. Method and Materials: A self made brain phantom and quality assurance phantom were used to compare the dosimetric and geometric accuracy between planning CT and kV‐CBCT with bow‐tie filter added. The quality of the kV‐CBCT volume images acquired using phantom was evaluated by measuring the spatial accuracy, contrast, hounsfield units (HU), and converting HU to electron density. The kV‐CBCT was registered to the CT image using normalized mutual information. Results: In both phantom studies, the DVH based on kV‐CBCT images were in excellent agreement with DVH based on planning CT images. CBCT images were dependent on image uniformity, linearity and it needed verify the difference the mean HU value of the center ROI and peripheral ROI using histogram. The difference (<1%) is found in the calculated dose to the target for a complex inhomogeneous phantom between using kV‐CBCT images and planning CT images. These results indicate that kV‐CBCT images can be used to calculate dosimetric parameter accurately in radiotherapy treatment planning. In a patient study, doses for targets volume plans calculated on kV‐CBCT images agreed within 5% with those calculated on planning CT. Conclusion: We have investigated the feasibility and usefulness of acquiring on‐board kV‐CBCT images for adaptive radiotherapy treatment planning and tested the accuracy. It is feasible to use kV‐CBCT to determine dosimetric consequences resulting from tumor volume changes. The kV‐CBCT has potential to become a very useful tool for adaptive radiotherapy treatment planning.
SU‐GG‐I‐24: A Quantitative Assessment of the Effects of a Simple Dead Detector Pixel Correction Method for Megavoltage Cone Beam CT Images
Authors: Flynn R , Shukla H , Nixon E , Bayouth J
Published: July 2008

Purpose: Determining the extremes such that correction methods for missing or truncated projection data begin to fail could aid in the design of more efficient imaging systems in the future. We quantitatively assessed the effectiveness of a dead detector pixel correction method for megavoltage cone beam computed tomography (MVCBCT). Method and Materials: Ninety‐six MVCBCT images of an image quality phantom were reconstructed from projections that were acquired from four MVision™‐equipped Siemens Oncor™ linacs with 1024×1024 amorphous silicon electronic portal imaging devices (EPIDs). Both 8 monitor unit (MU) and 60 MU head‐and‐neck scanning protocols were used for the acquisitions. Dead pixel maps were simulated for the cases of randomly distributed singular dead pixels and 13‐dead‐pixel clusters, each with six dead pixel percentages: 2%, 25%, 75%, 80%, 90%, and 95%. Transmission images were corrected in orthogonal directions using a 1‐D line‐by‐line linear interpolation algorithm. Results: Image quality for the baseline case (< 0.5% dead pixels) and the case of 75% coverage by 13‐dead‐pixel clusters was similar. Image quality began to degrade severely after the EPID was covered to 80% by 13‐dead‐pixel clusters and 90% for singular dead pixels. Higher acquisition MU decreased the standard deviation of the difference images (corrected minus baseline), but had no effect on the means of the difference images. Conclusion: With a simple correction method, MVCBCT images are relatively insensitive to randomly distributed dead detector pixels until 80–90% of the EPID is covered with dead detector pixels. Image degradation for the same percentage of dead detectors was more pronounced when the EPID was covered with clusters of 13 dead pixels than with singular dead pixels, and was only weakly dependent on the MU used during the image acquisition.
SU‐GG‐I‐30: Magnitude of Scattered Radiation and Dose Efficiency in Volume‐Of‐Interest (VOI) Cone Beam CT
Authors: Lai C , Chen L , Han T , Liu X , Shen Y , Wang T , Shaw C
Published: July 2008

The magnitude of scattered radiation and dose efficiency inside and outside the VOI was investigated for VOI cone beam computed tomography (CBCT) technique. For experiments, a bench‐top CBCT system with a flat‐panel digital detector was constructed. Two cylindrical polycarbonate phantoms (11 cm and 15 cm in diameter) were used to simulate breasts. To implement the VOI scanning technique, a lead filter with a rectangular opening was placed between the x‐ray source and the phantoms. The x‐ray tube voltage setting was 80 kVp. The phantoms were imaged without and with the VOI filter for the open filed and the VOI field, respectively. Slot scanning technique with varying slot width was used to measure SPR values at the detector plane. Dose measurement was performed using TLD dosimeters at five different locations for the 11‐cm phantom and six locations for the 15 cm phantom. The results showed that the SPR value inside the VOI were about 0.37 and 0.039 for the open field and the VOI field, respectively, for the 11 cm phantom. This indicates that the SPR can be reduced by a factor of 9 inside the VOI. The results also showed that dose increases from the center toward to the edge for the open field, but decreases for the VOI field. The dose can be reduced by a factor of 3 or more outside the VOI and by a factor of 1.6 at the center of the phantom for the 11 cm phantom (this work was supported in part by a grant CA104759 from the NCI and a research grant EB00117 from the NIBIB).
SU‐GG‐I‐34: Comparison of Radiation Doses for Optimal and Dose Modulation Techniques in Abdominal CT Examinations
Authors: Livingstone R
Published: July 2008

Purpose: To compare reduction in radiation dose using dose modulation techniques and optimal exposure parameters and its impact on image quality for biphasic abdominal CT examination performed using multidetector CT scanner. Method and Materials: A prospective study of 426 patients undergoing biphasic contrast‐enhanced abdominal examination involving arterial and venous regions were performed using optimal and dose modulation techniques in a six‐section multidetector CT scanner. For the optimal setting, images were acquired using constant tube potential (arterial phase with 90 kV and venous phase with 120 kV) and varying tube current‐time product according to patient's body weight. Using angular dose modulation (D‐DOM) and z‐axis dose modulation (Z‐DOM) techniques, images were acquired with constant tube potential similar to optimal settings. The effective doses were calculated using the DLP values. The signal to noise ratio (SNR) was also studied from the image obtained at the region of the liver. In a blinded review, one radiologist rated the CT scans for overall image quality. Radiation dose and image noise for optimal and dose modulation techniques with similar settings used for patients were also studied using an acrylic body phantom. Results: The effective dose using optimal, D‐DOM and Z‐DOM techniques were 11.3 mSv, 9.5 mSv and 8.2 mSv respectively for patient's of body weight 40 to 60 Kgs. The mean SNR value for arterial phase and (venous phase) was 7.7 (6.2), 8.3 (6.5) and 8.5 (7.9) for optimal, D‐DOM and Z‐DOM respectively for patient's of body weight 40 to 60 Kgs Conclusion: This study indicates the potential of significant dose reduction in abdominal CT. Use of dose modulation techniques resulted in a dose reduction of 16 – 28% with acceptable diagnostic quality in comparison to the optimal settings.
SU‐GG‐I‐46: An Automatic Region Detection Algorithm for Analyzing Module 1 of the ACR CT Accreditation Phantom
Authors: Kwan A , Mah E , Boone J
Published: July 2008

Purpose: A region identification algorithm has been developed to facilitate the automatic analysis of Module 1 of the ACR CT accreditation phantom. Method and Materials: The ACR CT accreditation phantom was scanned using a GE Lightspeed QX/i scanner, and a preliminary algorithm was developed to identify the centers of the air and bone‐mimicking areas in Module 1 of the phantom. The air and the “bone” regions in the CT image were first isolated by binarizing the image with a threshold of −500 and 800 HU, respectively. Next, a Canny edge detector was applied to the air‐only binary images to detect the edges, and the center of the phantom was then identified using a Hough‐based circular object detection algorithm. Lastly, the edge of the phantom was removed and the center of the air‐only region is subsequently detected. A similar procedure was used to identify the center of the “bone” region. Results: To assess the algorithm, the CT image from Module 1 of the ACR CT phantom was computationally rotated to various orientations. The centers of the air and “bone” regions were then located using the preliminary algorithm. The resulting averages for both regions were very reproducible (within 1 HU). Conclusion: The preliminary results above have demonstrated that the algorithm can robustly identify the centers of the air and bone regions. Once the centers of these two regions are located, the required ROIs can be extracted from the original CT image, and the required statistics computed. Since the phantom is a rigid object, this implies that the other areas of interest in Module 1 can be easily identified. This will be demonstrated in the presentation.
SU‐GG‐I‐56: Internal Dosimetry of Iodine 131 in Patients with Thyroid Carcinoma in the Instituto Nacional De Cancerologia, Bogota‐Colombia
Authors: Veloza S , De los Reyes A
Published: July 2008

Purpose: with the purpose of determining the iodine 131 biodistribution in patients with thyroid cancer, a patient‐specific dosimetry protocol was developed and applied, using the administration of a tracer amount of this radionuclide and the methodology of the Medical Internal Radiation Dose. The dosimetry method consists in a determination of the maximum tolerated activity that will deliver 2 Gy to the blood, and the corresponding ablative lesion dose. Method and Materials: Fifteen patients with thyroid‐stimulating hormone (TSH) level of 30 mU/L and a suppressed iodine diet were orally administered with a tracer activity (111 – 148 MBq). The activity determination in whole body, lungs, stomach, thyroid and metastatic targets were done using a region‐of‐interest (ROI) technique. Individual ROIs were drawn on both anterior and posterior projections at 2, 4, 24, 48 and 72 hours. Calculations were based on the geometric mean of anterior and posterior counts, including corrections for photon scatter, attenuation, septal penetration, and other effects in the gamma camera. Results: the data were fitted to multicomponent exponential retention functions or in closed compartment models using the Organ Level Internal Dose Assessment (a software program OLINDA, Vanderbilt University), and, subsequently, the calculation of radiation absorbed doses to the different organs and tissues. Conclusion: The internal dosimetry method implemented has the advantage of being ambulatory and the tumor doses was prescribed for those cases in which tumor uptake give ablative lesion dose of 300 Gy. The internal dosimetry is useful in determine the optimal amount of administered activity in radioiodine therapy, so that the absorbed doses to the organs of interest turn out to be the optimal, without overcoming the maximum tolerated dose in red marrow and the maximum tolerated dose to the lungs.
SU‐GG‐I‐70: Patient Dose Measurements for Establishing Guidance Levels for Medical Exposures in Diagnostic Radiology
Authors: Duhaini I , Assafiri Y , El‐Nachef L
Published: July 2008

Patient dose measurements in diagnostic radiology are conducted for common and specialized radiological procedures. The Objective of this study is to obtain a range of radiation doses received by patients undergoing diagnostic radiology examinations in Lebanon, to investigate the variability of patient doses in relation to x‐ray equipment used to compare the results with international guidance levels and to implement corrective actions to reduce doses.