bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dosimetric effects of an air cavity for the SAVI™ partial breast irradiation applicator
Authors: Richardson Susan L. , Pino Ramiro 
Published: July 2010

Purpose:To investigate the dosimetric effect of the air inside the SAVI™ partial breast irradiation device.Methods:The authors have investigated how the air inside the SAVI™ partial breast irradiation device changes the delivered dose from the homogeneously calculated dose. Measurements were made with the device filled with air and water to allow comparison to a homogenous dose calculation done by the treatment planning system. Measurements were made with an ion chamber, TLDs, and film. Monte Carlo (MC) simulations of the experiment were done using the EGSnrc suite. The MC model was validated by comparing the water‐filled calculations to those from a commercial treatment planning system.Results:The magnitude of the dosimetric effect depends on the size of the cavity, the arrangement of sources, and the relative dwell times. For a simple case using only the central catheter of the largest device, MC results indicate that the dose at the prescription point 1 cm away from the air‐water boundary is about 9% higher than the homogeneous calculation. Independent measurements in a water phantom with a similar air cavity gave comparable results. MC simulation of a realistic multidwell position plan showed discrepancies of about 5% on average at the prescription point for the largest device.Conclusions:The dosimetric effect of the air cavity is in the range of 3%–9%. Unless a heterogeneous dose calculation algorithm is used, users should be aware of the possibility of small treatment planning dose errors for this device and make modifications to the treatment delivery, if necessary.
Advantage in image fidelity and additional computing time of JPEG2000 3D in comparison to JPEG2000 in compressing abdomen CT image datasets of different section thicknesses
Authors: Lee Hyunna , Lee Kyoung Ho , Kim Kil Joong , Park Seongjin , Seo Jinwook , Shin Yeong‐Gil , Kim Bohyoung 
Published: July 2010

Purpose:This study aimed to assess the advantage of the Joint Photographic Experts Group 2000 (JPEG2000) 3D (part 2) over JPEG2000 in compressing abdomen computed tomography (CT) image data sets of different section thicknesses (STs).Methods:Twenty CT scans were reconstructed with six STs (0.67, 1, 2, 3, 4, and 5 mm) and were then compressed to seven compression ratios (CRs) (reversible, 6:1, 8:1, 10:1, 12:1, 14:1, and 16:1) using JPEG2000 and JPEG2000 3D algorithms. Computing (encoding and decoding) times were measured. The image fidelity of the compressed images was quantitatively measured with two computerized image fidelity metrics, peak signal‐to‐noise ratio (PSNR) and multiscale structural similarity (MS‐SSIM). For 120 selected case‐relevant images , five radiologists independently compared original and compressed images and assessed the fidelity of the compressed images on a four‐grade scale. Wilcoxon signed‐rank tests and Friedman tests with post hoc Dunn tests were used for the comparisons between the two compressions and among the six STs, respectively.Results:For each combination of the ST and irreversible CR, JPEG2000 3D showed higher image fidelity than JPEG2000 in terms of PSNR, MS‐SSIM , and five radiologists’ grading (‐values ranged from to 0.003). At each CR, the advantage of JPEG2000 3D in image fidelity, measured as the differences in the two computerized image fidelity metrics (PSNR and MS‐SSIM), significantly increased as the ST increased from 0.67 to 2 mm, and then slowly decreased as the ST increased from 2 to 5 mm. Similar trends were observed in visual analyses of 120 selected images by five radiologists. At each CR, the 3D‐to‐2D encoding‐time ratio significantly decreased as the ST increased from 0.67 to 2 mm, and then slowly increased as the ST increased from 2 to 5 mm. The 3D‐to‐2D decoding‐time ratio at each CR did not show a notable biphasic trend across the ST.Conclusions:In compressing abdomen CT image data sets of different STs, the advantage of JPEG2000 3D over JPEG2000 increases as the ST increases from 0.67 to 2 mm, and then slowly decreases as the ST increases from 2 to 5 mm. The practical advantage of JPEG2000 3D is limited for a submillimeter ST due to its greater computing time with only a marginal improvement in image fidelity.
Measurement of absorbed dose, quality factor, and dose equivalent in water phantom outside of the irradiation field in passive carbon‐ion and proton radiotherapies
Authors: Yonai Shunsuke , Kase Yuki , Matsufuji Naruhiro , Kanai Tatsuaki , Nishio Teiji , Namba Masao , Yamashita Wataru 
Published: July 2010

Purpose:Successful results in carbon‐ion and proton radiotherapies can extend patients’ lives and thus present a treatment option for younger patients; however, the undesired exposure to normal tissues outside the treatment volume is a concern. Organ‐specific information on the absorbed dose and the biological effectiveness in the patient is essential for assessing the risk, but experimental dose assessment has seldom been done. In this study, absorbed doses, quality factors, and dose equivalents in water phantom outside of the irradiation field were determined based on lineal energy distributions measured with a commercial tissue equivalent proportional counter (TEPC) at passive carbon‐ion and proton radiotherapy facilities.Methods:Measurements at eight positions in the water phantom were carried out at the Heavy‐Ion Medical Accelerator in Chiba of the National Institute of Radiological Sciences for 400 and 290 MeV/u carbon beams and at the National Cancer Center Hospital East for a 235 MeV proton beam.Results:The dose equivalent per treatment absorbed dose at the center of the range‐modulated region decreased as the position became farther from the beam axis and farther from the phantom surface. The values of ranged from 6.7 to 0.16 mSv/Gy for the 400 MeV/u carbon beam, from 1.3 to 0.055 mSv/Gy for the 290 MeV/u carbon beam, and from 4.7 to 0.24 mSv/Gy for the 235 MeV proton beam. The values of the dose‐averaged quality factor ranged from 2.4 to 4.6 for the 400 MeV/u beam, from 2.8 to 5.3 for the 290 MeV/u beam, and from 5.1 to 8.2 for the proton beam. The authors also observed differences in the distributions of and between the carbon and proton beams.Conclusions:The authors experimentally obtained absorbed doses, dose‐averaged quality factors, and dose equivalents in water phantom outside of the irradiation field in passive carbon‐ion and proton radiotherapies with TEPC. These data are very useful for estimating the risk of secondary cancer after receiving passive radiotherapies and for verifying Monte Carlo calculations.
Two‐stage multishape segmentation of brain structures using image intensity, tissue type, and location informationa)
Authors: Akhondi‐Asl Alireza , Soltanian‐Zadeh Hamid 
Published: July 2010

Purpose:The authors propose a fast, robust, nonparametric, entropy‐based, coupled, multishape approach to segment subcortical brain structures from magnetic resonance images (MRIs).Methods:The proposed method uses three types of information: Image intensity, tissue types, and locations of structures. The image intensity information is captured by estimating the probability density function (pdf) of the image intensities in each structure. The tissue type information is captured by applying an unsupervised tissue segmentation method to the image and estimating a probability mass function (pmf) for the tissue type of each structure. The location information is captured by estimating pdf of the location of each structure from the training datasets. The resulting pmf's and pdf's are used to define an entropy function whose minimum corresponds to a desirable segmentation of the structures. The authors propose a three‐step optimization strategy for the segmentation method. In the first step, a powerful automatic initialization method is developed based on tissue type and location information of the structures. In the second step, a quasi‐Newton method is used to optimize the parameters of the energy function. To speed up the iterations, derivatives of the energy function with respect to its parameters are analytically derived and used in the optimization process. In the last step, the limitations related to the prior shape model are removed and a level‐set method is applied for the fine tuning of the segmentation results.Results:The proposed method is applied to two different datasets and the results are compared to those of previous methods in literature. Experimental results are presented for lateral ventricles, caudate, thalamus, putamen, pallidum, hippocampus, and amygdala.Conclusions:The results illustrate superior performance of the proposed segmentation method compared to other methods in literature. The execution time of the algorithm is a few minutes, suitable for a variety of applications.
Evaluating the extent of cell death in 3D high frequency ultrasound by registration with whole‐mount tumor histopathologya)
Authors: Vlad Roxana M. , Kolios Michael C. , Moseley Joanne L. , Czarnota Gregory J. , Brock Kristy K. 
Published: July 2010

Purpose:High frequency ultrasound imaging, 10–30 MHz, has the capability to assess tumor response to radiotherapy in mouse tumors as early as 24 h after treatment administration. The advantage of this technique is that the image contrast is generated by changes in the physical properties of dying cells. Therefore, a subject can be imaged before and multiple times during the treatment without the requirement of injecting specialized contrast agents. This study is motivated by a need to provide metrics of comparison between the volume and localization of cell death, assessed from histology, with the volume and localization of cell death surrogate, assessed as regions with increased echogeneity from ultrasound images.Methods:The mice were exposed to radiation doses of 2, 4, and 8 Gy. Ultrasound images were collected from each tumor before and 24 h after exposure to radiation using a broadband 25 MHz center frequency transducer. After radiotherapy, tumors exhibited hyperechoic regions in ultrasound images that corresponded to areas of cell death in histology. The ultrasound and histological images were rigidly registered. The tumors and regions of cell death were manually outlined on histological images. Similarly, the tumors and hyperechoic regions were outlined on the ultrasound images. Each set of contours was converted to a volumetric mesh in order to compare the volumes and the localization of cell death in histological and ultrasound images.Results:A shrinkage factor ofwas calculated from the difference in the tumor volumes evaluated from histological and ultrasound images. This was used to correct the tumor and cell death volumes assessed from histology. After this correction, the average absolute difference between the volume of cell death assessed from ultrasound and histological images wasand the volume overlap was.Conclusions:The method provided metrics of comparison between the volume of cell death assessed from histology and that assessed from ultrasound images. It was applied here to evaluate the capability of ultrasound imaging to assess early tumor response to radiotherapy in mouse tumors. Similarly, it can be applied in the future to evaluate the capability of ultrasound imaging to assess early tumor response to other modalities of cancer treatment. The study contributes to an understanding of the capabilities and limitation of ultrasound imaging at noninvasively detecting cell death. This provides a foundation for future developments regarding the use of ultrasound in preclinical and clinical applications to adapt treatments based on tumor response to cancer therapy.
The Swiss IMRT dosimetry intercomparison using a thorax phantom
Authors: Schiefer H. , Fogliata A. , Nicolini G. , Cozzi L. , Seelentag W. W. , Born E. , Hasenbalg F. , Roth J. , Schnekenburger B. , Münch‐Berndl K. , Vallet V. , Pachoud M. , Reiner B. , Dipasquale G. , Krusche B. , Fix M. K. 
Published: July 2010

Purpose:In 2008, a national intensity modulated radiation therapy (IMRT) dosimetry intercomparison was carried out for all 23 radiation oncology institutions in Switzerland. It was the aim to check the treatment chain focused on the planning, dose calculation, and irradiation process.Methods:A thorax phantom with inhomogeneities was used, in which thermoluminescence dosimeter (TLD) and ionization chamber measurements were performed. Additionally, absolute dosimetry of the applied beams has been checked. Altogether, 30 plan‐measurement combinations have been used in the comparison study. The results have been grouped according to dose calculation algorithms, classified as “type a” or “type b,” as proposed by Knöös et al. [“Comparison of dose calculation algorithms for treatment planning in external photon beam therapy for clinical situations,” Phys. Med. Biol. 51, 5785–5807 (2006)].Results:Absolute dosimetry check under standard conditions: The mean ratio between the dose derived from the single field measurement and the stated dose, calculated with the treatment planning system, was for the ionization chamber and ( deviation) for the TLD measurements. IMRT Plan Check: In the lung tissue of the planning target volume, a significantly better agreement between measurements (TLD, ionization chamber) and calculations is shown for type b algorithms than for type a . In regions outside the lungs, the absolute differences between TLD measured and stated dose values, relative to the prescribed dose, , are and , respectively. These data show the same degree of accuracy between the two algorithm types if low‐density medium is not present.Conclusions:The results demonstrate that the performed intercomparison is feasible and confirm the calculation accuracies of type a and type b algorithms in a water equivalent and low‐density environment. It is now planned to offer the intercomparison on a regular basis to all Swiss institutions using IMRT techniques.
Collimator angle influence on dose distribution optimization for vertebral metastases using volumetric modulated arc therapya)
Authors: Mancosu Pietro , Cozzi Luca , Fogliata Antonella , Lattuada Paola , Reggiori Giacomo , Cantone Marie Claire , Navarria Pierina , Scorsetti Marta 
Published: July 2010

Purpose:The cylindrical symmetry of vertebrae favors the use of volumetric modulated arc therapy in generating a dose “hole” on the center of the vertebrae limiting the dose to the spinal cord. The authors have evaluated if collimator angle is a significant parameter for dose distribution optimization in vertebral metastases.Methods:Three patients with one‐three vertebrae involved were considered. Twenty‐one differently optimized plans (nine single‐arc and 12 double‐arc plans) were performed, testing various collimator angle positions. Clinical target volume was defined as the whole vertebrae, excluding the spinal cord canal. The planning target volume (PTV) was defined as. Dose prescription was with normalization to PTV mean dose. The dose at of spinal cord was limited to 11.5Gy.Results:The best plans in terms of target coverage and spinal cord sparing were achieved by two arcs and Arc1–80° and Arc2–280° collimator angles for all the cases considered (i.e., leaf travel parallel to the spinal cord primary orientation). If one arc is used, only 80° reached the objectives.Conclusions:This study demonstrated the role of collimation rotation for the vertebrae metastasis irradiation, with the leaf travel parallel to the spinal cord primary orientation to be better than other solutions. Thus, optimal choice of collimator angle increases the optimization freedom to shape a desired dose distribution.
Extraction of depth‐dependent perturbation factors for parallel‐plate chambers in electron beams using a plastic scintillation detector
Authors: Lacroix Frédéric , Guillot Mathieu , McEwen Malcolm , Cojocaru Claudiu , Gingras Luc , Beddar A. Sam , Beaulieu Luc 
Published: July 2010

Purpose: This work presents the experimental extraction of the overall perturbation factor in megavoltage electron beams for NACP‐02 and Roos parallel‐plate ionization chambers using a plastic scintillation detector (PSD).Methods: The authors used a single scanning PSD mounted on a high‐precision scanning tank to measure depth‐dose curves in 6, 12, and 18 MeV clinical electron beams. The authors also measured depth‐dose curves using the NACP‐02 and PTW Roos chambers.Results: The authors found that the perturbation factors for the NACP‐02 and Roos chambers increased substantially with depth, especially for low‐energy electron beams. The experimental results were in good agreement with the results of Monte Carlo simulations reported by other investigators. The authors also found that using an effective point of measurement (EPOM) placed inside the air cavity reduced the variation of perturbation factors with depth and that the optimal EPOM appears to be energy dependent.Conclusions: A PSD can be used to experimentally extract perturbation factors for ionization chambers. The dosimetry protocol recommendations indicating that the point of measurement be placed on the inside face of the front window appear to be incorrect for parallel‐plate chambers and result in errors in the of approximately 0.4 mm at 6 MeV, 1.0 mm at 12 MeV, and 1.2 mm at 18 MeV.
Radiation dose evaluation in tomosynthesis and C‐arm cone‐beam CT examinations with an anthropomorphic phantom
Authors: Koyama Shuji , Aoyama Takahiko , Oda Nobuhiro , Yamauchi‐Kawaura Chiyo 
Published: July 2010

Purpose:The objective of this study was to evaluate organ dose and the effective dose to patients undergoing tomosynthesis (TS) and C‐arm cone‐beam computed tomography (CBCT) examinations and to compare the doses to those in multidetector CT (MDCT) scans.Methods:Patient doses were measured with small sized silicon‐photodiode dosimeters, 48 in number, which were implanted at various tissue and organ positions within an anthropomorphic phantom. Output signals from photodiode dosimeters were read out on a personal computer, from which organ and effective doses were computed. The doses in head, chest, abdomen, and hip‐joint TS, and in head and abdomen C‐arm CBCT were evaluated for routine protocols on Shimadzu TS and C‐arm CBCT systems, and the doses in MDCT with the same scan regions as in TS and CBCT were on Toshiba 64‐detector‐row CT scanners.Results:In TS examination of the head, chest, abdomen, and hip‐joint, organ doses for organs within scan ranges were 1–4 mGy, and effective doses were 0.07 mSv for the head scan and around 1 mSv for other scans. In C‐arm CBCT examinations of the head and abdomen, organ doses within scan range were 2–37 mGy, and effective doses were 1.2 mSv for the head scan and 4–5 mSv for abdominal scans. Effective doses in TS examinations were approximately a factor of 10 lower, while the doses in CBCT examinations were nearly the same level, compared to the doses in the corresponding MDCT examinations.Conclusions:TS examinations with low doses and excellent resolutions in coronal images compared to recent MDCT would widely be used in tomographic examinations of the chest, abdomen, pelvis, skeletal‐joints, and knee instead of MDCT examinations with significantly high doses. Since patient dose in C‐arm CBCT was nearly the same level as that in recent MDCT, the same consideration for high radiation dose would be required for the use of CBCT.
Validation of a treatment plan‐based calibration method for 2D detectors used for treatment delivery quality assurance
Authors: Olch Arthur J. , Whitaker Matthew L. 
Published: July 2010

Purpose:Dosimetry using film, CR, electronic portal imaging, or other 2D detectors requires calibration of the raw image data to obtain dose. Typically, a series of known doses are given to the detector, the raw signal for each dose is obtained, and a calibration curve is created. This calibration curve is then applied to the measured raw signals to convert them to dose. With the advent of IMRT, film dosimetry for quality assurance has become a routine and labor intensive part of the physicist's day. The process of calibrating the film or other 2D detector takes time and additional film or images for performing the calibration, and comes with its own source of errors. This article studies a new methodology for the relative dose calibration of 2D imaging detectors especially useful for IMRT QA, which relies on the treatment plan dose image to provide the dose information which is paired with the raw QA image data after registration of the two images (plan‐based calibration).Methods:Validation of the accuracy and robustness of the method is performed on ten IMRT cases performed using EDR2 film with conventional and plan‐based calibration. Also, for each of the ten cases, a 5 mm registration error was introduced and the Gamma analysis was reevaluated. In addition, synthetic image tests were performed to test the limits of the method. The Gamma analysis is used as a measure of dosimetric agreement between plan and film for the clinical cases and a dose difference metric for the synthetic cases.Results:The QA image calibrated by the plan‐based method was found to more accurately match the treatment plan doses than the conventionally calibrated films and also to reveal dose errors more effectively when a registration error was introduced. When synthetic acquired images were systematically studied, localized and randomly placed dose errors were correctly identified without excessive falsely passing or falsely failing pixels, unless the errors were concentrated in a majority of pixels in a contiguous narrow dose band. Irregularities seen in the calibration curve expose these errors.Conclusions:The plan‐based calibration method was found to be an accurate, efficient procedure, capable of detecting IMRT QA relative dosimetry errors as well as, or better than conventional calibration methods.
High‐resolution x‐ray guided three‐dimensional diffuse optical tomography of joint tissues in hand osteoarthritis: Morphological and functional assessments
Authors: Yuan Zhen , Zhang Qizhi , Sobel Eric S. , Jiang Huabei 
Published: July 2010

Purpose:The aim of this study was to investigate the potential use of multimodality functional imaging techniques to identify the quantitative optical findings that can be used to distinguish between osteoarthritic and normal finger joints.Methods:Between 2006 and 2009, the distal interphalangeal finger joints from 40 female subjects including 22 patients and 18 healthy controls were examined clinically and scanned by a hybrid imaging system. This system integrated x‐ray tomosynthetic setup with a diffuse optical imaging system. Optical absorption and scattering images were recovered based on a regularization‐based hybrid reconstruction algorithm. A receiver operating characteristic curve was used to calculate the statistical significance of specific optical features obtained from osteoarthritic and healthy joints groups.Results:The three‐dimensional optical and x‐ray images captured made it possible to quantify optical properties and joint space width of finger joints. Based on the recovered optical absorption and scattering parameters, the authors observed statistically significant differences between healthy and osteoarthritis finger joints.Conclusions:The statistical results revealed that sensitivity and specificity values up to 92% and 100%, respectively, can be achieved when optical properties of joint tissues were used as classifiers. This suggests that these optical imaging parameters are possible indicators for diagnosing osteoarthritis and monitoring its progression.