bluuebunny/crossref_metadata_2025_split huggingface dataset:
A compact mechatronic system for 3D ultrasound guided prostate interventions
Authors: Bax Jeffrey , Smith David , Bartha Laura , Montreuil Jacques , Sherebrin Shi , Gardi Lori , Edirisinghe Chandima , Fenster Aaron 
Published: February 2011

Purpose:Ultrasound imaging has improved the treatment of prostate cancer by producing increasingly higher quality images and influencing sophisticated targeting procedures for the insertion of radioactive seeds during brachytherapy. However, it is critical that the needles be placed accurately within the prostate to deliver the therapy to the planned location and avoid complications of damaging surrounding tissues.Methods:The authors have developed a compact mechatronic system, as well as an effective method for guiding and controlling the insertion of transperineal needles into the prostate. This system has been designed to allow guidance of a needle obliquely in 3D space into the prostate, thereby reducing pubic arch interference. The choice of needle trajectory and location in the prostate can be adjusted manually or with computer control.Results:To validate the system, a series of experiments were performed on phantoms. The 3D scan of the string phantom produced minimal geometric error, which was less than 0.4 mm. Needle guidance accuracy tests in agar prostate phantoms showed that the mean error of bead placement was less then 1.6 mm along parallel needle paths that were within 1.2 mm of the intended target and 1° from the preplanned trajectory. At oblique angles of up to 15° relative to the probe axis, beads were placed to within 3.0 mm along a trajectory that were within 2.0 mm of the target with an angular error less than 2°.Conclusions:By combining 3D TRUS imaging system to a needle tracking linkage, this system should improve the physician's ability to target and accurately guide a needle to selected targets without the need for the computer to directly manipulate and insert the needle. This would be beneficial as the physician has complete control of the system and can safely maneuver the needle guide around obstacles such as previously placed needles.
CT image construction of a totally deflated lung using deformable model extrapolation
Authors: Sadeghi Naini Ali , Pierce Greg , Lee Ting‐Yim , Patel Rajni V. , Samani Abbas 
Published: February 2011

Purpose:A novel technique is proposed to construct CT image of a totally deflated lung from a free‐breathing 4D‐CT image sequence acquired preoperatively. Such a constructed CT image is very useful in performing tumor ablative procedures such as lung brachytherapy. Tumor ablative procedures are frequently performed while the lung is totally deflated. Deflating the lung during such procedures renders preoperative images ineffective for targeting the tumor. Furthermore, the problem cannot be solved using intraoperative ultrasound (U.S.) images because U.S. images are very sensitive to small residual amount of air remaining in the deflated lung. One possible solution to address these issues is to register high quality preoperative CT images of the deflated lung with their corresponding low quality intraoperative U.S. images. However, given that such preoperative images correspond to an inflated lung, such CT images need to be processed to construct CT images pertaining to the lung's deflated state.Methods:To obtain the CT images of deflated lung, we present a novel image construction technique using extrapolated deformable registration to predict the deformation the lung undergoes during full deflation. The proposed construction technique involves estimating the lung's air volume in each preoperative image automatically in order to track the respiration phase of each 4D‐CT image throughout a respiratory cycle; i.e., the technique does not need any external marker to form a respiratory signal in the process of curve fitting and extrapolation. The extrapolated deformation field is then applied on a preoperative reference image in order to construct the totally deflated lung's CT image. The technique was evaluated experimentally usingex vivo porcine lung.Results:Theex vivo lung experiments led to very encouraging results. In comparison with the CT image of the deflated lung we acquired for the purpose of validation, the constructed CT image was very similar. The intensity mean absolute difference between these two images was calculated to be at 1%. Tumor center as well as a number of anatomical fiducial markers were traced in different corresponding slices of the two images. The average misalignment obtained for the constructed CT image was (0.64, 0.39, 0.11) mm, which indicates a very desirable accuracy for lung brachytherapy applications.Conclusions:The image construction accuracy obtained in this research is suitable for intraoperative tasks; e.g., tumor localization and fusing with real time navigation data in lung brachytherapy. These applications involve image registration with intraoperative U.S. images in order to enhance their poor quality. The proposed technique is also useful for preoperative tasks such as planning of lung brachytherapy treatment.
Co‐60 tomotherapy: A treatment planning investigation
Authors: Cadman Patrick , Bzdusek Karl 
Published: February 2011

Purpose:The authors investigate the plan quality and treatment times that may be achieved with Co‐60 tomotherapy delivery for clinical IMRT cases.Methods:A research version ofPINNACLE treatment planning system software (V9.1) enabled the authors to specify custom source profiles for modeling of cylindrical Co‐60 sources. The calculated profiles were validated against measurements for simulated MLC leaf openings. The reduction in dose due to a partially obscured source was analyzed. The thread effect was investigated for a source of typical linac spot dimensions and 2.0 and 2.8 cm diameter cylindrical Co‐60 sources. Co‐60 tomotherapy plans for three clinical treatment sites—prostate, brain, and head‐and‐neck—were generated for the Co‐60 sources and compared to linac‐based segmental IMRT plans in terms of the DVHs produced. Treatment times were also determined.Results:The custom source profile utility allowed the authors to obtain good agreement between calculated and measured profiles for simulated MLC leaf openings with the commercial Co‐60 source. It was found that the thread effect is significantly reduced for Co‐60 sources and is not a clinical concern even for the large slice width (4.8 cm) and pitch value (0.5) studied. Co‐60 tomotherapy plans for three clinical treatment sites compared favorably to the original segmental IMRT plans in terms of the DVHs produced. Treatment times, comparable to the actual segmental IMRT treatment times, may be achieved for a high activity Co‐60 source and dual‐slice delivery may reduce these times further.Conclusions:It may be possible to achieve clinically viable treatment times with Co‐60 tomotherapy delivery without unacceptable loss of plan quality in terms of the DVHs produced.
Organ and effective dose estimates for patients undergoing hepatic arterial embolization for treatment of liver malignancy
Authors: Dauer Lawrence T. , Thornton Raymond , Boylan Daniel C. , Holahan Brian , Prins Robert , Quinn Brian , St. Germain Jean 
Published: February 2011

Purpose:Effective doseis useful as a dose index for patient exposures in interventional radiology; therefore, the authors estimatedfrom the kerma‐area productutilized during hepatic embolization interventional radiology cases performed at a cancer center and determined the variation of such doses over a representative patient population.Methods:A single‐center, IRB‐approved retrospective study was performed to estimate doses from consecutive hepatic embolization procedures performed during 2006. Organ dosesandwere determined from patient height, weight,, procedure geometry factors, beam quality, thePCXMCMonte Carlo model, and the International Commission on Radiological Protection organ weighting factors.Results:One hundred thirteen patients were included in the study population, 72 males and 41 females, with a median age of 63 yr (29–89 yr), weight of 79 kg (42–111 kg), height of 170 cm (147–188 cm), andof.was directly correlated with, with a medianof. Theratio was inversely and exponentially correlated with weight. The median(mSv) for the study patient population was 44 mSv (2.0–255 mSv).Conclusions:Values ofcan be estimated utilizing patient‐specific and procedure‐specific parameters. The strong inverse correlation ofwith patient weight allows simple estimation offromand patient weight. There is a wide variation in effective dose in oncologic hepatic embolizations with doses up to an order of magnitude higher than diagnostic imaging of the abdomen by CT radiology. Variation is likely due to patient geometry, clinical technique factors, and procedure complexity.
The feasibility of patient size‐corrected, scanner‐independent organ dose estimates for abdominal CT exams
Authors: Turner Adam C. , Zhang Di , Khatonabadi Maryam , Zankl Maria , DeMarco John J. , Cagnon Chris H. , Cody Dianna D. , Stevens Donna M. , McCollough Cynthia H. , McNitt‐Gray Michael F. 
Published: February 2011

Purpose:A recent work has demonstrated the feasibility of estimating the dose to individual organs from multidetector CT exams using patient‐specific, scanner‐independent‐to‐organ‐dose conversion coefficients. However, the previous study only investigated organ dose to a single patient model from a full‐body helical CT scan. The purpose of this work was to extend the validity of this dose estimation technique to patients of any size undergoing a common clinical exam. This was done by determining the influence of patient size on organ dose conversion coefficients generated for typical abdominal CT exams.Methods:Monte Carlo simulations of abdominal exams were performed using models of 64‐slice MDCT scanners from each of the four major manufacturers to obtain dose to radiosensitive organs for eight patient models of varying size, age, and gender. The scanner‐specific organ doses were normalized by corresponding values and averaged across scanners to obtain scanner‐independent ‐to‐organ‐dose conversion coefficients for each patient model. In order to obtain a metric for patient size, the outer perimeter of each patient was measured at the central slice of the abdominal scan region. Then, the relationship between ‐to‐organ‐dose conversion coefficients and patient perimeter was investigated for organs that were directly irradiated by the abdominal scan. These included organs that were either completely (“fully irradiated”) or partly (“partially irradiated”) contained within the abdominal exam region. Finally, dose to organs that were not at all contained within the scan region (“nonirradiated”) were compared to the doses delivered to fully irradiated organs.Results:‐to‐organ‐dose conversion coefficients for fully irradiated abdominal organs had a strong exponential correlation with patient perimeter. Conversely, partially irradiated organs did not have a strong dependence on patient perimeter. In almost all cases, the doses delivered to nonirradiated organs were less than 5%, on average across patient models, of the mean dose of the fully irradiated organs.Conclusions:This work demonstrates the feasibility of calculating patient‐specific, scanner‐independent‐to‐organ‐dose conversion coefficients for fully irradiated organs in patients undergoing typical abdominal CT exams. A method to calculate patient‐specific, scanner‐specific, and exam‐specific organ dose estimates that requires only knowledge of the for the scan protocol and the patient's perimeter is thus possible. This method will have to be extended in future studies to include organs that are partially irradiated. Finally, it was shown that, in most cases, the doses to nonirradiated organs were small compared to the dose to fully irradiated organs.
Position‐probability‐sampled Monte Carlo calculation of VMAT, 3DCRT, step‐shoot IMRT, and helical tomotherapy dose distributions using BEAMnrc/DOSXYZnrc
Authors: Belec Jason , Ploquin Nicolas , La Russa Daniel J. , Clark Brenda G. 
Published: February 2011

Purpose:The commercial release of volumetric modulated arc therapy techniques using a conventional linear accelerator and the growing number of helical tomotherapy users have triggered renewed interest in dose verification methods, and also in tools for exploring the impact of machine tolerance and patient motion on dose distributions without the need to approximate time‐varying parameters such as gantry position, MLC leaf motion, or patient motion. To this end we have developed a Monte Carlo‐based calculation method capable of simulating a wide variety of treatment techniques without the need to resort to discretization approximations.Methods:The ability to perform complete position‐probability‐sampled Monte Carlo dose calculations was implemented in the BEAMnrc/DOSXZYnrc user codes of EGSnrc. The method includes full accelerator head simulations of our tomotherapy and Elekta linacs, and a realistic representation of continous motion via the sampling of a time variable. The functionality of this algorithm was tested via comparisons with both measurements and treatment planning dose distributions for four types of treatment techniques: 3D conformal, step‐shoot intensity modulated radiation therapy, helical tomotherapy, and volumetric modulated arc therapy.Results:For static fields, the absolute dose agreement between the EGSnrc Monte Carlo calculations and measurements is within 2%/1 mm. Absolute dose agreement between Monte Carlo calculations and treatment planning system for the four different treatment techniques is within 3%/3 mm. Discrepancies with the tomotherapy TPS on the order of 10%/5 mm were observed for the extreme example of a small target located 15 cm off‐axis and planned with a low modulation factor. The increase in simulation time associated with using position‐probability sampling, as opposed to the discretization approach, was less than 2% in most cases.Conclusions:A single Monte Carlo simulation method can be used to calculate patient dose distribution for various types of treatment techniques delivered with either tomotherapy or a conventional linac. The method simplifies the simulation process, improves dose calculation accuracy, and involves an acceptably small change in computation time.
Technical Note: A fast laser‐based optical‐CT scanner for three‐dimensional radiation dosimetry
Authors: Papadakis A. E. , Maris T. G. , Zacharakis G. , Papoutsaki V. , Varveris C. , Ripoll J. , Damilakis J. 
Published: February 2011

Purpose:To introduce a novel laser‐based optical‐CT scanner for the readout of three‐dimensional (3D) radiation dosimeters.Methods:The scanner employs a diode laser, a cylindrical lens, a motorized linear rail, a rotation stage, and a charge‐coupled device camera. The scanner operates in a translate‐rotate fashion and may be set up in two configurations depending on the orientation of the cylindrical lens. The attenuation coefficient versus dose response was determined for a normoxic N‐vinylpyrrolidone based polymer gel dosimeter. Cylindrical dosimeters, 2 cm diameter, were homogenously irradiated to known doses up to 60 Gy using a 6 MV linear accelerator. For a test irradiation, a 5 cm diameter dosimeter was irradiated along its cylindrical axis using a rectangular irradiation beam. The dose readout of this scanner was compared to the corresponding readout of a common wide illumination and area detector optical‐CT scanner.Results:The attenuation coefficient versus dose response of the laser‐based system was found to be linear up to 60 Gy compared to the wide field illumination based optical‐CT scanner, which exhibits linearity up to 32 Gy . The noise in the reconstructed attenuation coefficient maps was versus for the laser‐based system and the wide field illumination system, respectively.Conclusions:We have developed a novel laser‐based optical‐CT scanner, which is capable of generating fast 3D dosimetric data using a scattering polymer gel dosimeter. Our data demonstrate that the dose readout of this scanner preserves the advantage of existing laser‐based optical‐CT scanners in providing measurements, which are minimally affected by scattered light. For accurate reconstruction of the attenuation coefficients, noise reduction techniques need to be applied.
Modification of Kirchhoff migration with variable sound speed and attenuation for acoustic imaging of media and application to tomographic imaging of the breast
Authors: Schmidt Steven , Duric Nebojsa , Li Cuiping , Roy Olivier , Huang Zhi‐Feng 
Published: February 2011

Purpose:To explore the feasibility of improving cross‐sectional reflection imaging of the breast using refractive and attenuation corrections derived from ultrasound tomography data.Methods:The authors have adapted the planar Kirchhoff migration method, commonly used in geophysics to reconstruct reflection images, for use in ultrasound tomography imaging of the breast. Furthermore, the authors extended this method to allow for refractive and attenuative corrections. Using clinical data obtained with a breast imaging prototype, the authors applied this method to generate cross‐sectional reflection images of the breast that were corrected using known distributions of sound speed and attenuation obtained from the same data.Results:A comparison of images reconstructed with and without the corrections showed varying degrees of improvement. The sound speed correction resulted in sharpening of detail, while the attenuation correction reduced the central darkening caused by path length dependent losses. The improvements appeared to be greatest when dense tissue was involved and the least for fatty tissue. These results are consistent with the expectation that denser tissues lead to both greater refractive effects and greater attenuation.Conclusions:Although conventional ultrasound techniques use time‐gain control to correct for attenuation gradients, these corrections lead to artifacts because the true attenuation distribution is not known. The use of constant sound speed leads to additional artifacts that arise from not knowing the sound speed distribution. The authors show that in the context of ultrasound tomography, it is possible to construct reflection images of the breast that correct for inhomogeneous distributions of both sound speed and attenuation.
The effects of compensator and imaging geometry on the distribution of x‐ray scatter in CBCT
Authors: Bootsma G. J. , Verhaegen F. , Jaffray D. A. 
Published: February 2011

Purpose:X‐ray scatter contributes significantly to image degradation in cone‐beam CT (CBCT) reconstructed images in the form of CT number inaccuracy image artifacts and loss of contrast. The need for an understanding of the relationship between the scatter distribution and common imaging parameters (cone angle, air gap, filtration, object size) is an essential element to developing methods for efficiently correcting for the effects of scatter in CBCT. The first objective of this study is to validate the scatter distributions calculated using a CBCT Monte Carlo (MC) model against measured scatter estimates. The second objective is to use the CBCT MC model to investigate the effects of common imaging parameters and bowtie compensators on the resulting scatter distribution.Methods:This investigation employs the use of a CBCT MC model, developed using the EGSnrc code, to simulate the primary and scatter fluence arriving at the detector. The simulation is validated against projection images, scatter‐to‐open field ratio (SOR), and scatter‐to‐primary ratio (SPR) measurements taken using a bench‐top CBCT system. The CBCT MC model is used to simulate the scatter distribution arriving at the detector for different cone angles {1.4°, 2.8°, 5.7°, and 11.3°}, source‐to‐axis distances (SADs) {50, 75 and 100 cm}, and axis‐to‐detector distances (ADDs) {9, 18, 30, 44, 56 cm} for both a 16.4 and 30.6 cm diameter water cylinder. The effects of different bowtie filters are also simulated using the CBCT MC model for the aforementioned cylinder sizes.Results:Profiles of the simulated and measured projection images agree within 6%. The measurements of the SOR and SPR, taken using beam stop techniques, show good agreement with the simulated results. Limitations of current beam stop techniques in estimating scatter profiles of objects with varying thickness are also demonstrated. A functional relationship between scatter (SOR, SPR) and air gap, cone angle is reported. The bowtie filter was found to have the beneficial effect of decreasing the magnitude of scatter in the projection images (SPR decreased by 56%) as well as altering the spatial distribution of the scatter.Conclusions:The CBCT MC model accurately simulates scatter and primary fluences in the CBCT imaging components and geometry. The CBCT MC model provides a useful tool in investigating the effects of varying CBCT imaging parameters on the scatter distribution. Increasing the air gap, decreasing the cone angle, and the use of bowtie filtration were all found to be effective ways to minimize scatter in CBCT. The bowtie filter was particularly effective in both minimizing the magnitude and modifying the spatial distribution of the scattered photons. This observation directs further research in optimizing bowtie filter design in an effort to minimize scatter induced artifacts.
Irradiation of gold nanoparticles by x‐rays: Monte Carlo simulation of dose enhancements and the spatial properties of the secondary electrons production
Authors: Leung Michael K. K. , Chow James C. L. , Chithrani B. Devika , Lee Martin J. G. , Oms Barbara , Jaffray David A. 
Published: February 2011

Purpose:The aim of this study is to understand the characteristics of secondary electrons generated from the interaction of gold nanoparticles (GNPs) with x‐rays as a function of nanoparticle size and beam energy and thereby further the understanding of GNP‐enhanced radiotherapy.Methods:The effective range, deflection angle, dose deposition, energy, and interaction processes of electrons produced from the interaction of x‐rays with a GNP were calculated by Monte Carlo simulations. TheGEANT4 code was used to simulate and track electrons generated from a 2, 50, and 100 nm diameter GNP when it is irradiated with a 50 kVp, 250 kVp, cobalt‐60, and 6 MV photon beam in water.Results:When a GNP was present, depending on the beam energies used, secondary electron production was increased by 10‐ to 2000‐fold compared to an absence of a GNP. Low‐energy photon beams were much more efficient at interacting with the GNP by two to three orders of magnitude compared to MV energies and increased the deflection angle. GNPs with larger diameters also contributed more dose. The majority of the energy deposition was outside the GNP, rather than self‐absorbed by the nanoparticle. The mean effective range of electron tracks for the beams tested ranged from approximately to 1 mm.Conclusions:These simulated results yield important insights concerning the spatial distributions and elevated dose in GNP‐enhanced radiotherapy. The authors conclude that the irradiation of GNP at lower photon energies will be more efficient for cell killing. This conclusion is consistent with published studies.