bluuebunny/crossref_metadata_2025_split huggingface dataset:
A methodology for direct quantification of over‐ranging length in helical computed tomography with real‐time dosimetry
Authors: Tien Christopher J. , Winslow James F. , Hintenlang David E. 
Published: February 2017

In helical computed tomography (CT), reconstruction information from volumes adjacent to the clinical volume of interest (VOI) is required for proper reconstruction. Previous studies have relied upon either operator console readings or indirect extrapolation of measurements in order to determine the over‐ranging length of a scan.(1–5) This paper presents a methodology for the direct quantification of over‐ranging dose contributions using real‐time dosimetry. A Siemens SOMATOM Sensation 16 multislice helical CT scanner is used with a novel real‐time “point” fiber‐optic dosimeter system with 10 ms temporal resolution to measure over‐ranging length, which is also expressed in dose‐length‐product (DLP).(6) Film was used to benchmark the exact length of over‐ranging. Over‐ranging length varied from 4.38 cm at pitch of 0.5 to 6.72 cm at a pitch of 1.5, which corresponds to DLP of 131 to 202 mGy‐cm. The dose‐extrapolation method of Van der Molen et al. yielded results within 3%, while the console reading method of Tzedakis et al.(2,4) yielded consistently larger over‐ranging lengths. From film measurements, it was determined that Tzedakis et al.(2,4) overestimated over‐ranging lengths by one‐half of beam collimation width. Over‐ranging length measured as a function of reconstruction slice thicknesses produced two linear regions similar to previous publications.(1–4) Over‐ranging is quantified with both absolute length and DLP, which contributes about 60 mGy‐cm or about 10% of DLP for a routine abdominal scan. This paper presents a direct physical measurement of over‐ranging length within 10% of previous methodologies.(1–4) Current uncertainties are less than 1%, in comparison with 5% in other methodologies. Clinical implantation can be increased by using only one dosimeter if codependence with console readings is acceptable, with an uncertainty of 1.1% This methodology will be applied to different vendors, models, and postprocessing methods – which have been shown to produce over‐ranging lengths differing by 125%.(4)PACS number: 87.57.qp
A quality assurance phantom for electronic portal imaging devices
Authors: Das Indra J. , Cao Minsong , Cheng Chee‐Wai , Misic Vladimir , Scheuring Klaus , Schüle Edmund , Johnstone Peter A.S. 
Published: February 2017

Electronic portal imaging device (EPID) plays an important role in radiation therapy portal imaging, geometric and dosimetric verification. Consistent image quality and stable radiation response is necessary for proper utilization that requires routine quality assurance (QA). A commercial ‘EPID QC’ phantom weighing 3.8 kg with a dimension of is used for EPID QA. This device has five essential tools to measure the geometric accuracy, signal‐to‐noise ratio (SNR), dose linearity, and the low‐ and the high‐contrast resolutions. It is aligned with beam divergence to measure the imaging and geometric parameters in both X and Y directions, and can be used as a baseline check for routine QA. The low‐contrast tool consists of a series of holes with various diameters and depths in an aluminum slab, very similar to the Las Vegas phantom. The high‐resolution contrast tool provides the modulation transfer function (MTF) in both the x‐ and y‐dimensions to measure the focal spot of linear accelerator that is important for imaging and small field dosimetry. The device is tested in different institutions with various amorphous silicon imagers including Elekta, Siemens and Varian units. Images of the QA phantom were acquired at 95.2 cm source‐skin‐distance (SSD) in the range 1–15 MU for a field and phantom surface is set normal to the beam direction when gantry is at 0° and 90°. The epidSoft is a software program provided with the EPID QA phantom for analysis of the data. The preliminary results using the phantom on the tested EPID showed very good low‐contrast resolution and high resolution, and an MTF (0.5) in the range of 0.3–0.4 lp/mm. All imagers also exhibit satisfactory geometric accuracy, dose linearity and SNR, and are independent of MU and spatial orientations. The epidSoft maintains an image analysis record and provides a graph of the temporal variations in imaging parameters. In conclusion, this device is simple to use and provides testing on basic and advanced imaging parameters for daily QA on any imager used in clinical practices.PACS number: 87.57 C‐, 87.57 N‐
Can Hyperpolarized Helium MRI add to radiation planning and follow‐up in lung cancer?
Authors: Allen Aaron M. , Albert Mitchell , Caglar Hale B. , Zygmanski Piotr , Soto Ricardo , Killoran Joseph , Sun Yangping 
Published: February 2017

Locally advanced non‐small‐cell lung cancer (NSCLC) is a common disease with a low overall survival even with aggressive treatments. Standard imaging (CT and PET/CT) provide no information about normal lung function. We therefore, sought to pilot HeMRI in patients with non‐small‐cell lung cancer before and after definitive radiotherapy (RT). Five patients with NSCLC receiving RT were enrolled on a prospective IRB approved study. Patients underwent CT, FDG‐PET and HeMRI before and (within 10 days) following RT. All images (CT, FDG‐PET and HeMRI) were co‐registered. The CT and PET GTVs were contoured, as well as the ventilation defects on HeMRI caused by the tumor. Patients also underwent pulmonary function tests (PFTs). Correlations between the images and PFTs were evaluated by linear regression. CT and FDG‐PET tumor volumes were highly correlated before treatment and 0.99 following RT). There was less correlation between HeMRI and CT or PET ( (CT) and 0.38 (PET)) prior to treatment and 0.27 following RT). However, HeMRI volumes correlated very well with FEV1, both prior to and following RT. and 0.83, respectively). MRI scanning is feasible in NSCLC before and after treatment. HeMRI provides important functional information in addition to CT and CT/PET scanning.PACS number: 87.55.D‐
Proton dose distribution measurements using a MOSFET detector with a simple dose‐weighted correction method for LET effects
Authors: Kohno Ryosuke , Hotta Kenji , Matsuura Taeko , Matsubara Kana , Nishioka Shie , Nishio Teiji , Kawashima Mitsuhiko , Ogino Takashi 
Published: February 2017

We experimentally evaluated the proton beam dose reproducibility, sensitivity, angular dependence and depth‐dose relationships for a new Metal Oxide Semiconductor Field Effect Transistor (MOSFET) detector. The detector was fabricated with a thinner oxide layer and was operated at high‐bias voltages. In order to accurately measure dose distributions, we developed a practical method for correcting the MOSFET response to proton beams. The detector was tested by examining lateral dose profiles formed by protons passing through an L‐shaped bolus. The dose reproducibility, angular dependence and depth‐dose response were evaluated using a 190 MeV proton beam. Depth‐output curves produced using the MOSFET detectors were compared with results obtained using an ionization chamber (IC). Since accurate measurements of proton dose distribution require correction for LET effects, we developed a simple dose‐weighted correction method. The correction factors were determined as a function of proton penetration depth, or residual range. The residual proton range at each measurement point was calculated using the pencil beam algorithm. Lateral measurements in a phantom were obtained for pristine and SOBP beams. The reproducibility of the MOSFET detector was within 2%, and the angular dependence was less than 9%. The detector exhibited a good response at the Bragg peak (0.74 relative to the IC detector). For dose distributions resulting from protons passing through an L‐shaped bolus, the corrected MOSFET dose agreed well with the IC results. Absolute proton dosimetry can be performed using MOSFET detectors to a precision of about 3% (1 sigma). A thinner oxide layer thickness improved the LET in proton dosimetry. By employing correction methods for LET dependence, it is possible to measure absolute proton dose using MOSFET detectors.PACS number: 87.56.‐v
Advances in fiducial‐free image‐guidance for spinal radiosurgery with CyberKnife – a phantom study
Authors: Fürweger Christoph , Drexler Christian , Kufeld Markus , Muacevic Alexander , Wowra Berndt 
Published: February 2017

The image‐guided CyberKnife radiosurgery system is capable of tracking spinal targets without fiducial implants. Recently, a new version of this fiducial‐free image guidance modality (“enhanced Xsight spine tracking”) has been introduced. We assessed the accuracy of this novel technique versus its precursor in a comparative phantom study. The CyberKnife consists of a 6 MV linac on a six‐axis robot and a stereoscopic kV image guidance system. An anthropomorphic head‐and‐neck phantom with a cervical spine section was mounted on the linac nozzle. The robotic manipulator was used to precisely move the phantom to defined positions in the CyberKnife workspace. Multiple stereoscopic images were acquired at different translational and rotational positions. The enhanced Xsight spine tracking readouts were recorded and compared to the nominal phantom position. These tests were repeated with the original Xsight spine tracking version to analyze potential differences. Enhanced Xsight spine tracking correctly reported translational offsets with an RMS error of less than 0.4 mm. Yaw and roll rotations were detected with an accuracy of 0.2°, 0.25°. Pitch offsets were slightly underestimated, with up to 0.3° for an offset of . Nominal X (left‐right) translational offsets were partially misinterpreted as roll (0.2° at a 10 mm offset). Apart from this, no correlation between rotational and translational directions was found. In comparison, the original Xsight spine tracking showed identical results for translations, but larger systematic and statistical errors for rotations. Enhanced Xsight spine tracking measurably improves precision in fiducial‐free spinal radiosurgery with the CyberKnife.PACS number: 87.53.Ly
Effects of voxel size and iterative reconstruction parameters on the spatial resolution of SPECT/CT
Authors: Kappadath S. Cheenu 
Published: February 2017

The purpose of this study was to evaluate the effects of voxel size and iterative reconstruction parameters on the radial and tangential resolution for SPECT as a function of radial distance from isocenter. SPECT/CT scans of eight coplanar point sources of size smaller than containing high concentration solution were acquired on a SPECT/CT system with 5/8 inch NaI(Tl) detector and low‐energy, high‐resolution collimator. The tomographic projection images were acquired in step‐and‐shoot mode for 360 views over 360° with 250,000 counts per view, a zoom of 2.67, and an image matrix of pixels that resulted in a SPECT voxel size over 230 mm field‐of‐view. The projection images were also rebinned to image matrices of and to yield SPECT voxel sizes of and , respectively. The SPECT/CT datasets were reconstructed using the vendor‐supplied iterative reconstruction software that incorporated collimator‐specific resolution recovery, CT‐based attenuation correction, and dual‐energy window‐based scatter correction using different combinations of iterations and subsets. SPECT spatial resolution was estimated as the full width at half maximum of the radial and tangential profiles through the center of each point source in reconstructed SPECT images. Both radial and tangential resolution improved with higher iterations and subsets, and with smaller voxel sizes. Both radial and tangential resolution also improved with radial distance further away from isocenter. The magnitude of variation decreased for smaller voxel sizes and for higher number of iterations and subsets. Tangential resolution was found not to be equal to the radial resolution, and the nature of the anisotropy depended on the distribution of the radionuclide and on the reconstruction parameters used. The tangential resolution converged faster than the radial resolution, with higher iterations and subsets. SPECT resolution was isotropic and independent of radial distance when reconstructed using filtered back‐projection. SPECT spatial resolution and therefore quantification of SPECT uptake via partial‐volume correction in clinical images were found to depend on the nature of activity distribution within the SPECT field‐of‐view and on the specific choice of iterative reconstruction parameters.PACS number: 87.57.uh, 87.57.cf, 87.87.nf
The dosimetric effect of mixed‐energy IMRT plans for prostate cancer
Authors: Park Jong Min , Choi Chang Heon , Ha Sung Whan , Ye Sung‐Joon 
Published: February 2017

We investigated the effect of mixing high‐ and low‐energy photon beams on the quality of intensity‐modulated radiation therapy (IMRT) plans for patients with prostate cancer. Three different plans for each of twenty patients were generated using either 6 MV or 15 MV alone, and both 6 and 15 MV beams. All the planning parameters, goals, and constraints were set to be identical except beam energy. The dose distributions were similar in terms of target coverage, conformity, and homogeneity regardless of beam energy. The of rectal wall in 6 MV, 15 MV and mixed‐energy plans was 16.7%, 17.9%, and 16.3%, respectively, while was 55.6%, 53.2%, and 50%. The mean dose to femoral heads in 6 MV, 15 MV, and mixed‐energy plans were 31.7 Gy, 26.3 Gy, and 26.2 Gy, respectively. The integral dose of 6 MV plans was 7% larger than those of 15 MV or mixed‐energy plans. These results indicated that mixed‐energy IMRT plans could take advantage of the dosimetric characteristics of low‐ and high‐energy beams. Even though the reduction of dose to the organs at risk may not be clinically relevant, mixing energy in an IMRT plan for deep‐seated tumors can improve the overall plan quality.PACS number: 87.55.ne
Comparative analysis of SmartArc‐based dual arc volumetric‐modulated arc radiotherapy (VMAT) versus intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma
Authors: Lee Tsair‐Fwu , Chao Pei‐Ju , Ting Hui‐Min , Lo Su‐Hua , Wang Yu‐Wen , Tuan Chiu‐Ching , Fang Fu‐Min , Su Te‐Jen 
Published: February 2017

The purpose of this study was to evaluate and quantify the planning performance of SmartArc‐based volumetric‐modulated arc radiotherapy (VMAT) versus fixed‐beam intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) using a sequential mode treatment plan. The plan quality and performance of dual arc‐VMAT (DA‐VMAT) using the Smart‐Arc system (clinical version 9.0; Philips, Fitchburg, WI, USA) were evaluated and compared with those of seven‐field (7F)‐IMRT in 18 consecutive NPC patients. Analysis parameters included the conformity index (CI) and homogeneity index (HI) for the planning target volume (PTV), maximum and mean dose, normal tissue complication probability (NTCP) for the specified organs at risk (OARs), and comprehensive quality index (CQI) for an overall evaluation in the 11 OARs. Treatment delivery time, monitor units per fraction (MU/fr), and gamma evaluations were also analyzed. DA‐VMAT achieved similar target coverage and slightly better homogeneity than conventional 7F‐IMRT with a similar CI and HI. NTCP values were only significantly lower in the left parotid gland (for xerostomia) for DA‐VMAT plans. The mean value of CQI at indicated a 2% benefit in sparing OARs by DA‐VMAT. The MU/fr used and average delivery times appeared to show improved efficiencies in DA‐VMAT. Each technique demonstrated high accuracy in dose delivery in terms of a high‐quality assurance (QA) passing rate of the criterion. The major difference between DA‐VMAT and 7F‐IMRT using a sequential mode for treating NPC cases appears to be improved efficiency, resulting in a faster delivery time and the use of fewer MU/fr.PACS number: 87.53.Tf, 87.55.x, 87.55.D, 87.55.dk
Expanding the use of real‐time electromagnetic tracking in radiation oncology
Authors: Shah Amish P. , Kupelian Patrick A. , Willoughby Twyla R. , Meeks Sanford L. 
Published: February 2017

In the past 10 years, techniques to improve radiotherapy delivery, such as intensity‐modulated radiation therapy (IMRT), image‐guided radiation therapy (IGRT) for both inter‐ and intrafraction tumor localization, and hypofractionated delivery techniques such as stereotactic body radiation therapy (SBRT), have evolved tremendously. This review article focuses on only one part of that evolution, electromagnetic tracking in radiation therapy. Electromagnetic tracking is still a growing technology in radiation oncology and, as such, the clinical applications are limited, the expense is high, and the reimbursement is insufficient to cover these costs. At the same time, current experience with electromagnetic tracking applied to various clinical tumor sites indicates that the potential benefits of electromagnetic tracking could be significant for patients receiving radiation therapy. Daily use of these tracking systems is minimally invasive and delivers no additional ionizing radiation to the patient, and these systems can provide explicit tumor motion data. Although there are a number of technical and fiscal issues that need to be addressed, electromagnetic tracking systems are expected to play a continued role in improving the precision of radiation delivery.PACS number: 87.63.‐d
4D CT image acquisition errors in SBRT of liver identified using correlation
Authors: Szegedi Martin , Sarkar Vikren , Rassiah‐Szegedi Prema , Wang Brian , Huang Y.Jessica , Zhao Hui , Salter Bill 
Published: February 2017

In the AAPM Report 80,(1) the imaging modality of 4D CT and respiration‐correlated CT was declared a “promising solution for obtaining high‐quality CT data in the presence of respiratory motion”. To gather anatomically correct data over time, the existence of correlation between the internal organ movement and an external surrogate has to be assumed. For the in‐house evaluation of such correlation, we retrospectively analyzed 21 four‐dimensional computer tomography (4D CT) scans of five patients, out of which the artifacts experienced in three patients are shown here. To provide context and a baseline for the analysis of patient motion, a real‐tissue liver phantom was used with a solid water block and liver tissue. The superior–inferior motion of fiducials in phantom and patients was correlated to the recorded anterior–posterior motion of an external surrogate marker on the chest. The use of a solid water block yielded a measurable correlation coefficient of 0.98 or better using a sinusoidal animation pattern. With sinusoidally‐animated liver tissue, the minimum correlation observed was 0.96. Comparing this to retrospective patient data, we found three cases of a change in the correlation coefficient, or simply a low correlation. The source of this low correlation was investigated by careful examination of the breathing traces and the CT‐phase assignments used to reconstruct the datasets. Consequences of nonregular breathing are elaborated on. We demonstrate the impact of wrong phase assignments and missing image information in the 4D CT phase sampling processes. We also show how daily patient‐based correlation analysis can indicate changes in breathing traces, which can be significant enough to decrease, or completely eliminate, previously existing correlation.PACS numbers: 87.57.‐s, 87.57.Q‐, 87.57.cp, 87.57.N‐, 87.55.Qr
Image quality of an investigational imaging panel for use with the imaging beam line cone‐beam CT
Authors: Beltran Chris 
Published: February 2017

The purpose of this study was to measure and compare the contrast‐to‐noise ratio (CNR) as a function of dose for the cone‐beam CT (CBCT) produced by the imaging beam line (IBL) for the standard and an investigational imaging panel. Two Siemens Artiste linear accelerators were modified at our institution such that the MV‐CBCT would operate under an investigational IBL. The imaging panel from one of the machines was replaced with an investigational imaging panel. After the modification, a set of CBCT for a large and small phantom consisting of eight tissue‐equivalent inserts was acquired for the standard imager and for the investigational imager with and without the standard copper plate. Ten dose settings for each phantom using the IBL in combination with the standard and investigational imaging panel were acquired. The CNR for each tissue‐equivalent insert was calculated. Resolution measurements in line pairs per mm (lp/mm) of the CBCT for the various imaging panel setups were made. In addition, CBCT images of two patients that were imaged with each panel configuration were displayed for a group of physicians and therapists who were asked to identify the best and worst CBCT for each patient. This was used as a qualitative judge of practical image quality. The CNR of the muscle insert for the large phantom with 1.5 cGy at isocenter was 1.3 for the standard imager, 1.5 for the investigational imager with the copper plate, and 1.9 without the plate. Under the same conditions, the CNR of the trabecular bone insert was 5.9, 7.3, and 9.7, respectively. For the small phantom with the same dose to isocenter, the CNR for muscle was 1.7, 2.1, and 3.3, respectively. For the trabecular bone, the CNR was 8.1, 9.6, and 12.1 respectively. The resolution for 1 cGy at isocenter was 0.37 lp/mm for the standard imager, 0.32 and 0.33 for the investigational imager with and without the copper plate. The qualitative test ranked the CBCT of the investigational imager without the copper plate to be the best image, and the standard imager to be the worst. The investigational imaging panel improves image quality as compared to the standard imager for IBL CBCTs. A 1 cGy IBL CBCT, no matter which imager is used, is sufficient for bony anatomy localization. The investigational imager without the copper plate was judged clinically to produce the best IBL CBCT.PACS numbers: 87.57.Q, 87.57.cj
A study of segment weight optimization with the CMS XiO step‐and‐shoot IMRT technique for prostate cancer
Authors: Prabhakar Ramachandran , Cramb Jim , Gehrke Christopher , Anderson Justin , Andrews Judy 
Published: February 2017

The aim of this study was to compare IMRT optimization in the CMS XiO radiotherapy treatment planning system, with and without segment weight optimization. Twenty‐one prostate cancer patients were selected for this study. All patients were initially planned with step‐and‐shoot IMRT (S‐IMRT). A new plan was then created for each patient by applying the segment weight optimization tool (SWO‐IMRT). Analysis was performed on the (SWO‐IMRT) and (S‐IMRT) plans by comparing the total number of segments, monitor units, rectal and bladder dose. The study showed a statistically significant reduction in the total number of segments (mean: 25.3%; range: 16.8%–31.1%) with SWO‐IMRT as compared to S‐IMRT . Similarly, a mean reduction of 3.8% (range: 0.4%–7.7%) in the total MU was observed with SWO‐IMRT . The study showed an average rectal dose decrease of 13.7% (range: 7.9%–21.4%) with SWO‐IMRT . We also observed a statistically significant reduction of 26.7% (range: 16.0%–41.4%; p < 0.0001) in the mean dose to the posterior one‐third rectum and an overall reduction in mean bladder dose of 2.2% (range: 0.1%–6.1%) for SWO‐IMRT . This study shows that the segment weight optimization method significantly reduces the total number of segments and the dose to the rectum for IMRT prostate cancer. It also resulted in fewer monitor units for most of the prostate cases observed in this study.PACS numbers: 85.55.ne; 87.55.de; 87.55.kd