Radiological Physics and Technology Journal Impact Factor & Information

Publisher: Springer Verlag

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ISSN 1865-0341
OCLC 212414506
Material type Document, Periodical, Internet resource
Document type Internet Resource, Computer File, Journal / Magazine / Newspaper

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Springer Verlag

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Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Our aim was to determine whether a third-party quality assurance (QA) tool was suitable for the measurement of rotational output and beam quality in place of on-board detector signals. A Rotational Therapy Phantom 507 (507 Phantom) was used as a QA tool. The rotational output constancy (ROC507) and the beam quality index ([Formula: see text]) were evaluated by analysis of signals from an ion chamber inserted into the 507 Phantom. On-board detector signals were obtained for comparisons with the data from the 507 Phantom. The rotational output (ROCdetector) and beam quality (corrected cone ratio; CCR) were determined by analysis of on-board detector signals that were generated by irradiation. The tissue phantom ratio at depth 20 and 10 cm (TPR20, 10) was measured with a Farmer-type ionization chamber inserted in a plastic-slab phantom. For rotational output measurement, the correlation coefficient between ROC507 and ROCdetector values was 0.68 (p < 0.001). ROC507 and ROCdetector values showed a reduced coefficient of variation after magnetron replacement, which was done during the measurement period. In addition, ROC507 values were reduced significantly along with ROCdetector values after target replacement (p < 0.001). Regarding the beam quality index, [Formula: see text] showed a change similar to CCR and an increase similar to TPR20, 10 after magnetron/target replacement. This QA tool could check for daily rotational output and detect changes in rotational output and beam quality caused by magnetron or target failure as well as when on-board detector signals were used. Without needing a tomotherapy quality assurance license, we could effectively and quantitatively estimate the rotational output and beam quality at a low cost.
    Radiological Physics and Technology 08/2015; DOI:10.1007/s12194-015-0333-2
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    ABSTRACT: Practical simulations of low-dose CT images have a possibility of being helpful means for optimization of the CT exposure dose. Because current methods reported by several researchers are limited to specific vendor platforms and generally rely on raw sinogram data that are difficult to access, we have developed a new computerized scheme for producing simulated low-dose CT images from real high-dose images without use of raw sinogram data or of a particular phantom. Our computerized scheme for low-dose CT simulation was based on the addition of a simulated noise image to a real high-dose CT image reconstructed by the filtered back-projection algorithm. First, a sinogram was generated from the forward projection of a high-dose CT image. Then, an additional noise sinogram resulting from use of a reduced exposure dose was estimated from a predetermined noise model. Finally, a noise CT image was reconstructed with a predetermined filter and was added to the real high-dose CT image to create a simulated low-dose CT image. The noise power spectrum and modulation transfer function of the simulated low-dose images were very close to those of the real low-dose images. In order to confirm the feasibility of our method, we applied this method to clinical cases which were examined with the high dose initially and then followed with a low-dose CT. In conclusion, our proposed method could simulate the low-dose CT images from their real high-dose images with sufficient accuracy and could be used for determining the optimal dose setting for various clinical CT examinations.
    Radiological Physics and Technology 08/2015; DOI:10.1007/s12194-015-0332-3
  • Radiological Physics and Technology 07/2015; DOI:10.1007/s12194-015-0330-5
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    ABSTRACT: Our purpose in this study was to construct a 3-dimensional (3D) region of interest (ROI) for analyzing the time-signal intensity curve (TIC) semi-automatically in dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging of the breast. DCE-MR breast imaging datasets were acquired by a 3.0-Tesla MR system with the use of a 3D fast gradient echo sequence. The essential idea in the new method was to analyze each pixel and to construct an ROI made up of pixels with similar TICs. First, an analyst selected a starting point in the contrast media-enhanced tumor. Second, we calculated Pearson's correlation coefficients (CCs) between the TIC in the starting coordinate selected by the analyst and the TIC in the other coordinates. Third, ROI pixels were selected if their CC threshold satisfied a level of coefficient variation of the ROI determined by prior research performed in our institution. We made a retrospective review of patients who underwent breast DCE-MR examination for pre-operative diagnosis. To confirm the feasibility of the resulting 3D-ROI from TIC analysis, we compared Fischer's score obtained from 3D-ROI by applying a new method to a score obtained from a manually selected 2-dimensional (2D) ROI which was used during routine clinical examination. The Fischer's scores obtained from both the automatically selected 3D-ROI and the manually selected 2D-ROI showed almost equivalent results. Thus, we considered that the new method was comparable to the conventional method. Furthermore, the new method has the potential to be used for evaluation of the extent of tumors.
    Radiological Physics and Technology 07/2015; DOI:10.1007/s12194-015-0329-y
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    ABSTRACT: Our objective in this study was to create AAPM TG 119 test plans for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in the Monaco planning system. The results were compared with the published studies, and the performance of the Monaco planning system was analyzed. AAPM TG 119 proposed a set of test cases called multi-target, mock prostate, mock head and neck and C-shape to ascertain the overall accuracy of IMRT planning, measurement, and analysis. We used these test cases to investigate the performance of the Monaco planning system for the complex plans. For these test cases, we created IMRT plans with static multi-leaf collimator (MLC) and dynamic MLC by using 7-9 static beams as explained in TG-119. VMAT plans were also created with a 320° arc length and a single or double arc. The planning objectives and dose were set as described in TG 119. The dose prescriptions for multi-target, mock prostate, mock head and neck, and C-shape were taken as 50, 75.6, 50 and 50 Gy, respectively. All plans were compared with the results of TG 119 and the study done by Mynampati et al. Point dose and fluence measurements were done with a CC13 chamber and ArcCHECK phantom, respectively. Gamma analysis was done for the calculated and measured dose. Using the Monaco planning system, we achieved the goals mentioned in AAPM TG-119, and the plans were comparable to those of other studies. A comparison of point dose and fluence showed good results. From these results, we conclude that the performance of the Monaco planning system is good for complex plans.
    Radiological Physics and Technology 07/2015; DOI:10.1007/s12194-015-0328-z
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    ABSTRACT: Our purpose in this study was to evaluate the clinical usefulness of a new skyline-view imaging technique for axial projection of the patella with use of the anterior border of the patella and tibial tuberosity as position indicators. Our database consisted of pairs of axial images of the patella of the same patients, obtained with use of conventional and new techniques for the radiographic diagnosis of knee-joint diseases. A total of 118 pairs of knee images were obtained from 103 patients ranging in age from 16 to 86 years (mean age 49.7 years). The patellar axial positioning errors were determined in each of the images obtained with the two techniques. The relative error according to the patellar tilt was determined from each of the axial images of the patellas of the same patients obtained with the conventional and new techniques for the radiographic diagnosis of knee-joint diseases. The patellar axial positioning error was 0.40 with the conventional technique, whereas that with the new technique was significantly different at 0.30. This clinical study confirmed that the new skyline-view imaging technique, which uses the anterior border of the patella and the tibial tuberosity as position markers that can be confirmed by palpation, provides more accurate axial images than the conventional imaging technique.
    Radiological Physics and Technology 07/2015; 8(2). DOI:10.1007/s12194-014-0305-y
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    ABSTRACT: Rheumatoid arthritis (RA) is a systemic disease that is caused by autoimmunity. RA causes synovial proliferation, which may result in bone erosion and joint space narrowing in the affected joint. Tomosynthesis is a promising modality which may detect early bone lesions such as small bone erosion and slight joint space narrowing. Nevertheless, so far, the optimal reconstruction filter for detection of early bone lesions of fingers on tomosynthesis has not yet been known. Our purpose in this study was to determine an optimal reconstruction filter setting by using a bone phantom. We obtained images of a cylindrical phantom with holes simulating bone erosions (diameters of 0.6, 0.8, 1.0, 1.2, and 1.4 mm) and joint spaces by aligning two phantoms (space widths from 0.5 to 5.0 mm with 0.5 mm intervals), examining six reconstruction filters by using tomosynthesis. We carried out an accuracy test of the bone erosion size and joint space width, done by one radiological technologist, and a test to assess the visibility of bone erosion, done by five radiological technologists. No statistically significant difference was observed in the measured bone erosion size and joint space width among all of the reconstruction filters. In the visibility assessment test, reconstruction filters of Thickness+- and Thickness-- were among the best statistically in all characteristics except the signal-to-noise ratio. The Thickness+- and Thickness-- reconstruction filter may be optimal for evaluation of RA bone lesions of small joints in tomosynthesis.
    Radiological Physics and Technology 06/2015; DOI:10.1007/s12194-015-0327-0
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    ABSTRACT: We devised a new noise filtering method to reduce the noise in the line spread function (LSF) for presampled modulation transfer function (MTF) analysis with the edge method. A filter was designed to reduce noise effectively using a position-dependent filter controlled by the boundary frequency b for low-pass filtering, which is calculated by 1/2d (d: distance from the LSF center). In this filtering process, strong filters with very low b can be applied to regions distant from the LSF center, and the region near the LSF center can be maintained simultaneously by a correspondingly high b. Presampled MTF accuracies derived by use of the proposed method and an edge spread function (ESF)-fitting method were compared by use of simulated ESFs with and without noise, resembling a computed radiography (CR) and an indirect-type flat panel detector (FPD), respectively. In addition, the edge images of clinical CR, indirect-type FPD, and direct-type FPD systems were examined. For a simulated ESF without noise, the calculated MTFs of the variable filtering method agreed precisely with the true MTFs. The excellent noise-reduction ability of the variable filter was demonstrated for all simulated noisy ESFs and those of three clinical systems. Although the ESF-fitting method provided excellent noise reduction only for the CR-like simulated ESF with noise, its noise elimination performance could not be demonstrated due to the lesser robustness of the fitting.
    Radiological Physics and Technology 06/2015; 8(2). DOI:10.1007/s12194-015-0325-2
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    ABSTRACT: Metabolic syndrome increases the risk of developing diabetes and cardiovascular disease, particularly heart failure. Abdominal obesity is commonly assessed by measurement of the waist circumference, which exhibits a positive correlation with the visceral fat area measured on computed tomography (CT). CT is an excellent technique for measurement of cross-sectional areas of adipose tissue, but the exposure to ionizing radiation limits broad and repeated application in healthy subjects. Our purpose in this study was to determine the reliability of low-dose CT for abdominal fat quantification as compared with a standard CT protocol. A phantom was scanned by use of changes in the volume of vegetable oil, simulating visceral and subcutaneous adipose tissue, and by changes in the tube current-time products (25-300 mAs). We measured the volume of vegetable oil for each mAs value, and we calculated the minimal detectable change (MDC) in the volume by making repeated measurements. The measured volume of vegetable oil at 50 mAs and higher was not significantly different (p > 0.05), but that at 25 mAs was significantly different (p < 0.001), from that at 300 mAs. The MDC was less than 0.4 ml regardless of the mAs value at all mAs values assessed. We suggest that the adipose tissue volume is determined accurately by CT at 50 mAs (75 % reduction of radiation exposure compared with the standard dose).
    Radiological Physics and Technology 06/2015; 8(2). DOI:10.1007/s12194-015-0322-5
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    ABSTRACT: The signal-to-noise ratio (SNR) and parallel imaging (PI) performance of two commercial phased-array coils (PACs) were examined in magnetic resonance imaging (MRI) of the brain. All measurements were performed on a 3.0 T MRI instrument. The SNR and PI performance were evaluated with 32-channel and 15-channel PACs. A gradient echo sequence was used for obtaining images of a phantom. SNR and geometry factor (g-factor) maps were calculated from two images with identical parameters. Horizontal and vertical profiles were taken through the SNR maps in the axial plane. The average g-factor was measured in a circular region of interest in the g-factor maps for the axial plane. The SNR map of the 32-channel coil showed a higher SNR than that of the 15-channel coil at the phantom's posterior and lateral surfaces. The SNR profiles for the 32-channel coil also showed a 1.3-fold increase at the phantom's center. The average g-factor of the 32-channel coil was lower than that of the 15-channel coil at the same acceleration factor. These results indicate that the 32-channel coil can provide a higher spatial resolution and/or a faster imaging speed. Horizontal and vertical profiles are useful for evaluation of the performance of commercially available PACs.
    Radiological Physics and Technology 05/2015; 8(2). DOI:10.1007/s12194-015-0321-6
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    ABSTRACT: This paper presents an iterative image reconstruction method for radial encodings in MRI based on a total variation (TV) regularization. The algebraic reconstruction method combined with total variation regularization (ART_TV) is implemented with a regularization parameter specifying the weight of the TV term in the optimization process. We used numerical simulations of a Shepp-Logan phantom, as well as experimental imaging of a phantom that included a rectangular-wave chart, to evaluate the performance of ART_TV, and to compare it with that of the Fourier transform (FT) method. The trade-off between spatial resolution and signal-to-noise ratio (SNR) was investigated for different values of the regularization parameter by experiments on a phantom and a commercially available MRI system. ART_TV was inferior to the FT with respect to the evaluation of the modulation transfer function (MTF), especially at high frequencies; however, it outperformed the FT with regard to the SNR. In accordance with the results of SNR measurement, visual impression suggested that the image quality of ART_TV was better than that of the FT for reconstruction of a noisy image of a kiwi fruit. In conclusion, ART_TV provides radial MRI with improved image quality for low-SNR data; however, the regularization parameter in ART_TV is a critical factor for obtaining improvement over the FT.
    Radiological Physics and Technology 05/2015; 8(2). DOI:10.1007/s12194-015-0320-7
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    ABSTRACT: To standardize educational programs and clinical training for medical physics students, the Japanese Board for Medical Physicist Qualification (JBMP) began to accredit master's, doctorate, and residency programs for medical physicists in 2012. At present, 16 universities accredited by the JBMP offer 22 courses. In this study, we aimed to survey the current status of educational programs and career paths of students after completion of the medical physicist program in Japan. A questionnaire was sent in August 2014 to 32 universities offering medical physicist programs. The questionnaire was created and organized by the educational course certification committee of the JBMP and comprised two sections: the first collected information about the university attended, and the second collected information about characteristics and career paths of students after completion of medical physicist programs from 2008 to 2014. Thirty universities (16 accredited and 14 non-accredited) completed the survey (response rate 94 %). A total of 209, 40, and 3 students graduated from the master's, doctorate, and residency programs, respectively. Undergraduates entered the medical physicist program constantly, indicating an interest in medical physics among undergraduates. A large percentage of the students held a bachelor's degree in radiological technology (master's program 94 %; doctorate program 70 %); graduates obtained a national radiological technologist license. Regarding career paths, although the number of the graduates who work as medical physicist remains low, 7 % with a master's degree and 50 % with a doctorate degree worked as medical physicists. Our results could be helpful for improving the medical physicist program in Japan.
    Radiological Physics and Technology 05/2015; 8(2). DOI:10.1007/s12194-015-0317-2
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    ABSTRACT: Contrast-enhanced CT employs a standard uniphasic single-injection method (SIM), wherein administration is based on two parameters: the iodine administration rate (mgI/s) and the injection duration (s). However, as the SIM uses a fixed iodine administration rate, only a uniform contrast enhancement can be achieved with this method. The iodine administration rate can be increased only by increasing the iodine dose or shortening the injection duration, and no arbitrary adjustments can be made to the peak enhancement characteristics of the time-enhancement curves (TECs) at the fixed injection parameters used in the SIM. To address this problem, we developed a variable injection method (VIM) with a new parameter, the variation factor (VF), to adjust the TECs. A phantom study with the VIM indicated that arbitrary adjustments to the iodine administration rate could be made without changing the injection duration or increasing the iodine load. In our study, VFs of 0.3 and 0.5, which showed earlier achievement of peak enhancements, showed better temporal separation between arterial vasculature and parenchyma or the venous vasculature than that obtained with the SIM. The higher peak enhancement provided by the VF of 0.3 was also considered to improve the contrast in qualitative diagnostic examinations. A VF of 0.5 increased the duration of the enhancement and was considered to produce stable enhancement of contrast in vascular investigations. The VF is now an essential parameter, and the VIM is useful as a reasonable contrast method that may contribute to both improved visualization and improvement in the accuracy of morphologic diagnosis.
    Radiological Physics and Technology 05/2015; 8(2). DOI:10.1007/s12194-015-0314-5
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    ABSTRACT: Our aim in this study was to clarify the effects of respiratory-gated PET in the evaluation of lung cancer according to the (18)F-FDG uptake in an orthotopic transplantation mouse model. We created such a model, and we performed PET/CT. The mice were divided into two groups according to tumor volume: a small-tumor group (<20 mm(3)) and a large-tumor group (>20 mm(3)). We reconstructed the following conditions based on list-mode data: non-gated (3D) images and gated (4D) images, divided based on the respiratory cycle (expiration phase, stable phase, and inspiration phase). We calculated the maximum standardized uptake values (SUVmax) in each phase. We used the % difference [= (4D SUVmax - 3D SUVmax)/3D PET SUVmax × 100 (%)] to evaluate the differences in the 4D SUVmax and 3D SUVmax. The 4D SUVmax values were significantly higher than the 3D SUVmax, regardless of the tumor size. The % difference for the small tumors was greater than that for the large tumors, and it was highest in the stable phase. We conclude that the SUVmax in the stable phase under respiratory-gated PET are the most reliable. The SUVmax observed under non-gated PET are considered to be more frequently underestimated in cases involving small tumors than in those involving large tumors. In the chronologic study evaluating the time course of tumor development, the size of the tumor is small in early stage, and respiratory-gated PET is effective in reducing the underestimation of such tumors caused by respiratory motion.
    Radiological Physics and Technology 04/2015; 8(2). DOI:10.1007/s12194-015-0316-3
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    ABSTRACT: In this study, we evaluated hemodynamics using simulated models and determined how cerebral aneurysms develop in simulated and patient-specific models based on medical images. Computational fluid dynamics (CFD) was analyzed by use of OpenFOAM software. Flow velocity, stream line, and wall shear stress (WSS) were evaluated in a simulated model aneurysm with known geometry and in a three-dimensional angiographic model. The ratio of WSS at the aneurysm compared with that at the basilar artery was 1:10 in simulated model aneurysms with a diameter of 10 mm and 1:18 in the angiographic model, indicating similar tendencies. Vortex flow occurred in both model aneurysms, and the WSS decreased in larger model aneurysms. The angiographic model provided accurate CFD information, and the tendencies of simulated and angiographic models were similar. These findings indicate that hemodynamic effects are involved in the development of aneurysms.
    Radiological Physics and Technology 04/2015; 8(2). DOI:10.1007/s12194-015-0315-4
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    ABSTRACT: During examinations and/or treatment, a dentist in the examination room needs to view images with a proper display system. However, they cannot operate the image display system by hands, because dentists always wear gloves to be kept their hands away from unsanitized materials. Therefore, we developed a new image operating system that uses a motion sensor. We used the Leap motion sensor technique to read the hand movements of a dentist. We programmed the system using C++ to enable various movements of the display system, i.e., click, double click, drag, and drop. Thus, dentists with their gloves on in the examination room can control dental and panoramic images on the image display system intuitively and quickly with movement of their hands only. We investigated the time required with the conventional method using a mouse and with the new method using the finger operation. The average operation time with the finger method was significantly shorter than that with the mouse method. This motion sensor method, with appropriate training for finger movements, can provide a better operating performance than the conventional mouse method.
    Radiological Physics and Technology 04/2015; 8(2). DOI:10.1007/s12194-015-0313-6
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    ABSTRACT: To extend layer-stacking irradiation to accommodate intrafractional organ motion, we evaluated the carbon-ion layer-stacking dose distribution using a numeric lung phantom. We designed several types of range compensators. The planning target volume was calculated from the respective respiratory phases for consideration of intrafractional beam range variation. The accumulated dose distribution was calculated by registering of the dose distributions at respective phases to that at the reference phase. We evaluated the dose distribution based on the following six parameters: motion displacement, direction, gating window, respiratory cycle, range-shifter change time, and prescribed dose. All parameters affected the dose conformation to the moving target. By shortening of the gating window, dose metrics for superior-inferior (SI) and anterior-posterior (AP) motions were decreased from a D95 of 94 %, Dmax of 108 %, and homogeneity index (HI) of 23 % at T00-T90, to a D95 of 93 %, Dmax of 102 %, and HI of 20 % at T40-T60. In contrast, all dose metrics except the HI were independent of respiratory cycle. All dose metrics in SI motion were almost the same in respective motion displacement, with a D95 of 94 %, Dmax of 108 %, Dmin of 89 %, and HI of 23 % for the ungated phase, and D95 of 93 %, Dmax of 102 %, Dmin of 85 %, and HI of 20 % for the gated phase. The dose conformation to a moving target was improved by the gating strategy and by an increase in the prescribed dose. A combination of these approaches is a practical means of adding them to existing treatment protocols without modifications.
    Radiological Physics and Technology 04/2015; 8(2). DOI:10.1007/s12194-015-0312-7
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    ABSTRACT: The present study aimed to validate the accuracy of normal databases (NDBs) with respect to variable injected doses and acquisition times by use of three-dimensional stereotactic surface projections (3D-SSP) in N-isopropyl-p-[123I]-iodoamphetamine (I-123-IMP) brain perfusion images. We constructed NDBs based on brain SPECT images obtained from 29 healthy volunteers. Each NDB was rebuilt under simulated unique conditions by use of dynamic acquisition datasets and comprised injected doses (222, 167, and 111 MBq) and acquisition times (30, 20, and 15 min). We selected seven of 29 datasets derived from the volunteers to simulate patients' data (PD). The simulated PD were designed to include regions of hypoperfusion. The study comprised protocol A (same conditions for PD and NDB) and protocol B (mismatched conditions for PD and NDB). We used 3D-SSP to compare with the Z score and detection error. The average Z scores were decreased significantly in protocol A [PD (High)-NDB (High) vs. PD (Low)-NDB (Low); PD (30 m)-NDB (30 m) vs. PD (15 m)-NDB (15 m) and PD (20 m)-NDB (20 m)].The average Z scores of PD (High) and PD (Medium) with NDB (High) did not differ significantly in protocol B, whereas all others were decreased significantly. The error of detection increased 6.65 % (protocol A) and 32.05 % (protocol B). The Z scores were specific to the injected dose and acquisition time used in 3D-SSP studies, and the calculated Z scores were affected by mismatched injected doses and acquisition times between PD and selected NDBs.
    Radiological Physics and Technology 03/2015; 8(2). DOI:10.1007/s12194-015-0311-8