A blurring correction method suitable to analyze quantitative x-ray images derived from energy-resolving photon counting detector

Objective. The purpose of this study is to propose a novel blurring correction method that enables accurate quantitative analysis of the object edge when using energy-resolving photon counting detectors (ERPCDs). Although the ERPCDs have the ability to generate various quantitative analysis techniques, such as the derivations of effective atomic number (Zeff) and bone mineral density (BMD) values, at the object edge in these quantitative images, accurate quantitative information cannot be obtained. This is because image blurring prevents the gathering of accurate primary X-ray attenuation information. Approach. We developed the following procedure for blurring correction. A 5 × 5 pixels masking region was set as the processing area, and the pixels affected by blurring were extracted from the analysis of pixel value distribution. The blurred pixel values were then corrected to the proper values estimated by analyzing minimum and/or maximum values in the set mask area. The suitability of our correction method was verified by a simulation study and an experiment using a prototype ERPCD. Main results. When Zeff image of aluminum objects (Zeff = 13) were analyzed without applying our correction method, regardless of raw data or correction data applying a conventional edge enhancement method, the proper Zeff values could not be derived for the object edge. In contrast, when applying our correction method, 82% of pixels affected by blurring were corrected and the proper Zeff values were calculated for those pixels. As a result of investigating the applicability limits of our method through simulation, it was proven that it works effectively for objects with 4 × 4 pixels or more. Significance. Our method is effective in correcting image blurring when the quantitative image is calculated based on multiple images. It will become an in-demand technology for putting a quantitative diagnosis into actual medical examinations.


Knowledge-based model building for treatment planning for prostate cancer using commercial treatment planning quality assurance software tools


Simplified assessment for chemical exchanged saturation transfer (CEST) imaging: local offset frequency and CEST effect

The aim of this study is to develop a novel phantom for the evaluation of clinical CEST imaging settings, e.g., B0 and B1 field inhomogeneities, CEST contrast, and post-processing. We made a phantom composed of two slice sections: a grid section for local offset frequency evaluation and a sample section for CEST effect evaluation using different concentrations of an egg white albumin solution. On a 3 Tesla MR scanner, a phantom study was performed using CEST imaging; the mean B1 amplitudes were set at 1.2 and 1.9 µT, and CEST images with and without B0 corrections were acquired. Next, region of interest (ROI) analysis was performed for each slice. Then, CEST images with and without B0 corrections were compared at each B1 amplitude. The B0 corrected Z-spectrums at each local region in the grid section showed a shifting of the curve bottom to 0 ppm. Z-spectrum at B1 = 1.9 µT showed a broader curve shape than that at 1.2 µT. Moreover, MTRasym values at 3.5 ppm for each albumin sample at B1 = 1.9 µT were about two times higher than those at 1.2 µT. Our phantom enabled us to evaluate and optimize B0 inhomogeneity and the CEST effect at the B1 amplitude.


Differences of white matter structure for diffusion kurtosis imaging using voxel-based morphometry and connectivity analysis


Conversion Map from Quantitative Parameter Mapping to Myelin Water Fraction: Comparison with R1·R2* and Myelin Water Fraction in White Matter.

Magnetic Resonance Materials in Physics, Biology and Medicine


Differences between professionals in planning treatment for patients with stage III lung cancer using treatment-planning QA software

Reports of Practical Oncology and Radiotherapy


Determination of Alzheimer's disease based on morphology and atrophy using machine learning combined with automated segmentation

To evaluate the degree of cerebral atrophy for Alzheimer's disease (AD), voxel-based morphometry has been performed with magnetic resonance imaging. Detailed morphological changes in a specific tissue area having the most evidence of atrophy were not considered by the machine-learning technique. To develop a machine-learning system that can capture morphology features for determination of atrophy of brain tissue in early-stage AD and classification of healthy participants or patients. Three-dimensional T1-weighted (3D-T1W) data were obtained from AD Neuroimaging Initiative (200 healthy controls and 200 patients with early-stage AD). Automated segmentation of 3D-T1W data was performed. Deep learning (DL) and support vector machine (SVM) were trained using 66-segmented volume values as input and AD diagnosis as output. DL was performed using 66 volume values or gray matter (GM) and white matter (WM) volume values. SVM learning was performed using 66 volume values and six regions with high variable importance. 3D convolutional neural network (3D-CNN) was trained using the segmented images. Accuracy and area under curve (AUC) were obtained. Variable importance was evaluated from logistic regression analysis. DL for GM and WM volume values, accuracy 0.6; SVM for all volume values, accuracy 0.82 and AUC 0.81; DL for all volume values, accuracy 0.82 and AUC 0.8; 3D-CNN using segmental images of the whole brain, accuracy 0.5 and AUC 0.51. SVM using volume values of six regions, accuracy 0.82; image-based 3D-CNN, highest accuracy 0.69. Our results show that atrophic features are more considerable than morphological features in the early detection of AD.


Myelin Water Atlas Template Derived from Quantitative Parameter Mapping


Evaluation of Biological Metabolic Activity within an Atherosclerotic Plaque using Chemical Exchange Saturation Transfer Imaging


Diffusion weighted-viscosity imaging for atherosclerotic plaques


Myelin-weighted imaging derived from quantitative parameter mapping

We developed a novel method which is applicable to visualize contrast according to myelin components in the human brain using relaxation time derived from quantitative parameter mapping magnetic resonance imaging (QPM-MRI). Using healthy volunteer data (n = 10), we verified that our method demonstrated that the myelin-weighted contrast increased proportionally by products R and R*, i.e., QPM-myelin-weighted image, in which modified T-weighted/T-weighted (Tw/Tw) ratio mapping method was applied. We compared measurement values in white matter (WM) and gray matter (GM) regions of the Tw/Tw ratio and R·R* product maps of healthy volunteers. Linear regression analysis between each value. Mann Whitney U test between WM and GM signals in each myelin map. In addition, Additionally, QPM-myelin-weighted image was applied to a 32-year-old female MS patient. Linear regression analysis showed a highly significant correlation between conventional Tw/Tw ratios and R·R* products derived from QPM (R = 0.73, P < 0.0001). Moreover, there is a significant difference between WM and GM structures in each myelin images (both, P < 0.0001). Additionally, in a clinical case, MS lesions enabled observation of not only MS plaques but also heterogeneous myelin signal loss associated with demyelination more clearly than Tw image and conventional Tw/Tw ratio image. Our myelin-weighted imaging technique using QPM may be useful for myelin visualization and is expected to become independent of measurement conditions due to having quantitative characteristics of QPM itself.


Determination of white matter structure index for voxel basedmorphometry and connectivity analysis.


Development of a B1 correction method without additional scanning VFA T1 map.


Evaluation of brain tumor and surrounding tissue activity using multi-pool CEST imaging on 3 Tesla scanner


Development of self-calibrating B1 correction for three-dimensional variable flip angle T1 mapping


Conversion map from quantitative parameter mapping to myelin water fraction


Determination of Alzheimer's disease based on morphology and atrophy using machine learning combined with automated segmentation.


Quantitative parameter mapping of contrast agent concentration and relaxivity and brain tumor extracellular pH

In clinical magnetic resonance imaging, gadolinium-based contrast agents are commonly usedfor detecting brain tumors and evaluating the extent of malignancy. We present a new method toevaluate relaxivity (r1) and contrast agent concentration separately in contrast-enhanced lesions usingquantitative parameter mapping (QPM). Furthermore, we also aimed to estimate the extracellularpH (pHe) of tumor lesions. We demonstrated that it is possible to evaluate pathophysiological tumorchanges due to therapeutic efficacy by measuring r1 in contrast-enhanced lesions. In this study, theprimary brain tumor group showed significantly higher r1 values than other brain disease groups(P< 0.001). Moreover, mean pHe value showed a trend for tumor malignancy having a lower pHevalue and primary brain tumor having a significantly lower pHe than other brain diseases (P< 0.001).Our results might suggest that QPM can separately quantify r1 and CA concentration in brain tumorsand that pHe brain tumor mapping could serve as a tumor biomarker. In conclusion, our method haspotential clinical applications for assessing the treatment effects.


Daily Dietary Supplementation with Steamed Soybean Improves Muscle Volume and Strength in Healthy People Lacking Exercise.

Various dietary protein supplements are used by the elderly and bedridden to maintain their skeletal muscle mass and functions. High-quality proteins act as an anabolic driver and help to improve muscle strength and performance. Previously, we reported that soy protein significantly attenuates denervation-induced loss of muscle mass and myofiber cross sectional area in mice with inhibition of ubiquitination and degradation of IRS-1 in tibialis anterior muscle. It also increased muscle volume and strength in bedridden patients. In the present study, we investigated the effects of dietary soybean supplementation on muscle functions in taxi drivers lacking vigorous physical exercise. We conducted a case-control study on 25 healthy, male taxi drivers between the ages of 36 and 71 y performing minimal physical exercise. They were divided into two dietary groups: the soybean diet group (n=13) who ate daily meals (dinner) supplemented with 50 g of steamed soybean for 30 d and the control diet group (n=12) who received no soybean supplement. Next, we measured the muscle cross-sectional area (CSA) and muscle strength and function in both the groups before and after 30 d of soybean intake. The body weights of both diet groups did not differ significantly over time. However, after 30 d of soybean supplementation, the soybean-fed group developed significantly higher muscle CSA and grip strength compared to the control groups. In conclusion, dietary soybean supplementation improved muscle function in taxi drivers who lacked exercise.

Journal of Nutritional Science and Vitaminology


Bone and soft-tissue images extraction through derivation of effective atomic number image using photon-counting detector.


A novel algorithm for extracting soft-tissue and bone images measured using a photon-counting type X-ray imaging detector with the help of effective atomic number analysis


Estimation of X-ray Energy Spectrum of Cone-Beam Computed Tomography Scanner Using Percentage Depth Dose Measurements and Machine Learning Approach

Journal of the Physical Society of Japan


Derivation of Water Exchange Constants between Components using Quantitative Parameter Mapping (QPM)


Myelin imaging derived quantitative parameter mapping compared to myelin water fraction


A disposable OSL dosimeter for in-vivo measurement of rectum dose during brachytherapy

We aimed to develop a disposable rectum dosimeter and to demonstrate its ability to measure exposure dose to the rectum during brachytherapy for cervical cancer treatment using high-dose rate Ir. Our rectum dosimeter measures the dose with an optically stimulated luminescence (OSL) sheet which was furled to a catheter. The catheter we used is 6 mm in diameter; therefore, it is much less invasive than other rectum dosimeters. The rectum dosimeter developed in this study has the characteristics of being inexpensive and disposable. It is also an easy-to-use detector that can be individually sterilized, making it suitable for clinical use. To obtain a dose calibration curve, phantom experiments were performed. Irradiation was performed using a cubical acrylic phantom, and the response of the OSL dosimeter was calibrated with the calculation value predicted by the treatment planning system (TPS). Additionally, the dependence of catheter angle on the dosimeter position and repeatability were evaluated. We also measured the absorbed dose to the rectum of patients who were undergoing brachytherapy for cervical cancer (n = 64). The doses measured with our dosimeters were compared with the doses calculated by the TPS. In order to examine the causes of large differences between measured and planned doses, we classified the data into common and specific cases when performing this clinical study. For specific cases, the following three categories were considered: (a) patient movement, (b) gas in the vagina and/or rectum, and (c) artifacts in the X-ray image caused by applicators. A dose calibration curve was obtained in the range of 0.1 Gy-10.0 Gy. From the evaluation of the dependence of catheter angle on the dosimeter position and repeatability, we determined that our dosimeter can measure rectum dose with an accuracy of 3.1% (k = 1). In this clinical study, we succeeded in measuring actual doses using our rectum dosimeter. We found that the deviation of the measured dose from the planned dose was derived to be 12.7% (k = 1); this result shows that the clinical study included large elements of uncertainty. The discrepancies were found to be due to patient motion during treatment, applicator movement after planning images were taken, and artifacts in the planning images. We present the idea that a minimally invasive rectum dosimeter can be fabricated using an OSL sheet. Our clinical study demonstrates that a rectum dosimeter made from an OSL sheet has sufficient ability to evaluate rectum dose. Using this dosimeter, valuable information concerning organs at risk can be obtained during brachytherapy.


Effective atomic number image determination with an energy-resolving photon-counting detector using polychromatic X-ray attenuation by correcting for the beam hardening effect and detector response


Evaluation of calibration factor of OSLD toward eye lens exposure dose measurement of medical staff during IVR

Journal of Applied Clinical Medical Physics


乳腺ダイナミックMRIにおける腫瘍辺縁部と腫瘍中心部の時間信号曲線の違いについてー病理組織との対比ー

日本がん健診・診断学会誌

日本がん健診・診断学会誌


An idea to reduce angular dependence of dosimeter having a disk-shaped detection region


Quantitative analysis of vibration waves based on Fourier transform in magnetic resonance elastography

We developed a novel magnetic resonance elastography (MRE) analysis method based on Fourier transform to assess the responsive characteristics for different tissue stiffness and degree of transmission of the vibration wave emanating from a passive driver during MRE. A phantom tissue study was conducted with an MRE sequence and vibration wave system using a clinical MR scanner. The phantom tissue consisted of two layers of agar: 0.75 wt% and 1.0 wt%. Phase-unwrapped images derived from acquired MRE phase images were used to generate a phase profile curve, with a line plotted for the phase-unwrapped images. Fourier transform was performed, and the peak value of the power spectrum was derived. The damping rate/ratio was calculated using the Hilbert transform of the phase profile. We found that the mean shear stiffness value of 1.0 wt% agar was higher than that of 0.75 wt% agar. The responsive frequency of the 0.75 wt% agar layer showed a wider range and the damping rate of the signal showed a higher value than the respective values of the 1.0 wt% agar layer. In conclusion, Fourier transform analysis of MRE enabled us to obtain more detailed information of the tissue characteristics and vibration-wave conditions.


Reproducibility and Variability of Quantitative Cerebral Blood Flow Measured by Multi-delay 3D Arterial Spin Labeling According to Sex and Menstrual Cycle

Purpose : To determine the reproducibility of corrected quantitative cerebral blood flow (qCBF) through measurement of transit flow time using multi-delay three-dimensional pseudo-continuous arterial spin labeling (pCASL) in healthy men and women and to evaluate the differences in qCBF between not only men and women, but also the follicular and luteal phases of the women's menstrual cycle. Methods : The participants were 16 healthy volunteers (8 men and 8 women ; mean age, 25.3 years). Two MRI were conducted for all participants ; female participants were conducted in the follicular and luteal phases. The reproducibility of qCBF values was evaluated by the intraclass correlation coefficient (ICC) and differences between the two groups were estimated by voxel-based morphometry (VBM) analysis. Results : The qCBF values were lower in men than in women, and those in females were significantly different between the follicular and luteal phases (P < 0.05). In VBM analysis, the qCBF values of the lower frontal lobes were significantly higher in women than in men (P < 0.05). The qCBF values of the frontal pole were significantly higher in the follicular phase than in the luteal phase (P < 0.01). Conclusion : Multi-delay pCASL can reveal physiological and sex differences in cerebral perfusion. J. Med. Invest. 67 : 321-327, August, 2020.

The Journal of Medical Investigation : JMI


Characterization of Brain Tumors using Amide Proton and Nuclear Overhauser Effect at 3 Tesla MR Scanner

Proceedings of the 28th Virtual Conference of ISMRM


Chemical Exchange Saturation Transfer Imaging for Atherosclerotic Plaques

Proceedings of 28th Virtual Meeting of ISMRM


Dose calibration factor of an OSL dosimeter during CT examination to measure exposure dose of patients taking into consideration proper X-ray quality


Multi-components analysis of brain using ultrashort echo time magnetic resonance imaging


Multicomponent T1 Relaxometry Analysis using Quantitative Parameter Mapping Magnetic Resonance Imaging


Proceedings of the 27th Annual Meeting of ISMRM


Myelin imaging derived from quantitative parameter mapping


Appropriate echo time selection for quantitative susceptibility mapping.

The purpose of our study was to clarify the dependence of quantitative susceptibility mapping (QSM) on echo time (TE). We constructed a phantom consisting of six tubes; three tubes were filled with different concentrations (0.5, 1.0, and 2.5 mM) of gadopentetate dimeglumine (Gd-DTPA), and three were filled with different concentrations (100, 200, and 350 mg/mL) of calcium hydroxyapatite. Real and imaginary images from multi-echo spoiled gradient-echo data (12 echoes) were acquired. We then used four datasets with three serial echoes. The QSM procedure consists of four steps: field map estimation, phase unwrapping, background removal, and dipole inversion. For each sample, we compared the measured mean susceptibility value with the theoretical susceptibility value and conducted a linear regression analysis. Accordingly, the relationship between the measured susceptibility and concentration of Gd-DTPA was shown to agree well with the theoretical values (TEs = 16.4, 20.8, and 25.2 ms; slope = 0.24, R = 1.00). Furthermore, the relationship between the measured susceptibility and concentration of hydroxyapatite also showed good linearity (TEs = 16.4, 20.8, and 25.2 ms; slope = - 0.00121, R = 1.00). In conclusion, the optimization of the TE in QSM makes it possible to obtain more detailed information regarding the susceptibility of biomaterials.


Comparing neural networks for synthesizing FLAIR images from T1WI and T2WI


Determining the difference of calibration factors in diagnostic X-rays and mono-energetic X-rays of the small type OSL dosimeter for a more precise dose evaluation in diagnostic X-ray examinations


Where do the scattering X-rays to eye lens exposure come from during neonatal cardiac CT examination?


Applicability of a Practical Calibration for the Small-type OSL Dosimeter for Measuring Doses from Direct X-rays and Penetrating X-rays Affected by Scattered Radiation

Progress in Nuclear Science and Technology


Direct Dose Measurement of Patients during Pediatric Computed Tomography Examination


Energy and Angular Dependence of the Small-Type OSL Dosimeter in Nuclear Medicine Regions using Monte Carlo Simulation


Development of Novel Rectum Dosimeter using OSL sheet with the aim of Direct Dose Measurement of Organ Dose during Brachytherapy


Direct Radiation Dose Measurement of Rectum during High-Dose-Rate 192Ir Brachytherapy for Cervical Cancer Treatment


Correlation and Characteristics of Intravoxel Incoherent Motion and Arterial Spin Labeling Techniques Versus Multiple Parameters Obtained on Dynamic Susceptibility Contrast Perfusion MRI for Brain Tumors.

Purpose : To compare data on brain tumors derived from intravoxel incoherent motion (IVIM) and arterial spin labeling (ASL) imaging with multiple parameters obtained on dynamic susceptibility contrast (DSC) perfusion MRI and to clarify the characteristics of IVIM and ASL perfusion data from the viewpoint of cerebral blood flow (CBF) analysis. Methods : ASL-CBF and IVIM techniques as well as DSC examination were performed in 24 patients with brain tumors. The IVIM data were analyzed with the two models. The relative blood flow (rBF), relative blood volume (rBV) corrected relative blood volume (crBV), mean transit time (MTT), and leakage coefficient (K2) were obtained from the DSC MRI data. Results : The ASL-CBF had the same tendency as the perfusion parameters derived from the DSC data, but the permeability from the vessels had less of an effect on the ASL-CBF. The diffusion coefficient of the fast component on IVIM contained more information on permeability than the f value. Conclusion : ASL-CBF is more suitable for the evaluation of perfusion in brain tumors than IVIM parameters. ASL-CBF and IVIM techniques should be carefully selected and the biological significance of each parameter should be understood for the correct comprehension of the pathological status of brain tumors. J. Med. Invest. 66 : 308-313, August, 2019.

The Journal of Medical Investigation : JMI


Feasibility study of photon counting detector for producing effective atomic number image


Exposure dose measurement during diagnostic pediatric X-ray examination using an optically stimulated luminescence (OSL) dosimeter based on precise dose calibration taking into consideration variation of X-ray spectra


Reproduction of response functions of a multi-pixel-type energy-resolved photon counting detector while taking into consideration interaction of X-rays, charge sharing and energy resolution


Does the amount of signal change depend on calcium concentration in lipid-rich core plaque?

Proceedings of the 26th Annual Meeting of ISMRM


T1 dependency of magnetization transfer effect in human brain


Nuclear Overhauser enhancement effect of low B1 power CEST RF in human brain at 3.0 T


B1 Power Optimization for Chemical Exchange Saturation Transfer Imaging: A Phantom Study Using Egg White for Amide Proton Transfer Imaging Applications in the Human Brain

The chemical exchange saturation transfer (CEST) effect on an egg white suspension was investigated for optimization of magnetization transfer (MT) power (B1,rms) and pH dependency with addition of lactic acid. Applying a higher magnetization transfer (MT) pulse, B1,rms, Z-spectrum shows higher asymmetry and the MTRasym signal increases to around 1-3.5 ppm, indicating a higher CEST effect. Amide proton (-NH) transfer (APT) at 3.5 ppm shows a signal elevation in MTRasym with the application of higher B1,rms power and high pH. In addition, the hydroxyl (-OH) proton signal in MTRasym increases as pH is reduced by lactic acid. In Z-spectrum of B1,rms at 1.0 T and 2.0 T, the dependence on CEST effect of amide (-NH) and hydroxyl (-OH) proton could be observed by using an egg white suspension phantom. The CEST MT power was optimized on the egg white suspension phantom with pH dependency and further confirmed on volunteers. In addition, APT imaging at 3.5 ppm using B1,rms at 1.0 T performed on two human brains with different pathophysiological conditions indicated appropriate ATP effect.


Development of correction for signal-to-noise ratio using a T2* with improved Phase method

This study aims to improve the signal-to-noise ratio (SNR) of the phase image focusing T2 and to develop an improved phase (iPhase) image acquired high SNR. The iPhase images of phantom and brain were acquired with multi-echo spoiled gradient-echo. The phantom component was a gadopentetate dimeglumine (Gd-DTPA) solution made of different concentrations (0.1, 0.5, and 1 wt%) and Gd-DTPA (0.1, 0.5, and 1 wt%) with agar (1.0 wt%). We applied the iPhase image to susceptibility weighed image (SWI) and evaluated SNR of SWI. In phantom study, SNRs of conventional SWI at each sample were 19.8, 15.7, 7.4, 20.0, 17.4, and 27.3, respectively. Signal-to-noise ratios of SWI derived from iPhase method were 29.5, 33.7, 21.7, 28.5, 24.3, and 14.7, respectively. Then, the SNR showed an improvement of 196% at maximum (for the Gd-DTPA 1 wt% sample). In healthy volunteer study, SWI derived from iPhase method had the good contrast between white matter and gray matter. The iPhase image was able to improve the phase SNR. Moreover, iPhase method makes it possible to obtain a high SNR image when applying to SWI.


Phantom study using an OSL dosimeter with the aim of accurate measurement of eye lens dose exposure of operator during transfemoral cardiac catheterization using fluoroscopic examination


Internal evaluation of impregnation treatment of waterlogged wood; relation between concentration of internal materials and relaxation time using magnetic resonance imaging


CEST and Binding Water MT Separation in Brain Tumor by Multi Pool Model CEST Peak Extraction Method

Proceedings of the 25th Annual Meeting of ISMRM


Baseline of Chemical Exchange Saturation Transfer Imaging for Brain


Precise material identification method based on a photon counting technique with correction of the beam hardening effect in X-ray spectra

The aim of our study is to develop a novel material identification method based on a photon counting technique, in which the incident and penetrating X-ray spectra are analyzed. Dividing a 40-kV X-ray spectra into two energy regions, the corresponding linear attenuation coefficients are derived. We can identify the materials precisely using the relationship between atomic number and linear attenuation coefficient through the correction of the beam hardening effect of the X-ray spectra.


Entrance surface dose measurements using a small OSL dosimeter with a computed tomography scanner having 320 rows of detectors

Entrance surface dose (ESD) measurements are important in X-ray computed tomography (CT) for examination, but in clinical settings it is difficult to measure ESDs because of a lack of suitable dosimeters. We focus on the capability of a small optically stimulated luminescence (OSL) dosimeter. The aim of this study is to propose a practical method for using an OSL dosimeter to measure the ESD when performing a CT examination. The small OSL dosimeter has an outer width of 10 mm; it is assumed that a partial dose may be measured because the slice thickness and helical pitch can be set to various values. To verify our method, we used a CT scanner having 320 rows of detectors and checked the consistencies of the ESDs measured using OSL dosimeters by comparing them with those measured using Gafchromic™ films. The films were calibrated using an ionization chamber on the basis of half-value layer estimation. On the other hand, the OSL dosimeter was appropriately calibrated using a practical calibration curve previously proposed by our group. The ESDs measured using the OSL dosimeters were in good agreement with the reference ESDs from the Gafchromic™ films. Using these data, we also estimated the uncertainty of ESDs measured with small OSL dosimeters. We concluded that a small OSL dosimeter can be considered suitable for measuring the ESD with an uncertainty of 30 % during CT examinations in which pitch factors below 1.000 are applied.


Basic study for internal dose evaluation during CT examination by means of small-type OSL dosimeter

[Aims and objectives] We plan to manage the patient dose exposure during computed tomography (CT) examination using a small-type OSL dosimeter. The OSL dosimeter can measure entrance skin dose (ESD) directly, but the internal dose can't be measured. The aim of this study is to clarify the relationship between the ESD and internal dose during the CT examination. [Methods and materials] We constructed an abdominal phantom, in which OSL dosimeters can be implanted in, and used this phantom to measure external and internal doses during CT examination. The typical irradiation conditions were as follow, 64 rows of detectors, 120 kV, 600 mA, PF (pitch factor) = 1.484 in helical scan mode. Additionally, we analyzed the contribution of X-rays, which were generated from different angles to the dosimeter; namely, angular dependences of 0-360 degrees at 45 degree intervals were evaluated experimentally. [Results] The ESDs and internal doses showed similar values, however the deviations between them were completely different; maximum deviation of ESD was found to be 30% and that of internal dose was at the most 5%. The deviation in ESDs is explained by the phenomenon in which some dosimeters were irradiated by direct X-ray and others were not. However, the small deviation between internal doses was explained by the phenomenon in which dosimeters were mainly irradiated by scattered X-rays. [Conclusion] In this study, we analyzed the relationship between ESD and internal dose for direct dose measurement of patient dose undergoing CT examination. The ESDs show relatively large fluctuations, on the other hand, the internal doses show small deviations.


Preliminary study for exposure dose measurement of people assisting during a pediatric X-ray procedure by means of a small-type OSL dosimeter

[Aims and objectives] During a pediatric X-ray procedure, medical staff or other people such as parents may assist to hold children during the X-ray examination. In this situation, these assistances are exposed by scattered X-rays, but there are no precise data concerning exposure doses. The aim of this study is to measure exposure dose of people assisting during the X-ray procedure. [Methods and materials] We used small-type OSL dosimeter (Landauer), which was sufficiently initialized. The detection limit of our system was estimated to be 0.5 micro-Gy. The OSL dosimeter was attached outside the lead protector which was worn by the assistant. In order to reduce contamination from background X- and/or gamma-rays, the exposed dosimeters were analyzed within 12 hours. The X-ray diagnostic system consisted of X-ray equipment and flat-panel detector which has auto-exposure control. The typical irradiation condition was SID=1.1 m, 3.2 mAs, and 53 kV. [Results] The exposure doses of assistances in the position outside the lead protector were approximately 3 micro-Gy. We measured 5 cases, in which patient's ages were 7 months to 1 year 6 months. Patient age showed no significant differences in exposure doses. [Conclusion] For the first time, using the small-type OSL dosimeter, we measured exposure dose of people assisting during a pediatric X-ray examination in a position outside the lead protector. The measured value was extremely low. Our actual data supports the justification of the situation in which someone should hold a child during an X-ray procedure.


An improvement of signal-to-noise ratio for phase image


T1 dependence of magnetization transfer effect for macromolecules

Purpose: To assess the relationship between T1 and magnetization transfer (MT) effect on macromolecules, we determined T1 map derived from variable flip angle (VFA) method with MT pulse. Materials and Methods: On a 3.0 T magnetic resonance (MR) system, we performed a phantom study using spoiled gradient-echo sequences; TR, 600 ms; TE, 5.8 ms; FA, 5, 20, 40, 60, and 90 degrees; without and with MT pulse (offset frequency, 800 ,1200 , and 1600 Hz). The phantom components were six samples; water and polyethylene glycol (PEG) solutions at different concentrations (10, 20, 30, 40, and 50 wt%). We calculated T1 maps from image datasets without and with MT pulse. Then, the MT ratio (MTR) maps were calculated from each FA image. Results: The mean T1 range without MT pulse for each sample was from 1200 to 2039 ms. The mean T1 ranges with MT pulse of each sample were from 1322 to 1886 at 800 Hz; from 1310 to 1926 ms at 1200 Hz; from 1300 to 1909 ms at 1600 Hz. The MTR of each sample showed the highest value at FA 5 degrees and offset 800 Hz. The mean MTR values of each sample were 6.54 ± 2.78, 3.94 ± 1.92, 2.50 ± 1.67, 1.96 ± 1.33, 1.44 ± 1.15, and 1.78 ± 1.53%. Conclusion: Determination of T1 with MT pulse makes it possible to obtain more detailed information of macromolecules.


Development of a novel method based on a photon counting technique with the aim of precise material identification in clinical X-ray diagnosis

Progress in Biomedical Optics and Imaging - Proceedings of SPIE


Response functions of multi-pixel-type CdTe detector --- Toward development of precise material identification on diagnostic X-ray images by means of photon counting


Necessity of Direct Dose Measurement during Current X-ray Diagnosis --- Our Approach Using a Small-type OSL Dosimeter


Visualization of magnetic transfer effect in polyethylene glycol impregnated waterlogged wood.


Estimation of identification limit for a small-type OSL dosimeter on the medical images by measurement of X-ray spectra

Our aim in this study is to derive an identification limit on a dosimeter for not disturbing a medical image when patients wear a small-type optically stimulated luminescence (OSL) dosimeter on their bodies during X-ray diagnostic imaging. For evaluation of the detection limit based on an analysis of X-ray spectra, we propose a new quantitative identification method. We performed experiments for which we used diagnostic X-ray equipment, a soft-tissue-equivalent phantom (1 20 cm), and a CdTe X-ray spectrometer assuming one pixel of the X-ray imaging detector. Then, with the following two experimental settings, corresponding X-ray spectra were measured with 40 120 kVp and 0.5 1000 mAs at a source-to-detector distance of 100 cm: (1) X-rays penetrating a soft-tissue-equivalent phantom with the OSL dosimeter attached directly on the phantom, and (2) X-rays penetrating only the soft-tissue-equivalent phantom. Next, the energy fluence and errors in the fluence were calculated from the spectra. When the energy fluence with errors concerning these two experimental conditions was estimated to be indistinctive, we defined the condition as the OSL dosimeter not being identified on the X-ray image. Based on our analysis, we determined the identification limit of the dosimeter. We then compared our results with those for the general irradiation conditions used in clinics. We found that the OSL dosimeter could not be identified under the irradiation conditions of abdominal and chest radiography, namely, one can apply the OSL dosimeter to measurement of the exposure dose in the irradiation field of X-rays without disturbing medical images.


Simple noise reduction for diffusion weighted images

Our purpose in this study was to reduce the noise in order to improve the SNR of Dw images with high b-value by using two correction schemes. This study was performed with use of phantoms made from water and sucrose at different concentrations, which were 10, 30, and 50 weight percent (wt%). In noise reduction for Dw imaging of the phantoms, we compared two correction schemes that are based on the Rician distribution and the Gaussian distribution. The highest error values for each concentration with use of the Rician distribution scheme were 7.3 % for 10 wt%, 2.4 % for 30 wt%, and 0.1 % for 50 wt%. The highest error values for each concentration with use of the Gaussian distribution scheme were 20.3 % for 10 wt%, 11.6 % for 30 wt%, and 3.4 % for 50 wt%. In Dw imaging, the noise reduction makes it possible to apply the correction scheme of Rician distribution.


Simple improvement method of uniformity of MR elastography on liver

Proceedings of the 24th Annual Meeting of ISMRM


Practical method for determination of air-kerma by using an ionization chamber toward the construction of secondary X-ray field to be used in clinical examination rooms


Evaluation of energy dependence of nanoDot optically stimulated luminescence (OSL) dosimeter using characteristic X-ray induced by medical X-ray equipment


Development of leaf electroscope to understand ionization for novice practical training


Compact irradiation system for evaluation of basic characteristics of the nanoDot OSL dosimeter toward direct measurement of exposure dose of patients


Fabrication and analysis of phantoms providing the equal-image-density for basic experiment of next-generation-type X-ray diagnosis


Proposal of quantitative identification method of a small-type OSL dosimeter: Verification that the dosimeter is not detected in the medical image


Precise determination of the scattered X-ray contamination rate using diagnostic X-ray equipment for the construction of the secondary X-ray field


Experimental evaluation of response functions of a CdTe detector in the diagnostic region with the aim of carrying out a basic experiment concerning a next generation photon counting system


Energy dependence measurement of small-type optically stimulated luminescence (OSL) dosimeter by means of characteristic X-rays induced with general diagnostic X-ray equipment

For X-ray inspections by way of general X-ray equipment, it is important to measure an entrance-skin dose. Recently, a small optically stimulated luminescence (OSL) dosimeter was made commercially available by Landauer, Inc. The dosimeter does not interfere with the medical images; therefore, it is expected to be a convenient detector for measuring personal exposure doses. In an actual clinical situation, it is assumed that X-rays of different energies will be detected by a dosimeter. For evaluation of the exposure dose measured by a dosimeter, it is necessary to know the energy dependence of the dosimeter. Our aim in this study was to measure the energy dependence of the OSL dosimeter experimentally in the diagnostic X-ray region. Metal samples weighing several grams were irradiated and, in this way, characteristic X-rays having energies ranging from 8 to 85 keV were generated. Using these mono-energetic X-rays, the dosimeter was irradiated. Simultaneously, the fluence of the X-rays was determined with a CdTe detector. The energy-dependent efficiency of the dosimeter was derived from the measured value of the dosimeter and the fluence. Moreover, the energy-dependent efficiency was calculated by Monte-Carlo simulation. The efficiency obtained in the experiment was in good agreement with that of the simulation. In conclusion, our proposed method, in which characteristic X-rays are used, is valuable for measurement of the energy dependence of a small OSL dosimeter in the diagnostic X-ray region.


Comparison with statistical analysis of signal correction in diffusion weighted MR image


Noise estimation for diffusion weighted MR image


Clinical Approach of T1-mapping for Hemodynamic Analysis

Medical Imaging and Information Sciences


Practical calibration curve of small-type optically stimulated luminescence (OSL) dosimeter for evaluation of entrance-skin dose in the diagnostic X-ray region

For X-ray diagnosis, the proper management of the entrance skin dose (ESD) is important. Recently, a small-type optically stimulated luminescence dosimeter (nanoDot OSL dosimeter) was made commercially available by Landauer, and it is hoped that it will be used for ESD measurements in clinical settings. Our objectives in the present study were to propose a method for calibrating the ESD measured with the nanoDot OSL dosimeter and to evaluate its accuracy. The reference ESD is assumed to be based on an air kerma with consideration of a well-known back scatter factor. We examined the characteristics of the nanoDot OSL dosimeter using two experimental conditions: a free air irradiation to derive the air kerma, and a phantom experiment to determine the ESD. For evaluation of the ability to measure the ESD, a calibration curve for the nanoDot OSL dosimeter was determined in which the air kerma and/or the ESD measured with an ionization chamber were used as references. As a result, we found that the calibration curve for the air kerma was determined with an accuracy of 5 %. Furthermore, the calibration curve was applied to the ESD estimation. The accuracy of the ESD obtained was estimated to be 15 %. The origin of these uncertainties was examined based on published papers and Monte-Carlo simulation. Most of the uncertainties were caused by the systematic uncertainty of the reading system and the differences in efficiency corresponding to different X-ray energies.


Development of new educational apparatus to visualize scattered X-rays.

European Congress of Radiology 2015 (EPOS)


Optimization of imaging parameter in contrast-enhanced three-dimensional T1 weighted MRI with fat saturation for head disease.


Hemodynamic analysis of bladder tumors using T1-dynamic contrast-enhanced fast spin-echo MRI

Objectives: To evaluate the hemodynamics of bladder tumors, we developed a method to calculate change in R 1 value (ΔR 1) from T 1-dynamic contrast-enhanced fast spin-echo magnetic resonance imaging (T 1DCE-FSE-MRI). Materials and methods: On a 1.5-T MR system, T 1DCE-FSE-MRI was performed. This study was applied to 12 patients with urinary bladder tumor, i.e. urothelial carcinoma. We compared ΔR 1-time and ΔSI-time between a peak in the ΔR 1-time and ΔSI-time curve occurred during the first pass within 60 s. Next, we assessed the slope of increase for 180 s after CA injection (Slope 0-180). Results: The mean slope of the first pass was significantly higher for bladder tumors on both the ΔR 1-time and the ΔSI-time curve compared with normal bladder walls. Moreover, a significant difference was apparent between bladder tumors and normal bladder walls on the mean Slope 0-180 in the ΔR 1-time curve. However, no significant difference in the mean Slope 0-180 was observed on the ΔSI-time curve between bladder tumors and normal bladder walls. Conclusion: T 1DCE-FSE-MRI offers three advantages: quantitative analysis; high-quality (i.e., artifact-free) images; and high temporal resolution even for SE images. Use of ΔR 1 analysis with T 1DCE-FSE-MRI allows more detailed information on the hemodynamics of bladder tumors to be obtained and assists in differentiation between bladder tumors and the normal bladder wall. © 2011 Elsevier Ireland Ltd. All rights reserved.


Why do we have to calculate T1 when evaluation of carotid plaque?

European Congress of Radiology 2011 (EPOS)


高速スピンエコー法を用いた T1・T2同時計測MRI

高速スピンエコー法を用いた T1・T2同時計測MRI


Evaluation of Imaging Parameters for T1 Dynamic Contrast Enhanced MRI with Fast Spin-echo

高速スピンエコー法を用いた造影ダイナミックT1値計測MRIの最適条件の検討

For the purpose of continual measurement of the T1 value using the FSE (fast spin-echo) sequence and evaluation of the hemodynamics, we assessed T1 values when the imaging parameters were changed. Moreover, with the imaging parameters derived from this study, dynamic contrast-enhanced MR imaging (MRI) was examined in prostatic disease. First, the T1 value before contrast agent injection was measured with imaging parameters that had different TR and fixed TE. Next, dynamic contrast-enhanced imaging data were acquired for the imaging parameters using TE and TR in the same way as before contrast agent injection, and the T1 value of the tissue at contrast enhancement was measured. In the phantom studies, the TSE imaging parameters with short TE, long TR, and few ETL were connected with the mixed sequence. In dynamic study of the prostate, the difference between normal prostate and prostate cancer became clearer with the time-relaxation rate curve than the time-signal curve. This method using TSE is able to evaluate in greater detail in formation on hemodynamics and to perform dynamic study with the spin-echo sequence in extensive tissues.

For the purpose of continual measurement of the T1 value using the FSE (fast spin-echo) sequence and evaluation of the hemodynamics, we assessed T1 values when the imaging parameters were changed. Moreover, with the imaging parameters derived from this study, dynamic contrast-enhanced MR imaging (MRI) was examined in prostatic disease. First, the T1 value before contrast agent injection was measured with imaging parameters that had different TR and fixed TE. Next, dynamic contrast-enhanced imaging data were acquired for the imaging parameters using TE and TR in the same way as before contrast agent injection, and the T1 value of the tissue at contrast enhancement was measured. In the phantom studies, the TSE imaging parameters with short TE, long TR, and few ETL were connected with the mixed sequence. In dynamic study of the prostate, the difference between normal prostate and prostate cancer became clearer with the time-relaxation rate curve than the time-signal curve. This method using TSE is able to evaluate in greater detail information on hemodynamics and to perform dynamic study with the spin-echo sequence in extensive tissues.

Japanese Journal of Radiological Technology


Fundamental Study of Turbo Spin Echo Sequence with Driven Equilibrium Pulse

Driven Equilibrium Pulseを利用したTurbo Spin Echo法(DRIVE)の基礎的検討

When MR images are obtained with the turbo spin echo (TSE) sequence, DRIVE can be used as a sequence in which the driven equilibrium pulse (DE pulse), a reset pulse, is applied at the TSE echo train to accelerate relaxation time and return to the equilibrium of Mz magnetization. In this study, we examined the extent to which TR could be shortened in DRIVE and how the other parameters of the turbo spin echo sequence influence it. Results: 1) DRIVE is effective when the T2 value is long. 2) It is necessary to set TR at 1000ms or more to obtain image contrast with free water and fat in T2-weighted images for which a conventional turbo spin echo sequence using DRIVE is employed in clinical examination. 3) It is not necessary to consider the influence of the TSE factor when using DRIVE.


Characterization of Movement Disorders Using Multimodal Neuroimaging


Endogenous/exogenous tracers in CEST for pH measurement at 3T MRI


Evaluation of Blood Flow and Plaque Vulnerability in Carotid Artery Stenosis Focusing on Morphological and Component Characteristics

Proceedings of the 2022 ISMRM & SMRT ANNUAL MEETING & EXHIBITION, No.3783, 2022


Brain Tumor Characterization and Assessment using Automatic Detection of Extracellular pH Change

Proceedings of the 2021 ISMRM & SMRT ANNUAL MEETING & EXHIBITION


Calculation of Concentration of Contrast Media, Relaxivity, Extracellular pH and Oxygen Extraction Fraction for Brain Tumor Characterization

Proceedings of the 28th Annual Meeting of ISMRM


Calculation of molar relaxivity and concentration map of Gd-DTPA map using quantitative parameter map before and after injection for brain metastasis

Proceedings of the 27th Annual Meeting of ISMRM


Chemical exchange saturation transfer imaging depending on several neurodegenerative diseases at 3T


Which number of b-value is better for accurate calculation of virtual MR elastography?


Why are shear stiffness and estimated intravoxel incoherent motion map correlated in the liver?


Chemical exchange saturation transfer imaging for neurodegenerative diseases

Proceedings of the 26th Annual Meeting of ISMRM