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Radiological Physics and Technology

Shiro Nishiyama, Satoru Ishibashi, Ryo Takahashi, Hidenobu Tachibana
An add-on micro multi-leaf collimator (mMLC) is used for stereotactic radiosurgery (SRS) and brain stereotactic radiotherapy (SRT), in which rotational radiotherapy may make more complex and time-consuming. We performed a retrospective study of an independent dose calculation verification for brain SRS and SRT in two institutions to show the accuracy of the verification system and propose a tolerance value for the verification. Several comparisons of static plans and patients' plans were conducted using a phantom measurement, and patients' plans using the patients' own computed tomography image...
April 19, 2017: Radiological Physics and Technology
Sayed Ahmad Zikri Bin Sayed Aluwee, Xiangrong Zhou, Hiroki Kato, Hiroshi Makino, Chisako Muramatsu, Takeshi Hara, Masayuki Matsuo, Hiroshi Fujita
We propose an approach to supporting pre-surgical planning for the uterus by integrating medical image analysis and physical model generation based on 3D printing. With our method, we first segment the patient-specific anatomy and lesions of the uterus on MR images; then, we create a 3D physical model, an exact replica of the patient's uterus in terms of size and softness, with transparency for easy observation of the internal structures of the uterus. In our experiments, we created pre-surgical models of hysterectomy for five patients who had been diagnosed to have uterine endometrial cancer...
April 12, 2017: Radiological Physics and Technology
Shunichi Motegi, Takehiro Shimada, Norio Hayashi, Hiroyuki Nagase, Ayako Taketomi-Takahashi, Yoshito Tsushima
We propose a practical method for setting the optimal inversion times (TI) for double inversion recovery (DIR) sequences. Our method used the measurement of signal intensity (SI) from real images to set the optimal TI for white-matter (WM) and gray-matter (GM)-attenuated inversion recovery (WAIR and GAIR, respectively) images. 3D-DIR images of healthy volunteers were obtained on 1.5- and 3.0-T magnetic resonance (MR) scanners and the SIs of GM, WM, and cerebrospinal fluid (CSF) were evaluated on real images...
April 9, 2017: Radiological Physics and Technology
Akio Ogura, Aoi Kamakura, Youhei Kaneko, Tomoya Kitaoka, Norio Hayashi, Anna Taniguchi
Medical images are increasingly being rendered as digital images that are displayed on a monitor to provide diagnoses. However, these images are often rendered in grayscale. In this context, we compare the detectability of low-contrast signals between digital grayscale images and color-scale images. Low-contrast phantom images were rendered with the use of five color tables (gray, blue, red, yellow, and green). The 32 acquired images sorted in random order were evaluated by nine observers, and their observations were subjected to receiver operating characteristic analysis...
March 27, 2017: Radiological Physics and Technology
Carina Marques Coelho, Raquel Calçada, Sofia Rodrigues, Juan Antonio Barragán, Ana Cravo Sá, Ana Paula Macedo, Maria de Fátima Monsanto
This study aimed to assess the administered dose based on portal imaging in craniospinal pediatric irradiation by evaluating cases in which portal images did or did not account for the total administered dose. We also intended to calculate the mean increase in total administered dose. Data were collected from General University Hospital Gregorio Marañón; we evaluated the total dose administered, total dose planned, number of portal images per treatment and corresponding monitor units of two different groups: one in which the dose from portal images is deducted from the total administered dose (D), and another in which it was not (N)...
March 21, 2017: Radiological Physics and Technology
Nobuhiro Yada, Hideo Onishi, Masahiro Miyai, Kentarou Ozasa, Takashi Katsube, Keiichi Onoda, Masuo Haramoto, Yasushi Yamamoto, Shuhei Yamaguchi, Hajime Kitagaki
We evaluated a novel normal database (NDB) generated using single photon emission computed tomography (SPECT) data obtained from healthy brains by using a SPECT/CT system, analyzed using a resolution recovery (RR) technique applied to the three-dimensional stereotactic surface projection (3D-SSP) technique. We used a three-dimensional ordered subset expectation maximization method (3D-OSEM) with applied scatter correction (SC), attenuation correction, and RR to reconstruct the data. We verified the accuracy of the novel NDB's values (Z, extent, and error scores), and compared the novel NDB to the 3D-SSP technique by using simulated misery perfusion-related patient data from a conventional NDB...
February 4, 2017: Radiological Physics and Technology
Masayuki Kanamoto, Tosiaki Miyati, Kazuki Terashima, Kei Katahira, Ryoji Ida, Daisaku Suga, Nobukazu Fuwa
The purpose of this study was to compare between superparamagnetic iron oxide (SPIO)-enhanced three-dimensional balanced turbo field-echo (B-TFE) sequence with T2 preparation pulse (T2 prep) and T2*-weighted imaging (T2*WI) for the simultaneous detection of hepatocellular carcinoma (HCC) and vessel thrombus. For 1.5-T magnetic resonance imaging, SPIO was administered to 23 patients with a portal or venous tumor thrombus, and B-TFE with T2 prep and T2*WI were acquired. Regions of interest in the B-TFE and T2*WI were selected for the tumor, liver, tumor thrombus, and vessels...
February 3, 2017: Radiological Physics and Technology
Kunio Doi, Fujio Araki, Masahiro Endo, Tomoyuki Hasegawa, Shigehiko Katsuragawa, Yoshie Kodera, Shigeru Sanada
No abstract text is available yet for this article.
March 2017: Radiological Physics and Technology
Bram van Ginneken
Half a century ago, the term "computer-aided diagnosis" (CAD) was introduced in the scientific literature. Pulmonary imaging, with chest radiography and computed tomography, has always been one of the focus areas in this field. In this study, I describe how machine learning became the dominant technology for tackling CAD in the lungs, generally producing better results than do classical rule-based approaches, and how the field is now rapidly changing: in the last few years, we have seen how even better results can be obtained with deep learning...
March 2017: Radiological Physics and Technology
Katsuyuki Taguchi
Energy-sensitive photon counting detectors (PCDs) have recently been developed for medical X-ray computed tomography (CT) imaging and a handful of prototype PCD-CT systems have been built and evaluated. PCDs detect X-rays by using mechanisms that are completely different from the current CT detectors (i.e., energy integrating detectors or EIDs); PCDs count photons and obtain the information of the object tissues (i.e., the effective atomic numbers and mass densities) to be imaged. Therefore, these PCDs have the potential not only for evolution-to improve the current CT images such as providing dose reduction-but also for a revolution-to enable novel applications with a new concept such as molecular CT imaging...
March 2017: Radiological Physics and Technology
Masahiro Hashida, Ryousuke Kamezaki, Makoto Goto, Junji Shiraishi
The ability to predict hazards in possible situations in a general X-ray examination room created for Kiken-Yochi training (KYT) is quantified by use of free-response receiver-operating characteristics (FROC) analysis for determining whether the total number of years of clinical experience, involvement in general X-ray examinations, occupation, and training each have an impact on the hazard prediction ability. Twenty-three radiological technologists (RTs) (years of experience: 2-28), four nurses (years of experience: 15-19), and six RT students observed 53 scenes of KYT: 26 scenes with hazardous points (hazardous points are those that might cause injury to patients) and 27 scenes without points...
March 2017: Radiological Physics and Technology
Masaru Sekiya, Michio Yamasaki
No abstract text is available yet for this article.
March 2017: Radiological Physics and Technology
Yasuhiro Fujiwara, Yoshiyuki Muranaka
Three-dimensional time-of-flight magnetic resonance angiography (TOF MRA) has been widely used in clinics. TOF MRA can cause dephasing artifacts, which lead to an intraluminal signal decrease. Silent MRA is a novel imaging technique that uses arterial spin labeling to achieve an ultrashort echo time (uTE), which is expected to decrease these effects and allow for accurate assessment of the flow in blood vessels. This study quantified the accuracy of Silent MRA images for visualizing the turbulent flow in flow-phantom and in vivo studies...
March 2017: Radiological Physics and Technology
Haruo Yamashita, Yuki Kase, Shigeyuki Murayama
In radiotherapy involving craniospinal irradiation (CSI), field junctions of therapeutic beams are necessary, because a CSI target is generally several times larger than the maximum field size of the beams. The purpose of this study was to develop a simplified method for estimating dose uniformity around the field junctions in proton CSI. We estimated the dose profiles around the field junctions of proton beams using a simplified field-junction model, in which partial lateral dose distributions around the field edge were assumed to be approximated using the error function...
March 2017: Radiological Physics and Technology
Yoshinori Tanabe, Takayuki Ishida
A new method was developed for quantifying the accuracy limits of image registration devices and the distortion of anatomical structures in verification images without image registration. A correlation was found between peak signal-to-noise ratio (PSNR) and the amount of parallel movement (1-10 mm at 1-mm intervals) of a rectangular parallelepiped phantom [correlation coefficient (CC) -0.91, contribution ratio (CR) 0.83]. Rotating the phantom from 1° to 10° at 1° intervals produced a similar correlation with PSNR (CC -0...
March 2017: Radiological Physics and Technology
Bimali Sanjeevani Weerakoon, Toshiaki Osuga
The observation of molecular diffusion by means of magnetic resonance imaging (MRI) is significant in the evaluation of the metabolic activity of living tissues. Series of MRI examinations were conducted on a diffusion model to study the behaviour of the diffusion process of different-molecular-weight (MW) paramagnetic MRI contrast agents in an isotropic agar hydrogel medium. The model consisted of a solidified 1 % agar gel with an initial concentration of 0.5 mmol/L contrast solution layered on top of the gel...
March 2017: Radiological Physics and Technology
Shuji Nagamine, Toshioh Fujibuchi, Yoshiyuki Umezu, Kazuhiko Himuro, Shinichi Awamoto, Yuji Tsutsui, Yasuhiko Nakamura
In this study, we estimated the ambient dose equivalent rate (hereafter "dose rate") in the fluoro-2-deoxy-D-glucose (FDG) administration room in our hospital using Monte Carlo simulations, and examined the appropriate medical-personnel locations and a shielding method to reduce the dose rate during FDG injection using a lead glass shield. The line source was assumed to be the FDG feed tube and the patient a cube source. The dose rate distribution was calculated with a composite source that combines the line and cube sources...
March 2017: Radiological Physics and Technology
Francisco Albiol, Alberto Corbi, Alberto Albiol
We explore three different alternatives for obtaining intrinsic and extrinsic parameters in conventional diagnostic X-ray frameworks: the direct linear transform (DLT), the Zhang method, and the Tsai approach. We analyze and describe the computational, operational, and mathematical background differences for these algorithms when they are applied to ordinary radiograph acquisition. For our study, we developed an initial 3D calibration frame with tin cross-shaped fiducials at specific locations. The three studied methods enable the derivation of projection matrices from 3D to 2D point correlations...
March 2017: Radiological Physics and Technology
Fumio Hashimoto, Atsushi Teramoto, Yasuki Asada, Shoichi Suzuki, Hiroshi Fujita
Recently, region-setting computed tomography (CT) has been studied as a region of interest imaging method. This technique can strongly reduce the radiation dose by limiting the irradiation field. Although mathematical studies have been performed for reduction of the truncation artifact, no experimental studies have been performed so far. In this study, we developed a three-dimensional region-setting CT system and evaluated its imaging properties. As an experimental system, we developed an X-ray CT system with multileaf collimators...
March 2017: Radiological Physics and Technology
Nobuyuki Kudomi, Yukito Maeda, Tetsuhiro Hatakeyama, Yuka Yamamoto, Yoshihiro Nishiyama
PET enables quantitative imaging of the rate constants K 1, k 2, k 3, and k 4, with a reversible two tissue compartment model (2TCM). A new method is proposed for computing all of these rates within a reasonable time, less than 1 min. A set of differential equations for the reversible 2TCM was converted into a single formula consisting of differential and convolution terms. The validity was tested on clinical data with (18)F-FLT PET for patients with glioma (n = 39). Parametric images were generated with the formula that was developed...
March 2017: Radiological Physics and Technology
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