Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 68, Issue 12
Displaying 1-16 of 16 articles from this issue
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Opening Article
Editorial
Originals
  • Relationship between Image Quality and Cross-sectional Area of Phantom in Three-dimensional Positron Emission Tomography Scan
    Atsushi Osawa, Kenta Miwa, Kei Wagatsuma, Tomohiro Takiguchi, Shintaro ...
    2012 Volume 68 Issue 12 Pages 1600-1607
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1600
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    The image quality in 18FDG PET/CT often degrades as the body size increases. The purpose of this study was to evaluate the relationship between image quality and the body size using original phantoms of variable cross-sectional areas in PET/CT. We produced five water phantoms with different cross-sectional areas. The long axis of phantom was 925 mm, and the cross-sectional area was from 324 to 1189 cm2. These phantoms with the sphere (diameter 10 mm) were filled with 18F-FDG solution. The radioactivity concentration of background in the phantom was 1.37, 2.73, 4.09 and 5.46 kBq/mL. The scanning duration was 30 min in list mode acquisition for each measurement. Background variability (N10 mm), noise equivalent count rates (NECRphantom), hot sphere contrast (QH,10 mm) as physical evaluation and visual score of sphere detection were measured, respectively. The relationship between image quality and the various cross-sectional areas was also analyzed under the above-mentioned conditions. As cross-sectional area increased, NECRphantom progressively decreased. Furthermore, as cross-sectional area increased, N10 mm increased and QH,10 mm decreased. Image quality became degraded as body weight increased because noise and contrast contributed to image quality. The visual score of sphere detection deteriorated in high background radioactivity concentration because a false positive detection in cross-sectional area of the phantom increased. However, additional increases in scanning periods could improve the visual score. We assessed tendencies in the relationship between image quality and body size in PET/CT. Our results showed that time adjustment was more effective than dose adjustment for stable image quality of heavier patients in terms of the large cross-sectional area.
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  • Availability of Normal Database by Single Photon Emission Computed Tomography System with Use of 3 Dimensional-stereotactic Surface Projections
    Hideo Onishi, Jun Hatazawa, Jyoji Nakagawara, Kengo Ito, Sang Kil Ha-K ...
    2012 Volume 68 Issue 12 Pages 1608-1616
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1608
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    Purpose: The present study aims to quantitatively investigate a normal database (NDB) created under the same acquisition and reconstruction conditions for three gamma camera systems (four types of collimator systems) with use of three-dimensional stereotactic surface projections (3D-SSP). We rebuilt a NDB with use of the N-isopropyl-p-123I-iodoamphetamine (123I-IMP) SPECT data derived from 30 healthy individuals at 20 institutions nationwide. We standardized the acquisition and reconstruction conditions, evaluated Z scores using patient data (PD) and examined each compensation effect. Results: Z scores determined using the advanced NDB were the same value. Artifacts were often generated in Z score maps derived from the conventional NDB (CONDB). The Z score of the own site NDB (OWNDB) was 70% of that calculated based on the CONDB. The combinatorial difference in compensation (scatter and attenuation) resulted in many artifacts being generated in Z score map images. Discussions: More artifacts were generated in Z score map images using the novel NDB compared with the CONDB. The novel NDB was comparable to the performance of OWNB. The accuracy of brain function image analysis can be improved the reconstruction conditions and correcting for scatter and attenuation on both the novel NDB and PD.
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  • Development of the Computerized Scheme for Reconstructing Three Dimensions Ultrasonography from the Conventional Two Dimensions Dynamic Images
    Mai Nakamura, Masanori Komi, Masayuki Tanaka, Junji Shiraishi
    2012 Volume 68 Issue 12 Pages 1617-1623
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1617
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    In this study, a computerized scheme for reconstructing three dimension (3D)-ultrasonography (US) of a breast mass using off-line B-mode two dimension (2D) dynamic US images obtained by conventional 2D equipment was developed. Two off-line 2D dynamic US images were obtained with two orthogonal directions for each mass. The z axis of reconstructed 3D-US of a breast mass was estimated by using a length of the mass on the orthogonal image. In order to verify whether the 3D-US reproduces the real form of a breast mass, the correlation between two image features (volume and effective diameter of a mass), which were calculated from 3D-US, and visual assessment reported by physicians were evaluated. For seventy-nine breast masses used in this study, estimated mass volumes obtained from 3D-US had a high correlation (R=0.925) with those obtained from diagnostic reports. In conclusion, it was suggested that our computerized scheme could reproduce the 3D form of breast masses with relatively small errors.
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  • Impact of Iterative Reconstruction on Shape Reproducibility of Three-dimensional Computed Tomography
    Takashi Hoshino, Katsuhiro Ichikawa, Syouichi Terakawa, Yasuyuki Katsu ...
    2012 Volume 68 Issue 12 Pages 1624-1630
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1624
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    The purpose of this study was to evaluate the effect of an iterative reconstruction method (IR) on shape reproducibility in three-dimensional (3D) computed tomography images. We used an IR (sinogram-affirmed iterative reconstruction: SAFIRE) implemented in a 64-channel multi slice computed tomography system (Siemens, SOMATOM Definition AS). We scanned a simulated vessel phantom with 180-HU vessel contrast at various radiation doses and reconstructed axial images of filtered back projection (FBP) and SAFIRE. Then we reconstructed multi-planar reconstruction (MPR) and volume rendering (VR) images from the axial images. Roundness was evaluated from MPR images and vessel surface roughness was evaluated from pixel value profiles of a vessel in VR images and visual evaluation by radiological technologists. In comparison on equivalent dose, the roundness and roughness were improved with increase of SAFIRE strength level. However, in comparison on equivalent noise (standard deviation: SD) of axial images, SAFIRE strength levels of 2 to 5 were significantly inferior to FBP (p<0.05). SAFIRE strength of 1 with a dose reduction of 19% maintained the shape reproducibility in all evaluations. Therefore, it would be not appropriate to use the SD of axial image as index for the dose reduction rate determination of 3D-CT images.
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  • Investigation of Vessel Visibility of Iterative Reconstruction Method in Coronary Computed Tomography Angiography Using Simulated Vessel Phantom
    Takeshi Inoue, Katsuhiro Ichikawa, Takanori Hara, Atsushi Urikura, Tak ...
    2012 Volume 68 Issue 12 Pages 1631-1636
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1631
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    Iterative reconstruction methods can reduce the noise of computed tomography (CT) images, which are expected to contribute to the reduction of patient dose CT examinations. The purpose of this study was to investigate impact of an iterative reconstruction method (iDose4, Philips Healthcare) on vessel visibility in coronary CT angiography (CTA) by using phantom studies. A simulated phantom was scanned by a CT system (iCT, Philips Healthcare), and the axial images were reconstructed by filtered back projection (FBP) and given a level of 1 to 7 (L1-L7) of the iterative reconstruction (IR). The vessel visibility was evaluated by a quantitative analysis using profiles across a 1.5-mm diameter simulated vessel as well as visual evaluation for multi planar reformation (MPR) images and volume rendering (VR) images in terms of the normalized-rank method with analysis of variance. The peak CT value of the profiles decreased with IR level and full width at half maximum of the profile also decreased with the IR level. For normalized-rank method, there was no statistical difference between FBP and L1 (20% dose reduction) for both MPR and VR images. The IR levels higher than L1 sacrificed the spatial resolution for the 1.5-mm simulated vessel, and their visual vessel visibilities were significantly inferior to that of the FBP.
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  • A Novel Method of Noise Power Spectrum Measurement for Computed Tomography Images with Adaptive Iterative Reconstruction Method
    Eiji Nishimaru,, Katsuhiro Ichikawa, Takanori Hara, Shoichi Terakawa, ...
    2012 Volume 68 Issue 12 Pages 1637-1643
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1637
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    Adaptive iterative reconstruction techniques (IRs) can decrease image noise in computed tomography (CT) and are expected to contribute to reduction of the radiation dose. To evaluate the performance of IRs, the conventional two-dimensional (2D) noise power spectrum (NPS) is widely used. However, when an IR provides an NPS value drop at all spatial frequency (which is similar to NPS changes by dose increase), the conventional method cannot evaluate the correct noise property because the conventional method does not correspond to the volume data natures of CT images. The purpose of our study was to develop a new method for NPS measurements that can be adapted to IRs. Our method utilized thick multi-planar reconstruction (MPR) images. The thick images are generally made by averaging CT volume data in a direction perpendicular to a MPR plane (e.g. z-direction for axial MPR plane). By using this averaging technique as a cutter for 3D-NPS, we can obtain adequate 2D-extracted NPS (eNPS) from 3D NPS. We applied this method to IR images generated with adaptive iterative dose reduction 3D (AIDR-3D, Toshiba) to investigate the validity of our method. A water phantom with 24 cm-diameters was scanned at 120 kV and 200 mAs with a 320-row CT (Acquilion One, Toshiba). From the results of study, the adequate thickness of MPR images for eNPS was more than 25.0 mm. Our new NPS measurement method utilizing thick MPR images was accurate and effective for evaluating noise reduction effects of IRs.
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Clinical Technologies
  • Comparison of Setup Accuracy between ExacTrac X-ray 6 Dimensions and Cone-beam Computed Tomography for Intracranial and Pelvic Image-guided Radiotherapy
    Tsuyoshi Kudo, Kaoru Ono, Kengo Furukawa, Sachie Fujimoto, Yukio Akagi ...
    2012 Volume 68 Issue 12 Pages 1644-1651
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1644
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    The aim of this study was to compare the setup difference measured with ExacTrac X-ray 6D (ETX6D) and cone-beam computed tomography (CBCT) for non-invasive fractionated radiotherapy. Setup data were collected on a Novalis Tx treatment unit for both a head phantom and patients with intracranial tumors and a pelvic phantom and patients with prostate cancer. Initially, setup was done for a phantom using ETX6D. Secondly, a treatment couch was shifted or rotated by each already known value. Thirdly, ETX6D and CBCT scans were obtained. Finally, setup difference was determined: the registrations of ETX6D images with the corresponding digitally reconstructed radiographs using ETX6D fusion, and registrations of CBCT images with the planning CT using online 6D fusion. The setup difference between ETX6D and CBCT was compared. The impact of shifts and rotations on the difference was evaluated. Patients’ setup data was similarly analyzed. In phantom experiments, the root mean square (RMS) of difference of the shift and rotation was less than 0.45 mm for translations, and 0.17 degrees for rotations. In intracranial patients’ data, the RMS of that was 0.55 mm and 0.44 degree, respectively. In prostate cancer patients’ data, the RMS of that was 0.77 mm and 0.79 degree, respectively. In this study, we observed modest setup differences between ETX6D and CBCT. These differences were generally less than 1.00 mm for translations, and 1.00 degrees for rotations, respectively.
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  • Importance of Three Dimensional-fusion Image after Stent-assisted Coil Embolization of Unruptured Aneurysm
    Takumi Kuriyama, Nobuyuki Sakai, Norimitu Niida, Hajime Furukawa, Kumi ...
    2012 Volume 68 Issue 12 Pages 1652-1661
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1652
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    Purpose: We made the fusion image of both stent and platinum coil after embolization of an unruptured aneurysm. Method: After scanning with cone beam computed tomography, we made three dimensional (3D) images of stent and coil and fused them. Conclusion: We can evaluate unruptured aneurysm after embolization by using a fusion image. 3D-fusion image is useful on clinical cases.
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Data
  • Evaluation of Slavic Continuity for electrocardiograph (ECG)-gated Non-helical Scan Using Multi Detector-row Computed Tomography with 64 Data Acquisition System
    Masataka Shiotani, Masato Ogawa, Ryo Watanabe, Tamotsu Shinohara
    2012 Volume 68 Issue 12 Pages 1662-1668
    Published: December 20, 2012
    Released on J-STAGE: December 20, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.12.1662
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    Multi detector-row computed tomography with 64 data acquisition systems are widely used for coronary CT angiography with an electrocardiograph (ECG) gated helical scan (HS). Step and shoot with ECG gated non-helical scan (snap shot pulse: SSP) could reduce exposure dose but banding artifact-like discontinuity was observed between adjacent slabs on volume rendering (VR) and curved planner reconstruction (CPR). Therefore, we investigated the factors that influence continuity of VR and CPR images by calculating image properties of Z-axis direction of slab. The observer performance studies were performed for evaluating continuity of simulated blood vessels of VR and CPR images at simulated heart rates: 50, 55, 57 and 60 beat per minute (bpm). As a result, the value of SD at both slab edges in SSP were 20.5% lower than middle part of slab and differences of value of SD were up to 4.4 between adjacent slab edges. Slice thickness of both slab edges were 20.3% thinner than that of the peripheral part of slab. At the border of the adjacent slab, the position of the simulated blood vessel was shifted. VR images of SSP at 57 bpm was indicated as the highest score and HS was significantly superior to SSP at 55 and 60 bpm (p<0.05). In CPR images, there were no significant differences at all simulated heart rates. In conclusion, we considered that VR images of SSP were influenced heart rates except 57 bpm (resonance case) and there was little difference of visibility for discontinuity of both CPR images obtained by SSP and HS.
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Lecture for JSRT Members
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