Yasuhiro Hiai

Kumamoto University, Kumamoto, Kumamoto Prefecture, Japan

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Publications (26)36.73 Total impact

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    ABSTRACT: Purpose: Routine clinical practice involves the application of diverse scanning parameters that can affect apparent diffusion coefficient (ADC) values. We evaluated interimager variability in ADC values with respect to their potential effect in clinical applications.Methods: In 7 healthy volunteers, we obtained diffusion-weighted (DW) images using routine clinical parameters and 1.5- (n = 9) and 3-tesla (n = 3) magnetic resonance (MR) imagers from 5 different vendors, performing 84 MR imaging studies. To evaluate the differences in ADC values among the imagers, vendors, and magnetic field strengths, we measured the mean pixel values of the frontal white matter and thalamus (gray matter) in both cerebral hemispheres of the 7 volunteers and used repeated-measures analysis of variance for multiple comparisons.Results: The laterality of ADC values in the bilateral structures ranged from one to 3% for the 12 imagers. Although the relative difference in ADC values of white matter was 7% for scanners yielding the highest and lowest mean ADC values (P < 0.01), it was within 2 to 4% for instruments from the same vendors. For gray matter, the interimager difference was 4 to 12%, even among the same vendors (P < 0.05). Among the 3T imagers, the difference for white and gray matter was approximately 3%.Conclusions: There were significant interimager differences in ADC values, especially with respect to gray matter. Taking into consideration the existing laterality, however, the differences among our 3T imagers may be acceptable despite the use of diverse scanning parameters. In routine clinical practice, the existing variability must be considered imager by imager.
    Magnetic Resonance in Medical Sciences 04/2014; · 0.75 Impact Factor
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    ABSTRACT: 3D-susceptibility-weighted angiography (SWAN) can produce high-resolution images that yield excellent susceptibility-weighted contrast at a relatively short acquisition time. To compare SWAN- and 2D-T2*-weighted gradient-echo images (T2*-WI) for their sensitivity in the depiction of cerebral hemorrhagic lesions. We subjected 75 patients with suspected cerebral hemorrhagic lesions to SWAN and T2*-WI at 3T. We first measured the contrast-to-noise ratio (CNR) using an agar phantom that contained different concentrations of superparamagnetic iron oxide (SPIO). The acquisition time for SWAN and T2*-WI was similar (182 vs. 196 s). Neuroradiologists compared the two imaging methods for lesion detectability and conspicuity. The CNR of the phantom was higher on SWAN images. Of the 75 patients, 50 were found to have a total of 278 cerebral hemorrhagic lesions (microbleeds, n = 229 [82.4%]; intracerebral hemorrhage, n = 18 [6.5%]; superficial siderosis, n = 13 [4.7%]; axonal injuries, n = 8 [2.9%]; subarachnoid hemorrhage [SAH] or brain contusion, n = 3 each [1.0%]; subdural hematoma, n = 2 [0.7%]; cavernous hemangioma or dural arterteriovenous fistula, n = 1 each [0.4%]). In none of the lesions was the SWAN sequence inferior to T2*-WI with respect to lesion detectability and conspicuity. In fact, SWAN yielded better lesion conspicuity in patients with superficial siderosis and SAH: it detected significantly more lesions than T2*-WI (P < 0.01) and it was particularly useful for the detection of microbleeds and lesions near the skull base. SWAN is equal or superior to standard T2*-WI for the diagnosis of various cerebral hemorrhagic lesions. Because its acquisition time is reasonable it may replace T2*-WI.
    Acta Radiologica 08/2013; · 1.33 Impact Factor
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    ABSTRACT: PURPOSE The globus pallidus is subdivided into the medial (GPm) and lateral (GPl) segments. Deep-brain stimulation has shown therapeutic benefits for several neurodegenerative disorders including Parkinson’s disease (PD); the GPm is one of the targets. However, the conventional MR imaging often fails to depict the GPm. “Phase Difference Enhanced Imaging (PADRE)” which we have developed can enhance the phase differences between objective and surrounding tissue. Our objective is to clarify if the high-spatial-resolution PADRE can reveal the anatomical structures within the GP in the patients with PD. METHOD AND MATERIALS Thirteen patients with PD were enrolled in this study. Axial images were acquired covering the entire basal ganglia at 3T MR system. Our PADRE imaging consisted of a three-dimensional fast spoiled gradient-echo (3D fast SPGR) sequence, which was acquired with parameters of 45 msec /28 msec /12 minutes (repetition time/echo time/imaging time), a 22 cm field of view (FOV), a 512 x 512 matrix, and 1.4-mm thick sections. The neuroradiologists evaluated the GP on PADRE, SWI-like images, and conventional MRI (T1WI and T2WI), and classified the delineation of the GP into following 4 grades; grade 0 = no visualization of the GP, grade 1= inadequate to identify the GP, grade 2=adequate to identify the GP, but the GPm and GPl are not delineated, grade 3= the GPm and GPl are clearly delineated. RESULTS Regarding the visualization of the GP, the image quality with PADRE was scored to be grade 3 in 10 (77%) of all 13 patients, grade 2 in 3 (23%), grade 1 in 0 (0%), although all 13 patients were scored as grade 1 with conventional MRI. The mean qualitative image score with PADRE were significantly superior to that with SWI-like images (2.83 vs 2.41, P <.005). CONCLUSION PADRE technique is able to depict the internal structures of the GP that has been difficult to appreciate on conventional MR imaging; in addition, the PADRE seems superior to SWI. CLINICAL RELEVANCE/APPLICATION For the DBS of GP in PD patients, the preoperative PADRE may provide the useful additional information to understand individual anatomy and to help determine the appropriate surgical approach.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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    ABSTRACT: OBJECTIVES: To determine whether it is possible to diagnose patients with Parkinson's disease (PD) on an individual basis using magnetic resonance imaging with phase difference enhanced imaging (PADRE). METHODS: PADRE delineated the crural fibres as a layer of low signal intensity and the substantia nigra as a layer of medium signal intensity in a healthy volunteer, and showed a clear boundary between the crural fibres and the substantia nigra (BCS). Twenty-four PD patients and 24 control subjects were enrolled. Contrast ratios between the substantia nigra and occipital white matter were calculated, and two radiologists independently reviewed the PADRE findings regarding BCS obscuration. RESULTS: Mean contrast ratio in PD patients was significantly higher than in control subjects (0.56 vs 0.39, P < 0.01). The BCS on PADRE was obscured significantly more frequently in any subgroups with PD patients compared with control subjects (P < 0.01). The observation of BCS obscuration had a sensitivity, specificity and accuracy for the diagnosis of PD of 92 %, 88 % and 90 % for radiologist 1 and 83 %, 88 % and 85 % for radiologist 2, respectively. CONCLUSION: PADRE is able to identify PD in patients as a loss of delineation between the crural fibres and the substantia nigra on an individual basis. KEY POINTS: • High-resolution phase difference enhanced 3-T MR imaging offers new insights into Parkinson's disease • Phase imaging can delineate the boundary between crural fibres and substantia nigra • The boundary between crural fibres and substantia nigra is obscured in Parkinson's disease • Phase difference enhanced imaging (PADRE) can identify individual patients with Parkinson's disease.
    European Radiology 10/2012; · 4.34 Impact Factor
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    ABSTRACT: Phase difference enhanced (PADRE) imaging technique can selectively enhanced the phase difference between the target and surrounding tissue. Our purpose is to assess the delineations of the optic radiation and primary visual cortex (stria of Gennari) using PADRE. The subjects were 6 healthy volunteers. Axial and coronal high-spatial resolution PADRE images were acquired covering the entire optic radiation using a 3T magnetic resonance system. Two radiologists evaluated the PADRE and susceptibility-weighted imaging (SWI)-like images for the delineation of four layers at the optic radiation (tapetum, internal sagittal stratum, external sagittal stratum, and adjacent white matter) on the basis of the anatomic appearances of the cadaveric specimens stained with Bodian's method and Kluver-Barrera method. The radiologists also assessed the delineations of the stria of Gennari on PADRE and SWI-like images. In all 6 healthy subjects, the PADRE images clearly identified the four layers at the optic radiation, as well as the stria of Gennari, which were difficult to appreciate in SWI-like images. The anatomic appearances of the optic radiation on PADRE images were more similar to those seen in the specimens stained with Kluver-Barrera method than with Bodian's method. The PADRE technique can delineate the four layers at the optic radiation and the stria of Gennari; the differences in myelin densities can also be enhanced. The PADRE technique may have the potential to reinforce the clinical utility of MRI in the diagnosis of diseases that affect the optic radiation and primary visual cortex.
    Academic radiology 07/2012; 19(10):1283-9. · 2.09 Impact Factor
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    ABSTRACT: To prospectively compare the image contrast of various brain lesions on two-dimensional (2D) and three-dimensional (3D) fluid-attenuated inversion-recovery (FLAIR) images and to highlight the pitfalls of 3D FLAIR. Institutional review board approval was obtained. We examined 94 brain lesions with 2D and 3D FLAIR at 3T. First, we optimized the repetition time and echo time of 3D FLAIR with a volunteer study. Then, we assessed the conspicuity and detection of the various lesions qualitatively, and the contrast ratio between the gray or white matter and lesions was calculated as a quantitative assessment. We also performed a phantom study to investigate the effects of different flow velocities on 2D and 3D FLAIR. With regard to the conspicuity and detection of most lesions (multiple sclerosis, ischemic lesions or infarction, brain tumors, or chronic trauma), 3D FLAIR was equal or superior to 2D FLAIR. For these lesions, the mean contrast ratios were higher on 3D FLAIR than on 2D FLAIR images. In terms of lesion conspicuity in the patients with hippocampal sclerosis and leptomeningeal metastasis, however, 3D FLAIR was equal or inferior to 2D FLAIR. The ivy sign in patients with moyamoya disease was frequently obscured on 3D FLAIR. The phantom study demonstrated that the signal-intensity ratio on 3D FLAIR decreased more rapidly with increasing velocity than that on 2D FLAIR. Although 3D FLAIR may replace 2D FLAIR images for most patients, radiologists should keep in mind that 3D has some pitfalls.
    Academic radiology 07/2012; 19(10):1225-32. · 2.09 Impact Factor
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    ABSTRACT: Various three-dimensional fast spin echo (3D-FSE) sequences are used for non-contrast magnetic resonance angiography (MRA). Differences in the ability to detect vascular stenosis using these sequences, however, have not yet been evaluated. The purpose of this study is to evaluate the usefulness of each sequence for the detection of vascular stenosis by using a vascular phantom. The phantom consisting of silicon tubes with 30% and 70% stenosis of luminal diameter and fluids close to T 2 value of blood were used for the study. Non-contrast MRA with half-Fourier acquisition single-shot turbo spin echo (HASTE)-noncontrast magnetic resonance angiography of arteries and veins (NATIVE), sampling perfection with application optimized contrasts using different flip angle evolutions (SPACE)-NATIVE, fresh blood imaging (FBI) and triggered angiography non contrast enhanced (TRANCE) sequences was performed by using the phantom which can be varied in terms of the steady flow velocity. Each stenosis was quantitatively estimated by the stenosis index (SI) calculated from the signal intensities on acquired images. The signal intensity of the non-stenotic vascular site markedly decreased at more than a flow rate of 20 cm/s in all sequences. Significant decrease in the signal intensity was observed in the distal point from the stenosis area on these images acquired by using HASTE-NATIVE and FBI sequences. FBI and TRANCE sequences showed a more accurate SI for 30% stenosis than HASTE-NATIVE and SPACE-NATIVE sequences. SI for 70% stenosis was overestimated in all sequences at 5 cm/s of diastolic flow rate. In conclusion, the ability to detect vascular stenosis on non-contrast MRA image using 3D-FSE sequences depends on the image quality during diastolic phase in the cardiac cycle. FBI and TRANCE sequences are useful to detect the mild arterial stenosis.
    Nippon Hoshasen Gijutsu Gakkai zasshi 01/2012; 68(7):817-24.
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    ABSTRACT: PURPOSE Although T2WI and T2*WI demonstrate the increased iron content of the substantia nigra (SN) in patients with Parkinson's disease (PD), it is difficult to apply this finding to the diagnosis of individual PD cases in clinical practice. Recently, we have developed new phase-weighted MR imaging, “Phase Difference Enhanced Imaging (PADRE)”, in which phase difference between objective and surrounding tissue is selected in order to enhance the contrast of objective tissue. Our objective is to clarify whether the high resolution PADRE reveals the anatomical structures within the SN and is useful for the diagnosis of PD. METHOD AND MATERIALS First, we investigated the effects of varying the reconstitution parameters of PADRE imaging on the depiction of the anatomical structures of the midbrain using three healthy volunteers. The optimized PADRE could display the subregions of the SN as a striped appearance consisting of pars compacta and reticulate. Then, 12 patients with PD and 12 healthy controls (age- and gender-matched) underwent MRI including the optimized PADRE. For each subject, the contrast ratio (CR) between SN and ventral tegmental area was calculated, and two neuroradiologists analyzed the striped appearance of the SN according to the following scores: score 2 = clearly visualized; score 1 = partially visualized; and score 0 = obscured. RESULTS PD patients showed significantly higher mean CR than healthy controls (0.65 vs. 0.49, P <.001). The stripe of SN was obscured more frequently in PD than in healthy controls (0.44 vs 1.78, P <.001). When the obscuration of the SN stripe (score 0) was used as a diagnostic criterion of PD, the sensitivity and specificity were 100% and 90%, respectively. CONCLUSION The nigral stripe on PADRE was frequently obscured in patients with PD. This finding showed high accuracy for the diagnosis of PD. CLINICAL RELEVANCE/APPLICATION For the diagnosis of PD, the obscuration of nigral stripe on phase difference enhanced imaging seems to have higher accuracy than any other MR findings previously reported.
    Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; 11/2011
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    ABSTRACT: To develop a new tract imaging technique for visualising small fibre tracts of the brainstem and for detecting the abnormalities in multiple system atrophy of the cerebellar type (MSA-C) using a phase difference enhanced (PADRE) imaging technique, in which the phase difference between the target and surrounding tissue is selectively enhanced. Two neuroradiologists compared the high-spatial-resolution PADRE imaging, which was acquired from six healthy volunteers, three patients with MSA-C, and 7 patients with other types of neurodegenerative diseases involving the brainstem or cerebellum. Various fine fibre tracts in the brainstem, the superior and inferior cerebellar peduncles, medial lemniscus, spinothalamic tract, medial longitudinal fasciculus, central tegmental tract, corticospinal tract and transverse pontine fibres, were identified on PADRE imaging. PADRE imaging from MSA-C demonstrated the disappearance of transverse pontine fibres and significant atrophy of the inferior cerebellar peduncles, while the superior cerebellar peduncles were intact. PADRE imaging also demonstrated that the transverse pontine fibres and inferior cerebellar peduncle were not involved in the other neurodegenerative diseases. PADRE imaging can offer a new form of tract imaging of the brainstem and may have the potential to reinforce the clinical utility of MRI in differentiating MSA from other conditions.
    European Radiology 05/2011; 21(10):2202-10. · 4.34 Impact Factor
  • Kengo Nakato, Yasuhiro Hiai, Seiji Tomiguchi
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    ABSTRACT: Contrast-enhanced magnetic resonance angiography (CE-MRA) is frequently performed in body and extremity studies because of its superior ability to detect the vascular stenosis. However, nephrotoxicity of the contrast medium has been emphasized in recent years. Non-contrast MRA using the three-dimensional electrocardiogram-synchronized fast spin echo method (FBI, NATIVE and TRANCE) is recommended as a substitute for CE-MRA. There are a few reports in the literature that evaluate the detectability of vascular stenosis using non-contrast MRA on 3.0 T MRI. The purpose of this study was to evaluate the detectability of vascular stenosis using non-contrast MRA at 3.0 T with an original vascular phantom. The vascular phantom consisted of silicon tubes. 30% and 70% stenosis of luminal diameter were made. Each silicon tube connected a pump producing a pulsatile flow. A flowing material to was used in this study to show the similarity of the intensity to blood on MRI. MRA without a contrast medium (NATIVE sequence) were performed in the vascular phantom by changing the image matrix, static magnetic field strength and flow velocity. In addition, the NATIVE sequence was used with or without flow compensation. Vascular stenosis was quantitatively estimated by measurement of the signal intensities in non-contrast MRA images. MRA with NATIVE sequence demonstrated an accurate estimation of 30% vascular stenosis at slow flow velocity. However, 30% stenosis was overestimated in cases of high flow velocity. Estimation was improved by using a flow compensation sequence. 70% stenosis was overestimated on MRA with NATIVE sequence. Estimation of 70% stenosis was improved by using a flow compensation sequence. Accurate estimation of vascular stenosis in MRA with a NATIVE sequence is improved by using the flow compensation technique. MRA with NATIVE sequence is considered to be a promising method for the evaluation of patients with severe renal dysfunction as a substitute for CT angiography or CE-MRA.
    Nippon Hoshasen Gijutsu Gakkai zasshi 08/2010; 66(8):863-9.
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    ABSTRACT: In magnetoencephalogram studies, the primary gustatory area, area G, is not always seen in the same coronal plane in both hemispheres. We investigated possible asymmetry in right-handed and left-handed individuals by functional MRI. Group analyses revealed a significant difference in the antero-posterior coordinates of the area G between the right and left hemispheres in the right-handed group, but not in the left-handed group, indicating significant morphometric asymmetry in the former group and ambiguous morphometric asymmetry in the latter. However, in left-handed individuals with motor speech areas detected in the right hemisphere, area G was more posteriorly located in the right than in the left hemisphere. These findings suggest that the motor speech area contributes to the asymmetric location of area G.
    Neuroreport 04/2009; 20(4):450-5. · 1.40 Impact Factor
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    ABSTRACT: PURPOSE Although blood-oxygen-level-dependent functional MRI study usually employs two-dimensional echo-planar imaging (2D EPI) and is widely used for evaluating various brain functions, it has some limitations, e.g. low spatial resolution and indirect observation of brain activity. Three-dimensional (3D) principle of echo shifting with a train of observations (PRESTO) with sensitivity encoding (SENSE) facilitates the acquisition of high-resolution phase estimates. The purpose of this study was to evaluate the feasibility of using the 3D PRESTO-SENSE sequence for the evaluation of blood-oxygen-level-dependent effects in the brain at 3 T MRI. METHOD AND MATERIALS Functional MR scans using 3D PRESTO-SENSE and 2D EPI sequences were performed at a 3T MR scanner. Six healthy volunteers (5 males and 1 female, age range, 24–43 years, mean age 31 years) performed hand grasping during the functional test. For 3D PRESTO-SENSE imaging, image data were collected with a 256 x 256 matrix during two 90-sec scan sessions of activation and rest. For conventional 2D EPI, image data were collected with a 64 x 64 matrix during 6 scan sessions of activation and rest (30 sec each). On subtracted 3D PRESTO-SENSE images of each subject, the overall image quality was evaluated. Activation of the hand motor area of the primary motor cortex was analyzed with NIH software. The summation of cross-sectional areas of activated pixels on subtracted 2-mm axial reconstructed images was compared bilaterally using the Wilcoxon matched-pair signed-rank test. RESULTS In all 6 volunteers the overall image quality was at least good. On both 3D PRESTO-SENSE and 2D EPI, activation in the primary motor cortex was observed in the hand motor area contralateral to the task. With respect to the number of activated pixels and the summation of cross-sectional areas of activated pixels, laterality was significantly different in all cases (p < 0.01). On 3D PRESTO-SENSE images, the location of activated areas was more often localized to the cortex than the sulcus. CONCLUSION Blood-oxygen-level-dependent functional MRI using a 3D PRESTO-SENSE sequence is feasible and may provide high-spatial-resolution functional information. CLINICAL RELEVANCE/APPLICATION Blood-oxygen-level-dependent functional MRI using the 3D PRESTO-SENSE sequence is a novel functional MR technique that provides high-spatial-resolution functional information.
    Radiological Society of North America 2008 Scientific Assembly and Annual Meeting; 12/2008
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    ABSTRACT: To analyze the influence of matrix and echo time (TE) of three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA) on the depiction of residual flow in aneurysms embolized with platinum coils at 1.5T and 3T. A simulated intracranial aneurysm of the vascular phantom was loosely packed to maintain the patency of some residual aneurysmal lumen with platinum coils and connected to an electromagnetic flow pump with pulsatile flow. MRAs were obtained altering the matrix and TE of 3D TOF sequences at 1.5T and 3T. The increased spatial resolution and the shorter TE offered better image quality at 3T. For the depiction of an aneurysm remnant, the high-spatial-resolution 3T MRA (matrix size of 384 x 224 and 512 x 256) with a short TE of < or =3.3 msec were superior to the 1.5T MRA obtained with any sequences. 3T MRA is superior to 1.5T MRA for the assessment of aneurysms embolized with platinum coils; the combination of the 512 x 256 matrix and short TE (3.3 msec or less) seems feasible at 3T.
    Journal of Magnetic Resonance Imaging 07/2008; 28(1):13-20. · 2.57 Impact Factor
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    ABSTRACT: A 3-T magnetic resonance imaging system provides a better signal-to-noise ratio and inflow effect than 1.5 T in three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA). The purpose of this study is to analyze the influence of matrix, parallel imaging, and acquisition time on image quality of 3D TOF MRA at 1.5 and 3 T, and to illustrate whether the combination of larger matrixes with parallel imaging technique is feasible, by evaluating the visualization of simulated intracranial aneurysms and aneurysmal blebs using a vascular phantom with pulsatile flow. An anthropomorphic vascular phantom was designed to simulate the various intracranial aneurysms with aneurysmal bleb. The vascular phantom was connected to an electromagnetic flow pump with pulsatile flow, and we obtained 1.5- and 3-T MRAs altering the parameters of 3D TOF sequences, including acquisition time. Two radiologists evaluated the depiction of simulated aneurysms and aneurysmal blebs. The aneurysmal blebs were not sufficiently visualized on the high-spatial resolution 1.5-T MRA (matrix size of 384 x 256 or 512 x 256), even with longer acquisition time (9 or 18 min). At 3 T with acquisition time of 4.5 min using parallel imaging technique, however, the depiction of aneurysmal blebs was significantly better for the high-spatial resolution sequence than for the standard resolution sequence. For the high-spatial resolution sequence, the longer acquisition times did not improve the depiction of aneurysmal blebs in comparison with 4.5 min at 3 T. For 3D TOF MRA, the combination of the large matrix with parallel imaging technique is feasible at 3 T, but not at 1.5 T.
    Academic Radiology 06/2008; 15(5):635-40. · 1.91 Impact Factor
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    ABSTRACT: The objective of this study is to compare the detectability of brain metastases at 3T among three contrast-enhanced sequences, spin-echo (SE) sequence, inversion recovery fast SE (IR-FSE) sequence (both with section thickness of 6 mm), and three-dimensional fast spoiled gradient-echo (3D fast SPGR) sequence with 1.4 mm isotropic voxel. First, phantom studies were performed to quantify the contrast-enhancement ratio (CER) with three sequences. In 21 consecutive patients with brain metastases, axial images of three sequences at 3T were obtained after administration of gadoteridol. Two neuroradiologists assessed the detectability of brain metastases for the three sequences. In the phantom study, no evident difference in the CER was demonstrated among three sequences. Significantly more brain metastases were detected with 3D fast SPGR than with SE and IR-FSE (a total of 97 lesions with 3D fast SPGR vs. 64 with SE and 63 with IR-FSE). In particular, 3D fast SPGR was superior to the other two sequences in detection of the small lesions (<3 mm). At 3T, the contrast-enhanced 3D fast SPGR with 1.4 mm isotropic voxel is clinically more valuable for detecting small brain metastases than the SE and IR-FSE with section thickness of 6 mm.
    European Radiology 10/2007; 17(9):2345-51. · 4.34 Impact Factor
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    ABSTRACT: To determine the sensitivity of susceptibility-weighted imaging (SWI) for depicting hemorrhagic hypointense foci of the brain in comparison with gradient-recalled echo (GRE)- and GRE-type single-shot echo-planar imaging (GREI, GRE-EPI), and to assess the basic characteristics of the susceptibility effect by using a phantom. We prospectively examined 16 patients (9 males, 7 females, aged 10-74 years, mean 43 years) with hypointense foci using SWI, GREI, and GRE-EPI at a 1.5-T magnetic resonance (MR) unit. The contrast-to-noise ratio (CNR), sensitivity to small hypointese foci, and artifacts were evaluated. To assess the basic characteristics of SWI, we performed a phantom study using different concentrations of superparamagnetic iron oxide (SPIO). The CNR of lesions was significantly greater for SWI than the other images (P < .0001). SWI detected the greatest number of small hypointense foci, even in the near-skull-base and infratentorial regions. Quantitative and qualitative analyses in our clinical and phantom studies demonstrated that the degree of artifacts was similar with SWI and GREI. SWI was best for detecting small hemorrhagic hypointense foci. Artifacts of SWI were similar to GREI.
    Academic Radiology 09/2007; 14(9):1011-9. · 1.91 Impact Factor
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    ABSTRACT: To evaluate whether positional MR images of the lumbar spine, obtained with a horizontally open-configuration MR unit, demonstrate positional changes of the dural sac, and to assess whether there are significant differences in positional changes between healthy volunteers and patients with chronic low back pain. The study population consisted of 15 patients with chronic low back pain and 14 healthy volunteers. MR images were obtained using a horizontally open-configuration 0.4-T MR unit. After conventional lumbar MR examinations, images were obtained in the flexion, neutral, and extension positions, using a positioning device. The anteroposterior diameter of the dural sac at the level of each lumbar disk was measured in the three positions and quantitative data were compared. Our MR protocol was tolerated by all patients. In both patients and volunteers, the mean anteroposterior diameter of the dural sac was smaller in the extension positions than in the flexion positions. In the mean rate of change (RC) in the dural sac diameter at the site of the degenerated disks, the difference between the volunteers and patients was significant (P < 0.05). There was no significant difference in the mean RC between patients and volunteers without degenerative disks. Using a horizontally open-configuration MR unit, positional MR imaging provided position-dependent change of the dural sac. Positional changes at the site of the degenerated disks may be different in patients with and without chronic low back pain.
    Journal of Magnetic Resonance Imaging 09/2007; 26(3):525-8. · 2.57 Impact Factor
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    ABSTRACT: A tool to support the subject is generally used for kinematic joint imaging with an open MRI apparatus because of difficulty setting the image plane correctly. However, use of a support tool requires a complicated procedure to position the subject, and setting the image plane when the joint angle changes is time consuming. Allowing the subject to move freely enables better diagnoses when kinematic joint imaging is performed. We therefore developed an interactive scan control (ISC) to facilitate the easy, quick, and accurate setting of the image plane even when a support tool is not used. We used a 0.4T magnetic resonance (MR) imaging system open in the horizontal direction. The ISC determines the image plane interactively on the basis of fluoroscopy images displayed on a user interface. The imaging pulse is a balanced steady-state acquisition with rewound gradient echo (SARGE) sequence with update time less than 2 s. Without using a tool to support the knee, we positioned the knee of a healthy volunteer at 4 different joint angles and set the image plane through the patella and femur at each of the angles. Lumbar imaging is also demonstrated with ISC. Setting the image plane was easy and quick at all knee angles, and images obtained clearly showed the patella and femur. Total imaging time was less than 10 min, a fourth of the time needed when a support tool is used. We also used our ISC in kinematic imaging of the lumbar. The ISC shortens total time for kinematic joint imaging, and because a support tool is not needed, imaging can be done more freely in an open MR imaging apparatus.
    Magnetic Resonance in Medical Sciences 02/2007; 6(4):241-8. · 0.75 Impact Factor
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    ABSTRACT: To prospectively compare in vivo hepatic automated volumetry with manual volumetry and measured liver volume. The study was conducted in accordance with the guidelines of the Institutional Review Board of Kumamoto University (Japan). Patient informed consent was obtained. Preoperative multisection computed tomography (CT) was performed in 35 consecutive patients (21 men, 14 women; mean age, 42.8 years; range, 28-72 years) with hepatic disease awaiting living related liver transplantation. The CT scans covered the entire liver at a section thickness of 2.5 mm. Liver volume was estimated by using both the automated and the manual methods. Actual liver weight was obtained for all patients and was converted to hepatic volume on the basis of a predetermined relationship between actual liver weight and volume. Processing time required for both methods was also recorded. Two-tailed paired t test, correlation coefficient, and Bland-Altman tests were used for statistical analyses. Mean liver weight was 881.7 g +/- 249.8 (standard deviation), and mean measured liver volume was 956.00 cm(3) +/- 280.10. Volumetry performed with the automated and manual methods provided liver volumes of 982.99 cm(3) +/- 301.98 and 937.10 cm(3) +/- 301.31, respectively. There was good correlation between measured and estimated volumes obtained with the automated method (r = 0.792, P < .01). The manual and automated methods required 32.8 minutes +/- 6.9 and 4.4 minutes +/- 1.9, respectively. The automated method reduced the time required for volumetry of the liver and provided acceptable measurements.
    Radiology 09/2006; 240(3):743-8. · 6.34 Impact Factor
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    ABSTRACT: Soft copy reading of digital images has been practiced commonly in the PACS environment. In this study, we compared liquid-crystal display (LCD) and cathode-ray tube (CRT) monitors for detection of pulmonary nodules and interstitial lung diseases on digital chest radiographs by using receiver operating characteristic (ROC) analysis. Digital chest images with a 1000x1000 matrix size and a 8 bit grayscale were displayed on LCD/CRT monitor with 2M pixels in each observer test. Eight and ten radiologists participated in the observer tests for detection of nodules and interstitial diseases, respectively. In each observer test, radiologists marked their confidence levels for diagnosis of pulmonary nodules or interstitial diseases. The detection performance of radiologists was evaluated by ROC analyses. The average Az values (area under the ROC curve) in detecting pulmonary nodules with LCD and CRT monitors were 0.792 and 0.814, respectively. In addition, the average Az values in detecting interstitial diseases with LCD and CRT monitors were 0.951 and 0.953, respectively. There was no statistically significant difference between LCD and CRT for both detection of pulmonary nodules (P=0.522) and interstitial lung diseases (P=0.869). Therefore, we believe that the LCD monitor instead of the CRT monitor can be used for the diagnosis of pulmonary nodules and interstitial lung diseases in digital chest images.
    Nippon Hoshasen Gijutsu Gakkai zasshi 06/2006; 62(5):734-41.

Publication Stats

122 Citations
36.73 Total Impact Points

Institutions

  • 2007–2012
    • Kumamoto University
      • • Graduate School of Health Sciences
      • • Department of Radiological Science
      • • Department of Diagnostic Radiology
      Kumamoto, Kumamoto Prefecture, Japan
    • Hitachi Medical Corporation
      Edo, Tōkyō, Japan