Biomedical subjects

Hideyuki Iwanaga

Publications and source records attributed to Hideyuki Iwanaga.

8 recordsLinked to original sources

PubMed2006

[Development of a new method of high-speed rotation multiplied projection single photon emission computed tomography of the triple-headed type: lung MAA SPECT based on phantom study].

PURPOSE: A chest phantom study was conducted to evaluate the image quality of newly developed high-speed rotation multiplied projection-single photon emission computed tomography (HSRMP-SPECT) images. MATERIALS AND METHODS: HSRMP-SPECT images of a chest phantom consisting of a simulated lung structure filled with 5000 ml of water containing 185 MBq Tc-99m-pertechnetate, and several small 11 mm simulated lung nodules of glass balls and one large 35 mm simulated lung nodule of a plastic sphere filled with water were obtained using a triple-headed SPECT system. During image acquisition, this phantom was regularly moving in the head-to-caudal direction with a range of 12 mm at a frequency of 15 cycles/min to simulate respiratory motion, and 360 degrees projection data of this moving phantom was acquired with an image acquisition time of 20 sec, which was repeated 10 times. To eliminate the setting time between projection and acquisition of multiple temporal samples of data, each detector was continuously rotated in the clockwise direction for 20 sec around a 120-degree arc. On the perspective SPECT images reconstructed from various numbers of the 20-sec projection data, the perfusion heterogeneity of the simulated lungs and perfusion defect clarity of the simulated nodules were assessed by the coefficient of variation (CV) of pixel counts and the defect-to-lung radioactivity ratios, respectively. The results were compared with those on conventional SPECT images of the moving phantom obtained with a data acquisition time of 8 min, and SPECT images of the standing phantom obtained with the same data acquisition time. RESULTS: The average CV value of 0.28+/-0.01 on the SPECT image reconstructed from 5 projection data sets was not significantly different from that of 0.27+/-0.01 on the SPECT image reconstructed from 10 projection data sets (p<0.05). The perfusion defect contrast of the simulated nodules obtained from 5 projection data was significantly higher than that on conventional SPECT images (0.50 vs. 0.73) . CONCLUSIONS: The present phantom study indicated that HSRMP-SPECT could be a useful technique for quickly obtaining high-quality SPECT images of a moving subject, thereby improving perfusion defect clarity in comparison with the conventional technique. This technique may have potential utility for obtaining high-quality breath-hold SPECT images of the chest in clinical practice.

Image Processing, Computer-Assisted↗

PubMed2006

[Examination of three-detector high-speed-rotation SPECT acquisition under breathhold in body: clinical application of 99mTc-MAA].

In traditional pulmonary perfusion single photon emission computed tomography (SPECT), respiratory lung motion and cyclically varying changes in lung volume during image acquisition inherently degrade the image sharpness of ill-defined perfusion defects. However, because of the lack of an adequate fast imaging technique, perfusion SPECT has never been acquired under breathhold conditions, whereas breathhold images are commonly used for pulmonary magnetic resonance (MR) and computed tomographic (CT) images. Although a high-speed imaging technique combined with a multidetector SPECT system may enable SPECT images to be obtained during a short period of breathholding, image quality would be degraded owing to decreased radioactivity counts and increased statistical noise. To resolve this problem, we developed an innovative SPECT imaging technique using a triple-head SPECT system and the high-speed-detector rotation-multiplied projection (HSRMP) technique, where a single SPECT image was reconstructed from multiple respiratory dimensional breathhold projection data obtained at the same angle. HSRMP provided noiseless high-quality perfusion SPECT images by compensating for decreased radioactivity counts caused by high-speed imaging, and significantly improved image quality and perfusion defect clarity compared with traditional non-breathhold SPECT images.

Female↗

PubMed2006

Nonlinear motion correction of respiratory-gated lung SPECT images.

We propose a method for correcting the motion of the lungs between different phase images obtained by respiratory-gated single photon emission computed tomography (SPECT). This method is applied to SPECT images that show a preserved activity distribution in the lungs such as 99m-Tc macro aggregated albumin (99m-Tc-MAA) perfusion images and 99m-Tc-Technegas ventilation images. In the proposed method, an objective function, which consists of both the degree of similarity between a reference image and a deformed image, and the smoothness of deformation is defined and optimized using a simulated annealing algorithm. For the degree of similarity term in the objective function, an expansion ratio, defined as the ratio of change in local volume due to deformation, is introduced to preserve the total activity during the motion correction process. This method was applied to data simulated from computer phantoms, data acquired from a physical phantom, and 17 sets of clinical data. In all cases, the motion correction between inspiration and expiration phase images was successfully achieved.

Algorithms↗

PubMed2005

[Selection of parameters for multi-objective frequency processing in CR mammography: visual evaluation of mammographic phantom images].

The multi-objective frequency processing installed in the FCR5000R (Fuji Film Medical) is superior to the conventional processing used in the FCR9000 (Fuji Film Medical) in evaluating frequency processing. A suitable combination of parameters for multi-frequency-processing in computed radiography (CR) mammography was evaluated. The paired-comparison method using phantom images was performed for the visual evaluation. Results showed that the evaluation score of mass and fiber lesions depended on the multi-frequency balance type (MRB) parameter, and the low-frequency-cycle emphasizing parameter had the highest score. In contrast, the score of microcalcifications depended on the degree of multi-frequency enhancement (MRE). The most suitable parameters for the multi-frequency processing of every size and type of breast lesion were not obtained. However, MRB=A, MRT=p, and MRE=1.0 can be recommend for CR mammography.

Humans↗

PubMed2005

Initial application of respiratory-gated 201Tl SPECT in pulmonary malignant tumours.

AIM: Respiratory-gated thallium-201 chloride (201Tl) single photon emission computed tomography (SPECT) was used in preliminary investigations to reduce the adverse respiratory motion effects observed on standard ungated SPECT images and to obtain reliable fusion images with computed tomography (CT) in patients with malignant lung tumours. METHODS: Fifteen patients with primary lung cancer (n=10) or metastatic lung tumours (n=5) underwent gated SPECT 20 min after intravenous injection of 148 MBq 201Tl, using triple-headed SPECT and laser light respiratory tracking units. Projection data were acquired by a step and shoot mode, with 20 stops over 120 degrees for each detector and a preset time of 30 s for each 6 degrees stop. Gated end-inspiratory and ungated images were obtained from 1/8 data centred at peak inspiration for each regular respiratory cycle and for the full respiratory cycle data, respectively. The degree and size of tumour 201Tl uptake were compared between these images by regions of interest (ROI) analysis. Gated SPECT images were registered with rest inspiratory CT images using an automated three-dimensional (3D) image registration tool. Registration mismatch was assessed by measuring the 3D distance of the centroid of 14 201Tl-avid peripheral tumours. Attenuation correction of gated SPECT images was performed using CT attenuation values of these fusion images. RESULTS: Gated SPECT images improved image clarity and contrast of tumour 201Tl uptakes compared with ungated images, regardless of the decreased count density due to the use of gated images. The lesion-to-normal (L/N) lung count ratios and ROI size in 18 well-circumscribed 201Tl-avid tumours were significantly higher and smaller on gated images (both P<0.0001). Gated images showed positive 201Tl uptakes in two small peripheral tumours, although negative on ungated images, and demarcated 201Tl-avid tumours from adjacent 201Tl-avid lymph node or surrounding focal 201Tl uptakes caused by other pathology, although these were not clearly demarcated on ungated images. On fusion images, gated images yielded a significantly better SPECT-CT matching compared with ungated images (P<0.0001). Fusion images accurately localized 201Tl uptakes of tumour/lymph node and other focal pathological/physiological conditions. Attenuation-corrected gated SPECT images further facilitated the detection of 201Tl uptake in small or deeply located lesions, with significantly increased L/N ratios. CONCLUSION: Gated SPECT images facilitate the detection of tumour 201Tl uptake and provide reliable SPECT-CT fusion images, which contribute to accurate interpretation and attenuation correction of Tl SPECT images.

Adult↗

PubMed2005

Enhanced perfusion defect clarity and inhomogeneity in smokers' lungs with deep-inspiratory breath-hold perfusion SPECT images.

PURPOSE: Deep-inspiratory breath-hold (DIBrH) Tc-99m-macroaggregated albumin (MAA) SPECT images were developed to accurately evaluate perfusion impairment in smokers' lungs. METHODS: DIBrH SPECT was performed in 28 smokers with or without low attenuation areas (LAA) on CT images, using a triple-headed SPECT system and a laser light respiratory tracking device. DIBrH SPECT images were reconstructed from every 4 degrees projection of five adequate 360 degrees projection data sets with almost the same respiratory dimension at 20 sec DIBrH. Perfusion defect clarity was assessed by the lesion (defect)-to-contralateral normal lung count ratios (L/N ratios). Perfusion inhomogeneity was assessed by the coefficient of variation (CV) values of pixel counts and correlated with the diffusing capacity of the lungs for carbon monoxide/alveolar volume (DLCO/VA) ratios. The results were compared with those on conventional images. RESULTS: Five DIBrH projection data sets with minimal dimension differences of 2.9+/-0.6 mm were obtained in all subjects. DIBrH images enhanced perfusion defects compared with conventional images, with significantly higher L/N ratios (P<0.0001), and detected a total of 109 (26.9%) additional detects (513 vs. 404), with excellent inter-observer agreement (kappa value of 0.816). CV values in the smokers' lungs on DIBrH images were also significantly higher compared with those on conventional images (0.31+/-0.10 vs. 0.19+/-0.06, P<0.0001). CV values in smokers on DIBrH images showed a significantly closer correlation with DLCO/VA ratios compared with conventional images (R = 0.872, P<0.0001 vs. R=0.499, P<0.01). CONCLUSION: By reducing adverse effect of respiratory motion, DIBrH SPECT images enhance perfusion defect clarity and inhomogeneity, and provide more accurate assessment of impaired perfusion in smokers' lungs compared with conventional images.

Artifacts↗

PubMed2002

[Study of image quality (contrast) and reduction of patient dose by using heavy metal filters].

We studied image quality (contrast) and patient dose reduction using heavy metal filters in lumbar spine and abdomen x-ray examination. Heavy metal filters used in this study are gadolinium, holmium and ytterbium and these combinations. These filters have k-absorption edge in the range from 50 to 70 keV. Image quality and patient dose in 70-90 kV tube voltage with heavy metal filters were compared with 80 kV tube voltage without filter. Image quality was improved in four percent and patient dose could be reduced by 30%. However, tube loading increased from 1.6 to 2.2 times. It was found that the best filter choices gave better image and reduced patient dose compared to without filter.

Filtration↗

PubMedDate not supplied

Comprehensive assessment of lung CT attenuation alteration at perfusion defects of acute pulmonary thromboembolism with breath-hold SPECT-CT fusion images.

Regional computed tomography attenuation (CTA) alteration at perfusion defects in acute pulmonary thromboembolism (PTE) was comprehensively assessed using deep-inspiratory breath-hold SPECT-CT fusion images. Subjects were 14 acute and 9 chronic PTE patients and 13 control subjects. Regional perfusion, CTA, and intravascular clots were correlated on deep-inspiratory breath-hold SPECT-unenhanced/angiographic CT fusion images. Fusion images visualized hypo-CTA in 57% of the acute PTE patients, which preferentially occurred at extensively and severely decreased perfusion areas caused by central clots. CTA at 35 defects of acute PTE was significantly decreased compared with that of normal lungs (P<0.001), but the degree was less compared with chronic PTE (P<0.0001). Fusion images also revealed variable relationships of clots and regional perfusion/CTA in the distal lungs of each central clot. Fusion images provide important information about the actual effects of intravascular clots on peripheral perfusion/CTA and indicate that lung CTA can be decreased at perfusion defects in acute PTE.

Adult↗