Biomedical subjects

Kazuo Iwai

Publications and source records attributed to Kazuo Iwai.

4 recordsLinked to original sources

PubMed2003

A comparison of a new limited cone beam computed tomography machine for dental use with a multidetector row helical CT machine.

OBJECTIVE: We sought to compare a new limited cone beam computed tomography (CT) machine for dental use (3DX) with the multidetector CT machine for image quality and skin doses. STUDY DESIGN: Images of the right maxillary central incisor and the left mandibular first molar of an anthropomorphic phantom were taken by both the 3DX and the multidetector CT. A 5-point method was used to evaluate the depiction of cortical and cancellous bone, enamel, dentin, pulp cavity, periodontal ligament space, lamina dura, and overall impressions. Furthermore, the skin doses for both modalities were compared. RESULTS: The image quality of the 3DX was better than the multidetector CT for all items (P < .01). Moreover, the mean skin doses with the multidetector CT were 458 mSv per examination, whereas the doses with the 3DX were 1.19 mSv per examination. CONCLUSIONS: These results clearly indicate the superiority of the 3DX in the display of hard tissues in the dental area while substantially decreasing the dose to the patient.

Humans↗

PubMed2003

[Air pollution].

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Air Pollution↗

PubMed2002

Dose evaluation and effective dose estimation from multi detector CT.

Computed tomography (CT) has evolved remarkably through device improvement and advancement of peripherals, including computers. In 1999, multi detector-row CT (MDCT) appeared and rapid high-speed scanning became possible. However, usefulness of MDCT in actual clinical application cannot be assessed until the exposure doses are assessed appropriately. Since CT examinations need a comparatively high dose, it is necessary to evaluate patient exposure for introduction of MDCT. Patient doses by three types of MDCTs were evaluated for cases of scanning of the chest and abdomen-pelvis. The examination conditions were the same as those in actual clinical examinations. The obtained effective doses were 9.4-28 mSv for the chest examination and 13-28 mSv for the abdomen-pelvis. The average surface doses varied between 16-43 mGy for the chest examination and 20-37 mGy for the abdomen-pelvis. The highest surface dose was 57 mGy for the abdomen-pelvis examination. The exposed doses differed according to scanning method and imaging conditions such as tube current, slice thickness and so on. It seemed that there is room for dose reduction by proper adjustment of scan conditions in MDCT examinations.

Humans↗

PubMed2001

Dose evaluation and effective dose estimation from CT fluoroscopy-guided lung biopsy.

The development of computerized tomography (CT) has made CT fluoroscopy possible with real-time CT images. However examination are expected to have high medical and occupational exposures. Then, exposures to patients and operating and assisting physicians during the CT fluoroscopy-guided lung biopsy were estimated. And changes in the examination conditions to lower the dose were made. Patient exposure was measured using an anthropomorphic phantom by simulation of clinical examination conditions. The surface dose to the physician was measured during actual clinical examinations. The average effective dose for the patient was 34+/-22mSv. The highest surface dose amounted to 1.9 Gy, although this was in a very narrow field. Patient doses could be reduced by a factor of 2.5-3 by changing examination methods while still retaining diagnostic quality. The highest dose to the operating physician was 10mGy which was recorded on the back of the hand and the average effective dose was estimated as 5.99&mgr;Sv per 1-minute examination. Doses were reduced by about a factor of 50 by lowering the tube voltage from 120kV to 80 kV and using a supplementary tool. The doses for assisting physicians were not significant. The exposure for physicians and patients was much affected by lowering the tube voltage used for fluoroscopy. Using a supplementary tool was effective for reducing the dose for physicians.

Journal Article↗