Biomedical subjects

Yasuo Nakazawa

Publications and source records attributed to Yasuo Nakazawa.

8 recordsLinked to original sources

PubMed2006

[Status of measures against angiography room infection as determined by questionnaire].

Although the cleanliness of the angiography room and that of the operating room have long been equally attended to, the concept of Standard Precautions (including the basic measures and procedures to prevent infection) of the Centers for Disease Control and Prevention (CDC), 1996, as well as the introduction of transmission-based precautions, have been changing to preventive measures that are based on concrete measures. Therefore, a questionnaire was introduced in order to determine the actual status of countermeasures against infection used in the angiography room. The questionnaire was sent to 530 institutions, and 286 responded, a response rate of 54.0%. Its results significantly revealed the following: 1) unexpectedly low recognition of the need and importance for the CDC preventive measures against infection, 2) a considerable number of institutions continuing to perform the conventional preventive measures, 3) problems with education systems on preventive measures, and 4) handwashing, the most important measure against infection, failing to be adequately carried out noticeably among radiological technologists.

Angiography↗

PubMed2006

[Importance of an initial check-up for diagnostic radiology apparatus management].

The management of apparatus for diagnostic imaging is an important job for radiological technologists. In the last 10 years we have encountered 2227 malfunctions in 3652 days. We detected 163 cases at the initial check-up, which accounted for 7.3% of total cases. By performing an initial check-up, we detected one malfunction every 21 days and were able to keep the effects of mishaps to a minimum, prevent accidents, and obtain stable-quality images.

Equipment Failure↗

PubMed2006

[Examination of incident angle for photography of axial projection of zygomatic arch].

In axial zygomatic arch roentgenography, the radiographic angle is determined by taking account of the light field-projected image. However, this method is technically difficult and has poor reproducibility because the body target surface is uncertain at the time of positioning. Therefore, we obtained 3D-CT images from CT examinations of the facial or paranasal sinus, and we assessed the X-ray beam angle where the zygomatic arch is most clearly delineated in terms of sex and age by taking the acanthion-meatal line (France horizon) as the reference. The zygomatic arch was most clearly seen when the X-ray beam angle was perpendicular to the acanthion-meatal line. Excellent images were obtained, and reproducibility of the images was improved using the radiographic technique based on this result.

Adolescent↗

PubMed2005

[Accuracy of quantitative coronary angiography for different directions of the coronary artery].

We evaluated the effect of changes in the direction of the coronary artery in terms of the accuracy and precision of vessel diameter measurement in a quantitative coronary angiography system (QCA system). Vessel phantoms sized 0.3, 0.5, 1.0, 1.5, 2.0, and 2.5 mm in diameter were evaluated. The phantoms were aligned on an acrylic plate, and the angle to the television (TV) camera was altered. The deployed angles were 0 (perpendicular), 45, 90, and 135 degrees in clockwise order. The phantoms were imaged with matrices of 1024 x 1024 (1024(2)), 512 x 512 (512(2)), and 512 x 1024. Image size was 7 inches, and the frame rate was 15 frames per second. Minimal lumen diameters were measured on the ACA system. The results revealed that, in the 1024(2) matrix, overall accuracy for the 90-degree angle was significantly underestimated compared with the 0-degree angle (-0.14 vs. -0.014 mm; p=0.007). Accuracy for the 90-degree angle was better than that for the 0-degree angle when the vessel diameter was 1 mm or smaller (-0.02+/-0.16 vs. 0.10+/-0.22 mm). In addition, precision was better at the 90-degree angle than with the other angles in the 1024(2) matrix (overall precision=0.002 mm). In the 512(2) matrix, overall accuracy for the 90-degree angle was significantly underestimated compared with the 45-degree angle (-0.077 vs. 0.096 mm; p=0.02). In addition, accuracy for the 90-degree angle was better than that for the 45-degree angle below 1 mm (0.05+/-0.24 mm vs. 0.26+/-0.47 mm). In terms of overall accuracy, the 45-degree angle in the 512(2) matrix showed significant overestimation compared with that in the 1024(2) matrix (0.096 vs. -0.069 mm; p=0.015). There was no difference in accuracy in the 512 x 1024 matrix. Our results suggest that the direction of the vessel against the TV image affects accuracy of measurement in the QCA system.

Coronary Angiography↗

PubMed2004

[Trial of finger contamination reduction of the operator in nerve block treatment: comparison of over- and under-table systems].

Fluoroscopy-guided intervention of the lumbar spine, such as nerve block, plays an important role in the management of disc hernia patients. However, irradiation of operators' fingers remains a problem even with careful collimation and operation, especially when performed by non-radiologists. We compared the irradiation doses of under-table and over-table fluoroscopy systems, and we discuss the most advantageous method of reducing irradiation. The effectiveness and conditions of use of lead protection gloves were also evaluated. Skin dose was monitored using polymethyl methacrylate (PMMA) and an electronic dose meter. The skin doses of over- and under-table fluoroscopy were compared using C-arm fluoroscopy. Finger irradiation dose with 0.03 mmPb protection gloves was also measured. The under-table method reduced skin dose by 95% compared with the over-table method. Thicker PMMA resulted in a higher rate of irradiation reduction. Protection gloves reduced radiation dose by half, although this reduction was cancelled when automatic brightness control (ABC) was utilized. Under-tube fluoroscopy was superior to over-tube fluoroscopy in reducing irradiation to the fingers.

Fingers↗

PubMed2002

Two pedigrees of hereditary prostate cancer.

We encountered two pedigrees of hereditary prostate cancer. In one family, the father and his two sons had prostate cancer, and in the other family, three brothers developed prostate cancer. The mean age of these six individuals at the first examination was 65.3 years. Two individuals had stage B disease; three individuals, stage D disease; and one individual, disease of unknown stage. Histopathologically, two, one, and three individuals had well-, moderately, and poorly differentiated adenocarcinoma, respectively. As of September 28,2000, five of the six individuals were still alive. In a search of the literature, these were found to be the seventh and eighth pedigrees in Japan that met the criteria of hereditary prostate cancer proposed by Carter and colleagues in 1993.

Adenocarcinoma↗

PubMed2002

[CT scanners with automatic focus alteration capability].

Heat accumulation in X-ray tubes results in disarrangement of focus owing to heat expansion of the anode. CT scanners with automatic focus alteration capability have been developed to counteract this problem. We compared CT scanners with and without focus alteration capabilities and discuss the effect of focus disarrangement on the CT images. Images were obtained when heat accumulation was high and low. Subtraction images were made to define the disarrangement of focus. A comparison was made between CT scanners with and without automatic focus alteration capability. ROI was selected and changes in CT values, SD, and slice thickness were observed under changing anode heat accumulation. Results indicated that images from both scanners showed disarrangement of the focus and elevation of CT values as anode heat accumulated. However, the scanner with automatic focus alteration produced images with less focus disarrangement from the center of the slice and less elevation of CT values. Scanners with automatic focus alteration are less prone to the focus disarrangement and elevation of CT values caused by anode heat accumulation and enable reproducible images to be obtained.

Electrodes↗

PubMed2002

[Improvement of dose distribution of esophageal irradiation using the field-within-a-field technique].

The wide radiation field for mediastinal dose distribution should be inhomogeneous with the usual simple opposed beam irradiation. The purpose of this study was to improve the dose distribution of the mediastinum using a conventional planning system with a dose-volume histogram (DVH) and the field-in-field technique. Three-dimensional (3D) dose distribution is obtained in bilateral opposed-field irradiation. An overdose area obtained from the 3D dose distribution is defined and reprojected into the irradiation field. A new reduced field is created by removing the reprojected overdose area. A 3D dose distribution is again obtained and compared with the results from first one. Procedures were repeated until each of the target volumes was within +/-5% of the prescribed dose and the irradiation volume within 107% or less of the prescribed dose. From the DVH analysis, our field-within-a-field technique resulted in a more uniform dose distribution within the conventional planning. The field-within-a-field technique involves many parameters, and an inverse planning algorithm is suitable for computation. However, with our method, the forward planning system is adequate for planning, at least in a relatively straightforward planning system such as bilateral opposed fields therapy.

Esophageal Neoplasms↗