Biomedical subjects

Hiroji Iida

Publications and source records attributed to Hiroji Iida.

7 recordsLinked to original sources

PubMed2006

[Estimation of the effective dose of patient in interventional radiology: study of coronary angiography].

The applications of interventional radiology (IVR) increasingly are being used in clinical examinations, where they tend to extend examination time. In addition, the risk of occupational exposure necessarily is increasing with this technology. In this study, the dose distributions in a sliced acrylic-acid phantom involving the bore for each irradiation condition were measured using a thermoluminescence dosimeter (TLD). Four patterns of set-up for the fluoroscopy unit were chosen as references for the conditions generally used clinically. Exposure also was measured with dose area product (DAP), and we then calculated the entrance skin dose and effective dose for the patient. The results showed that the effective dose was 7.0 mSv to 8.0 mSv at LAO45 degrees and RAO30 degrees; 100 kV, 2.3 mSv to 3.3 mSv at LAO45 degrees and RAO30 degrees; 80 kV. The effective dose is greatly influenced by the setup of fluoroscopy in IVR. The change in DAP is especially influenced. We found that the relation between DAP and effective dose was corrected with the exponential function. The effective doses were not necessarily less than those of other radiation examinations, and increase. When PCI and TAE are repeated many times in IVR, we propose that the effective dose should be taken into consideration together with the skin dose for dose control management.

Acrylates↗

PubMed2006

[Measurement of patient skin dose in interventional radiology using passive integrating dosimeter].

To avoid radiation injury from interventional radiology (IVR), quality assurance (QA) of IVR equipment based on dosimetry is important. In this study, we investigated the usefulness of measuring patient skin dose with a passive integrating dosimeter and water phantom. The optically stimulated luminescence dosimeter (OSLD) was chosen from among various passive integrating dosimeters. The characteristics of the OSLD were compared with a reference ionization dosimeter. The effective energy obtained from the OSLD was compared with that found by the aluminum attenuation method for using the reference ionization dosimeter. Doses and effective energies measured by OSLD correlated well with those of the reference ionization dosimeter. (dose: y=0.971x, r=0.999, effective energy: y=0.990x, r=0.994). It was suggested that OSLD could simultaneously and correctly measure both patient skin dose and effective energy. Patient skin dose rate and effective energy for 15 IVR units of 10 hospitals were investigated using OSLD and a water phantom for automatic brightness control fluoroscopy. The measurement was performed at the surface of a water phantom that was located on the interventional reference point, and source image intensifier distance was fixed to 100 cm. When the 9-inch field size was selected, the average patient skin dose rate was 16.3+/-8.1 mGy/min (3.6-32.0 mGy/min), the average effective energy was 34.6+/-4.1 keV (30.5-42.5 keV). As a result, it was suggested that QA should be performed not only for patient dose but also for effective energy. QA of equipment is integral to maintaining consistently appropriate doses. Consequently, the dosimetry of each IVR unit should be regularly executed to estimate the outline of patient skin dose. It was useful to investigate patient skin dose/effective energy with the passive integrating dosimeter for IVR equipment.

Humans↗

PubMed2005

[Measurement of environmental radiation in X-ray room with passive integrating dosimeter].

Radiation dose limits in the controlled area of an X-ray room have been prescribed at 1.3 mSv/3 months by the Enforcement Regulations of the Medical Service Law. Leakage effective dose must be measured once within a period that does not exceed six months. Scattered radiation and leakage effective dose were measured in 4 X-ray rooms (chest X-ray room, general-purpose X-ray room, skull and neck X-ray room, and X-ray CT room) with the optically stimulated luminescence dosimeter (OSLD), which is a passive integrating dosimeter. The availability of the measurement method for radiation control with OSLD was evaluated. Scattered radiation in the inside wall surface of the skull and neck X-ray room was less than 1.3 mSv/3 months of the dose limits. There was more scattered radiation in the X-ray CT room than in other X-ray rooms, and the maximum dose was 428 mSv/3 months, measured on the floor. All measurements of leakage effective dose in the 4 X-ray rooms were less than the radiation dose limit, and most measurements of leakage effective dose were less than the detection limits of the dosimeter. Leakage effective dose as calculated by Law 188 (Law 188-Dose) was less than the radiation dose limits in three X-ray rooms, the exception being the X-ray CT room. The Law 188-Dose of the X-ray CT room exceeded 1.3 mSv/3 months at the walls where primary X-rays were directed. The measurement method of leakage effective dose with an ionization survey meter was not able to guarantee the workload of each X-ray apparatus. Therefore, we were not able to confirm the security of X-ray rooms by measurement with an ionization survey meter. Scattered radiation in X-ray rooms was generated intermittently and showed a low dose rate. Consequently, it was established that dose leakage from X-ray rooms must be measured with an integrating dosimeter. It was suggested that the measurement method of environmental dose with OSLD was useful to measurement for radiation control.

Environmental Exposure↗

PubMed2004

[Evaluation and estimation of entrance skin dose in patients during diagnostic and interventional radiology procedures].

A study was performed to evaluate the total entrance skin dose (ESD) of patients during diagnostic and interventional radiology procedures (IVR) and to estimate ESD with body mass index (BMI) and fluoroscopy time. The study included 26 cases of transcatheter arterial embolization therapy (TAE) for hepatocellular carcinoma (HCC) and 19 cases of diagnostic digital subtraction angiography (DSA) for HCC. The ESD of patients was evaluated with a zinc-cadmium sensor linked to a digital counter (SDM: skin dose monitor). Exposure doses were measured with SDM attached to the front of the X-ray beam-limiting device like a dose area product monitor. ESD was calculated from the measured exposure dose. In 26 TAE for HCC, ESD was 1793.7+/-739.1 mGy, with the mean fluoroscopic time of 23.5 minutes and 4.4 DSA acquisitions. The fluoroscopic dose rate was 52.4+/-11.5 mGy/min. In 19 diagnostic DSA for HCC, ESD was 962.9+/-375.2 mGy, with the mean fluoroscopic time of 11.1 minutes and 4.0 DSA acquisitions. The fluoroscopic dose rate was 32.7+/-12.7 mGy/min. Although 33.2% of ESD was from fluoroscopy in diagnostic procedures, the figure was 68.8% in TAE procedures. It was demonstrated that the increase in ESD during IVR was caused by the rise of fluoroscopy dose rate caused by high-magnification fluoroscopy and the extension of fluoroscopy time. In order to reduce ESD, it is necessary to use a low fluoroscopy dose rate with low-rate pulse fluoroscopy, in addition to shortening fluoroscopy time. Fluoroscopy time was a poor predictor of risk because it did not correlate well with ESD during IVR (diagnostic procedures r(2)= 0.897, IVR r(2)= 0.594). However, ESD correlated well with the product of BMI and fluoroscopy time (diagnostic procedures r(2)= 0.910, IVR r(2)= 0.783). The linear relationship between ESD and the product of BMI and fluoroscopy time provides a simple monitoring mechanism of the ESD delivered to the patient during interventional radiology procedures. This linear relationship needs to be established for other types of interventional procedures.

Angiography, Digital Subtraction↗

PubMed2004

[Creation and clinical application of real-time dose monitor using dose area product meter].

The management of patient dose has become more of an issue in recent years. Dose can be determined non-invasively and in real time through the use of a dose area product meter, but it is the area dose value that is obtained. Therefore, we created a program that estimates entrance skin dose (ESD) in real time from area dose values obtained during procedures. We used Microsoft Visual C++ 6.0 (Standard Edition) for the programming language and C language for the programming environment. The value was a maximum 285.4 mGy at ileus tube insertion when measuring ESD for radiography of the digestive organ and non-vascular type IVR using the created program and seeking the average according to the procedures. The program that we created can be considered valid for monitoring ESD correctly and in real time.

Body Surface Area↗

PubMed2004

[Evolution of radiation exposure to operator in diagnostic and interventional radiology procedures and reduction of radiation exposure to operator with protective device].

A study was performed to evaluate operator dose during diagnostic and interventional radiology procedures (IVR) and to establish methods of operator dose reduction with a radiation protective device. Operator dose was measured by glass dosimeters worn on the neck and on the abdomen outside the lead apron. In addition, the dose of the primary beam at the collimator surface was measured, which made it possible to define the correlation between the entrance air kerma, measured with Skin Dose Monitor, and operator dose exposed during the monitored procedure. IVR protectors were developed to decrease the amount of scatter radiation received by operators performing the procedures, and their effects were evaluated in abdominal and cardiac angiography procedures. The average effective dose and doses of the neck and abdomen outside the lead apron, estimated for individual procedures, were as follows: abdominal angiography procedures: effective dose, 0.07 mSv; neck area, 0.18 mSv; abdominal area, 0.51 mSv; cardiac angiography procedures: effective dose, 0.07 mSv; neck area, 0.13 mSv; abdominal area, 0.68 mSv. Operator doses were well correlated with exposure dose in abdominal angiography procedures (diagnostic procedure r=0.84, IVR r=0.77). It was found that 68.0% of the effective dose in abdominal angiography procedures and 43.0% of the effective dose in cardiac angiography procedures could be reduced by the use of IVR protectors. Operator and patient doses in interventional radiology were interdependent. The minimization of operator doses is particularly important during interventional radiology, and it is necessary to be aware of practical radiation protection procedures. Measures that reduce patient dose will also reduce occupational exposure. Moreover, operator dose could be substantially reduced by the use of IVR protectors in addition to wearing a protective lead apron during IVR. It was suggested that IVR protectors are effective radiation protective devices in interventional radiology procedures.

Angiography↗

PubMed2002

[The radiation protective devices for interventional procedures using computed tomography].

A scattered dose and a surface dose from phantom measurements during interventional procedures with computed tomography (IVR-CT) were evaluated. To reduce the personnel exposure in IVR-CT, the new protective devices were developed and its effect evaluated. Two radiation protection devices were experimentally made using a lead vinyl sheet with lead equivalent 0.125mmPb. The first device is a lead curtain which shields the space of CT-gantry and phantom for the CT examination. The second device is a lead drape which shields on the phantom surface adjacent to the scanning plane for the CT-fluoroscopy. Scattered dose and phantom surface dose were measured with an abdominal phantom during Cine-CT (130 kV, 150 mA, 5 seconds, 10 mm section thickness). They were measured by using ionization chamber dosimeter. They were measured with and without a lead curtain and a lead drape. Scattered dose rate was measured at distance of 50-150 cm from the scanning plane. And, surface dose was measured at distance of 4-21 cm from the scanning plane on the phantom. On operator's standing position, scattered dose rates were from 8.4 to 11.6 micro Gy/sec at CT examination. The lead curtain and the lead drape reduced scattered dose rate at distance of 50 cm from the scanning plane by 66% and 58.3% respectively. Surface dose rate were 118 micro Gy/sec at distance of 5 cm from the scanning plane at CT-fluoroscopy. The lead drape reduced the surface dose by 60.5%. High scattered exposure to personnel may occur during interventional procedures using CT. They were considerably reduced during CT-arteriography by attaching the lead curtain in CT equipment. And they were substantially reduced during CT-fluoroscopy by placing the lead drape adjacent to the scanning plane, in addition, operator's hand would be protected from unnecessary radiation scattered by phantom. It was suggested that the scattered exposure to personnel could be sufficiently reduced by using radiation protection devices in IVR-CT. The radiation protection devices and the CT equipment should be improved or developed based on the radiation protection.

Humans↗