[Visualization of Effectiveness of the Medical Safety Measures -Suggestion of the Evaluation Technique for Rare Medical Incident].

For events with a low occurrence rate, such as medical incidents, we were able to determine the evaluation before and after taking medical safety measures by statistical methods (testing for differences in population rate). The point of this method is that we evaluated the occurrence rate of incidents to the total number of examinations (number of incident occurrence real number plus number of examinations carried out without any problems). Our results suggest that this technique becomes the evaluation technique as the effective method of medical safety measures. The present studies demonstrated that the evaluation technique by the testing for differences in population rate become the indicator to judge the effectiveness of the medical safety measures in the following cases. (1) When we evaluate the decrease in incident for the long term before and after safety measures. (2) When we evaluate the effectiveness of measures in the middle evaluation after safety measures.

[Examination of Ability to Support the Interpreting of CT Images of Emergency Transport Patients by the Radiological Technologist─About the Factors That Influences Image Interpretation Assistance─].

The Japanese Ministry of Health, Labor and Welfare announced a revision of the law about the expansion of duties by the radiological technologist in team medical care in April, 2010. In that respect, the importance of reading images with support from the radiological technologist became higher. We compared the interpretation results of the radiologist with the image analysis by the radiological technologist of the CT images of emergency patients. And we checked for symptoms and diseases which were frequently overlooked by the technologists. Inexperienced radiological technologists overlooked considerably more than experienced radiological technologists. Our results showed that abdominal or chest image analysis differed more often than head scan analysis. The reasons given for the differences include a lack of clear indication for abdominal tumors, and we overlooked a lot of diseases such as pneumonia and enteritis. We also had several cases of abdominal and chest images over-reading by radiological technologists. To improve these, radiological technologists should deepen their knowledge of normal anatomy and work to improve recalling diseases that are inferred from the patient's symptoms. This will greatly improve the image interpretation support by the radiological technologists.

[Analysis of the Environmental Factor of a Patient Falls in Department of Radiology-Proposal of Scientific Analysis Method in Patient Safety].

We analyzed 197 fall incidents in the questionnaire survey about the incident that occurred in Department of Radiology. In the past paper about the patient safety, there is no report that evaluated incident data directly. The purpose of this paper is to analyze the factor of the medical incidents using statistical technique scientifically. In this paper, we do not suggest concrete precaution. At first, we found the number of patients (each gender, modality, generation) in the five facilities of the coworker of one week. We found an incident rate from this patient total number, and we normalized data. As a result, we were able to do each risk evaluation because a risk ratio and relative risk degree was found. And, we were able to identify modality and the generation with the significant difference using the testing for differences in population rate. By our analyses, we revealed the chapter which must strengthen safety management.

[The Knowledge Gained from Questionnaire Survey of the Patients Fall in the Radiological Examinations -Focus on the Severity Due to Fall Accidents].

PURPOSE: The purpose of this study is to analyze the factors of patient's fall that causes serious injury in the radiological examinations. METHODS: We conducted a questionnaire survey on cases of medical accidents occurring in the radiological examination department in medical institutions. The number of responses to the questionnaire surveys was 372. Among them, 197 cases were related to fall. The incident influence classification divided into eight clusters (0, 0H, 1, 2, 3a, 3b, 4, 5) was divided into three clusters (tiny, moderate, serious injury) depending on severity. We analyzed the factors that cause serious injury. RESULTS: In the case of patient's fall, several factors have been found to cause serious injury. The factors were general radiography, standing position, outside working hours. CONCLUSION: All falls can cause serious injury. To reduce falls, it is important to analyze what kind of patient and in what situation tend to fall, and prevent falls in advance.

[The Actual Condition of Fall Accident and Suggestion of Improvement for Accident Prevention in the Department of Radiology].

We conducted a questionnaire survey (situation, patient factor, environmental factor, operator factor, degree of disability, countermeasure etc.) on cases that occurred up to the present to investigate the actual situation of the medical accidents that occur in the radiological examination department of medical institutions. There were 373 questionnaires collected. Among them, there were 197 cases of falls. In this study, we examined the age of patients who fell, the background of the accident, and factors. As for the accident, 11.7% of accidents with risk impact level 3b or higher occurred including the fatal accident. Of the accidents, 44.2% were foreseeable and 55.8% were unforeseeable. The most accident-prone age was elderly in their 60s to 80s. As the causative factor for the accident, the patient factor was the largest at 63.5%. We can prevent about 30% of the accident by improving the operator factor and the environmental factor which are parts other than patient factor. It is important for us to understand what kind of people tend to fall. Among foreseeable accidents, the causes of patient factors can be reduced.

[The Prevention of the Root Accident in the Department of Radiological Examination Room -Analysis of the Results of Questionnaire Survey about Medical Accident to Many Hospital].

PURPOSE: The purpose of this paper is to analyze the characteristics of incidents related to routes and drains that occur in the radiological examination room for the prevention of these incidents. METHODS: We conducted a questionnaire survey on incident cases that occurred in the radiological examination room. There were 373 responses, of which 76 responses were related to routes and drains. The question contents were the number of hospital beds, radiology department of occurrence, time of occurrence, patient's situation, method of visiting, years of experience of the radiological technologists, and countermeasures, and so on. Based on these answers to these questions, we analyzed which factors were involved in the occurrence of the incidents. RESULTS: Incidents related to routes and drains often occur when moving examination table or transferring the patients to the examination table using the slider. On the other hand, the years of experience of the radiological technologists hardly participated in the factor of these incidents. From these answers to questions, 75% of incidents might predictable, and these incidents could be prevented by improvement of human factors accounted for the majority rather than that of physical factors. CONCLUSION: The number of incidents related to routes and drains may reduce by that all staff involved in the radiological examination recognizing the characteristic of these incidents.

The Safety of MR Conditional Cochlear Implant at 1.5 Tesla Magnetic Resonance Imaging System.

In magnetic resonance imaging (MRI) examination of the patients with the cochlear implant, only limited data have a mention for safety information in the instruction manual supplied by the manufacturers. Therefore, imaging operators require more detailed safety information for implant device. We conducted detailed examination about displacement force, torque, and demagnetizing of the cochlear implant magnet based on American Society for Testing and Materials (ASTM) standard using the PULSAR and CONCERTO (MED-EL) with 1.5 tesla MRI system. As a result, the displacement force and the torque of the implant magnet were less than the numerical values descried in the manual. Therefore, these have almost no effect on the body under the condition described in a manual. In addition, the demagnetizing factor of the cochlear implant magnet occurred by a change magnetic field. The demagnetization depended on the direction of a line of magnetic force of the static magnetic field and the implant magnet. In conclusion, the operator must warn the position of the patients on inducing in the magnet room.

Apparent Diffusion Coefficient Value Is Not Dependent on Magnetic Resonance Systems and Field Strength Under Fixed Imaging Parameters in Brain.

OBJECTIVE: The aim of the study was to investigate the causes of apparent diffusion coefficient (ADC) measurement errors and to determine the optimal scanning parameters that are independent of the field strength and vendors of the magnetic resonance (MR) system. MATERIALS AND METHODS: Brain MR images of 10 healthy volunteers were scanned using 6 MR scanners of different field strengths and vendors in 2 different institutions. Ethical review board approvals were obtained for this study, and all volunteers gave their informed consents. Coefficient of variation (CV) of ADC values were compared for their differences in various MR scanners and in the scanned subjects. RESULTS: The CV of ADC values for 6 different scanners of 6 brains was 3.32%. The CV for repeated measurements in 1 day (10 scans per day) and in 10 days (scan per day for 10 days) for 1 subject was 1.72% and 2.96%, respectively (n = 5, P < 0.001). The CV of measurements for 10 healthy subjects was 5.22%. The measurement errors of the ADC values for 6 different MR units in 1 subject were higher than the intrascanner variance for the same subject but were lower than the intersubject variance for the same scanner. CONCLUSIONS: The variance in the ADC values for different MR scanners is reasonably small if appropriate scanning parameters (repetition time, >3000 ms; echo time, minimum; and high enough signal-to-noise ratio of high-b diffusion-weighted image) are used.

[Analysis of accidents for magnetically induced displacement of the large ferromagnetic material in magnetic resonance systems].

To improve magnetic resonance (MR) safety, we surveyed the accidents caused by large ferromagnetic materials brought into MR systems accidentally. We sent a questionnaire to 700 Japanese medical institutions and received 405 valid responses (58%). A total of 97 accidents in 77 institutions were observed and we analyzed them regarding incidental rate, the detail situation and environmental factors. The mean accident rate of each institute was 0.7/100,000 examinations, which was widely distributed (0-25.6/100,000) depending on the institute. In this survey, relatively small institutes with less than 500 beds tend to have these accidents more frequently (p<0.01). The institutes in which daily MR examination counts are more than 10 patients have fewer accidents than those with less than 10 daily examinations. The institutes with 6-10 MR examinations daily have significantly more accidents than that with more than 10 daily MR examinations (p<0.01). The main mental factors of the accidents were considered to be "prejudice" and "carelessness" but some advocate "ignorance." Though we could not find significant reduction in the institutes that have lectures and training for MR safety, we should continue lectures and training for MR safety to reduce accidents due to "ignorance."

[Effects of region of interest settings in signal-to-noise ratio measurement of clinical images using arrays of multiple receiver coils].

In many clinical imaging procedures using arrays of multiple receiver coils, a uniform sensitivity process is performed using the sensitivity distribution from the body coil. This causes the noise to be uneven, and background noise cannot be used when measuring the signal-to-noise ratio (SNR). The SNR of clinical images with sensitivity correction using arrays of multiple receiver coils sets the region of interest (ROI) in the region where the signal is uniform, and is limited to the identical ROI method where measurements are taken with noise from the identical region. When SNR is measured with the identical ROI method, uneven noise caused by sensitivity correction as well as the signal strength distribution within the ROI of the object is reflected in the noise. Therefore, evaluation must be performed in as localized a position as possible. Measurement error becomes small on images with higher resolution, and if ROI larger than 10×10 pixels can be set in a region of even signal, SNR measurement of clinical images with less underestimation may be possible.

[The effect of the surroundings to the apparent diffusion coefficient on diffusion weighted imaging].

Diffusion weighted imaging (DWI) is now widely used in magnetic resonance (MR) imaging of the head and body. Moreover, the Apparent diffusion coefficient (ADC) value is often used for the differential diagnosis of the tumor. However, the effect of the surroundings on the ADC value has not been reported. In this study, we used the phantom completely sealed up to measure the change in the ADC value depending on the surroundings material. The results showed that the ADC value decreased according to the density of superparamagnetic iron oxide (SPIO) in the surroundings. Clinically, hemorrhage or iron deposit around the tumor may affect the ADC value of the tumor and result in under-estimation.

[Influence of imaging parameters on the measurement of apparent diffusion coefficient].

The apparent diffusion coefficient (ADC) values are calculated by using signal intensity in diffusion-weighted images (DWIs) with two or more different b-value. Therefore, the signal to noise ratio (SNR) of DWI with higher b-value may have a big influence on the measured ADC value. We examined the influence of the imaging parameters on the calculated ADC values. The SNR of DWI increased by using a larger voxel size, by means of a decreased number of matrix, an increased slice thickness, and an increased field of view (FOV). However, when the number of excitations was increased to improve the SNR of DWI, the signal intensity of background noise was observed to be slightly increased. It was suggested that the consistency of measured ADC was not preserved when the signal of the DWIs with higher b-value dropped close to the noise level.

[Distortion in diffusion weighted imaging].

The definitional equation of the distortion of echo planar imaging(EPI)was examined. We compared measured values with calculated values by using the definitional equation of the chemical shift of the EPI method that first composed the diffusion-weighted image, and examined the possibility of applying it to the distortion. The results showed that the chemical shift with the definitional equation and the measurement corresponded, and the correlation between the chemical shift and the distortion was acquired. Next, the distortion of each images that composed DWI with the increase and the sign acceptable method difference of b value. The difference in the distortion between each image has increased with the increase in b value. It was assumed that the influence of the eddy currents was due to the high motion probing gradient.

[Signal-to-noise ratio measurement in parallel MRI with subtraction mapping and consecutive methods].

When measuring the signal-to-noise ratio (SNR) of an image the used parallel magnetic resonance imaging, it was confirmed that there was a problem in the application of past SNR measurement. With the method of measuring the noise from the background signal, SNR with parallel imaging was higher than that without parallel imaging. In the subtraction method (NEMA standard), which sets a wide region of interest, the white noise was not evaluated correctly although SNR was close to the theoretical value. We proposed two techniques because SNR in parallel imaging was not uniform according to inhomogeneity of the coil sensitivity distribution and geometry factor. Using the first method (subtraction mapping), two images were scanned with identical parameters. The SNR in each pixel divided the running mean (7 by 7 pixels in neighborhood) by standard deviation/radical2 in the same region of interest. Using the second (consecutive) method, more than fifty consecutive scans of the uniform phantom were obtained with identical scan parameters. Then the SNR was calculated from the ratio of mean signal intensity to the standard deviation in each pixel on a series of images. Moreover, geometry factors were calculated from SNRs with and without parallel imaging. The SNR and geometry factor using parallel imaging in the subtraction mapping method agreed with those of the consecutive method. Both methods make it possible to obtain a more detailed determination of SNR in parallel imaging and to calculate the geometry factor.