[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.

[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.

[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.

[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.

[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.

Magnetization and demagnetization of magnetic dental attachments in a 3-T MRI system.

The purpose of this study was to evaluate the magnetization and demagnetization of magnetic dental attachments in a 3.0-T magnetic resonance imaging (MRI) scanner. A high-field-strength (3.0 T) MRI scanner (Achieva 3.0 T, Philips, Amsterdam, Netherlands) was used. Magnetic flux leakage was measured using a gaussmeter. To evaluate the magnetization and demagnetization of the magnetic assemblies and keepers caused by the moving in and out of the MRI scanner, the magnetic force of the attachments was measured before and after the table was moved in and out. Two settings were used wherein the magnetic assemblies and keepers were positioned on the table at angles of 0° or 90° with respect to the magnetic flux of the static magnetic field. The movement of the table was repeated 15 times. In addition, the retentive force of the magnetic dental attachments was measured after magnetic field exposure. The magnetic force of the magnetic attachments positioned at 0° decreased significantly after moving in and out of the MRI scanner (p < 0.05). In contrast, the magnetic force of the magnetic attachments positioned at 90° was stable after the movement of the table. The magnetic force of the keepers placed at both 0° and 90° was slightly increased after the movement of the table. At 0°, the retentive force of the magnet-keeper combinations decreased when the magnetic assembly was exposed to the strong magnetic flux of the MRI scanner. Therefore, the removal of all removable magnetic dentures is recommended before an MRI examination.

Effects of Imaging Parameters on the Quality of Contrast-Enhanced MR Angiography of Cerebral Aneurysms Treated Using Stent-Assisted Coiling: A Phantom Study.

PURPOSE: To quantitatively investigate in vitro the effects of flip angle (FA), receiver bandwidth (BW), echo time (TE), and magnetic field strength (FS) on image noise and artifacts induced by stent-assisted coiling on contrast-enhanced MR angiography (CE-MRA) images, as a first step towards optimization of imaging parameters. METHODS: A phantom simulating a cerebral aneurysm treated using stent-assisted coiling was filled with diluted gadolinium contrast medium, and MR angiography were obtained using varied parameters: FA (10°-60°), BW (164-780 Hz/pixel), and FS (1.5 and 3.0T). The TE varied automatically with BW because the TE was set to the smallest value. Three kinds of indices were semi-automatically calculated to quantify the severity of stent- and coil-induced artifacts: artificial lumen narrowing (ALN) representing a decrease in the in-stent luminal area, and relative in-stent signal (RISS) and relative in-coil signal (RISC) representing an increase in the in-stent and in-coil signal intensities, respectively. We also measured the ratio of in-stent signal to noise (IS/N) for each parameter. The variation in these indices with variations in FA, BW (TE), and FS was analyzed. RESULTS: An increase in FA led to an increase of up to 65% in the RISS, while the IS/N increased by up to three times. The 1.5T scanner indicated fewer artifacts (71% lower ALN, two times higher RISS, and 40% higher RISC) than the 3.0T scanner. On the other hand, the 1.5T scanner worsened the IS/N compared with the 3.0T scanner, although the difference was relatively small. Variation in BW (and hence, TE) led to a trade-off between artifact severity and IS/N. CONCLUSION: A high FA and low FS should be used for improved artifact severity and IS/N on CE-MRA images of a stent-assisted coil. A wide BW (short TE) could improve artifact severity at the expense of the image noise.

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.

Optimization of dual-energy subtraction chest radiography by use of a direct-conversion flat-panel detector system.

We aimed to optimize the exposure conditions in the acquisition of soft-tissue images using dual-energy subtraction chest radiography with a direct-conversion flat-panel detector system. Two separate chest images were acquired at high- and low-energy exposures with standard or thick chest phantoms. The high-energy exposure was fixed at 120 kVp with the use of an auto-exposure control technique. For the low-energy exposure, the tube voltages and entrance surface doses ranged 40-80 kVp and 20-100 % of the dose required for high-energy exposure, respectively. Further, a repetitive processing algorithm was used for reduction of the image noise generated by the subtraction process. Seven radiology technicians ranked soft-tissue images, and these results were analyzed using the normalized-rank method. Images acquired at 60 kVp were of acceptable quality regardless of the entrance surface dose and phantom size. Using a repetitive processing algorithm, the minimum acceptable doses were reduced from 75 to 40 % for the standard phantom and to 50 % for the thick phantom. We determined that the optimum low-energy exposure was 60 kVp at 50 % of the dose required for the high-energy exposure. This allowed the simultaneous acquisition of standard radiographs and soft-tissue images at 1.5 times the dose required for a standard radiograph, which is significantly lower than the values reported previously.

[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.

[Relationship between the effect of medial rotation of the foot axis by ankle dorsiflexion and the ability to visualize the femoral neck axis in the hip joint anterio-posterior radiography: evaluation by magnetic resonance images].

In scanning of the hip joint anterio-posterior radiography, by changing the lower extremities to the extension position and moving the foot axis (base line of the foot) by medial rotation, the angle of anteversion of the femoral neck is corrected. In this study, we assessed the effects on medial rotation of the femoral neck when keeping the planta vertically-positioned by ankle dorsiflexion (intermediate position of the ankle) and making change of the medial rotation angle of the foot axis by scanning the magnetic resonance (MR) images of knee joints and hip joints. The subjects in this study were 12 males (age: 37.9±13.8, weight: 67.3±5.5 kg) and 7 females (age: 27.6±5.1, weight: 50.0±4.5 kg). We measured the medial rotation angles of knee joints and femoral necks on MR images. Also, differences of these angles between males and females were compared. Although the gender differences were not found in medial rotation angle of both joints at all leg positions (P>0.05), the medial rotation angles increased by approximately 1.5 to 2.0 times larger by putting them at the intermediate position, and there were significant differences between the naturally plantar-flexed position and the intermediate position (P<0.05). In conclusion, our results showed that the optimal leg position for correcting the angle of anteversion was 20 degrees medial rotation of the foot axis at the naturally plantar-flexed position, or 10 degrees medial rotation of the foot axis at the intermediate position, regardless of gender.