A National Survey on Safety Management at MR Imaging Facilities in Japan

PURPOSE

To investigate safety management at Japanese facilities performing human MRI studies.

METHODS

All Japanese facilities performing human MRI studies were invited to participate in a comprehensive survey that evaluated their MRI safety management. The survey used a questionnaire prepared with the cooperation of the Safety Committee of the Japanese Society for Magnetic Resonance in Medicine. The survey addressed items pertaining to the overall MRI safety management, questions on the occurrence of incidents, and questions specific to facility and MRI scanner or examination. The survey covered the period from October 2017 to September 2018. Automated machine learning was used to identify factors associated with major incidents.

RESULTS

Of 5914 facilities, 2015 (34%) responded to the questionnaire. There was a wide variation in the rate of compliance with MRI safety management items among the participating facilities. Among the facilities responding to this questionnaire, 5% reported major incidents and 27% reported minor incidents related to MRI studies. Most major incidents involved the administration of contrast agents. The most influential factor in major incidents was the total number of MRI studies performed at the facility; this number was significantly correlated with the risk of major incidents (P < 0.0001).

CONCLUSION

There were large variations in the safety standards applied at Japanese facilities performing clinical MRI studies. The total number of MRI studies performed at a facility affected the number of major incidents.

Global and Japanese regional variations in radiologist potential workload for computed tomography and magnetic resonance imaging examinations

PURPOSE

To investigate the global variation in radiologist potential workload for CT and MRI examinations, and the regional variation in potential workload and extent of radiologists' involvement in CT and MRI examinations in Japan.

METHODS

"Radiologist potential workload" was defined as the annual number of CT plus MRI examinations divided by the total number of diagnostic radiologists. The extent of radiologists' involvement was measured as the proportion of CT and MRI examinations to which "Added-fees for Radiological Managements on Imaging-studies (ARMIs)" were applied among eligible examinations. Maximum variation was computed as the ratio of the highest-to-lowest values among the countries or Japanese prefectures.

RESULTS

The radiologist potential workload in Japan was 2.78-4.17 times higher than those in other countries. A maximum prefecture-to-prefecture variation was 3.88. The average percentage of CT plus MRI examinations with ARMI applied was 43.3%, with a maximum prefecture-to-prefecture variation of 3.97. Prefectures with more radiologists tended to have a higher extent of radiologists' involvement.

CONCLUSIONS

Japan had a far greater radiologist potential workload compared with other countries, with a large regional variation among prefectures. Prefectures with more radiologists tended to have a higher extent of radiologists' involvement in CT and MRI examinations.

[Comparison of ERCP and MRCP: invasiveness and cost]

The purpose of this study was to compare ERCP and MRCP in terms of invasiveness and cost. A questionnaire regarding patient satisfaction was distributed to 23 ERCP patients and 63 MRCP patients. The practical cost of each examination and total yearly cost for 2002, including medication costs for post-ERCP pancreatitis, were calculated. On a trial basis, the total yearly cost for 2002 was also calculated as a percentage of the cost in 1996. Results of the questionnaire showed that patients tended to favor MRCP over ERCP. In our hospital, the practical costs of MRCP and ERCP were 2063 points and 3964 points, respectively. Medication costs for pancreatitis corresponded to about 3% of the total yearly cost for ERCP. The total yearly costs for both examinations and the medication costs for pancreatitis were about 1,360,000 points. The result of trial calculation with the examination percentage of 1996 was about 1,950,000 points. The results of our study demonstrated that MRCP is a noninvasive examination for patients and that its popularization contributed to a reduction in medical costs. For further popularization of equipment and advanced imaging methods, careful assessment of examination costs is important.

Kinetic analysis of cell proliferation using bromodeoxyuridine labeling and in situ detection of dying cells in the tympanic membrane and middle ear cholesteatoma

Using specimens from the posterior-superior quadrant of the human tympanic membrane, meatal skin, retroauricular skin and middle ear cholesteatoma, epidermal cell proliferation was studied by cultures in FC43 emulsion containing bromodeoxyuridine (BrdU), and cell death was detected by in situ labeling of nuclear DNA fragmentation (TUNEL staining). The culture of specimens with BrdU revealed labeling in the basal cell layer and/or the layer immediately above it. The counts of BrdU-labeled cells both at and beside the malleus handle and at the annulus were significantly higher than those in the tympanic membrane, meatal skin, retroauricular skin and cholesteatoma, indicating the existence of epidermal proliferation centers in the annulus and malleus handle. TUNEL-positive cells were observed in the uppermost layer of the epidermis, and counts of dying cells did not show any significant differences among specimens from the different areas. From these observations, we conclude that addition of newly proliferated cells at the proliferation center and uniform cell death cause epidermal cell migration over the tympanic membrane and ear canal. In addition, no proliferation center was seen in the epidermis of cholesteatoma, suggesting a disturbance of epidermal cell migration. Furthermore, BrdU-labeling at the margin of persistently perforated tympanic membranes from patients with chronic otitis media revealed that, at the perforation margin, the counts of BrdU-labeled cells were not higher than those of the normal tympanic membrane. In addition, a few BrdU-labeled cells were observed in the lamina propria and mucosal cell layer, indicating that persistent perforation of the tympanic membrane results from the failure of proliferating cells to increase at the margin of the perforation.

Cell dynamics in the germinal center of the human tonsil

Apoptosis of the human tonsillar germinal center was studied by means of immunocytochemical methods. It is generally accepted that the germinal center of the lymphoid tissues plays an important role both in cell proliferation and cell death. Although many studies on cell proliferation have been reported, the cell death mechanism is not yet well understood. According to recent studies, apoptosis is the result of programmed, not pathological cell death, and it plays an important role in the maintenance, immunity and development of life. The present study showed that the tingible body was a mass of nuclear chromatin of dead cells, and that cells with a tingible body are macrophages, called tingible-body macrophages. The purpose of this study was to examine the relationship between tingible-body macrophages and apoptosis. The structure of tingible-body macrophages were observed by immunostaining methods.

Apoptosis of germinal centers in postnatal development of rabbit tonsil

The purpose of this study was to clarify the relationship between the morphological maturation of the germinal center of newborn rabbit tonsil and the appearance of apoptosis in it. Germinal centers were observed using immunostaining. Apoptosis is shown to be scarce in immature type of germinal center, but abundant in mature type. The findings suggest apoptosis to have an important function in the germinal center of the tonsil.

Immunohistochemical study of transforming growth factor-alpha expression in normal and perforated tympanic membrane

An immunohistochemical study of transforming growth factor-alpha (TGF-alpha) distribution was carried out to clarify the mechanism responsible for accelerated epidermal cell proliferation after perforation of the rabbit tympanic membrane. In the normal tympanic membrane, TGF-alpha expression was not observed, whereas after perforation, over the whole tympanic membrane including the margin of the perforation, TGF-alpha-positive cells appeared and were scattered in the epidermal cell layer. After healing of the perforation, a marked decrease of TGF-alpha-positive cells in the tympanic membrane was observed. This finding suggests that TGF-alpha induces proliferation of epidermal cells after the perforation stimulus.

Epidermal cell migration and healing of the tympanic membrane: an immunohistochemical study of cell proliferation using bromodeoxyuridine labeling

A monoclonal antibody against bromodeoxyuridine (BrdU) was used to investigate cell proliferation in the tympanic membrane of white rabbits. The BrdU-labeled cells were observed mainly in the epidermis of the annulus, around the malleus handle, and in the anterior and posterior superior quadrants of the normal rabbit tympanic membrane at 2 hours after BrdU injection. At 5 days the localization of the BrdU-labeled cells had changed centrifugally from the malleus handle toward the annulus. This change in the distribution of BrdU-labeled cells suggested that epidermal cell migration is caused by cell proliferation and insertion of newly proliferated epidermal cells at the proliferation center. Immunohistochemical observation of BrdU-labeled cells in the artificially perforated tympanic membrane suggested that the process of healing of the perforation may be as follows. Epidermal cell proliferation in the whole tympanic membrane is accelerated by the perforation stimulus. Then the proliferated epidermal cells migrate to the edge of the perforation. In contrast, proliferation of connective tissue cells and mucosal cells is stimulated only around the perforation, and cooperates with the proliferated epidermal cells to close the perforation.