Liver-spleen contrast standardization of gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid-enhanced magnetic resonance imaging based on cross-calibration.

Background: Liver-spleen contrast in the hepatobiliary phase highly depends on the devices used for liver function tests. This study aimed to develop and validate a method to convert liver-spleen contrast data acquired with another device to reference liver-spleen contrast data, using the regression line of phantom contrasts (i.e., cross-calibration). Methods: As cohort studies, two-dimensional gradient echo images of T1-weighted fat-suppression in the hepatobiliary phase were retrospectively obtained and analyzed for a total of 126 patients who underwent gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid-enhanced magnetic resonance imaging using four different magnetic resonance imaging scanner-coil combinations. The liver-spleen contrast measured from these images was converted into reference liver-spleen contrast using cross-calibration with purified water and gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid phantoms of 0.06, 0.14, 0.27, 0.63, 1.37, and 2.82 mM/L. At this point, the error of the regression lines with phantom contrasts was assessed and corrected. Lastly, the liver-spleen and converted liver-spleen contrasts, which are the values before and after cross-calibration respectively, were compared with reference liver-spleen contrast in three cases using different coils and magnetic resonance imaging scanners from a reference device. Results: Regarding the regression lines with phantom contrasts, the coefficient of determination was 0.99. Although regression lines with phantom contrasts tended to be 0.0105 lower in logarithmic contrasts than those with liver-spleen contrast, no significant difference was observed between the two lines (P=0.0612) by analysis of covariance. In the case of different coils, there was a significant difference between liver-spleen and reference liver-spleen contrasts (P<0.00001), but there was no significant difference between converted liver-spleen and reference liver-spleen contrasts (P=0.492). Moreover, the regression equation between converted liver-spleen and reference liver-spleen contrasts corresponded with an identity line. Likewise, in the two cases of different magnetic resonance imaging scanners, there was a significant difference between liver-spleen and reference liver-spleen contrast (both P<0.00001), but there was no significant difference between converted liver-spleen and reference liver-spleen contrast (P=0.923 and P=0.541). Conclusions: Cross-calibration using the precision and valid regression lines with phantom contrasts had high accuracy and utility.

[About Gonad Protection Based on Ovarian Position in Hip Plain Radiography].

PURPOSE: In gonad protection, it is difficult to identify the position from the body surface during shielding because the position and size of the ovary vary from individual to individual, and it is not possible to evaluate whether the protective equipment is correctly placed at the position of the ovary. Therefore, the position of the ovary with respect to the pelvis was clarified, and the effectiveness of gonad protection in the front and side of the hip joint was evaluated. METHODS: From the image of the pelvis taken with an MRI device, the inner and outer edges of the ovary, the upper and lower edges and the long and short axes of the pelvis, and the depth of the ovary were measured, and the position of the ovary was calculated based on the ratio of the ovary to the pelvis. A pelvic schema was created, and the position of the ovary was synthesized on the schema. In addition, the shielding rate was calculated when lead-containing rubber for the protection of the gonads was used. RESULTS: In front of the pelvis, the ovaries were present throughout the pelvic cavity. On the anterior surface, placing the shield on the caudal side up to the line connecting the centers of the left and right femoral heads had a shielding effect of about 88%. On the lateral side, shielding the pubic upper limbs from the ischial body could reduce the exposure of the unhealthy ovaries by 99%. However, when the gonad protection was placed at the height of the line connecting the anterior superior iliac spines, the shielding rate from the left and right ovarian distribution was about 13%, so the disadvantage of using the protective equipment was greater. CONCLUSION: For gonad protection, the presence or absence of use should be judged by using the shielding rate according to the shape of the protective equipment as an index.

Comparison of liver scintigraphy and the liver-spleen contrast in Gd-EOB-DTPA-enhanced MRI on liver function tests.

The liver-spleen contrast (LSC) using hepatobiliary-phase images could replace the receptor index (LHL15) in liver scintigraphy; however, few comparative studies exist. This study aimed to verify the convertibility from LSC into LHL15. In 136 patients, the LSC, not at 20 min, but at 60 min after injecting gadolinium-ethoxybenzyl-diethylenetriaminepentaacetic acid was compared with the LHL15, albumin-bilirubin (ALBI) score, and the related laboratory parameters. The LHL15 was also compared with their biochemical tests. The correlation coefficients of LSC with LHL15, ALBI score, total bilirubin, and albumin were 0.740, -0.624, -0.606, and 0.523 (P < 0.00001), respectively. The correlation coefficients of LHL15 with ALBI score, total bilirubin, and albumin were -0.647, -0.553, and 0.569 (P < 0.00001), respectively. The linear regression equation on the estimated LHL15 (eLHL15) from LSC was eLHL15 = 0.460 · LSC + 0.727 (P < 0.00001) and the coefficient of determination was 0.548. Regarding a contingency table using imaging-based clinical stage classification, the degree of agreement between eLHL15 and LHL15 was 65.4%, and Cramer's V was 0.568 (P < 0.00001). Therefore, although the LSC may be influenced by high total bilirubin, the eLHL15 can replace the LSC as an index to evaluate liver function.

A multicenter study of radiation doses to the eye lenses of medical staff performing non-vascular imaging and interventional radiology procedures in Japan.

PURPOSE: This study aimed to measure the eye lens doses received by physicians and other medical staff participating in non-vascular imaging and interventional radiology procedures in Japan. MATERIAL AND METHODS: From October 2014 to March 2017, 34 physicians and 29 other medical staff engaged in non-vascular imaging and interventional radiology procedures at 18 Japanese medical facilities. These professionals wore radioprotective lead glasses equipped with small, optically stimulated luminescence dosimeters and additional personal dosimeters at the neck during a 1-month monitoring period. The Hp(3) and the Hp(10) and Hp(0.07) were obtained from these devices, respectively. The monthly Hp(3), Hp(10), and Hp(0.07) for each physician and other medical staff member were then rescaled to a 12-month period to enable comparisons with the revised occupational equivalent dose limit for the eye lens. RESULTS: Among physicians, the average annual Hp(3) values measured by the small luminescence dosimeters on radioprotective glasses were 25.5 ± 38.3 mSv/y (range: 0.4-166.8 mSv/y) and 9.3 ± 16.6 mSv/y (range: 0.3-82.4 mSv/y) on the left and right sides, respectively. The corresponding values for other medical staff were 3.7 ± 3.1 mSv/y (range: 0.4-10.4 mSv/y) and 3.2 ± 2.7 mSv/y (range: 0.5-11.5 mSv/y), respectively. CONCLUSIONS: The eye lens doses incurred by physicians and other medical staff who engaged in non-vascular imaging and interventional radiology procedures in Japan were provided. Physicians should wear radioprotective glasses and use additional radioprotective devices to reduce the amount of eye lens doses they receive.

SCATTERED X-RAY ENERGY DATA FROM INTEGRATED MULTI-FILTER PERSONAL DOSEMETERS WORN BY INTERVENTIONAL RADIOLOGY STAFF.

The accuracy and usability of scattered X-ray energy data obtained from multi-filter dosemeters were investigated by comparing the data with results obtained via Monte Carlo simulation. The energy data, which were read from integrated personal dosemeters used by interventional radiology (IR) staff in individual monitoring, were plotted against relative frequency and statistically assessed. The effective energy obtained from the multi-filter dosemeters was inversely proportional to detector size and lower than the results of the Monte Carlo simulation. All distributions of scattered X-ray energy to which the IR staff were exposed had only one peak value, which corresponded with the effective energy measured using a water phantom. For abdominal IR, there was a significant difference in the distributions between IR staff (p < 0.01). The results suggest that rectifying systematic errors resulting from oblique incidence of X-rays against the filters would make the energy data usable for optimisation of radiological protection.

Action research regarding the optimisation of radiological protection for nurses during vascular interventional radiology.

The optimisation and decision-making processes for radiological protection have been broadened by the introduction of re-examination or feedback after introducing protective measures. In this study, action research was used to reduce the occupational exposure of vascular interventional radiology (IR) nurses. Four radiological protection improvement measures were continuously performed in cooperation with the researchers, nurses and stakeholders, and the nurses' annual effective doses were compared before and after the improvements. First, the dosimetry equipment was changed from one electronic personal dosimeter (EPD) to two silver-activated phosphate glass dosimeters (PGDs). Second, the nurses were educated regarding maintaining a safe distance from the sources of scattered and leakage radiation. Third, portable radiation shielding screens were placed in the IR rooms. Fourth, the x-ray units' pulse rates were reduced by half. On changing the dosimetry method, the two PGDs recorded a 4.4 fold greater dose than the single EPD. Educating nurses regarding radiological protection and reducing the pulse rates by half decreased their effective doses to one-third and two-fifths of the baseline dose, respectively. No significant difference in their doses was detected after the placement of the shielding screens. Therefore, the action research effectively decreased the occupational doses of the vascular IR nurses.

Investigation of qualitative and quantitative factors related to radiological exposure to nursing staff during computed tomography examinations.

Radiologists or nurses intermittently stay in computed tomography rooms during computed tomography examinations; these actions are defined as "entrance actions." The qualitative and quantitative factors related to radiological exposure to computed tomography nursing staff were investigated to identify the protective measures against entrance actions. A questionnaire survey was used to investigate the frequency, motives, and causalities of entrance actions. Individual and area monitoring were simultaneously performed. The mean frequency of entrance actions was 1.2 times mo(−1). The primary motive for entrance actions was to dispel anxieties regarding collateral accidents during computed tomography. The nursing staff particularly engaged in close supervision to help the patients cope with contrast media extravasation. The average personal dose equivalent [Hp(10)] to the nurses was 0.21 mSv mo(−1). The ambient dose equivalent [H*(10)] rate was 1.4­3.7 mSv min(−1) at a distance of 1 m from CT gantry centre. Avoidance of entrance actions and collateral accidents would decrease the occupational exposures to nurses.

A novel removable shield attached to C-arm units against scattered X-rays from a patient's side.

OBJECTIVES: We invented a drape-like shield against scattered X-rays that can safely come into contact with medical equipment or people during fluoroscopically guided procedures. The shield can be easily removed from a C-arm unit using one hand. We evaluated the use of the novel removable shield during the endoscopic retrograde cholangiopancreatography (ERCP) procedure. METHODS: We measured the dose rate of scattered X-rays around endoscopists with and without this removable shield and surveyed the occupational doses to the ERCP staff. We also examined the endurance of the shield. RESULTS: The removable shield reduced the dose rate of scattered X-rays to one-tenth and reduced the monthly dose to an endoscopist by at least two-fifths. For 2.5 years, there was no damage to the shield and no loosening of the seam. The bonding of the hook-and-loop fasteners did not weaken, although the powerful double-sided tapes made especially for plastic did. CONCLUSIONS: The removable shield can reduce radiation exposure to the ERCP staff and may contribute to reducing the exposure to the eye lenses of operators. It would also be possible to expand its use to other fluoroscopically guided procedures besides ERCP because it is a light, simple, and useful device. KEY POINTS: • We invented a shield that can be removed from C-arm units with one hand. • The removable shield reduces the dose rate of X-rays to one-tenth. • The removable shield reduces operator exposure by two-fifths. • The removable shield is durable, lasting for several years. • The drape-like removable shield is light, simple, and useful.

Evaluation of the effectiveness of X-ray protective aprons in experimental and practical fields.

Few practical evaluation studies have been conducted on X-ray protective aprons in workplaces. We examined the effects of exchanging the protective apron type with regard to exposure reduction in experimental and practical fields, and discuss the effectiveness of X-ray protective aprons. Experimental field evaluations were performed by the measurement of the X-ray transmission rates of protective aprons. Practical field evaluations were performed by the estimation of the differences in the transit doses before and after the apron exchange. A 0.50-mm lead-equivalent-thick non-lead apron had the lowest transmission rate among the 7 protective aprons, but weighed 10.9 kg and was too heavy. The 0.25 and 0.35-mm lead-equivalent-thick non-lead aprons differed little in the practical field of interventional radiology. The 0.35-mm lead apron had lower X-ray transmission rates and transit doses than the 0.25-mm lead-equivalent-thick non-lead apron, and each of these differences exceeded 8% in the experimental field and approximately 0.15 mSv/month in the practical field of computed tomography (p < 0.01). Therefore, we concluded that the 0.25-mm lead-equivalent-thick aprons and 0.35-mm lead apron are effective for interventional radiology operators and computed tomography nurses, respectively.

[Examination of the means of measuring liver function in the hepatobiliary phase].

In a field of contrast-enhanced magnetic resonance imaging of the liver, attention has been focused on evaluation of liver function using gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid(EOB). In this study, we examined the possibility of obtaining liver function in only one hepatobiliary phase 60 minutes after injection. First, in regard to the difference between the signal intensity of two materials, we examined the effects of slice gap, surface coil intensity correction(SCIC), and others. Secondly, we compared the difference between liver and spleen signal intensity with biochemical laboratory tests, Child-Pugh class, liver damage class, and the two indices(HH(15) and LHL(15))calculated by 99mTc-DTPA-galactosyl-human serum albumin hepatic scintigraphy in patients with chronic liver diseases. Finally, we designated the "Liver EOB uptake index(L-EOB(60))" from those results, compared with HH(15) and LHL(15). The results demonstrated that the difference between the signal intensity of two materials increased in the lack of slice gap explained by cross talk, and decreased with SCIC. The difference between liver and spleen signal intensity decreased with worsened liver and kidney function. In the case of slice gap >20% and direct bilirubin <0.5 mg/dL without SCIC, the correlation coefficient between L-EOB(60) and LHL(15) was 0.97. L-EOB(60) was strongly proportional to LHL(15). We conclude that L-EOB(60) meeting the above conditions can be employed as a useful index to determine liver function.

[Optimal scan timing for Gd-EOB-DTPA enhanced liver dynamic MR imaging].

Gadoxetate Sodium (Gd-EOB-DTPA, EOB) is a new contrast agent for magnetic resonance (MR) imaging that allows both vascular and hepatobiliary imaging in one examination. Often in the arterial phase, however, appropriate scan timing is missed and contrast enhancement is not enough. In addition, to shorten the complete examination, some studies have been conducted to examine scan timing at the hepatobiliary phase earlier than 20 min after injection. We studied the optimal scan timing both at the arterial and the hepatobiliary phase. It was appropriate that multiphase acquisition of MR imaging at the arterial phase should be aimed around 25 sec after injection. Moreover, the liver-spleen contrast ratio (C(L-S)) at the hepatobiliary phase was highest at 60 min after injection, and the acquisition of an image earlier than 20 minutes lowered the C(L-S). In the future, it is desirable to establish how to use Gd-EOB-DTPA (EOB) for hepatic MR imaging after taking the extent of liver damage into consideration.

[Trial manufacture of a plunger shield for a disposable plastic syringe].

A syringe-type radiopharmaceutical being supplied by a manufacturer has a syringe shield and a plunger shield, whereas an in-hospital labeling radiopharmaceutical is administered by a disposable plastic syringe without the plunger shield. In cooperation with Nihon Medi-Physics Co. Ltd., we have produced a new experimental plunger shield for the disposable plastic syringe. In order to evaluate this shielding effect, we compared the leaked radiation doses of our plunger shield with those of the syringe-type radiopharmaceutical (Medi shield type). Our plunger shield has a lead plate of 21 mm in diameter and 3 mm thick. This shield is equipped with the plunger-end of a disposal plastic syringe. We sealed 99mTc solution into a plastic syringe (Terumo Co.) of 5 ml with our plunger shield and Medi shield type of 2 ml. We measured leaked radiation doses around syringes using fluorescent glass dosimeters (Dose Ace). The number of measure points was 18. The measured doses were converted to 70 microm dose equivalent at 740 MBq of radioactivity. The results of our plunger shield and the Medi shield type were as follows: 4-13 microSv/h and 3-14 microSv/h at shielding areas, 3-545 microSv/h and 6-97 microSv/h at non-shielding areas, 42-116 microSv/h and 88-165 microSv/h in the vicinity of the syringe shield, and 1071 microSv/h and 1243 microSv/h at the front of the needle. For dose rates of shielding areas around the syringe, the shielding effects were approximately the same as those of the Medi shield type. In conclusion, our plunger shield may be useful for reducing finger exposure during the injection of an in-hospital labeled radiopharmaceutical.

[Estimation of personal dose based on the dependent calibration of personal dosimeters in interventional radiology].

The purpose of present study is, in interventional radiology (IVR), to elucidate the differences between each personal dosimeter, and the dependences and calibrations of area or personal dose by measurement with electronic dosimeters in particular. We compare space dose rate distributions measured by an ionization survey meter with the value measured by personal dosimeter: an optically stimulated luminescence, two fluoroglass, and two electronic dosimeters. Furthermore, with electronic dosimeters, we first measured dose rate, energy, and directional dependences. Secondly, we calibrated the dose rate measured by electronic dosimeters with the results, and estimated these methods with coefficient of determination and Akaike's Information Criterion (AIC). The results, especially in electronic dosimeters, revealed that the dose rate measured fell by energy and directional dependences. In terms of methods of calibration, the method is sufficient for energy dependence, but not for directional dependence, because of the lack of stable calibration. This improvement poses a question for the future. The study suggested that these dependences of the personal dosimeter must be considered when area or personal dose is estimated in IVR.

[Examination of types of exposure and management methods for nurses in interventional radiology].

Although a large number of studies have been done on exposure to operators and doctors during interventional radiology(IVR), there have been very few reports on nurses. This study was carried out to clarify the situation regarding exposure for nurses, and provides examples of how to estimate and manage. We measured space dose-rate distributions with an ionization survey meter, and personal exposure dose by a small fluorescent grass dosimeter(Dose Ace). The experimental results disclosed that there tended to be two types of exposure depending on the task performed. Head and neck(collar level)were associated with the highest exposure dose, which was observed in nurses assisting operators. Alternatively, knees showed the highest exposure dose, which was observed in nurses observing and assisting the patient. When estimation of skin equivalent exposure at the knees is needed, it can be calculated by using the value measured at the collar level. Furthermore, in estimating exposure dose, the directional and energy characteristics of personal dosimeters should be considered adequate. For radiation management, a circular protective sheet can be placed around the patient's lower area and a protective screen near the patient's head, and basic and practical education can be given. We concluded that these are highly useful for the personal monitoring of nurses engaged in IVR.