铋屏蔽对头颈部多层螺旋CT中眼晶状体辐射剂量的降低作用

目的 探讨扫描平面内铋屏蔽在头颈部多层螺旋CT(MSCT)扫描中对影像质量的影响和眼晶状体辐射剂量的降低作用.方法 分别使用颅脑、颞骨和鼻窦临床扫描条件,在无屏蔽、1层、2层和3层铋屏蔽覆盖眼部区域时,对标准水模和离体头颅标本进行扫描,用热释光剂量片测量头颅标本每次扫描时的眼晶状体器官剂量.在屏蔽材料和被扫描体间放置5、10、15和20 mm厚的海绵时,使用鼻窦扫描条件采集影像,并测量眼晶状体的剂量.测量水模影像中与屏蔽物为2、4、6和8 cm距离处的CT值,主观评价头颅标本影像中伪影对解剖结构的影响.结果 颅脑、颞骨和鼻窦CT临床扫描中眼晶状体的器官剂量分别为24.31、27.60和20.01 mGy.使用铋屏蔽时,均使得眼晶状体剂量有显著下降,但下降幅度随着铋屏蔽物的增加而降低.在各种厚度的屏蔽物时,屏蔽物间隙越大,眼晶状体剂量的降低程度越小,测量兴趣区CT值的增加程度也显著降低.颅脑和颞骨CT扫描分别使用2层和3层铋屏蔽,在不影响诊断的前提下,可有效降低眼晶状体剂量分别为47.1%和59.1%;鼻窦CT扫描时,1层屏蔽无间隙、2层屏蔽1.5 cm间隙不影响诊断,可降低眼晶状体剂量分别为31.5%和34.5%.结论 扫描平面内铋屏蔽材料的合理应用,可有效降低头颈部CT扫描中眼晶状体的辐射剂量.     

Radioprotection to the eye during CT scanning.

BACKGROUND AND PURPOSE: The lens of the eye is sensitive to radiation. Children undergoing CT of the head and patients undergoing repeated CT scanning of the head are vulnerable to this complication. The purpose of this study was to test the ability of a heavy metal, bismuth, in reducing radiation to the lens of the eye during routine cranial CT. METHODS: Both phantom and human studies were done. Using a standard head-attenuating phantom, scanning was performed with detectors placed over the eye, first without the protectors, and then with shielding by one (1T), two (2T), or three thickness (3T) of bismuth-coated latex. The patient study included 30 patients randomized into one of three groups with eye protection provided by 1T, 2T, or 3T of the bismuth-coated latex. Control measurements were done using thermoluminescent dosimeters over the forehead above each eye. Image artifact from the bismuth shields was assessed. RESULTS: The phantom study demonstrated that the use of bismuth-coated shielding over the eyes decreased radiation dosage by 48.5%, 59.8%, and 65.4% using 1T, 2T, and 3T, respectively. The effect of eye shielding in decreasing radiation dosage to the eye was highly significant for all three thicknesses (P = 2.9 x 10(-81) to 1.9 x 10(-89)). In the patient study, the use of 1T, 2T, and 3T of bismuth-coated latex saved an average radiation dose of 39.6%, 43.5%, and 52.8%, respectively. While the use of shielding was statistically significant in saving radiation for all thicknesses (P = 2.2 x 10(-10) to 1.4 x 10(-21)), there was no statistical difference between 1T, 2T, and 3T of bismuth-coated latex shielding found in patients. However, the trend was for increased radiation savings to the eye with increased thickness of shielding used. A review of all 30 studies showed no significant artifact caused by the eye shielding, regardless of thickness. CONCLUSION: Bismuth-coated latex shielding of the eye during cranial CT is simple to apply, inexpensive, and causes up to a 50% reduction in radiation to the lens of the eye.     

New organ-based tube current modulation method to reduce the radiation dose during computed tomography of the head: evaluation of image quality and radiation dose to the eyes in the phantom study

A new organ-based tube current modulation (NOB-TCM) method was designed with the intent to decrease tube current by 30% over a prescribed 90° radial arc across the anterior aspect of the radiosensitive organ, without increasing tube current in the remaining radial arc. We compared a reference scan and five other dose-reducing methods with regard to effects on dose, practicality, and image quality to determine the most effective method for the reduction of the radiation dose to the eyes during CT examinations of the head. We compared the radiation doses to the eyes and physical image quality in different regions of interest for TCM and shielding scans. Three types of TCM scans were performed: longitudinal TCM, angular TCM, and NOB-TCM. A bismuth sheet and lead goggles were each applied for the shielding scan. Relative to the reference scan, the dose to the eye was reduced to 25.88% with NOB-TCM, 44.53% with lead goggles, and 36.91% with a bismuth shield. Relative to the reference scan, the mean signal-to-noise ratio (SNR) was decreased to 8.02% with NOB-TCM, 28.36% with lead goggles, and 32.95% with the bismuth shield. The SNR of the anterior region of interest was decreased to 11.89% with NOB-TCM and 87.89% with the bismuth shield. The average figure of merit was increased by 11.7% with longitudinal TCM and 13.39% with NOB-TCM, compared with the reference scan. NOB-TCM is a superior solution for head CT, including the orbital area, due to the reduction in radiation exposure without significant loss in image quality.     

Dose reduction to radiosensitive tissues in CT. Do commercially available shields meet the users' needs?

AIM: To assess the effectiveness and economy of routinely using commercially available in-plane bismuth shielding during CT scanning of the chest and brain. METHODS AND MATERIALS: Forty patients were scanned with thermoluminescent dosemeters (TLDs) in situ to measure the radiation dose to the thyroid and eye during CT scanning of the brain and chest. Half of the patients had the "AttenuRad" shield in place during scanning. RESULTS: Use of the shielding reduced the mean dose to the eye from 6.0 +/- 0.3 mGy to 4.9 mGy +/- 0.2 mGy and the thyroid dose from 16.4 mGy +/- 1.2 mGy to 7.1 mGy +/- 0.5 mGy. CONCLUSION: Use of the thyroid shield is recommended for all CT scanning of the chest. The eye shield does not produce as marked a reduction in radiation dose to the lens of the eye, when an angled gantry is used, since the eyes are not in the primary beam. Use of the eyeshield is justifiable where irradiation of the orbit is unavoidable, although whether artifacts would be a problem if the shield was used in this way was not assessed.     

铋屏蔽联合器官管电流调制技术在颅脑CT检查中应用的体模研究

目的 通过测量敏感器官的辐射剂量,评价铋屏蔽联合器官-管电流调制（X-care）技术在颅脑CT扫描中的应用价值。方法 使用德国德国西门子公司炫速双源CT对头颈体模进行相同容积CT剂量指数（CTDI_vol）下的X-care、铋屏蔽和X-care联合铋屏蔽3种方式扫描颅脑,及无铋屏蔽和铋屏蔽2种方式扫描双能量CT血管造影（DE-CTA）。选取铋屏蔽所在层面测量脑血管、邻近脑组织及脑脊液的CT值以及图像噪声,计算脑血管和脑实质的对比噪声比。通过放置热释光个人剂量计（TLD）的方式计算器官剂量当量（H_T）,并记录每次扫描后生成的CTDI_vol和剂量长度乘积（DLP）。结果 颅脑扫描在相同的CTDI_vol下,采用X-care、铋屏蔽和X-care联合铋屏蔽3种扫描方法的H_T,晶状体均值分别为（37.89±2.00）、（42.20±2.96）、（28.21±1.31） mSv,较颅脑常规序列扫描有明显下降（F=186.52,P<0.05）;采用铋屏蔽和X-care联合铋屏蔽,H_T,甲状腺为（0.77±0.07）和（0.89±0.08） mSv,较颅脑常规扫描和仅采用X-care有明显下降（F=103.26,P<0.05）;DE-CTA采用铋屏蔽扫描后H_T,晶状体和H_T,甲状腺分别为（11.56±1.04）和（0.32±0.03） mSv,较屏蔽前有明显下降（t=5.07,P<0.05）。用与不用X-care、铋屏蔽及X-care联合铋屏蔽,颅脑常规扫描的噪声和对比信噪比（CNR）值无显著性改变;用与不用铋屏蔽,双能量CTA扫描的噪声和CNR无显著性改变。结论 铋屏蔽联合器官管电流调制技术能够在保证一定图像质量的前提下,降低颅脑CT扫描中晶状体及甲状腺的器官剂量当量。     

In-plane bismuth breast shields for pediatric CT: effects on radiation dose and image quality using experimental and clinical data

OBJECTIVE: The purpose of our study was to evaluate the amount of radiation dose reduction and its effect on image quality when using an in-plane bismuth breast shield for multidetector CT (MDCT) of the chest and abdomen in female pediatric patients. SUBJECTS AND METHODS: Fifty consecutive MDCT examinations (chest, 29; abdomen, 21) of female pediatric patients (mean age, 9 years; range, 2 months-18 years) were performed with a 2-ply (1.7 g of bismuth per square centimeter) bismuth shield (three sizes to accommodate patients of varying sizes) overlying the patient's breasts. MDCT images were evaluated for a perceptible difference in image quality in the lungs at the anatomic level under the shield as compared with nonshielded lung and whether the images were of diagnostic quality. In addition, 2-mm regions of interest were placed in the peripheral anterior and posterior portions of each lung in shielded and nonshielded areas, and noise (standard deviation in Hounsfield units) was measured in the regions. Differences among the regions in noise were compared for shielded versus nonshielded areas (paired t test). To measure differences in actual dose, we also evaluated the breast shield with an infant anthropomorphic phantom using thermoluminescent detectors in the breast tissue. The phantom was imaged with and without the breast shield using identical MDCT parameters. RESULTS: All MDCT scans of patients were of diagnostic quality with no perceptible difference in image quality in shielded versus nonshielded lung. We found no statistically significant difference in noise between the shielded and nonshielded lung regions of interest (shielded: mean noise, 17.3 H; nonshielded: mean noise, 18.8 H; p = 0.5180). Phantom measurements revealed a 29% reduction in radiation dose to the breast when a medium-dose MDCT protocol was used. CONCLUSION: Bismuth in-plane breast shielding for pediatric MDCT decreased radiation dose to the breast without qualitative or quantitative changes in image quality.     

Coronary calcium scoring with MDCT: the radiation dose to the breast and the effectiveness of bismuth breast shield

OBJECTIVE: The purpose of our study was to determine the breast radiation dose during coronary calcium scoring with multidetector computerized tomography (MDCT). We also evaluated the degree of dose reduction by using a bismuth breast shield when performing coronary calcium scoring with MDCT. MATERIALS AND METHODS: The dose reduction achievable by shielding the adult (35 years or older) female breasts was studied in 25 women who underwent coronary calcium scoring with MDCT. All examinations were performed with a 16-MDCT scanner. To compare the shielded versus unshielded breast dose, the examinations were performed with (right breast) and without (left breast) breast shielding in all patients. With this technique the superficial breast doses were calculated. To determine the average glandular breast radiation dose, we imaged an anthropomorphic dosimetric phantom into which calibrated dosimeters were placed to measure the dose to the breast. The phantom was imaged using the same protocol. Radiation doses to the breasts with and without the breast shielding were measured and compared using the Student's t-test. RESULTS: The mean radiation doses with and without the breast shield were 5.71+/-1.1 mGy versus 9.08+/-1.5 mGy, respectively. The breast shield provided a 37.12% decrease in radiation dose to the breast with shielding. The difference between the dose received by the breasts with and without bismuth shielding was significant, with a p-value of less than 0.001. CONCLUSION: The high radiation during MDCT greatly exceeds the recommended doses and should not be underestimated. Bismuth in plane shielding for coronary calcium scoring with MDCT decreased the radiation dose to the breast. We recommend routine use of breast shields in female patients undergoing calcium scoring with MDCT.     

Bismuth breast and thyroid shield implementation for pediatric CT

Studies have indicated that infants and children are as much as ten times more susceptible to carcinogenesis from radiation than adults. Because data show bismuth breast and thyroid shields decrease radiation dose to sensitive areas without changes in image quality, Children's Healthcare of Atlanta implemented the use of bismuth shields in all patients undergoing CTexaminations. Staff education regarding the use of bismuth shielding was key to the success of this program.Their understanding of the benefits would ultimately assist in their support of shield use in the CT department. This program was made possible through a grant from the AHRA & Toshiba Putting Patients First Program. Otherwise, the cost of bismuth shielding would be supported by the operating budget of the organization and, with the decline in CT volume reported at many healthcare institutions,this cost may be too high for many hospitals.     

CT fluoroscopy shielding: decreases in scattered radiation for the patient and operator

PURPOSE: High-radiation exposure occurs during computed tomographic (CT) fluoroscopy. Patient and operator doses during thoracic and abdominal interventional procedures were studied in the present experiment, and a novel shielding device to reduce exposure to the patient and operator was evaluated. MATERIALS AND METHODS: With a 16-slice CT scanner in CT fluoroscopy mode (120 kVp, 30 mA), surface dosimetry was performed on adult and pediatric phantoms. The shielding was composed of tungsten antimony in the form of a lightweight polymer sheet. Doses to the patient were measured with and without shielding for thoracic and abdominal procedures. Doses to the operator were recorded with and without phantom, gantry, and table shielding in place. Double-layer lead-free gloves were used by the operator during the procedures. RESULTS: Tungsten antimony shielding adjacent to the scan plane resulted in a maximum dose reduction of 92.3% to the patient. Maximum 85.6%, 93.3%, and 85.1% dose reductions were observed for the operator's torso, gonads, and hands, respectively. The use of double-layer lead-free gloves resulted in a maximum radiation dose reduction of 97%. CONCLUSIONS: Methods to reduce exposure during CT fluoroscopy are effective and should be searched for. Significant reduction in radiation doses to the patient and operator can be accomplished with tungsten antimony shielding.     

Dose reduction in computed tomography: the effect of eye and testicle shielding on radiation dose measured in patients with beryllium oxide-based optically stimulated luminescence dosimetry

The aim of this study was to assess the effect of eye and testicle shielding on radiation dose to the lens and the testes of patients undergoing CT examinations. Fifty-one male patients underwent CT twice with identical protocols initially without, the second time with protective garments. Doses to the testes and the lenses were recorded with beryllium oxide-based dosimeters. The dose to the testes and lenses from CT exposure was reduced by 96.2% ± 1.7% and 28.2% ± 18.5%, when testicle and eye shielding was used, respectively. The effect of the eye shielding on the eye lens dose was found to depend on the x-ray tube position when the eye is primarily exposed during the scan. The maximum eye lens dose reduction achieved was found to be 43.2% ± 6.5% corresponding to the anterior position of the tube. A significant correlation between the patient’s body mass index and dose exposure could not be found. Eye and testicle shields, apart from being inexpensive and easy to use, were proven to be effective in reducing eye lens and testicle radiation dose burden from CT exposures.     

Female breast radiation exposure during thorax multidetector computed tomography and the effectiveness of bismuth breast shield to reduce breast radiation dose

OBJECTIVE: The purpose of our study was to determine the breast radiation dose when performing routine thoracic multidetector computed tomography (MDCT). We also evaluated dose reduction and the effect on image quality of using a bismuth breast shield when performing thoracic MDCT. MATERIAL AND METHODS: The dose reduction achievable by shielding the adult (18 years or older) female breasts was studied in 50 women who underwent routine thoracic MDCT. All examinations were performed with a 16-MDCT scanner (Sensation Cardiac 16; Siemens Medical Solutions). To compare the shielded/unshielded breast dose, the examination was performed with (right breast) and without (left breast) breast shielding in all patients. With this technique, the superficial breast doses were calculated. To determine the average glandular breast radiation dose, we imaged an anthropomorphic dosimetric phantom into which calibrated dosimeters were placed to measure the dose to breast. The phantom was imaged using the same protocol. Radiation doses to the breasts with and without the breast shielding were measured and compared using the Student t test. RESULTS: In the qualitative evaluation of the MDCT scans, all were considered to be of diagnostic quality. We did not see any differences in quality between the shielded and unshielded lung. The mean radiation doses to the breasts with the shield and to those without the shield were 8.6 +/- 2.33 versus 14.46 +/- 3.94 mGy, respectively. The breast shield enabled a 40.53% decrease in radiation dose to the breast. The difference between the dose received by the breasts with and that received by the breasts without bismuth shielding was significant, with a P value of less than 0.001. CONCLUSIONS: Bismuth in-plane shielding for routine thoracic MDCT decreased radiation dose to the breast without qualitative changes in image quality. The other radiosensitive superficial organs (eg, testes and thyroid gland) specifically must be protected with shielding.     

Radiation dose reduction to breast and thyroid during MDCT: effectiveness of an in-plane bismuth shield

PURPOSE: To evaluate dose reduction and image deterioration using in-plane bismuth breast-shielding and thyroid-shielding for MDCT. MATERIAL AND METHODS: Skin and organ doses of thyroid and breast were measured with thermoluminescent dosimeters in a female Alderson-Rando Phantom with and without a 4-ply in-plane bismuth shield. Routine neck (120 kVp, 150 mAs(eff); 16 x 1.5 mm) and chest (120 kVp, 100 mAs(eff); 16 x 1.5 mm) scan protocols were simulated on a 16-row MDCT scanner in three different settings: without shielding, with the shield directly on the surface, and with a 1-cm-thick cotton spacer between surface and shield. Image noise was quantified and compared using the t test. RESULTS: On average, shielding resulted in a 47% organ-dose reduction for the thyroid and 32% for the breast. Placement of the spacer between shield and surface had no significant impact on the measured doses, but significantly decreased the image noise (P < 0.05). CONCLUSION: In-plane bismuth breast and thyroid shielding significantly decreases radiation dose in MDCT without deteriorating image quality.     

Dose reduction in multislice CT by means of bismuth shields: results of in vivo measurements and computed evaluation

Purpose

We investigated the amount of patient dose reduction in the thyroid, lens of the eye and the breast when using bismuth protections in multislice computed tomography (CT) exams as well as their influence on the quality of diagnostic images.

Materials and methods

The radiation dose was measured by using thermoluminescence dosimeters. The study was conducted on the two CT scanners installed in our radiology department (64 and eight slices). The shield effects on the CT image were evaluated by measuring the signal-to-noise ratio in a phantom and in vivo, and by verifying the presence of artefacts on patients’ images. The obtained organ-dose reduction factors were used to evaluate the effects of shielding on the effective dose.

Results

The shielding attenuation ranged from 30% to 60% depending on the CT scan protocols and organs. The difference between shielded and unshielded signal-to-noise ratio was statistically significant but within the standard requirements for quality assurance. Results were in agreement with the radiologists’ perception of image quality. The use of the shields allowed up to 38% reduction of effective dose.

Conclusions

Use of bismuth shields significantly decreases both organ and effective radiation dose, with a consequent reduction in health risk for the patient, quantified in 1.4 fewer cases of radiation-induced tumours every 5 years in our centre (12,100 exams/year), in agreement with the risk factors proposed by Publication 60 of the International Commission on Radiological Protection (ICRP). The relative inexpensiveness of these protections, their easy application and their substantial lack of influence on image quality suggest their massive introduction into routine clinical practice.     

Effect of leaded glasses and thyroid shielding on cone beam CT radiation dose in an adult female phantom

Objectives:

This study aims to demonstrate the effectiveness of leaded glasses in reducing the lens of eye dose and of lead thyroid collars in reducing the dose to the thyroid gland of an adult female from dental cone beam CT (CBCT). The effect of collimation on the radiation dose in head organs is also examined.

Methods:

Dose measurements were conducted by placing optically stimulated luminescent dosemeters in an anthropomorphic female phantom. Eye lens dose was measured by placing a dosemeter on the anterior surface of the phantom eye location. All exposures were performed on one commercially available dental CBCT machine, using selected collimation and exposure techniques. Each scan technique was performed without any lead shielding and then repeated with lead shielding in place. To calculate the percent reduction from lead shielding, the dose measured with lead shielding was divided by the dose measured without lead shielding. The percent reduction from collimation was calculated by comparing the dose measured with collimation to the dose measured without collimation.

Results:

The dose to the internal eye for one of the scans without leaded glasses or thyroid shield was 0.450 cGy and with glasses and thyroid shield was 0.116 cGy (a 74% reduction). The reduction to the lens of the eye was from 0.396 cGy to 0.153 cGy (a 61% reduction). Without glasses or thyroid shield, the thyroid dose was 0.158 cGy; and when both glasses and shield were used, the thyroid dose was reduced to 0.091 cGy (a 42% reduction).

Conclusions:

Collimation alone reduced the dose to the brain by up to 91%, with a similar reduction in other organs. Based on these data, leaded glasses, thyroid collars and collimation minimize the dose to organs outside the field of view.     

Reduction of dose to the female breast in thoracic CT: a comparison of standard-protocol, bismuth-shielded, partial and tube-current-modulated CT examinations

We evaluated the potential for reduction of dose to the female breast in computed tomography (CT) of the thorax by using three different techniques: bismuth shielding, partial CT scanning and tube-current modulation (TCM). Measurements and simulations of dose and image quality were performed for a 64-slice CT system using a semi-anthropomorphic thorax phantom with breasts added. Three-dimensional dose distributions were calculated by Monte Carlo (MC) methods. Noise was determined by measurements and simulations. Bismuth shielding resulted in a dose reduction of about 50% for the breast, noise increased up to 40% and image quality was impaired by artifacts. In partial CT scans, not irradiating the breasts directly, dose to the breasts was reduced typically by 50%. To sustain a constant noise level, an increase of irradiation in the anteroposterior position resulted in a higher dose to the spine. Reduction of dose to the breasts of about 10% was achieved with TCM; distribution of noise was homogeneous and image quality uniform. Reduction of dose to the female breast was achieved by using all adapted CT methods. Bismuth shielding may compromise image quality, increase noise level and introduce streak artifacts. Partial and TCM examinations reduced dose to the breast without influencing image quality.     

Quantitative assessment of selective in-plane shielding of tissues in computed tomography through evaluation of absorbed dose and image quality

This study aimed at assessment of efficacy of selective in-plane shielding in adults by quantitative evaluation of the achieved dose reduction and image quality. Commercially available accessories for in-plane shielding of the eye lens, thyroid and breast, and an anthropomorphic phantom were used for the evaluation of absorbed dose and image quality. Organ dose and total energy imparted were assessed by means of a Monte Carlo technique taking into account tube voltage, tube current, and scanner type. Image quality was quantified as noise in soft tissue. Application of the lens shield reduced dose to the lens by 27% and to the brain by 1%. The thyroid shield reduced thyroid dose by 26%; the breast shield reduced dose to the breasts by 30% and to the lungs by 15%. Total energy imparted (unshielded/shielded) was 88/86 mJ for computed tomography (CT) brain, 64/60 mJ for CT cervical spine, and 289/260 mJ for CT chest scanning. An increase in image noise could be observed in the ranges were bismuth shielding was applied. The observed reduction of organ dose and total energy imparted could be achieved more efficiently by a reduction of tube current. The application of in-plane selective shielding is therefore discouraged.     

CT treatment planning of the liver

The article deals with CT treatment planning of the liver to maximize the dose to the liver but minimize the dose to the right kidney, spinal cord, and bowels. (The left kidney is out of the field due to the oblique angles of the fields.) This is achieved by right kidney shielding reconstruction from multislice CT treatment planning and by the oblique angles of the fields. Without CT, it is not possible to utilize oblique fields to cover the liver. With conventional AP-PA fields, not only is the whole liver treated but also most of the right kidney, half of the left kidney, bowels and spinal cord. Tolerance dose to the kidneys is exceeded if adequate dose is delivered to the liver. Some new computer algorithms display a bird's eye view of the shielding but this paper presents for the first time, a technique for actual shielding reconstruction from multislice CT treatment planning for use by the radiation oncologist when shielding blocks are drawn on the simulator films.     

Evaluation of additional lead shielding in protecting the physician from radiation during cardiac interventional procedures

Since cardiac interventional procedures deliver high doses of radiation to the physician, radiation protection for the physician in cardiac catheterization laboratories is very important. One of the most important means of protecting the physician from scatter radiation is to use additional lead shielding devices, such as tableside lead drapes and ceiling-mounted lead acrylic protection. During cardiac interventional procedures (cardiac IVR), however, it is not clear how much lead shielding reduces the physician dose. This study compared the physician dose [effective dose equivalent (EDE) and dose equivalent (DE)] with and without additional shielding during cardiac IVR. Fluoroscopy scatter radiation was measured using a human phantom, with an ionization chamber survey meter, with and without additional shielding. With the additional shielding, fluoroscopy scatter radiation measured with the human phantom was reduced by up to 98%, as compared with that without. The mean EDE (whole body, mean+/-SD) dose to the operator, determined using a Luxel badge, was 2.55+/-1.65 and 4.65+/-1.21 mSv/year with and without the additional shielding, respectively (p=0.086). Similarly, the mean DE (lens of the eye) to the operator was 15.0+/-9.3 and 25.73+/-5.28 mSv/year, respectively (p=0.092). In conclusion, although tableside drapes and lead acrylic shields suspended from the ceiling provided extra protection to the physician during cardiac IVR, the reduction in the estimated physician dose (EDE and DE) during cardiac catheterization with additional shielding was lower than we expected. Therefore, there is a need to develop more ergonomically useful protection devices for cardiac IVR.     

Estimated risks of radiation-induced fatal cancer from pediatric CT

OBJECTIVE: In light of the rapidly increasing frequency of pediatric CT examinations, the purpose of our study was to assess the lifetime cancer mortality risks attributable to radiation from pediatric CT. MATERIALS AND METHODS: Organ doses as a function of age-at-diagnosis were estimated for common CT examinations, and estimated attributable lifetime cancer mortality risks (per unit dose) for different organ sites were applied. Standard models that assume a linear extrapolation of risks from intermediate to low doses were applied. On the basis of current standard practice, the same exposures (milliampere-seconds) were assumed, independent of age. RESULTS: The larger doses and increased lifetime radiation risks in children produce a sharp increase, relative to adults, in estimated risk from CT. Estimated lifetime cancer mortality risks attributable to the radiation exposure from a CT in a 1-year-old are 0.18% (abdominal) and 0.07% (head)-an order of magnitude higher than for adults-although those figures still represent a small increase in cancer mortality over the natrual background rate. In the United States, of approximately 600,000 abdominal and head CT examinations annually performed in children under the age of 15 years, a rough estimate is that 500 of these individuals might ultimately die from cancer attributable to the CT radiation. CONCLUSION: The best available risk estimates suggest that pediatric CT will result in significantly increased lifetime radiation risk over adult CT, both because of the increased dose per milliampere-second, and the increased lifetime risk per unit dose. Lower milliampere-second settings can be used for children without significant loss of information. Although the risk-benefit balance is still strongly tilted toward benefit, because the frequency of pediatric CT examinations is rapidly increasing, estimates that quantitative lifetime radiation risks for children undergoing CT are not negligible may stimulate more active reduction of CT exposure settings in pediatric patients.     

Effect of bismuth breast shielding on radiation dose and image quality in coronary CT angiography

Background

Coronary computed tomographic angiography (CCTA) is associated with high radiation dose to the female breasts. Bismuth breast shielding offers the potential to significantly reduce dose to the breasts and nearby organs, but the magnitude of this reduction and its impact on image quality and radiation dose have not been evaluated.

Methods

Radiation doses from CCTA to critical organs were determined using metal-oxide-semiconductor field-effect transistors positioned in a customized anthropomorphic whole-body dosimetry verification phantom. Image noise and signal were measured in regions of interest (ROIs) including the coronary arteries.

Results

With bismuth shielding, breast radiation dose was reduced 46%-57% depending on breast size and scanning technique, with more moderate dose reduction to the heart, lungs, and esophagus. However, shielding significantly decreased image signal (by 14.6 HU) and contrast (by 28.4 HU), modestly but significantly increased image noise in ROIs in locations of coronary arteries, and decreased contrast-to-noise ratio by 20.9%.

Conclusions

While bismuth breast shielding can significantly decrease radiation dose to critical organs, it is associated with an increase in image noise, decrease in contrast-to-noise, and changes tissue attenuation characteristics in the location of the coronary arteries.