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.     

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.     

Absorbed radiation dose of the female breast during diagnostic multidetector chest CT and dose reduction with a tungsten-antimony composite breast shield: preliminary results

AIM: To determine the absorbed radiation dose to the female breast during chest computed tomography (CT), and whether a custom-designed breast shield can reduce that dose. MATERIALS AND METHODS: Bilateral breast phantoms were combined with an anthropomorphic torso phantom. Each breast phantom contained 20 thermoluminescent dosimeter (TLD) cavities. Eight cavities were used per phantom. Absorbed radiation was measured using TLD 100 s. Three-stacked TLDs comprised a set. Three sets of three TLDs were positioned at eight designated locations and three depths (surface; 1 cm; 4 cm). One set of three TLDs was positioned at eight additional designations, 1cm deep. Each breast was divided anatomically into quadrants. In total, 32 TLD sets/96 TLDs were deployed. The breast-torso phantom was consecutively imaged using a 16-detector array CT machine. Subsequently, 32 new TLD sets were similarly placed, the phantom re-imaged in a likewise manner, but with the application of a tungsten-antimony composite breast shield. TLD readings were averaged and calculated. RESULTS: Average absorbed radiation doses for unshielded right and left breast phantoms ranged from 13.83-19.36 mGy, and 14-20.47 mGy, respectively. The absorbed dose in the shielded right and left breast was reduced to 6.64-8.12 mGy, and 6.7-8.03 mGy, respectively. Average absorbed radiation doses based on the depth for the unshielded breasts ranged from 15.4-18.3 mGy. Shielding reduced this dose to 7-7.9 mGy. Unshielded absorbed radiation doses based on anatomic quadrants ranged from 17.5-18.9 mGy. Shielding reduced this dose to 7-7.5 mGy. CONCLUSIONS: The average absorbed radiation dose to the unshielded female breast phantom is approximately 14-20 mGy. An externally applied shield can reduce this absorbed dose by 56-61%.     

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.     

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.     

Female breast surface radiation exposure during FDG PET/CT examinations

BACKGROUND: The combined positron emission tomography (PET) and computed tomography (CT) scanners have been developed in which CT data can be used for both anatomical landmarks and attenuation correction of PET images. However, this modality potentially introduces more radiation burden to patients compared to conventional PET scanning as a result of the added radiation exposure received from CT examination. The purpose of our study was to determine the breast radiation doses of combined PET/CT examination. MATERIAL AND METHODS: Patients' superficial breast doses were calculated using thermoluminescence dosimeters (TLDs) placed onto the surface of the breasts. TLDs were positioned before FDG injection and removed after 24 h. We also determined the average superficial and glandular breast radiation doses from the anthropomorphic dosimetric phantom imaged using similar CT protocol (low dose) to the patients' study. RESULTS: The mean superficial breast dose of the breast skin measured from the PET/CT studies was 14.42+/-2.41 mGy. The average superficial and glandular breast doses of the anthropomorphic phantom measured from the low-dose CT was 9.50 mGy and 5.94 mGy, respectively. CONCLUSION: This study showed that radiation exposure to the breasts during PET/CT was higher than the recommended doses. Therefore, combined PET/CT scanning must be used for essential indications, particularly in women of reproductive age and preferentially a low-dose CT protocol should be implemented to avoid overexposure in such 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.     

Efficacy of breast shielding during CT of the head

In light of increasing frequency of CT examinations in the past decades, the aims of this prospective study were to investigate scatter radiation breast exposure in head CT and its dependence upon body constitution, and to assess the efficacy of lead shielding as a means of breast dose reduction. In 49 women referred to head CT for objective medical reasons one breast was covered with lead apron during CT scanning. Radiation doses were measured by use of thermoluminescent dosimeters, at skin of both breasts and over the apron. The doses were then compared as well as correlated to body mass index and meatus acusticus externus-to-dosimeter distance, respectively. Average exposure at the skin of the unshielded breast was 0.28 mGy (range 0.15–0.41 mGy), compared with 0.13 mGy (range 0.05–0.29 mGy) at the shielded breast. The doses showed a mean reduction by 57% due to lead shielding. At least half of breast exposure was imparted to the breast from outside, whereas the remainder results from internal scatter. The higher the body mass index, the higher the percentage of internal scatter in total breast dose. Although the level of scatter radiation to the breast is generally low during head CT examination, the use of lead cover enables recognizable further reduction of the exposure, and is recommended as a feasible and effective procedure of breast protection during CT of the head.     

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.     

Coronary artery calcium scoring with multislice computed tomography: in vitro assessment of a low tube voltage protocol

OBJECTIVES: We sought to compare an 80-kVp coronary calcium scoring protocol with the standard protocol of 120 kVp in terms of accuracy and reproducibility and to assess its dose reduction potential. MATERIALS AND METHOD: An anthropomorphic heart phantom with calcium cylinders was scanned with different tube currents at 80 kVp and 120 kVp using a 16-slice multislice CT (MSCT) scanner. An adapted threshold for 80 kVp was calculated. Accuracy and reproducibility for calcium mass, volume, and Agatston score were analyzed using F-tests. The radiation doses needed to produce artifact-free images were determined. RESULTS: Accuracy (measurement errors: mass 120 kVp +4.6%, mass 80 kVp -6.9%, volume 120 kVp +78.8%, volume 80 kVp +58.2%) and reproducibility (F-tests: mass: P = 0.4998, volume: P = 0.9168, Agatston: P = 0.5422) were comparable at both tube voltages. Avoiding the appearance of artificial lesions, a CTDI(w,eff) of 10.7 mGy was needed at 120 kVp versus 4.6 mGy at 80 kVp (dose reduction of 57%). CONCLUSIONS: Using an 80-kVp protocol in coronary calcium scoring, a relevant dose reduction is possible without compromising reproducibility and accuracy.     

MOSFET dosimetry for radiation dose assessment of bismuth shielding of the eye in children

OBJECTIVE: The purpose of our study was to measure radiation dose to the orbit during pediatric cranial CT with and without bismuth shielding using a novel dosimetry system. Cranial CT was performed on a pediatric anthropomorphic phantom, with and without bismuth eye shields. A solid-state metal oxide semiconductor field effect transistor (MOSFET) dosimeter was used to obtain real-time dose measurements. CONCLUSION: Bismuth shielding reduced radiation dose to the eye by up to 42%; shield artifact fell outside the diagnostic area of interest.     

Dedicated breast CT: radiation dose and image quality evaluation.

PURPOSE: To evaluate the feasibility of breast computed tomography (CT) in terms of radiation dose and image quality. MATERIALS AND METHODS: Validated Monte Carlo simulation techniques were used to estimate the average glandular dose (AGD). The calculated photon fluence at the detector for high-quality abdominal CT (120 kVp, 300 mAs, 5-mm section thickness) was the benchmark for assessing the milliampere seconds and corresponding radiation dose necessary for breast CT. Image noise was measured by using a 10-cm-diameter cylinder imaged with a clinical CT scanner at 10-300 mAs for 80, 100, and 120 kVp. A cadaveric breast was imaged in the coronal plane to approximate the acquisition geometry of a proposed breast CT scanner. RESULTS: The AGD for 80-kVp breast CT was comparable to that for two-view mammography of 5-cm breasts (compressed breast thickness). For thicker breasts, the breast CT dose was about one-third less than that for two-view mammography. The maximum dose at mammography assessed in 1-mm(3) voxels was far higher (20.0 mGy) than that at breast CT (5.4 mGy) for a typical 5-cm 50% glandular breast. CT images of an 8-cm cadaveric breast (AGD, 6.3 mGy) were subjectively superior to digital mammograms (AGD, 10.1 mGy) of the same specimen. CONCLUSION: The potential of high signal-to-noise ratio images with low anatomic noise, which are obtainable at dose levels comparable to those for mammography, suggests that dedicated breast CT should be studied further for its potential in breast cancer screening and diagnosis.     

Quantitative analysis of radiation dosage and image quality between digital breast tomosynthesis (DBT) with two-dimensional synthetic mammography and full-field digital mammography (FFDM)

PurposeCurrently in diagnostic setting for breast cancer, FFDM and DBT are performed conjunctively. However, performing two imaging modalities may increase radiation exposure by double. Two-dimensional reconstructed images created from DBT with 2DSM, has a potential to replace conventional FFDM in concerning both radiation dosage and image quality. With increasing concerns for individual radiation exposure, studies analyzing radiation dosage in breast imaging modalities are needed. This study compared radiation dosage and image quality between DBT + 2DSM versus FFDM.Methods and materials374 patients (mean age 52 years) who underwent both DBT and FFDM were retrospectively reviewed. Radiation dosage data were obtained by radiation dosage scoring and monitoring program Radimetrics (Bayer HealthCare, Whippany, NJ). Entrance dose and mean glandular doses in each breast were obtained for both modalities. To compare image quality of DBT + 2DSM and FFDM, a 5-point scoring system for lesion clarity was assessed. The parameters of radiation dosage (entrance dose, mean glandular dose) and image quality (lesion clarity scoring) were compared.ResultsFor entrance dose, DBT had lower mean dosage (14.8 mGy) compared with FFDM (21.8 mGy, p-value < 0.0001). Mean glandular doses for both breasts were lower in DBT (Left 1.74, Right 2.1) compared with FFDM (Left 2.85, Right 2.74, p-value < 0.0001). Lesion clarity score was higher in DBT with 2DSM (mean score 4.03) compared with FFDM (3.82, p-value < 0.0001).ConclusionDBT showed lower radiation entrance dose and mean glandular doses to both breasts compared with FFDM. DBT + 2DSM had better image quality than FFDM, suggesting that DBT with 2DSM has potential as an alternative to FFDM.     

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.     

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.     

Impact of the introduction of 16-row MDCT on image quality and patient dose: phantom study and multi-centre survey

The purpose was to compare the image quality and patient dose between 4- and 16-row MDCT units and to evaluate the dispersion of the dose delivered for common clinical examinations. Four 4- and 16-row MDCT units were used in the study. Image noise levels from images of a CatPhan phantom were compared for all units using a given CTDI_vol of 15.0±1.0 mGy. Standard acquisition protocols from ten centres, shifted from 4- to 16-row MDCT (plus one additional centre for 16-row MDCT), were compared for cerebral angiography and standard chest and abdomen examinations. In addition, the protocols used with 16-row MDCT units for diagnosis of the unstable shoulder and for cardiac examinations were also compared. The introduction of 16-MSCT units did not reduce the performance of the detectors. Concerning the acquisition protocols, a wide range in practice was observed for standard examinations; DLP varied from 800 to 5,120 mGy.cm, 130 to 860 mGy.cm, 410 to 1,790 mGy.cm and 850 to 2,500 mGy.cm for cerebral angiography, standard chest, standard abdomen and heart examinations, respectively.The introduction of 16-row MDCT did not, on average, increase the patient dose for standard chest and abdominal examinations. However, a significant dose increase has been observed for cerebral angiography. There is a wide dispersion in the doses delivered, especially for cardiac imaging.     

Radiation dose reduction to the male gonads during MDCT: the effectiveness of a lead shield

OBJECTIVE: Our study was designed to quantify the effect of a standard gonad shield on the testicular radiation exposure due to scatter during routine abdominopelvic MDCT. SUBJECTS AND METHODS: Routine abdominopelvic MDCT was performed in 34 patients with gonadal lead shielding and 32 patients without this shielding; the testes were not exposed to the direct beam during the examination. We estimated the testicular dose administered with thermoluminescent dosimetry, taking into account each patient's body weight and body mass index (BMI). RESULTS: With a 1-mm lead shield, the mean testicular dose was reduced from 2.40 to 0.32 mSv, a reduction of 87%. The difference was found to be statistically significant (p < 0.0001). No correlation between testicular dose and body weight or BMI was found. CONCLUSION: Shielding the male gonads reduces the testicular radiation dose during abdominopelvic MDCT significantly and can be recommended for routine use.     

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.     

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.     

Female breast radiation exposure during CT pulmonary angiography

OBJECTIVE: The objective of our study was to estimate the effective radiation dose to the female breast during CT pulmonary angiography compared with other routine diagnostic imaging techniques. MATERIALS AND METHODS: We retrospectively reviewed the demographic data of patients who underwent CT pulmonary angiography between May 2000 and December 2002, the diagnostic yield of those studies, and the estimated effective radiation dose to the breast incurred during CT. The estimated effective radiation dose was calculated using the ImPACT CT (Impact Performance Assessment of CT) dosimetry calculator and the CT dose index (CTDI) and was compared with the average glandular dose for two-view screening mammography. RESULTS: During the study period, 1,325 CT pulmonary angiograms were obtained. Sixty percent (797) of the scans were obtained on female patients. The mean age of scanned females was 52.5 years (range, 15-93 years). Of the studies performed in females, 401 (50.31%) were negative, 151 (18.95%) were nondiagnostic, and 245 (30.74%) were positive for pulmonary thromboembolism. The calculated effective minimum dose to the breast of an average 60-kg woman during CT was 2.0 rad (20 mGy) per breast compared with an average glandular dose of 0.300 rad (3 mGy) for standard two-view screening mammography. CONCLUSION: CT pulmonary angiography delivers a minimum radiation dose of 2.0 rad (20 mGy) to the breasts of an average-sized woman. This greatly exceeds the American College of Radiology recommendation of < or = 0.300 rad (3 mGy) or less for standard two-view mammography. The potential latent carcinogenic effects of such radiation exposure at this time remain unknown. We encourage the judicious use of CT pulmonary angiography and lower doses and nonionizing radiation alternatives when appropriate.