Organ-specific Radiation Doses Research Articles

Inaccurate table height setting affects the organ-specific radiation dose in computed tomography

PurposeWe aimed to prove that the locally absorbed doses in tissues and organs are affected by inaccurate table height in computed tomography. Materials and MethodsWe compared the volume CT dose index (CTDIvol) and the absorbed doses using an anthropomorphic phantom combined with a breast phantom. The phantom was set at the gantry center, from which the table height was changed every 20 mm between–40 mm and 40 mm. Data acquisition was performed using auto table height correction (AHC) for each table height. The CTDIvol was obtained from the CT console and the tube current value for each image slice (DICOM tag: 0018, 1151). The absorbed dose was measured by a glass dosimeter that was implanted at various positions in the phantom. ResultsThe tube current values in the lung were lower at a table height of + 40 mm than those at other heights. The CTDIvol was slightly lower at + 40 mm than at the center (12.78 mGy vs. 13.42 mGy, p < 0.05). The CTDIvol values were almost the same at the other table heights (13.30–13.40 mGy). The absorbed doses at the lens and mammary gland were significantly different from those at the gantry center (−27.27%–17.77% and –24.31%–12.83%, respectively). Compared with the center, both the lens and mammary gland had higher absorbed doses at a table height of –40 mm. ConclusionThe absorbed dose was affected by the table height, but the CTDIvol was maintained by AHC. The operator should appropriately position patients even when using AHC.

1275Lifetime cancer risks from occupational radiation exposure among workers at interventional radiology departments

Abstract Background Interventional medical radiation workers represent an under-studied population worldwide, although they receive relatively high occupational radiation doses. This study aimed to estimate the lifetime cancer risk from occupational radiation exposure among workers at interventional radiology departments. Methods A field survey of interventional medical workers in nationwide branches of the Korean Society of Interventional Radiology was conducted in 2017. Organ-specific radiation doses were estimated using national dose registry data and conversion coefficients provided by the International Commission on Radiological Protection. Lifetime attributable risk (LAR) and lifetime fractional risk (LFR) were calculated based on realistic exposure scenarios using a radiation risk assessment tool. Results LARs from occupational radiation exposure until the age of retirement for all cancers combined were 338 (90.3-796.1), 121 (33.5-288.7), and 156 (41.1-390.6) per 100,000 individuals for male radiologists, male radiologic technologists, and female nurses, respectively. LFR for all cancers combined ranged from 0.22% (0.06-0.53) to 0.63% (0.17-1.47). Regarding the organ site, the highest LAR and LFR among all groups were observed for thyroid cancer. Conclusions This study provides timely evidence of potential cancer burden from the current levels of occupational radiation exposure among workers at interventional radiology departments. The risks varied by occupational groups, and workers, particularly interventional radiologists, need to be carefully monitored for radiation. Key messages We projected lifetime cancer risks from occupational radiation exposure among workers at interventional radiology departments in South Korea. Particularly, interventional radiologists, should be prioritized for careful protection from the potential health risks of occupational radiation exposure.

A Preliminary Study of Personalized Head CT Scan in Pediatric Patients.

Objectives:In the present study, we introduced a practical approach to quantify organ-specific radiation doses and investigated whether low-dose head circumference (HC)-based protocols for non-enhanced head computed tomography (CT) could reduce organs-specific radiation dose in pediatric patients while maintaining high image quality.Methods:A total of 83 pediatric patients were prospectively recruited. Without limits to the HC, 15 patients were selected as a convention group (CON group) and underwent non-enhanced head CT scan with standard-dose protocols (tube current-time products of 250mAs). Low-dose group (LD group), including remaining 68 pediatrics were divided into 3 subgroups based on the HC: 54.1-57.0 cm for LD200mAs group (HC-based protocols of 200mAs), 51.1-54.0 cm for LD150mAs group (HC-based protocols of 150mAs), 48.1-51.0 cm for LD100mAs group (HC-based protocols of 100mAs). Subjective and objective image quality was evaluated and measured by 2 experienced radiologists. Radimetrics was used to calculate organs-specific radiation dose, including the brain, eye lenses, and salivary glands.Results:In CON250mAs group, radiation doses in the brain and salivary glands were conversely correlated with HC, and pediatric patients with smaller HC received higher organs-specific radiation dose. Reducing tube current-time product from 250 to 100mAs could significantly reduce the organ-specific radiation dose. The subjective image quality score ≥ 3.0 is acceptable for diagnosis purposes. The signal to noise ratio (SNR) and the contrast to noise ratio (CNR) of bilateral thalamus and centrum semiovale in 3 LD subgroups were not statistically different compared with the CON group.Conclusion:Our research indicated that low-dose HC-based protocols of non-enhanced head CT scan can evidently reduce the organ-specific radiation doses, while maintaining high image quality. HC can serve as a vital tool to guide personalized low-dose head CT scan for pediatric patients.

Lifetime cancer risks from occupational radiation exposure among workers at interventional radiology departments.

Interventional medical radiation workers represent an under-studied population worldwide, although they receive relatively high occupational radiation doses. This study aimed to estimate the lifetime cancer risk from occupational radiation exposure among workers at interventional radiology departments. A field survey of interventional medical workers in nationwide branches of the Korean Society of Interventional Radiology was conducted in 2017. Organ-specific radiation doses were estimated using national dose registry data and conversion coefficients provided by the International Commission on Radiological Protection. Lifetime attributable risk (LAR) and lifetime fractional risk (LFR) were calculated based on realistic exposure scenarios using a radiation risk assessment tool. LARs from occupational radiation exposure until the age of retirement for all cancers combined were 338 (90.3-796.1), 121 (33.5-288.7), and 156 (41.1-390.6) per 100,000 individuals for male radiologists, male radiologic technologists, and female nurses, respectively. LFR for all cancers combined ranged from 0.22% (0.06-0.53) to 0.63% (0.17-1.47). Regarding the organ site, the highest LAR and LFR among all groups were observed for thyroid cancer. This study provides timely evidence of potential cancer burden from the current levels of occupational radiation exposure among workers at interventional radiology departments. The risks varied by occupational groups, and workers, particularly interventional radiologists, need to be carefully monitored for radiation.

Benefits of Low-Dose CT Scan of Head for Patients With Intracranial Hemorrhage.

Objectives:For patients with intracranial hemorrhage (ICH), routine follow-up computed tomography (CT) scans are typically required to monitor the progression of intracranial pathology. Remarkable levels of radiation exposure are accumulated during repeated CT scan. However, the effects and associated risks have still remained elusive. This study presented an effective approach to quantify organ-specific radiation dose of repeated CT scans of head for patients with ICH. We also indicated whether a low-dose CT scan may reduce radiation exposure and keep the image quality highly acceptable for diagnosis.Methods:Herein, 72 patients with a history of ICH were recruited. The patients were divided into 4 groups and underwent CT scan of head with different tube current–time products (250, 200, 150, and 100 mAs). Two experienced radiologists visually rated scores of quality of images according to objective image noise, sharpness, diagnostic acceptability, and artifacts due to physiological noise on the same workstation. Organ-/tissue-specific radiation doses were analyzed using Radimetrics.Results:In conventional CT scan group, signal to noise ratio (SNR) and contrast to noise ratio (CNR) of ICH images were significantly higher than those in normal brain structures. Reducing the tube current–time product may decrease the image quality. However, the predilection sites for ICH could be clearly identified. The SNR and CNR in the predilection sites for ICH were notably higher than other areas. The brain, eye lenses, and salivary glands received the highest radiation dose. Reducing tube current–time product from 250 to 100 mA can significantly reduce the radiation dose.Discussion:We demonstrated that low-dose CT scan of head can still provide reasonable images for diagnosing ICH. The radiation dose can be reduced to ∼45% of the conventional CT scan group.

Radiation Dosimetry of Inhaled Radioactive Aerosols: CFPD and MCNP Transport Simulations of Radionuclides in the Lung

Despite extensive efforts in studying radioactive aerosols, including the transmission of radionuclides in different chemical matrices throughout the body, the internal organ-specific radiation dose due to inhaled radioactive aerosols has largely relied on experimental deposition data and simplified human phantoms. Computational fluid-particle dynamics (CFPD) has proven to be a reliable tool in characterizing aerosol transport in the upper airways, while Monte Carlo based radiation codes allow accurate simulation of radiation transport. The objective of this study is to numerically assess the radiation dosimetry due to particles decaying in the respiratory tract from environmental radioactive exposures by coupling CFPD with Monte Carlo N-Particle code, version 6 (MCNP6). A physiologically realistic mouth-lung model extending to the bifurcation generation G9 was used to simulate airflow and particle transport within the respiratory tract. Polydisperse aerosols with different distributions were considered, and deposition distribution of the inhaled aerosols on the internal airway walls was quantified. The deposition mapping of radioactive aerosols was then registered to the respiratory tract of an image-based whole-body adult male model (VIP-Man) to simulate radiation transport and energy deposition. Computer codes were developed for geometry visualization, spatial normalization, and source card definition in MCNP6. Spatial distributions of internal radiation dosimetry were compared for different radionuclides (131I, 134,137Cs, 90Sr-90Y, 103Ru and 239,240Pu) in terms of the radiation fluence, energy deposition density, and dose per decay.

This Month in Pediatric Urology

No AccessJournal of UrologyThis Month in Pediatric Urology1 Oct 2013This Month in Pediatric Urology Michael L. Ritchey Michael L. RitcheyMichael L. Ritchey More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.07.008AboutFull TextPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "This Month in Pediatric Urology." The Journal of Urology, 190(4), pp. 1153–1154 References 1 : Two-step Fowler-Stephens orchiopexy for intra-abdominal testes: a 28-year single institution experience. J Urol2013; 190: 1371. Link, Google Scholar 2 : Transcutaneous parasacral electrical neural stimulation in children with primary monosymptomatic enuresis: a prospective randomized clinical trial. J Urol2013; 190: 1359. Google Scholar 3 : National trends in augmentation cystoplasty in the 2000s and factors associated with patient outcomes. J Urol2013; 190: 1352. Link, Google Scholar 4 : Effective and organ specific radiation doses from videourodynamics in children. J Urol2013; 190: 1364. Link, Google Scholar © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 190Issue 4October 2013Page: 1153-1154 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Michael L. Ritchey More articles by this author Expand All Advertisement PDF downloadLoading ...

Effective and Organ Specific Radiation Doses from Videourodynamics in Children

Effective and organ specific doses of ionizing radiation during videourodynamics are unknown. We estimated radiation exposure in children undergoing videourodynamics, and identified patient and examination factors that contribute to higher dosing. Fluoroscopy data were collected from consecutive patients undergoing videourodynamics. Documented dose metrics were used to calculate entrance skin dose after applying a series of correction factors. Effective doses and organ specific doses (ovaries/testes) were estimated from entrance skin dose using Monte Carlo methods on a mathematical anthropomorphic phantom (ages 0, 1, 5, 10 and 15 years). Regression analysis was performed to determine patient and procedural factors associated with higher dosing. A total of 100 children (45% male, mean ± SD age 9.3 ± 5.7 years) were studied. Diagnoses included neurogenic bladder (73%), anatomical abnormality (14%) and functional/nonneurogenic disorder (13%). Mean fluoroscopy time was 0.17 ± 0.12 minutes. Mean age adjusted entrance skin dose, effective dose, and testis and ovary doses were 2.18 ± 2.00 mGy, 0.07 ± 0.05 mSv, 0.09 ± 0.10 mGy and 0.20 ± 0.13 mGy, respectively. On univariate analysis age, height, weight, body mass index, bladder capacity and fluoroscopy time were associated with effective dose. On multivariate adjusted analysis, body mass index, bladder capacity and fluoroscopy time were independently associated with effective dose. The average effective dose of ionizing radiation from videourodynamics was less compared to voiding cystourethrogram dose reported in the literature. Greater fluoroscopy time, body mass index and bladder capacity are independently associated with higher dosing.

Obesity Triples the Radiation Dose of Stone Protocol Computerized Tomography

Patients with recurrent nephrolithiasis are often evaluated and followed with computerized tomography. Obesity is a risk factor for nephrolithiasis. We evaluated the radiation dose of computerized tomography in obese and nonobese adults. We scanned a validated, anthropomorphic male phantom according to our institutional renal stone evaluation protocol. The obese model consisted of the phantom wrapped in 2 Custom Fat Layers (CIRS, Norfolk, Virginia), which have been verified to have the same radiographic tissue density as fat. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations in the phantoms to measure organ specific radiation doses. The nonobese and obese models have an approximate body mass index of 24 and 30 kg/m(2), respectively. Three runs of renal stone protocol computerized tomography were performed on each phantom under automatic tube current modulation. Organ specific absorbed doses were measured and effective doses were calculated. The bone marrow of each model received the highest dose and the skin received the second highest dose. The mean ± SD effective dose for the nonobese and obese models was 3.04 ± 0.34 and 10.22 ± 0.50 mSv, respectively (p <0.0001). The effective dose of stone protocol computerized tomography in obese patients is more than threefold higher than the dose in nonobese patients using automatic tube current modulation. The implication of this finding extends beyond the urological stone population and adds to our understanding of radiation exposure from medical imaging.

Abstract 9434: Cancer Risk Estimation from Cardiac Catheterization in Children with Heart Disease

Background: Radiation exposure is a concern in children because of their high radiosensitivity, small body size, and cancer risk. We evaluated the effective dose (ED) of radiation from cardiac catheterization to estimate the lifetime attributable risk (LAR) of cancer. Methods: Organ specific radiation doses were measured from conventional angiographic projections using dosimeters placed in 2 anthropomorphic phantoms representing 1 and 5 years of age. We used a proprietary radiation dose calculator developed from the phantom data to determine ED using catheterization fluoroscopy and cineangiography times for 3 patient cohorts (age &lt; 5yrs): those post Norwood operation, heart transplant and ASD device closure. Age- and sex-specific LARs of cancer above baseline were estimated using the approach of the Committee on Biological Effects of Ionizing Radiation (BEIR VII). Results: Eligible children undergoing catheterization between July 2005 and August 2011 were included in the analysis. The cohort consisted of 67 subjects post-Norwood (191 catheterizations, median time since Norwood: 161 days), 10 post-transplant (91 catheterizations, median time since transplant: 88 days) and 12 post-ASD closure (median age at catheterization 3.9 years). ED and LAR of cancer attributable to catheterization are presented for a single catheterization and for cumulative exposure in those cohorts that undergo repeat procedures (table). LAR of cancer varied depending on age at exposure, gender and ED and was &gt; 0.15% for 80% of all procedures. Adjusting for ED and age at exposure, the median LAR of cancer was twice as high in females vs. males (p&lt;0.01). Conclusion: Cardiac catheterization can result in radiation exposure that increases LAR of cancer to up to 6% above baseline in select populations. These data highlight the need for limiting radiation dose in females, children with normal life expectancy and children that require repeat catheterizations.

Cancer Mortality Following Radiotherapy for Benign Gynecologic Disorders

The purpose of this study is to quantify cancer mortality in relationship to organ-specific radiation dose among women irradiated for benign gynecologic disorders. Included in this study are 12,955 women treated for benign gynecologic disorders at hospitals in the Northeastern U.S. between 1925 and 1965; 9,770 women treated by radiation and 3,186 women treated by other methods. The average age at treatment was 45.9 years (range, 13-88 years), and the average follow-up period was 30.1 years (maximum, 69.9 years). Radiation doses to organs and active bone marrow were reconstructed by medical physicists using original radiotherapy records. The highest doses were received by the uterine cervix (median, 120 Gy) and uterine corpus (median, 34 Gy), followed by the bladder, rectum and colon (median, 1.7-7.2 Gy), with other abdominal organs receiving median doses ≤1 Gy and organs in the chest and head receiving doses <0.1 Gy. Standardized mortality rate ratios relative to the general U.S. population were calculated. Radiation-related risks were estimated in internal analyses using Poisson regression models. Mortality was significantly elevated among irradiated women for cancers of the uterine corpus, ovary, bladder, rectum, colon and brain, as well as for leukemia (exclusive of chronic lymphocytic leukemia) but not for cancer of the cervix, Hodgkin or non-Hodgkin lymphoma, multiple myeloma, or chronic lymphocytic leukemia. Evidence of a dose-response was seen for cancers of the ovary [excess relative risk (ERR) = 0.31/Gy, P < 0.001], bladder (ERR = 0.21/Gy, P = 0.02) and rectum (ERR = 0.23/Gy, P = 0.05) and suggested for colon (ERR = 0.09/Gy, P = 0.10), but not for cancers of the uterine corpus or brain nor for non-chronic lymphocytic leukemia. Relative risks of mortality due to cancers of the stomach, pancreas, liver and kidney were close to 1.0, with no evidence of dose-response over the range of 0-1.5 Gy. Breast cancer was not significantly associated with dose to the breast or ovary. Mortality due to cancers of heavily irradiated organs remained elevated up to 40 years after irradiation. Significantly elevated radiation-related risk was seen for cancers of organs proximal to the radiation source or fields (bladder, rectum and ovary), as well as for non-chronic lymphocytic leukemia. Our results corroborate those from previous studies that suggest that cells of the uterine cervix and lymphopoietic system are relatively resistant to the carcinogenic effects of radiation. Studies of women irradiated for benign gynecologic disorders, together with studies of women treated with higher doses of radiation for uterine cancers, provide quantitative information on cancer risks associated with a broad range of pelvic radiation exposures.

2296 ORGAN SPECIFIC RADIATION DOSE AND EFFECTIVE DOSE FOR RENAL STONE PROTOCOL COMPUTERIZED TOMOGRAPHY (CT)

You have accessJournal of UrologyStone Disease: Basic Research II1 Apr 20122296 ORGAN SPECIFIC RADIATION DOSE AND EFFECTIVE DOSE FOR RENAL STONE PROTOCOL COMPUTERIZED TOMOGRAPHY (CT) Muhammad W. Iqbal, Agnes J. Wang, Giao Nguyen, Gastón M. Astroza, Greta Toncheva, Natalie Januzis, Carolyn Lowry, Amy M. Neville, Michael N. Ferrandino, Terry T. Yoshizumi, Glenn M. Preminger, and Michael E. Lipkin Muhammad W. IqbalMuhammad W. Iqbal Durham, NC More articles by this author , Agnes J. WangAgnes J. Wang Durham, NC More articles by this author , Giao NguyenGiao Nguyen Durham, NC More articles by this author , Gastón M. AstrozaGastón M. Astroza Durham, NC More articles by this author , Greta TonchevaGreta Toncheva Durham, NC More articles by this author , Natalie JanuzisNatalie Januzis Durham, NC More articles by this author , Carolyn LowryCarolyn Lowry Durham, NC More articles by this author , Amy M. NevilleAmy M. Neville Durham, NC More articles by this author , Michael N. FerrandinoMichael N. Ferrandino Durham, NC More articles by this author , Terry T. YoshizumiTerry T. Yoshizumi Durham, NC More articles by this author , Glenn M. PremingerGlenn M. Preminger Durham, NC More articles by this author , and Michael E. LipkinMichael E. Lipkin Durham, NC More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.2476AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Patients with nephrolithiasis are at increased risk for radiation exposure. The amount of radiation these patients are exposed to from a CT scan is evolving, as protocols evolve. The concern over increased patient radiation exposure is related to the risk of developing a malignancy. Effective dose (ED) is a value that relates the amount of radiation absorbed to the risk of developing a malignancy. This study was done to measure organ specific radiation doses and determine the effective dose for a non-contrast CT abdomen/pelvis for the evaluation of nephrolithiasis performed at our institution. METHODS An anthropomorphic, adult male phantom validated for human organ dosimetry, was placed on a GE 64-slice Volume CT scanner in prone position. A non-contrast CT abdomen/pelvis was performed with the following settings: tube voltage 120 kV, tube current 700 mA, pitch 1.375:1, noise index 17.5. High sensitivity metal oxide semiconductor field effect transistors (MOSFET) dosimeters were placed at 20 organ locations and used to measure organ radiation doses. The organ doses were multiplied by their tissue weighting factors(Wt) and summed to determine the effective dose. Tissue weighting factors are obtained from the International Commission on Radiological Protection, publication (ICRP) 103. RESULTS The bone marrow was exposed to the highest absorbed dose, with cumulative dose of 13.4 milligray (mGy), followed by the skin entrance, 7.23 mGy and bladder 6.60 mGy. The ED for the renal stone CT was 3.04 milli Sieverts(mSv). CONCLUSIONS Radiation from CT scans contributes to the overall radiation exposure for patients with nephrolithiasis. A non-contrast CT performed for the evaluation of nephrolithiasis results in an effective dose of 3.04 mSv. Accurate determination of ED enables patients and clinicians to make informed decisions regarding CT imaging and allows calculation of cumulative ED in this high risk population. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e926-e927 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Muhammad W. Iqbal Durham, NC More articles by this author Agnes J. Wang Durham, NC More articles by this author Giao Nguyen Durham, NC More articles by this author Gastón M. Astroza Durham, NC More articles by this author Greta Toncheva Durham, NC More articles by this author Natalie Januzis Durham, NC More articles by this author Carolyn Lowry Durham, NC More articles by this author Amy M. Neville Durham, NC More articles by this author Michael N. Ferrandino Durham, NC More articles by this author Terry T. Yoshizumi Durham, NC More articles by this author Glenn M. Preminger Durham, NC More articles by this author Michael E. Lipkin Durham, NC More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

2196 OBESITY TRIPLES THE RADIATION EXPOSURE OF STONE PROTOCOL CT

You have accessJournal of UrologyImaging/Radiology: Uroradiology II1 Apr 20122196 OBESITY TRIPLES THE RADIATION EXPOSURE OF STONE PROTOCOL CT Zachariah G. Goldsmith, Agnes Wang, Chu Wang, Giao Nguyen, Carolyn Lowry, Gastón M. Astroza, Muhammad W. Iqbal, Michael N. Ferrandino, Leo Ding, Matthew D. Belley, Greta Toncheva, Terry T. Yoshizumi, Glenn M. Preminger, and Michael E. Lipkin Zachariah G. GoldsmithZachariah G. Goldsmith Durham, NC More articles by this author , Agnes WangAgnes Wang Durham, NC More articles by this author , Chu WangChu Wang Durham, NC More articles by this author , Giao NguyenGiao Nguyen Durham, NC More articles by this author , Carolyn LowryCarolyn Lowry Durham, NC More articles by this author , Gastón M. AstrozaGastón M. Astroza Durham, NC More articles by this author , Muhammad W. IqbalMuhammad W. Iqbal Durham, NC More articles by this author , Michael N. FerrandinoMichael N. Ferrandino Durham, NC More articles by this author , Leo DingLeo Ding Durham, NC More articles by this author , Matthew D. BelleyMatthew D. Belley Durham, NC More articles by this author , Greta TonchevaGreta Toncheva Durham, NC More articles by this author , Terry T. YoshizumiTerry T. Yoshizumi Durham, NC More articles by this author , Glenn M. PremingerGlenn M. Preminger Durham, NC More articles by this author , and Michael E. LipkinMichael E. Lipkin Durham, NC More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.2370AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Computed tomography (CT) utilization over the last three decades has exponentially increased. In urology, stone patients constitute a high-risk population for radiation exposure, as CT is frequently employed to diagnose and follow stone formers. Paralleling this growth in CT use is the epidemic of obesity. We theorize that there is a different amount of energy required to penetrate the tissues in an obese compared to a non-obese adult. METHODS A validated, anthropomorphic male phantom (Model 701-D; CIRS, Inc, Norfolk, VA) was scanned on a General Electric Lightspeed 64-slice Volume CT according to our institutional protocol. The obese model consisted of the phantom wrapped in two Custom Fat Layers for Model 701-D, E1397-1 and E1397-2, which have been verified to have the same radiographic tissue density as fat. High sensitivity metal oxide semiconductor field effect transistors (MOSFET) dosimeters (Best Medical, Ottawa, Canada) were placed at 20 organ locations in the phantom and used to measure organ specific radiation doses. The non-obese model has a BMI of 24 kg/m2 while the obese model has a BMI of 30 kg/m2. Three runs of the renal stone protocol CT were performed on each phantom, obese and non-obese. Organ-specific doses were measured and the effective doses were calculated. A paired student's t-test was used for statistical analysis. RESULTS For both models, the bone marrow received the highest dose, with the skin receiving the second highest dose. The mean effective dose for the non-obese model was 3.04 ± 0.34 milli-sieverts (mSv), while the effective dose for the obese model was 9.67 ± 0.44 mSv, P<0.0001. CONCLUSIONS The effective dose of stone protocol CT for obese patients is more than three times the dose for a non-obese patient. To our knowledge, this has not been reported before in the literature. When ordering CTs, the BMI of the patient should also be taken into consideration. The implication of this finding extends beyond the urologic stone population and adds to our understanding of radiation exposure from medical imaging. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e885-e886 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Zachariah G. Goldsmith Durham, NC More articles by this author Agnes Wang Durham, NC More articles by this author Chu Wang Durham, NC More articles by this author Giao Nguyen Durham, NC More articles by this author Carolyn Lowry Durham, NC More articles by this author Gastón M. Astroza Durham, NC More articles by this author Muhammad W. Iqbal Durham, NC More articles by this author Michael N. Ferrandino Durham, NC More articles by this author Leo Ding Durham, NC More articles by this author Matthew D. Belley Durham, NC More articles by this author Greta Toncheva Durham, NC More articles by this author Terry T. Yoshizumi Durham, NC More articles by this author Glenn M. Preminger Durham, NC More articles by this author Michael E. Lipkin Durham, NC More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Evaluation of S-values and dose distributions for90Y,131I,166Ho, and188Re in seven lobes of the rat liver

Rats have been widely used in radionuclide therapy research for the treatment of hepatocellular carcinoma (HCC). This has created the need to assess rat liver absorbed radiation dose. In most dose estimation studies, the rat liver is considered as a homogeneous integrated target organ with a tissue composition assumed to be similar to that of human liver tissue. However, the rat liver is composed of several lobes having different anatomical and chemical characteristics. To assess the overall impact on rat liver dose calculation, the authors use a new voxel-based rat model with identified suborgan regions of the liver.The liver in the original cryosectional color images was manually segmented into seven individual lobes and subsequently integrated into a voxel-based computational rat model. Photon and electron particle transport was simulated using the MCNPX Monte Carlo code to calculate absorbed fractions and S-values for (90)Y, (131)I, (166)Ho, and (188)Re for the seven liver lobes. The effect of chemical composition on organ-specific absorbed dose was investigated by changing the chemical composition of the voxel filling liver material. Radionuclide-specific absorbed doses at the voxel level were further assessed for a small spherical hepatic tumor.The self-absorbed dose for different liver lobes varied depending on their respective masses. A maximum difference of 3.5% was observed for the liver self-absorbed fraction between rat and human tissues for photon energies below 100 keV. (166)Ho and (188)Re produce a uniformly distributed high dose in the tumor and relatively low absorbed dose for surrounding tissues.The authors evaluated rat liver radiation doses from various radionuclides used in HCC treatments using a realistic computational rat model. This work contributes to a better understanding of all aspects influencing radiation transport in organ-specific radiation dose evaluation for preclinical therapy studies, from tissue composition to organ morphology and activity distribution.

Determination of Patient Radiation Dose During Ureteroscopic Treatment of Urolithiasis Using a Validated Model

We measured organ specific radiation dose rates and determined effective dose rates during simulated ureteroscopy using a validated model. To calculate the effective dose, patients were exposed to ureteroscopic management of stones at our institution. A validated anthropomorphic male phantom was placed on a fluoroscopy table and underwent simulated ureteroscopy. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ sites in the phantom and used to measure organ specific radiation doses. These dose rates were multiplied by the appropriate tissue weighting factor and summed to calculate effective dose rates. Also, we retrospectively reviewed the charts of patients who underwent ureteroscopy at our institution. A total of 30 nonobese males with data on fluoroscopy time were included in analysis. The median effective dose was determined by multiplying median fluoroscopy time by the effective dose rate. The skin entrance was exposed to the highest absorbed dose rate, followed by the small intestine (mean ± SD 0.3286 ± 0.0054 and 0.1882 ± 0.0194 mGy per second, respectively). The mean effective dose rate was 0.024 ± 0.0019 mSv per second. Median fluoroscopy time was 46.95 seconds (range 12.9 to 298.8). The median effective dose was 1.13 mSv (range 0.31 to 7.17). The fluoroscopy used during ureteroscopy contributes to overall radiation exposure in patients with nephrolithiasis. Nonobese males are exposed to a median of 1.13 mSv during ureteroscopy, similar to that of abdominopelvic x-ray. More data are needed to determine clinical implications but urologists must be aware and decrease patient radiation during ureteroscopy.

Estimates of the potential risk of radiation-related cancer from screening in the UK

Estimates of the potential risk of radiation-related cancer from screening in the UK

Organ-Specific Radiation Dose Rates and Effective Dose Rates During Percutaneous Nephrolithotomy

Radiation exposure during medical procedures continues to be an increasing concern for physicians and patients. We determined organ-specific dose rates and calculated effective dose rates during right and left percutaneous nephrolithotomy (PCNL) using a validated phantom model. A validated anthropomorphic adult male phantom was placed prone on an operating room table. Metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations in the model and were used to measure the organ dosages. A portable C-arm was used to provide continuous fluoroscopy for three 10 minute runs each to simulate a left and right PCNL. Organ dose rate (mGy/s) was determined by dividing organ dose by fluoroscopy time. The organ dose rates were multiplied by their tissue weighting factor and summed to determine effective dose rate (EDR) (mSv/s). Two-dimensional radiation distribution in the abdomen during a left-sided PCNL was visually determined using radiochromic film. The EDR for a left PCNL was 0.021 mSv/s ± 0.0008. The EDR for a right PCNL was 0.014 mSv/s ± 0.0004. The skin entrance was exposed to the greatest amount of radiation during left and right PCNL, 0.24 mGy/s and 0.26 mGy/s, respectively. Radiochromic film demonstrates visually the nonuniform dose distribution as the x-ray beam enters through the skin from the radiation source. The effective dose rate is higher for a left-sided PCNL compared with a right-sided PCNL. The distribution of radiation exposure during PCNL is not uniform. Further studies are needed to determine the long-term implications of these radiation doses during percutaneous stone removal.

Radiation Exposure During Pediatric Videourodynamics

Videourodynamics is useful for evaluating and treating neurological disorders in children. Traditional urodynamic parameters can be obtained while simultaneous visualization of the urinary system can reveal anatomical anomalies. This additional information comes at the cost of radiation exposure to the child. We characterized radiation exposure from videourodynamics. We reviewed all recent videourodynamic studies and recorded patient demographics, urological diagnoses, physical attributes, total fluoroscopy time, total radiation exposure in mGy, bladder capacity and the number of filling cycles performed. Multivariate linear regression was used to identify patient factors that independently influenced total radiation exposure. A total of 64 videourodynamic studies were performed in 34 female and 28 male patients with a mean age of 8.6 years (95% CI 7.2-10.0). The most common diagnosis was neurogenic bladder in 40 patients, although 49 had multiple diagnoses. Mean total fluoroscopy time was 1.8 minutes (95% CI 1.4-2.1) and mean total radiation exposure was 10 mGy (95% CI 7.5-13.3). On multivariate linear regression patient weight and bladder capacity were the only independent predictors of total radiation exposure. Videourodynamics entail significant radiation exposure. Patient weight and bladder capacity were independent predictors of total radiation exposure. Physician awareness of radiation exposure may result in the judicious use of fluoroscopy and aid in counseling parents on the risk of videourodynamics. Further research is needed to quantify organ specific doses of radiation due to medical imaging in children and the associated cancer risks.

Surveillance Computed Tomography Scans for Patients With Lymphoma: Is the Risk Worth the Benefits?

Concerns regarding the risks of cancer and cancer-related death as a result of radiation from computed tomography (CT) scans and the lack of data demonstrating a survival advantage for surveillance CT scans following lymphoma therapy have raised questions regarding their benefit. We compared the radiation-related lifetime cancer incidence (LCI) and mortality risks (LCMRs) associated with CT scans for staging and surveillance of non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma (HL) with the cumulative probability of lymphoma death (CPLD) during surveillance. The LCI and LCMR were calculated using published estimates of the cumulative organ-specific radiation doses from full-body CT scans and sex-, age-, and organ-dependent cancer risks per 0.1 Gy provided by the Biologic Effects of Ionizing Radiations VII report. Surveillance, Epidemiology, and End Results (SEER) data were used to identify cases between 2000 and 2006 from 17 SEER registries and calculate CPLD for specified cohorts. For a 70-year-old patient, a single full-body CT examination is associated with a LCI of 0.044% and 0.057%, and a LCMR of 0.032% and 0.044% for males and females, respectively. For 20-year-old patients the LCMRs were 0.071% for men and 0.108% for women. The LCI and LCMR were lower for males and were markedly less than the CPLD at 5 years for most lymphoma subtypes, but relevant for younger women with HL. Although the LCMR from CT scans is small compared with lymphoma-related deaths for most subgroups, these data should be discussed with patients in formulating plans for surveillance following lymphoma therapy.

Projected Cancer Risks From Computed Tomographic Scans Performed in the United States in 2007

The use of computed tomographic (CT) scans in the United States (US) has increased more than 3-fold since 1993 to approximately 70 million scans annually. Despite the great medical benefits, there is concern about the potential radiation-related cancer risk. We conducted detailed estimates of the future cancer risks from current CT scan use in the US according to age, sex, and scan type. Risk models based on the National Research Council's "Biological Effects of Ionizing Radiation" report and organ-specific radiation doses derived from a national survey were used to estimate age-specific cancer risks for each scan type. These models were combined with age- and sex-specific scan frequencies for the US in 2007 obtained from survey and insurance claims data. We estimated the mean number of radiation-related incident cancers with 95% uncertainty limits (UL) using Monte Carlo simulations. Overall, we estimated that approximately 29 000 (95% UL, 15 000-45 000) future cancers could be related to CT scans performed in the US in 2007. The largest contributions were from scans of the abdomen and pelvis (n = 14 000) (95% UL, 6900-25 000), chest (n = 4100) (95% UL, 1900-8100), and head (n = 4000) (95% UL, 1100-8700), as well as from chest CT angiography (n = 2700) (95% UL, 1300-5000). One-third of the projected cancers were due to scans performed at the ages of 35 to 54 years compared with 15% due to scans performed at ages younger than 18 years, and 66% were in females. These detailed estimates highlight several areas of CT scan use that make large contributions to the total cancer risk, including several scan types and age groups with a high frequency of use or scans involving relatively high doses, in which risk-reduction efforts may be warranted.