Lifetime Attributable Risk Of Cancer Research Articles

Wednesday, September 26, 2018 10:35 AM – 12:00 PM Cervical Spine Trauma: 25. CT imaging of the spine in pediatric trauma patients: prevalence of fractures and mechanisms of injury

BACKGROUND CONTEXT Computed tomography (CT) scans have become ubiquitous in the assessment of the trauma patient because of its diagnostic acuity in assessing head and axial skeletal pathology. Consensus recommendations exist for limiting the ionizing radiation dose as it pertains to CT head imaging in the pediatric population. However, little published data exist assessing the diagnostic yield of current practices in the pediatric population. As pressure mounts to diagnose emergent pathologies in the emergency department, children are at risk for a relatively high cumulative burden as sequela of medical imaging such as an increased lifetime attributable risk of cancer. PURPOSE To evaluate the diagnostic yield of CT scans of the spine in pediatric trauma patients STUDY DESIGN/SETTING Retrospective, Level I trauma center. PATIENT SAMPLE Patients 18 and under, undergoing CT scans in the ER 1/2013-12/2015. OUTCOME MEASURES Presence of fracture. METHODS Medical records of pediatric trauma patients who arrived at the emergency department and underwent spinal CT were reviewed. We reviewed the CT scans as well as the radiology reports for fractures. Medical records were reviewed for mechanism of injury and management for these patients as well as demographics. Factors associated with pediatric patients with fractures were then compared to those without fractures. RESULTS A total of 831 patients underwent CT scans in to the ER. Average age was 13.86 years (0.24-18.99) with 43% (355) females and 57% (476) males. The racial demographics were as follows: 70% Caucasian, 20% African American, 1.4% Asian, with the remainder listed as other or not available. The most common mechanism of injury (MOI) was motor vehicle accident (MVA) (26%) followed by sports injury (18%), then fall from height (15%) bicycle/motor bike (14%). Other mechanisms of injury were pedestrian struck (9.5%), assault (5%), syncope (3%), direct head blow (3%), neck pain (2%), fall from standing (1%), seizure (1%), strangulation/hanging ( CONCLUSIONS It is important to consider the long-term implications when deciding to expose a pediatric patient to radiation. In this study we found the overall axial fracture rate to be low (6.1%). The fractures were distributed throughout the mobile spine and sacrum. Of the fractures that were detected 54% were transverse process and compression fractures. Pediatric trauma CT scanning best practices focusing on MOI most likely resulting in spine fractures (MVA, bike/motor bike, sport injuries) should be investigated. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Subtle excess in lifetime cancer risk related to CT scanning in Spanish young people

BackgroundCT scan is a life-saving medical diagnostic tool, entailing higher levels of ionising radiation exposure than conventional radiography, which may result in an increase in cancer risk, particularly in children. Information about the use and potential health effects of CT scan imaging among young people in Spain is scarce. ObjectiveThis paper aims to estimate the number of radiation-related cancer cases which can be expected due to the use of CT scanning in Spanish children and young adults in a single year (2013). MethodsThe 2013 distribution of number and types of CT scans performed in young people was obtained for Catalonia and extrapolated to the whole Spain. Organ doses were estimated based on the technical characteristics of 17,406 CT examinations extracted from radiology records. Age and sex-specific data on cancer incidence and life tables were obtained for the Spanish population. Age and sex-specific risk models developed by the Committee on Health Risks of Exposure to Low Levels of Ionizing Radiations (BEIR VII) and Berrington de Gonzalez were used, together, with the dose estimates to derive the lifetime attributable risks of cancer in Spain due to one year of CT scanning and project the number of future cancer cases to be expected. ResultsIn 2013, 105,802 CT scans were estimated to have been performed in people younger than age 21. It was estimated that a total of 168.6 cancer cases (95% CrI: 30.1–421.1) will arise over life due to the ionising radiation exposure received during these CTs. Lifetime attributable risks per 100,000 exposed patients were highest for breast and lung cancer. The largest proportion of CTs was to the head and neck and hence the highest numbers of projected cancer cases were of thyroid and oral cavity/pharynx. ConclusionsDespite the undeniable medical effectiveness of CT scans, this risk assessment suggests a small excess in cancer cases which underlines the need for justification and optimisation in paediatric scanning. Given the intrinsic uncertainties of these risk projection exercises, care should be taken when interpreting the predicted risks.

Radiation dose management for pediatric cardiac computed tomography: a report from the Image Gently 'Have-A-Heart' campaign.

Children with congenital or acquired heart disease can be exposed to relatively high lifetime cumulative doses of ionizing radiation from necessary medical imaging procedures including radiography, fluoroscopic procedures including diagnostic and interventional cardiac catheterizations, electrophysiology examinations, cardiac computed tomography (CT) studies, and nuclear cardiology examinations. Despite the clinical necessity of these imaging studies, the related ionizing radiation exposure could pose an increased lifetime attributable cancer risk. The Image Gently "Have-A-Heart" campaign is promoting the appropriate use of medical imaging studies in children with congenital or acquired heart disease while minimizing radiation exposure. The focus of this manuscript is to provide a comprehensive review of radiation dose management and CT performance in children with congenital or acquired heart disease.

Computed Tomography Scans in Patients With Young Adult Hip Pain Carry a Lifetime Risk of Malignancy

To calculate the lifetime risk of malignancy in young adult patients with hip pain using 5 different imaging and radiation dose protocols with or without pre- and postoperative computed tomography (CT). Radiographic and CT patient radiation doses were retrospectively reviewed. Imaging protocols for hip pain composed of radiographs with or without pre- and postoperative CT scans were modeled and radiation doses were estimated using the PCXMC computer code. Based on these radiation doses, lifetime attributable risks of cancer and mortality for a 10- through 60-year-old male and female were calculated as published by the committee on the Biological Effects of Ionizing Radiation (BEIR) in the BEIR VII report. Relative risks and number needed to harm (NNH) were calculated for each protocol. Based on a review of our institutional database, 2 CT scan doses were used for this study: a high 5.06mSv and a low 2.86mSv. Effective doses of radiation ranged from 0.59 to 0.66mSv for radiographs alone to 10.71 to 10.78mSv for radiographs and CT both pre- and postoperatively at the higher dose. Lifetime attributable risk of cancer for radiographs alone was 0.006% and 0.011% for a 20-year-old male and female, respectively. Lifetime attributable risk of cancer for radiographs along with pre- and postoperative CT scans at higher dose was 0.105% and 0.177% for a 20-year-old male and female, respectively. Radiographs alone lead to an NNH of 16,667 for males and 9,090 for females, whereas the protocol with pre- and postoperative CT scans at the higher dose led to an NNH of 952 for males and 564 for females. The relative risk of this protocol compared to radiographs alone was 17.5 for males and 16.1 for females. Protocols with CT scans of the hip/pelvis pose a small lifetime attributable risk (0.034%-0.177% for a 20-year-old) but a large relative risk (5-17 times) of cancer compared with radiographs alone in the imaging evaluation for hip pain that decreases with increasing age. This study illustrates the need for clinicians to understand the imaging protocols used at their institution to understand the risks and benefits of using those protocols in their practice.

Cumulative Effective Dose and Cancer Risk of Pediatric Population in Repetitive Whole-Body Scan Using Dual-Energy X-Ray Absorptiometry

This study aims to quantitatively evaluate the cumulative effective dose and associated cancer risk of pediatric patients of US and Hong Kong population undergoing repetitive whole-body scans with dual-energy X-ray absorptiometry (DXA) during their diagnosis and follow-up periods. Organ-absorbed doses of pediatric patients undergoing DXA whole-body scan have been computer simulated using patient imaging parameters input to the Monte Carlo software PCXMC. Gender- and age-specific effective doses have been calculated with the simulated organ-absorbed doses using the ICRP-103 approach. The associated radiation-induced cancer risk, expressed as lifetime attributable cancer risk (LAR), has been estimated according to the method introduced in the Biological Effects of Ionizing Radiation VII report. Mathematical fitting for effective dose and for LAR, as a function of age at exposure, has been analytically obtained to quantitatively estimate the cumulated effective dose and LAR for pediatric patients of US and Hong Kong population with repetitive DXA whole-body scan during their follow-up period. The effective dose of a single DXA whole-body scan for patients exposed at the age between 5 and 18 years was calculated as 8.47–17.68 µSv. The corresponding LAR for US and Hong Kong population was between the range of 4.57 × 10−7 and 7.14 × 10−7. The cumulative effective dose of DXA whole-body scan for patients exposed annually at age between 5 and 18 years was calculated as 180 µSv for girls and 168 µSv for boys. The corresponding cumulative LAR for US and Hong Kong population was calculated as 3.77 × 10−6 to 5.48 × 10−6. Girls would be at a statistically significant higher cumulated cancer risk than boys under the same whole-body DXA protocol (p = 0.03). The probability of cumulative LAR for pediatric populations undergoing annual DXA whole-body scan is regarded as minimal. We demonstrate the use of computer simulation and analytic formulation to quantitatively obtain the cumulated effective dose and cancer risk at any age of exposure, which are useful information for medical personnel to track patient radiation dose and to alleviate patients' parents concern about radiation safety in repetitive whole-body scan using DXA.

Radiation overexposure from repeated CT scans in young adults with acute abdominal pain.

The purpose of this study is to assess the dose of ionizing radiation caused by repeated CT scans performed to investigate non-traumatic acute abdominal conditions in young adults. Over 26months, we collected a cohort of patients aged 18 to 45years who were subject to at least one urgent contrast-enhanced abdomen/pelvis CT. Patients affected with urolithiasis, HIV infection, tumors, and vascular and chronic inflammatory bowel diseases were excluded. All abdomen/pelvis CT scans carried out at our institution for over 6years were retrospectively tallied, and the effective doses (EDs) were computed by multiplying the total dose-length product by the appropriate anatomic conversion factor. Examples of age- and gender-adjusted lifetime attributable cancer risks were estimated using the online calculator Radiation Risk Assessment Tool. Sixty-one patients (average age 34.2years) received multiple CT scans (average 2.7 scans per patient). ED largely varied among single- and multi-phase acquisitions. Cumulative ED ranged from 14.1mSv to a maximum of 436.6mSv (average 70.1mSv per person). Twenty-five patients (40.9%) received more than 50mSv, 84% of them within year; 12 (19.7%) and 4 (6.6%) patients received more than 100 and 200mSv, respectively. Young adults are subject to repetitive CT imaging to monitor urogenital, intestinal, hepatobiliary, and pancreatic disorders during non-operative management to detect and follow up abdominal emergencies requiring surgical intervention and to assess post-surgical complications. In this population, the risk of accruing high cumulative radiation exposure should be considered.

Removal of scatter radiation in paediatric cardiac catheterisation: a randomised controlled clinical trial

Objective. This study sought to determine if DNA integrity was compromised by ionising radiation from paediatric cardiac catheterisations and if dose optimisation techniques allowed DNA integrity to be maintained. Materials and methods. Children were imaged using either: (i) an anti-scatter grid (current departmental protocol), (ii) no anti-scatter grid or, (iii) no anti-scatter grid and a 15 cm air-gap between the child and the x-ray detector. Dose area product and image quality were assessed, lifetime attributable cancer risk estimates were calculated and DNA double-strand breakages quantified using the γH2AX assay. Results. Consent was obtained from 70 parents/guardians/children. Image quality was sufficient for each procedure performed. Removal of the anti-scatter grid resulted in dose reductions of 20% (no anti-scatter grid) and 30% (15 cm air-gap), DNA double-strand break reductions of 30% (no anti-scatter grid) and 20% (15 cm air-gap) and a reduction of radiation-induced cancer mortality risk of up to 45%. Conclusion. Radiation doses received during paediatric cardiac catheterisation procedures resulted in a significant increase in DNA damage while maintaining acceptable image quality and diagnostic efficacy. It is feasible to remove the anti-scatter grid resulting in a reduction in DNA damage to the patient. The γH2AX assay may be used for assessment of dose optimisation strategies in children.

Exposure to low dose computed tomography for lung cancer screening and risk of cancer: secondary analysis of trial data and risk-benefit analysis

Objective To estimate the cumulative radiation exposure and lifetime attributable risk of cancer incidence associated with lung cancer screening using annual low dose computed tomography (CT).Design Secondary analysis of data...

A snapshot of patients' awareness of radiation dose and risks associated with medical imaging examinations at an Australian radiology clinic

BackgroundCumulative radiation exposure is linked to increasing the lifetime attributable risk of cancer. To avoid unnecessary radiation exposure and facilitate shared decision making, patients should be aware of these issues. This paper examines patients' awareness of radiation dose and risks associated with medical imaging examinations. MethodsConsecutive patients attending a private radiology clinic over a nine week period in 2014 in Metropolitan Melbourne were surveyed while waiting to undergo an imaging examination. Patients who were under 18 years of age, did not speak English and/or were referred for interventional imaging procedures were excluded from participation. Survey questions addressed patients' awareness of radiation dose associated with various imaging modalities' and patients' experience and preferences regarding communication of information about radiation. Data was analysed using SPSS (Ver 20.1). ResultsA total of 242 surveys were completed. Most participants were male (143/239, 59.8%) and aged between 33 and 52 years (109/242, 45%). Over half of participants were not concerned about radiation from medical imaging (130/238, 54.6%). Only a third of participants (80/234, 34.2%) correctly reported that CT has a higher radiation dose than X-ray. Very few participants correctly identified mammography, DEXA, PET and PET/CT as radiation emitting examinations. The majority of participants (202/236, 85.6%) indicated that they were not informed about radiation dose and risks by their referring doctor in advance. ConclusionThis paper provides information relevant to a single private radiology clinic in Australia. Nevertheless, our results have shown that patients presenting for medical imaging have little awareness of radiation dose and risks associated with these examinations and received little information by their referring physicians or staff at the radiology clinic.

Follow-up CT pulmonary angiograms in patients with acute pulmonary embolism.

Computed tomographic (CT) angiography is associated with a non-negligible lifetime attributable risk of cancer. The risk is considerably greater for women and younger patients. Recognizing that there are risks from radiation, the purpose of this investigation was to assess the frequency of follow-up CT angiograms in patients with acute pulmonary embolism. This was a retrospective cohort study of patients aged ≥18years with acute pulmonary embolism seen in three emergency departments from January 2013 to December 2014. Records of all patients were reviewed for at least 14months. Pulmonary embolism was diagnosed by CT angiography in 600 patients. At least one follow-up CT angiogram in 1year was obtained in 141 of 600 (23.5%). Two follow-ups in 1year were obtained in 40 patients (6.7%), 3 follow-ups were obtained in 15 patients (2.5%), and 4 follow-ups were obtained in 3 patients (0.5%). Among young women (aged ≤29years) with pulmonary embolism, 10 of 21 (47.6%) had at least 1 follow-up and 4 of 21 (19.0%) had 2 or more follow-ups in 1year. Among all patients, recurrent pulmonary embolism was diagnosed in 15 of 141 (10.6%) on the first follow-up CT angiogram and in 6 of 40 (15.0%) on the second follow-up. Follow-up CT angiograms were obtained in a significant proportion of patients with pulmonary embolism, including young women, the group with the highest risk. Alternative options might be considered to reduce the hazard of radiation-induced cancer, particularly in young women.

Abstract P6-01-01: Impact of imaging surveillance on the risk of radiation induced malignancies in breast cancer survivors

Abstract Introduction: After curative treatment of breast cancer (BC), relevant clinical guidelines recommend against the use of imaging procedures other than yearly mammography for surveillance, based on the lack of survival benefit for intensive surveillance strategies. Nevertheless, use of non-recommended imaging tests occurs frequently in this context. Most BC surveillance studies have focused on the potential benefit of detection of early relapse, on financial burden, and risk of false positives with different follow-up regimens. No study has analyzed the risk of imaging radiation induced malignancies (IRIM) in BC survivors exposed to repeated body imaging during surveillance. We previously reported on the IRIM risk in the BC clinical trials setting (Fresco R. The Oncologist 2015). In this current study we report on this risk during surveillance in clinical practice in BC survivors. Objective: To estimate IRIM risk in patients curatively treated for BC undergoing imaging tests during surveillance. Methodology: We defined 6 surveillance strategies with differing imaging requirements, from a non imaging-intensive one (yearly mammography only) to intensive ones (mammography + CT, Bone scan, PET-CT and/or MUGA) (Table 1). For each strategy we calculated the imaging dose and excess lifetime attributable cancer risk (LAR) for a 60 year-old BC survivor, using NCI's Radiation Risk Assessment Tool (RadRat). Results: Total effective imaging radiation dose received by a 60 year-old BC survivor during surveillance was 8.4 miliSieverts (mSv) when only yearly mammography is performed to 199.9 mSv when CT, MUGA and bone scan are added. Mean IRIM LAR ranges from 37.2/100,000 with the first strategy to 1,330/100,000 with the latter. Performing MUGA scans increased IRIM risk 31% compared to not performing it. The addition of any additional radiating imaging procedure to yearly mammography significantly increases LAR. Imaging effective dose and LAR in different surveillance strategiesFollow-up strategyImaging effective dose (mSv)Excess lifetime attributable cancer risk: mean (90% uncertainty range) (/100,000)Yearly mammography only8.437.2 (21.4-60.3)Yearly mammography + Chest/abdomen CT q6mo for 3y, then annually for 2y128.4857.0 (503.0-1,350.0)Yearly mammography + Chest/abdomen CT q6mo for 3y, then annually for 2y + Bone scan q12mo for 5y159.91,060.0 (603.0-1,640.0)Yearly mammography + Chest/abdomen CT q6mo for 3y, then annually for 2y + MUGA q6mo for 2y168.41,130.0 (642.0-1,800.0)Yearly mammography + Chest/abdomen CT q6mo for 3y, then annually for 2y + MUGA q6mo for 2y + Bone scan q12mo for 5y199.91,330.0 (792.0-2,080.0)Yearly mammography + PET-CT q6mo for 3y, then annually for 2y184.41,310.0 (802.0-1,990.0) Conclusions: A number of incremental second cancers could be derived from imaging performed during BC surveillance after curative treatment. Addition of non-recommended imaging for relapse detection increases IRIM risk compared to performing only mammography. This, in addition to the lack of proven benefit in BC endpoints, emphasizes the need to follow recommendations for surveillance clinical guidelines, and forgo imaging studies other than annual mammography to detect relapses. Substituting MUGA with echocardiogram for cardiac assessment could also reduce IRIM risk. Citation Format: Spera G, Gonzalez V, Meyer C, Fung H, Mackey JR, Fresco R. Impact of imaging surveillance on the risk of radiation induced malignancies in breast cancer survivors. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-01-01.

Abstract TP340: Imaging Related Radiation Dose and Cancer Risk Assessment of Brain in Acute Ischemic Stroke Patients

Background and aims: Recently, safety concerns were raised about the radiation dose for acute ischemic stroke (AIS) patients undergoing computed tomography (CT), CT angiography (CTA) and CT perfusion (CTP). We evaluated precise radiation dose to the brain during various imaging studies in our AIS patients. Methods: Brain imaging was performed with 64-detector row CT scanner (Phillips-iCT256) using standard protocols recommended by American Association of Physicist in Medicine. For each procedure, volume weighted CT dose index (CTDIvol, mGy) and dose-length product DLP (mGy.cm) were obtained from dose reports generated at the time of acquisition. Organ specific dose to brain, eye, bone marrow and thyroid were also obtained. The estimates of cancer risk were interpolated. Results: In this prospective study, a total of 18 patients who underwent CT, CTA as well as CTP were included. Mean DLP for non-enhanced CT, CTA and CTP were 1068.25, 1150 and 1197 mGy.cm, respectively. Corresponding whole body effective dose for the CT, CTA and CTP were calculated as 2.57, 2.6, 2.4 mSv, respectively. Cumulative doses to the brain, eyes, bone marrow and thyroid gland were 33.81, 32.8, 1.21 and 1.31 mGy for the non-contrast brain CT. CTDIvol measurements for different protocols tested by the phantom were in agreement with values given in dose reports. Conclusions: The effective radiation doses are less than previously reported and much below the radiation threshold level for deterministic effects for brain and optic lens (500-2000mGy). Estimated life-time attributable cancer risks are very low with the current radiation doses.

Significant but reasonable radiation exposure from computed tomography-related medical imaging in the ICU.

Admission to an intensive care unit (ICU) is associated with increased medical imaging and radiation exposure, yet few studies have estimated the risk of cancer associated with these examinations. The purpose of this study was to review computed tomography (CT) scans performed on patients admitted to two urban academic ICUs, predict their radiation exposure, and calculate their estimated lifetime attributable risk of cancer (LAR). An electronic chart review was performed on all CT scans performed between January 2007 and December 2011. The estimated effective dose of radiation was calculated for each CT, and the LAR for each patient was predicted. Mean radiation exposure was 22.2 ± 25.0 mSv with a mean LAR of 0.1 ± 0.2 % and a median of 0.6 % with a range of <0.001 to 3.4 %. Our cohort received radiation doses higher than recommended by guidelines; however, the critical nature of their admission may have warranted these imaging studies. Estimated risk of cancer in this population was overall low.

Cumulative radiation exposure and associated cancer risk estimates for scoliosis patients: Impact of repetitive full spine radiography

ObjectiveTo quantitatively evaluate the cumulative effective dose and associated cancer risk for scoliotic patients undergoing repetitive full spine radiography during their diagnosis and follow up periods. MethodsOrgan absorbed doses of full spine exposed scoliotic patients at different age were computer simulated with the use of PCXMC software. Gender specific effective dose was then calculated with the ICRP-103 approach. Values of lifetime attributable cancer risk for patients exposed at different age were calculated for both patient genders and for Asian and Western population. Mathematical fitting for effective dose and for lifetime attributable cancer risk, as function of exposed age, was analytically obtained to quantitatively estimate patient cumulated effective dose and cancer risk. ResultsThe cumulative effective dose of full spine radiography with posteroanterior and lateral projection for patients exposed annually at age between 5 and 30 years using digital radiography system was calculated as 15mSv. The corresponding cumulative lifetime attributable cancer risk for Asian and Western population was calculated as 0.08–0.17%. Female scoliotic patients would be at a statistically significant higher cumulated cancer risk than male patients under the same full spine radiography protocol. ConclusionWe demonstrate the use of computer simulation and analytic formula to quantitatively obtain the cumulated effective dose and cancer risk at any age of exposure, both of which are valuable information to medical personnel and patients’ parents concern about radiation safety in repetitive full spine radiography.

Imaging Radiation Doses and Associated Risks and Benefits in Subjects Participating in Breast Cancer Clinical Trials.

Medical imaging is commonly required in breast cancer (BC) clinical trials to assess the efficacy and/or safety of study interventions. Despite the lack of definitive epidemiological data linking imaging radiation with cancer development in adults, concerns exist about the risks of imaging radiation-induced malignancies (IRIMs) in subjects exposed to repetitive imaging. We estimated the imaging radiation dose and IRIM risk in subjects participating in BC trials. The imaging protocol requirements in 10 phase III trials in the adjuvant and advanced settings were assessed to estimate the effective radiation dose received by a typical and fully compliant subject in each trial. For each study, the excess lifetime attributable cancer risk (LAR) was calculated using the National Cancer Institute's Radiation Risk Assessment Tool, version 3.7.1. Dose and risk calculations were performed for both imaging intensive and nonintensive approaches to reflect the variability in imaging performed within the studies. The total effective imaging radiation dose was 0.4-262.2 mSv in adjuvant trials and 26-241.3 mSv in metastatic studies. The dose variability resulted from differing protocol requirements and imaging intensity approaches, with computed tomography, multigated acquisition scans, and bone scans as the major contributors. The mean LAR was 1.87-2,410/100,000 in adjuvant trials (IRIM: 0.0002%-2.41% of randomized subjects) and 6.9-67.3/100,000 in metastatic studies (IRIM: 0.007%-0.067% of subjects). IRIMs are infrequent events. In adjuvant trials, aligning the protocol requirements with the clinical guidelines' surveillance recommendations and substituting radiating procedures with equivalent nonradiating ones would reduce IRIM risk. No significant risk has been observed in metastatic trials, and potential concerns on IRIMs are not justified. Medical imaging is key in breast cancer (BC) clinical trials. Most of these procedures expose patients to ionizing radiation, and the risk of second cancer development after imaging has prompted recent concerns and controversy. Using accepted calculation models, the number of malignancies were estimated that were potentially attributable to the imaging procedures performed during a patient's participation in BC clinical trials. The results show that for patients participating in metastatic trials, the risk of imaging radiation-induced malignancies is negligible. In adjuvant trials, some second cancers due to imaging could be expected, and measures can be taken to reduce their risk.

Percutaneous cryoablation of renal masses under CT fluoroscopy: radiation doses to the patient and interventionalist.

Computed tomographic (CT) fluoroscopy-guided percutaneous cryoablation is an effective therapeutic method used to treat focal renal masses. The purpose of this study is to quantify the radiation dose to the patient and interventional radiologist during percutaneous cryoablation of renal masses using CT fluoroscopic guidance. Over a 1-year period, the CT fluoroscopy time during percutaneous cryoablation of renal masses was recorded in 41 patients. The level of complexity of each procedure was designated as simple, intermediate, or complex. Patient organ radiation doses were estimated using an anthropomorphic model. Dose to the interventional radiologist was estimated using ion chamber survey meters. The average CT fluoroscopy time for technically simple cases was 47s, 126s for intermediate cases, and 264s for complex cases. The relative risk of hematologic stomach and liver malignancy in patients undergoing this procedure was 1.003-1.074. The lifetime attributable risk of cancer ranged from 2 to 58, with the highest risk in younger patients for developing leukemia. The estimated radiation dose to the interventionalist without lead shielding was 390mR (3.9mGy) per year of cases. The radiation risk to the patient during CT fluoroscopy-guided percutaneous renal mass cryoablation is, as expected, related to procedure complexity. Quantification of patient organ radiation dose was estimated using an anthropomorphic model. This information, along with the associated relative risk of malignancy, may assist in evaluating risks of the procedure, particularly in younger patients. The radiation dose to the interventionist is low regardless of procedure complexity, but highlights the importance of lead shielding.

Lifetime Attributable Risk of Cancer From Radiation Exposure During Parathyroid Imaging: Comparison of 4D CT and Parathyroid Scintigraphy.

The purpose of this study is to measure the organ doses and effective dose (ED) for parathyroid 4D CT and scintigraphy and to estimate the lifetime attributable risk of cancer incidence associated with imaging. Organ radiation doses for 4D CT and scintigraphy were measured on the basis of imaging with our institution's protocols. An anthropomorphic phantom with metal oxide semiconductor field effect transistor detectors was scanned to measure CT organ dose. Organ doses from the radionuclide were based on International Commission for Radiological Protection report 80. ED was calculated for 4D CT and scintigraphy and was used to estimate the lifetime attributable risk of cancer incidence for patients differing in age and sex with the approach established by the Biologic Effects of Ionizing Radiation VII report. A 55-year-old woman was selected as the standard patient according to the demographics of patients with primary hyperparathyroidism. Organs receiving the highest radiation dose from 4D CT were the thyroid (150.6 mGy) and salivary glands (137.8 mGy). For scintigraphy, the highest organ doses were to the colon (41.5 mGy), gallbladder (39.8 mGy), and kidneys (32.3 mGy). The ED was 28 mSv for 4D CT, compared with 12 mSv for scintigraphy. In the exposed standard patient, the lifetime attributable risk for cancer incidence was 193 cancers/100,000 patients for 4D CT and 68 cancers/100,000 patients for scintigraphy. Given a baseline lifetime incidence of cancer of 46,300 cancers/100,000 patients, imaging results in an increase in lifetime incidence of cancer over baseline of 0.52% for 4D CT and 0.19% for scintigraphy. The ED of 4D CT is more than double that of scintigraphy, but both studies cause negligible increases in lifetime risk of cancer. Clinicians should not allow concern for radiation-induced cancer to influence decisions regarding workup in older patients.

Evaluation based on Monte Carlo simulation of lifetime attributable risk of cancer after neck X-ray radiography.

At present, concern regarding radiation exposure is increasing with the prevalence of radiologic examination. As radiation damages the human body, we have evaluated medical radiation dose values and studied the importance of optimizing radiation exposure. We measured entrance surface dose (ESD) values using a RANDO(®) phantom (neck) in 94 randomly selected locations in the central region of Korea. Thyroid and organ doses were calculated using Monte Carlo simulations (PCXMC 2.0.1) based on measured values. In addition, the lifetime attributable risk (LAR) of cancer was calculated for the thyroid, using the method proposed in the biological effects of ionizing radiation VII report. The average measured ESD values obtained using the RANDO(®) phantom (neck) were antero-posterior 1.33 mGy and lateral 1.23 mGy, for a total of 2.56 mGy. Based on the ESD values measured using the phantom, the organ doses were obtained using a Monte Carlo simulation (PCXMC 2.0.1). The thyroid dose was 1.48 mSv on average. In evaluating the LAR of thyroid cancer incidence, a frequency of 0.02 per 100,000 from 2.94 per 100,000 males and a frequency of 0.10 per 100,000 from 16.23 per 100,000 females were found. The risk of cancer was found to be higher when the patient's age was lower, and was also higher in females than in males. It was concluded that beneficial exams in the medical field should not be prohibited because of a statistically small risk, although acknowledgement of the dangers of ionizing radiation is necessary.

Letter by Harbron Regarding Article, “Cumulative Radiation Exposure and Cancer Risk Estimation in Children With Heart Disease”

Johnson et al1 have estimated cumulative radiation doses received by children treated for cardiac conditions along with associated lifetime attributable risk of cancer in relation to this dose. This is a very informative and timely study, although the choice of dose metric is of concern. The study involves using effective dose, derived from either experimental methods or from previous publications, in Biological Effects …

Benefits of brain magnetic resonance imaging over computed tomography in children requiring emergency evaluation of ventriculoperitoneal shunt malfunction: reducing lifetime attributable risk of cancer.

The rapid growth of computed tomography (CT) has resulted in increased concerns of ionizing radiation exposure and its subsequent risk of cancer development. We evaluated the impact of a new protocol using rapid sequence magnetic resonance imaging (rsMRI) instead of CT in children presenting with possible ventriculoperitoneal shunt (VPS) malfunction to promote patient safety. This is a retrospective case series of pediatric patients who received a neuroimaging study for emergency evaluation of possible VPS malfunction at New York University's Tisch Hospital Emergency Department between January 2010 and July 2011. Radiology Charge Master was queried to identify the patient database. The trend in the use of rsMRI and CT was calculated for 3 patient age groups and compared across 3 chronological intervals. The effective dose of ionizing radiation per CT scan was calculated using the CT dose index and dose-length product for each patient. Total of 365 patients with the mean age of 8.87 years received either rsMRI or CT study during the study period. One hundred forty-four of these patients required the imaging studies because of VPS malfunction. Overall, 62% of all VPS malfunction cases used rsMRI instead of CT. The ratio of the number of patients receiving rsMRI divided by CT studies has progressively increased from 1.4:1 to 2.1:1 over 3 chronologic periods. Children with VPS are subject to multiple neuroimaging studies throughout their lifetime. Rapid sequence MRI is an effective alternative to CT while providing no ionizing radiation exposure or risk of developing radiation-induced cancer.