Peak Skin Dose Research Articles

Impact of Hybrid Rooms with Image Fusion on Radiation Exposure during Endovascular Aortic Repair

To evaluate exposure to radiation during endovascular aneurysm repair (EVAR) performed with intraoperative guidance by preoperative computed tomographic angiogram fusion. All consecutive patients who underwent standard bifurcated (BIF) or thoracic (THO), and complex fenestrated (FEN) or branched (BR) EVAR were prospectively enrolled. Indirect dose-area product (DAP), fluoroscopy time (FT), and contrast medium volume were recorded. These data were compared with a previously published prospective EVAR cohort of 301 patients and to other literature. Direct DAP and peak skin dose were measured with radiochromic films. Results are expressed as median (interquartile range). From December 2012 to July 2013, 102 patients underwent standard (56.8%) or complex (43.2%) EVAR. The indirect DAP (Gy.cm(2)) was as follows: BIF 12.2 (8.7-19.9); THO 26.0 (11.9-34.9); FEN 43.7 (24.7-57.5); andBR 47.4 (37.2-108.2). The FT (min) was as follows: BIF 10.6 (9.1-14.7); THO 8.9 (6.0-10.5); FEN 30.7 (20.2-40.5); and BR 39.5 (34.8-51.6). The contrast medium volume (mL) was as follows: BIF 59.0 (50.0-75.0); THO 80.0 (50.0-100.0); FEN 105.0 (70.0-136.0); and BR 120.0 (100.0-170.0). When compared with a previous cohort, there was a significant reduction in DAP during BIF, FEN, and BR procedures, and a significant reduction of iodinated contrast volume during FEN and BR procedures. There was also a significant reduction in DAP during BIF procedures when compared with the literature (p<.01). DAP measurement on radiochromic films was strongly correlated with indirect DAP values (r(2)=.93). The exposure of patients and operators to radiation is significantly reduced by routine use of image fusion during standard and complex EVAR.

Dual‐axis rotational coronary angiography can reduce peak skin dose and scattered dose: a phantom study

The purpose of this study was to evaluate peak skin dose received by the patient and scattered dose to the operator during dual‐axis rotational coronary angiography (DARCA), and to compare with those of standard coronary angiography (SA). An anthropomorphic phantom was used to simulate a patient undergoing diagnostic coronary angiography. Cine imaging was applied on the phantom for 2 s, 3 s, and 5 s in SA projections to mimic clinical situations with normal vessels, and uncomplicated and complicated coronary lesions. DARCA was performed in two curved trajectories around the phantom. During both SA and DARCA, peak skin dose was measured with thermoluminescent dosimeter arrays and scattered dose with a dosimeter at predefined height (approximately at the level of left eye) at the operator's location. Compared to SA, DARCA was found lower in both peak skin dose (range: 44%–82%, p < 0.001) and scattered dose (range: 40%–70%, p < 0.001). The maximal reductions were observed in the set mimicking complicated lesion examinations (82% reduction for peak skin dose, p < 0.001; 70% reduction for scattered dose, p < 0.001). DARCA reduces both peak skin dose and scattered dose in comparison to SA. The benefit of radiation dose reduction could be especially significant in complicated lesion examinations due to large reduction in X‐ray exposure time. The use of DARCA could, therefore, be recommended in clinical practice to minimize radiation dose.PACS numbers: 87.53.‐j, 87.53.Bn, 87.59.‐e, 87.59.C‐, 87.59.cf, 87.59.Dj

Abstract 170: Improving Radiation Safety in the Cardiac Catheterization Lab

Objective: Ionizing radiation, while necessary for cardiac catheterization and angioplasty, is an ever present and often unappreciated safety concern for the patient and operator. Radiation exposure has both deterministic and stochastic effects, with risk estimated by peak Skin Dose and Air kerma Area product . Exposure guidelines have been set for radiation safety (4,000 mGray and 20,000 c Gray cm 2 ). Procedure: The frequency of guideline excessive radiation exposure for cardiac cath lab patients was tracked. Operator, patient, anatomic, procedural variables associated with high radiation exposures were identified and specific interventions to minimize radiation exposure identified. Results: Over a 3 year period 17% of interventions [2011- 220/1,543 (14.3%), 2012- 268/1,420 (18.9%), 2013- 270/1,476 (18.3%)] received excessive skin or total body radiation. In 2013 the average peak skin dose/patient for operators ranged from 1,250 -3,252; the average total area dose/patient ranged from 7,360- 20,988 for operators, with only one operator exceeding 20,000 as an average. Advances in equipment and operator experience have been offset by the increasing disease complexity of attempted interventions. Frequency of excessive radiation by operator ranged from 1.4 - 46% of interventions. Patient risk factors included: obesity, multivessel disease and lesion complexity, highly angled views, number, length, and frame rate of cine and fluoroscopy runs. Specific interventions that decreased the frequency of excess radiation administered included: increasing operator feedback and awareness of radiation used, shortening cine runs, decreased frame rate for fluoroscopy and cine, staging procedures, increase use of stored images and mapping capabilities. Physicians adopting safer radiation practices decreased excess radiation cases from 15.8% [35/222] in 2012 to 8.0% [18/224] in 2013. The default settings of X-Ray equipment have been modified to encourage safe and appropriate use of radiation in the cardiac catheterization lab (however, physician overide of settings is still possible). Conclusions: Patient factors (e.g. obesity, prior CABG) and complex, multivessel interventions are potentially frequently associated with excess radiation. Changing default settings and implementing radiation safety practices can significantly decrease radiation exposure to patients and staff.

Erratum: Calculating the peak skin dose resulting from fluoroscopically guided interventions. Part I: Methods.

The squared term was missing from the factor in the original article. This term needs to be squared, as it applies to both the horizontal and vertical collimator dimensions. The correct form of the expression was used in the examples in the companion article: Calculating the peak skin dose resulting from fluoroscopically guided interventions. Part II: Case studies . (2) We wish to thank Guang Li, PhD, for bringing this omission to our attention. We would like to take this opportunity to make one additional clarification regarding these articles. The DICOM tag 0x00181111 (Distance Source to Patient) must be used carefully when calculating peak skin dose. The actual distance stored in this tag is affected by the choice of method used to calibrate distances in the image. In many cases, the distance stored in this tag is calculated based on the default table-to-object (TOD) distance used in the configuration files of the fluoroscope. However, the TOD setting can be changed by the operator or another method may be used to calibrate the images (e.g., catheter choice, an object such as a coin placed in the field of view, etc.). It is important that this be considered when using the distance stored in this tag.

How accurately can the peak skin dose in fluoroscopy be determined using indirect dose metrics?

Skin dosimetry is important for fluoroscopically-guided interventions, as peak skin doses (PSD) that result in skin reactions can be reached during these procedures. There is no consensus as to whether or not indirect skin dosimetry is sufficiently accurate for fluoroscopically-guided interventions. However, measuring PSD with film is difficult and the decision to do so must be madea priori. The purpose of this study was to assess the accuracy of different types of indirect dose estimates and to determine if PSD can be calculated within ± 50% using indirect dose metrics for embolization procedures. PSD were measured directly using radiochromic film for 41 consecutive embolization procedures at two sites. Indirect dose metrics from the procedures were collected, including reference air kerma. Four different estimates of PSD were calculated from the indirect dose metrics and compared along with reference air kerma to the measured PSD for each case. The four indirect estimates included a standard calculation method, the use of detailed information from the radiation dose structured report, and two simplified calculation methods based on the standard method. Indirect dosimetry results were compared with direct measurements, including an analysis of uncertainty associated with film dosimetry. Factors affecting the accuracy of the different indirect estimates were examined. When using the standard calculation method, calculated PSD were within ± 35% for all 41 procedures studied. Calculated PSD were within ± 50% for a simplified method using a single source-to-patient distance for all calculations. Reference air kerma was within ± 50% for all but one procedure. Cases for which reference air kerma or calculated PSD exhibited large (± 35%) differences from the measured PSD were analyzed, and two main causative factors were identified: unusually small or large source-to-patient distances and large contributions to reference air kerma from cone beam computed tomography or acquisition runs acquired at large primary gantry angles. When calculated uncertainty limits [-12.8%, 10%] were applied to directly measured PSD, most indirect PSD estimates remained within ± 50% of the measured PSD. Using indirect dose metrics, PSD can be determined within ± 35% for embolization procedures. Reference air kerma can be used without modification to set notification limits and substantial radiation dose levels, provided the displayed reference air kerma is accurate. These results can reasonably be extended to similar procedures, including vascular and interventional oncology. Considering these results, film dosimetry is likely an unnecessary effort for these types of procedures when indirect dose metrics are available.

WE‐E‐18A‐03: How Accurately Can the Peak Skin Dose in Fluoroscopy Be Determined Using Indirect Dose Metrics?

Purpose:Skin dosimetry is important for fluoroscopically‐guided interventions, as peak skin doses (PSD) that Result in skin reactions can be reached during these procedures. The purpose of this study was to assess the accuracy of different indirect dose estimates and to determine if PSD can be calculated within ±50% for embolization procedures.Methods:PSD were measured directly using radiochromic film for 41 consecutive embolization procedures. Indirect dose metrics from procedures were collected, including reference air kerma (RAK). Four different estimates of PSD were calculated and compared along with RAK to the measured PSD. The indirect estimates included a standard method, use of detailed information from the RDSR, and two simplified calculation methods. Indirect dosimetry was compared with direct measurements, including an analysis of uncertainty associated with film dosimetry. Factors affecting the accuracy of the indirect estimates were examined.Results:PSD calculated with the standard calculation method were within ±50% for all 41 procedures. This was also true for a simplified method using a single source‐to‐patient distance (SPD) for all calculations. RAK was within ±50% for all but one procedure. Cases for which RAK or calculated PSD exhibited large differences from the measured PSD were analyzed, and two causative factors were identified: ‘extreme’ SPD and large contributions to RAK from rotational angiography or runs acquired at large gantry angles. When calculated uncertainty limits [−12.8%, 10%] were applied to directly measured PSD, most indirect PSD estimates remained within ±50% of the measured PSD.Conclusions:Using indirect dose metrics, PSD can be determined within ±50% for embolization procedures, and usually to within ±35%. RAK can be used without modification to set notification limits and substantial radiation dose levels. These results can be extended to similar procedures, including vascular and interventional oncology. Film dosimetry is likely an unnecessary effort for these types of procedures.

MO‐F‐16A‐04: Case Study: Estimation of Peak Skin Dose Following a Physician Reported “High Dose” Case and Sentinel Event Considerations

Purpose:This work offers as a teaching example a reported high dose fluoroscopy case and the workflow the institution followed to self‐report a radiation overdose sentinel event to the Joint Commission.Methods:Following the completion of a clinical case in a hybrid OR room with a reported air kerma of &gt;18 Gy at the Interventional Reference Point (IRP) the physicians involved in the case referred study to the institution's Radiation Safety Committee (RSC) for review. The RSC assigned a Diagnostic Medical Physicist (DMP) to estimate the patient's Peak Skin Dose (PSD) and analyze the case. Following the DMP's analysis and estimate of a PSD of &gt;15 Gy the institution's adverse event committee was convened to discuss the case and to self‐report the case as a radiation overdose sentinel event to the Joint Commission. The committee assigned a subgroup to perform the root cause analysis and develop institutional responses to the event.Results:The self‐reporting of the sentinel event and the associated root cause analysis resulted in several institutional action items that are designed to improve process and safety. A formal reporting and analysis mechanism was adopted to review fluoroscopy cases with air kerma greater than 6 Gy at the IRP. An improved and formalized radiation safety training program for physicians using fluoroscopy equipment was implemented. Additionally efforts already under way to monitor radiation exposure in the Radiology department were expanded to include all fluoroscopy equipment capable of automated dose reporting.Conclusion:The adverse event review process and the root cause analysis following the self‐reporting of the sentinel event resulted in policies and procedures that are expected to improve the quality and safe usage of fluoroscopy throughout the institution.

SU‐E‐J‐36: Combining CBCT Dose Into IMRT Treatment Planning

Purpose:Cone beam CT (CBCT) is increasingly used in patient setup for IMRT. Daily CBCT may provide effective localization, however, it introduces concern over excessive imaging dose. Previous studies investigated the calculation of excess CBCT dose, however, no study has yet treated this dose as a source of therapeutic radiation, optimized in consideration of PTV and OARs constrains. Here we present a novel combined MV+kV inverse optimization engine to weave the CBCT and MV dose together such that CBCT dose is used for both imaging and therapeutic purposes. This may mitigate some of the excess imaging dose effects of daily CBCT and allow complete evaluation of the CBCT dose prior to treatment.Methods:The EGSnrc Monte Carlo system was used to model a Varian Trilogy CBCT system and 6 MV treatment beam. Using the model, the dose to patient from treatment beam and imaging beam was calculated for ten patients. The standard IMRT objective function was modified to include CBCT dose. Treatment plan optimization using the MOSEK optimization tool was performed retrospectively with and without assuming kV radiation dose from CBCT, assuming one CBCT per fraction.Results:Across ten patients, the CBCT delivered peaks of between .4% and 3.0% of the prescription dose to the PTV, with average CBCT dose to the PTV between .3% and .8%. By including CBCT dose to skin as a constraint during optimization, peak skin dose is reduced by between 1.9% and 7.4%, and average skin dose is reduced by .2% to 3.3%.Conclusions:Pre‐treatment CBCT may deliver a substantial amount of radiation dose to the target volume. By considering CBCT dose to skin at the point of treatment planning, it is possible to reduce patient skin dose from current clinical levels, and to provide patient treatment with the improved accuracy that daily CBCT provides.

Radiation-induced skin injury after complex endovascular procedures

Radiation-induced skin injury is a serious potential complication of fluoroscopically guided interventions. Transient erythema occurs at doses of 2 to 5 Gy, whereas permanent epilation, ulceration, and desquamation are expected at doses above this level. Complex endovascular procedures (CEPs), such as fenestrated endovascular aortic aneurysm repair (FEVAR), are associated with high radiation doses, yet the prevalence of radiation-induced skin injury is unknown. We hypothesized that skin injury after these exposures is likely to be underrecognized and underreported. This study examined the frequency and severity of deterministic effects and evaluated patient characteristics that might predispose to radiation injury in CEP. CEP was defined as a procedure with a radiation dose ≥5 Gy (National Council on Radiation Protection and Measurements threshold for substantial radiation dose level [SRDL]). Radiation dose and operating factors were recorded for all CEPs performed in a hybrid room during a 30-month period. Patient medical records were retrospectively reviewed for evidence of skin injury. Patients were seen in follow-up daily until discharge and then at weeks 2 and 6, months 3 and 6, and 1 year. Phone interviews were conducted to determine the presence of any skin-related complaints. Peak skin dose (PSD) distributions were calculated for FEVARs with custom software employing input data from fluoroscopic machine logs. These calculations were validated against Gafchromic film (Ashland Inc, Covington, Ky) measurements. Dose was summed for the subset of patients with multiple procedures within 6 months of the SRDL event, consistent with Joint Commission recommendations. Sixty-one CEPs reached a reference air kerma (RAK) of 5 Gy (50 FEVARs, six embolizations, one thoracic endovascular aortic repair, one endovascular aneurysm repair, one carotid intervention, and two visceral interventions). The patient cohort was 79% male and had a mean body mass index of 31. The average RAK was 8 ± 2 Gy (5.0-15.9 Gy). Sixteen patients had multiple CEPs within 6 months of the SRDL event, with a mean cumulative RAK of 12 ± 3 Gy (7.0-18.4 Gy). The mean FEVAR PSD was 6.6 ± 3.6 Gy (3.7-17.8 Gy), with a mean PSD/RAK ratio of 0.78. Gafchromic film dose measurements were not statistically different from PSD estimations, with a constant of proportionality of 0.99. Three patients were lost to follow-up before their first postoperative visit. No radiation skin injuries were found. This study represents the largest analysis of deterministic skin injury after CEPs, and our results suggest that it is less frequent than expected and not increased in CEPs.

Patient-specific organ dose estimation during transcatheter arterial embolization using Monte Carlo method and adaptive organ segmentation

Abstract The purpose of this study was to evaluate organ doses for individual patients undergoing interventional transcatheter arterial embolization (TAE) for hepatocellular carcinoma (HCC) using measurement-based Monte Carlo simulation and adaptive organ segmentation. Five patients were enrolled in this study after institutional ethical approval and informed consent. Gafchromic XR-RV3 films were used to measure entrance surface dose to reconstruct the nonuniform fluence distribution field as the input data in the Monte Carlo simulation. XR-RV3 films were used to measure entrance surface doses due to their lower energy dependence compared with that of XR-RV2 films. To calculate organ doses, each patient׳s three-dimensional dose distribution was incorporated into CT DICOM images with image segmentation using thresholding and k -means clustering. Organ doses for all patients were estimated. Our dose evaluation system not only evaluated entrance surface doses based on measurements, but also evaluated the 3D dose distribution within patients using simulations. When film measurements were unavailable, the peak skin dose (between 0.68 and 0.82 of a fraction of the cumulative dose) can be calculated from the cumulative dose obtained from TAE dose reports. Successful implementation of this dose evaluation system will aid radiologists and technologists in determining the actual dose distributions within patients undergoing TAE.

PM420 Does The Presence of Diabetes Influence Referral for Coronary Revascularization after Myocardial Perfusion Imaging?

O ST E R A B ST R A C T S Results: Over a period of 8 weeks, 173 cases were included of which 111 were coronary angiography (64%) and the remainder PCI. There was a good correlation between PSD and FT r1⁄4 0.80, dose area product (DAP) r1⁄40.87 and Kar r1⁄40.92. 8 % of patients were regarded as high risk on PSD, 5% on Kar 4% on FT all of whom underwent PCI. 5 cases (3%) were only at risk on PSD. Patients undergoing angiography who were obese, had higher PSD (p 1⁄4 0.001), DAP (p1⁄4 0.001) and Kar (p 1⁄40.003). Radial access (n 1⁄4 57) compared with femoral conferred no difference in FT (6.7 vs 4.9 p 1⁄40.194,) Kar (0.696 vs 0.691 p 1⁄4 0.943) or PSD (0.322 vs 0.344 p 1⁄4 0.891). Conclusion: Peak skin dose as defined on DTS correlates well with Kar and fluoroscopy time. Whilst obesity is related to increased PSD, radial access site results in no increase. Real time PSD monitoring may allow greater risk stratification for patient safety in coronary procedures. Disclosure of Interest: None Declared

PM418 Cumulative Radiation Exposure and Peak Skin Dose Quantification using a real time dose tracking system in coronary procedures

PM418 Cumulative Radiation Exposure and Peak Skin Dose Quantification using a real time dose tracking system in coronary procedures

Measurement of skin dose from cone-beam computed tomography imaging

ObjectiveTo measure surface skin dose from various cone-beam computed tomography (CBCT) scanners using point-dosimeters.Materials & methodsA head anthropomorphic phantom was used with nanoDOT optically stimulated luminescence (OSL) dosimeters (Landauer Corp., Glenwood, IL) attached to various anatomic landmarks. The phantom was scanned using multiple exposure protocols for craniofacial evaluations in three different CBCT units and a conventional x-ray imaging system. The dosimeters were calibrated for each of the scan protocols on the different imaging systems. Peak skin dose and surface doses at the eye lens, thyroid, submandibular and parotid gland levels were measured.ResultsThe measured skin doses ranged from 0.09 to 4.62 mGy depending on dosimeter positions and imaging systems. The average surface doses to the lens locations were ~4.0 mGy, well below the threshold for cataractogenesis (500 mGy). The results changed accordingly with x-ray tube output (mAs and kV) and also were sensitive to scan field of view (SFOV). As compared to the conventional panoramic and cephalometric imaging system, doses from all three CBCT systems were at least an order of magnitude higher.ConclusionsPeak skin dose and surface doses at the eye lens, thyroid, and salivary gland levels measured from the CBCT imaging systems were lower than the thresholds to induce deterministic effects. However, our findings do not justify the routine use of CBCT imaging in orthodontics considering the lifetime-attributable risk to the individual.

Estimation of Radiation Exposure for Brain Perfusion CT: Standard Protocol Compared With Deviations in Protocol

The purpose of this study was to measure the organ doses and estimate the effective dose for the standard brain perfusion CT protocol and erroneous protocols. An anthropomorphic phantom with metal oxide semiconductor field effect transistor (MOSFET) detectors was scanned on a 64-MDCT scanner. Protocol 1 used a standard brain perfusion protocol with 80 kVp and fixed tube current of 200 mA. Protocol 2 used 120 kVp and fixed tube current of 200 mA. Protocol 3 used 120 kVp with automatic tube current modulation (noise index, 2.4; minimum, 100 mA; maximum, 520 mA). Compared with protocol 1, the effective dose was 2.8 times higher with protocol 2 and 7.8 times higher with protocol 3. For all protocols, the peak dose was highest in the skin, followed by the brain and calvarial marrow. Compared with protocol 1, the peak skin dose was 2.6 times higher with protocol 2 and 6.7 times higher with protocol 3. The peak skin dose for protocol 3 exceeded 3 Gy. The ocular lens received significant scatter radiation: 177 mGy for protocol 2 and 435 mGy for protocol 3, which were 4.6 and 11.3 times the dose for protocol 1, respectively. Compared with the standard protocol, erroneous protocols of increasing the tube potential from 80 kVp to 120 kVp will lead to a three- to fivefold increase in organ doses, and concurrent use of high peak kilovoltage with incorrectly programmed tube current modulation can increase dose to organs by 7- to 11-fold. Tube current modulation with a low noise index can lead to doses to the skin and ocular lens that are close to thresholds for tissue reactions.

Experimental estimates of peak skin dose and its relationship to the CT dose index using the CTDI head phantom.

A straightforward method is presented to estimate peak skin doses (PSDs) delivered by computed tomography (CT) scanners. The measured PSD values are related to the well-known volume CT dose index (CTDI(vol)), displayed on the console of CT scanners. PSD measurement estimates were obtained, in four CT units, by placing radiochromic film on the surface of a CTDI head phantom. Six different X-ray tube currents including the maximum allowed value were used to irradiate the phantom. PSD and CTDI(vol) were independently measured and later related to the CTDI(vol) value displayed on the console. A scanner-specific relationship was found between the measured PSD and the associated CTDI(vol) displayed on the console. The measured PSD values varied between 27 and 136 mGy among all scanners when the routine head scan parameters were used. The results of this work allow relating the widely used CTDI(vol) to an actual radiation dose delivered to the skin of a patient.

Three‐dimensional rotational X‐ray acquisition technique is reducing patients' cancer risk in coronary angiography

The purpose of this study was to assess patient-specific organ doses and cancer risk with 3D-rotational acquisitions versus the current standard of multiple single-plane coronary angiography (CA). Catheter-based CA remains one of the most commonly performed diagnostic invasive procedures delivering a relatively high radiation dose to the patient. With the introduction of flat-panel technology, three-dimensional rotational angiography became an alternative for the conventional two-dimensional angiography. However, limited information is available on the difference in patient radiation exposure with both acquisition techniques. Eighty adult patients (45 males, age 38-93 years) were randomly assigned to the rotational or standard angiography group. Exposure parameters were registered and skin dose distribution was measured during the procedure. Patient-specific organ doses and related cancer risks were assessed with dedicated software. Rotational angiograms were associated with 33% lower KAP-values (decrease from 49.99 Gycm(2) to 33.37 Gycm(2), P < 0.001). A significant (P < 0.001) lower peak skin dose was measured with rotational acquisitions (80 mGy, median) versus planar imaging (172 mGy, median). Moreover, the skin dose was smoothed over the whole chest of the patient. Contrast medium consumption decreased from 104 mL to 73 mL (P < 0.001) with the use of 3D-imaging. The reduction in radiation exposure resulted in a corresponding decrease of organ doses. The latter contributed to an overall cancer risk reduction of 21% for males and 50% for females. The current study demonstrates that in CA radiation risk reduction is feasible by using a rotational acquisition technique.

Overall measurements of dose to patients in common interventional cardiology procedures

This study was designed to measure peak skin dose (PSD), dose-area product (DAP), cumulative dose (CD) and fluoroscopy time (FT) for interventional cardiology procedures and to evaluate whether patient doses were higher than that in other published data. Three cardiac procedure types, including coronary angiography (CAG), percutaneous transluminal coronary angioplasty (PTCA) and radio frequency (RF) ablation, were entered into the study. Data of four special metrics (PSD, DAP, CD and FT) for these procedures were collected and measured. A total of 238 patients who underwent interventional radiology procedures participated in this study. For every procedure, data about PSD were resulted from six TLD arrays and DAP, CD and FT were collected from the displayed monitor. The mean, standard deviation (SD), range and third quartile of the distribution of PSD, DAP, CD and FT recorded and measured on spot were calculated for all procedures. High-dose cases were specifically recorded. There was wide variation in the doses observed for different instances of the same procedure. PSD for PTCA and RF ablation ranged from 0.1 Gy to more than 3 Gy. Of 238 instances, there were 22 (9.2 %) with PSDs greater than 2 Gy and 4 (1.7 %) than 3 Gy. The third quartile of the distribution for PTCA had exceeded the DIMOND preliminary reference levels by 41.1 % in DAP and 25.0 % in FT. Mean DAP was in the range of reported values for CAG procedure, but higher than all data obtained in literatures for PTCA. Data from this study are in the range of most reported values for CAG and RF ablation procedure, while higher than that obtained in some literatures for PTCA. In case of a constant delivering of high doses to patient and physician himself, thorough training of interventionalists and staff is necessary, and the legislation has to be revised and set dose constrains especially for the interventional high-dose procedures.

SU‐E‐I‐24: How Does C‐Arm Rotation Affect Peak Skin Dose in Interventional Cardiology?

Purpose: Rotating the C‐arm during an interventional cardiology (IC) procedure is believed to spread radiation dose on the skin. Previous studies have shown that this practice often increases peak skin dose (PSD) in interventional radiology (IR) procedures. We sought to determine whether C‐arm rotation reduces the PSD in IC procedures and, if so, under what circumstances. Methods: Simulations were performed using a numerical ray‐tracing algorithm to analyze the effect of C‐arm rotation on PSD across a range of patient sizes, C‐arm configurations, and procedure types. Specific data on modern fluoroscopes and patient dimensions were used as inputs to the simulations. Conclusion: In many cases, modest angles completely eliminated overlap between x‐ray field sites on the skin. C‐arm rotation was most effective for large patients and small x‐ray field sizes. In cases in which overlap remained, PSD increases were generally small, and the 95% area load was reduced. One exception was craniocaudal rotation, which tended to increase PSD, substantially in some cases. The use of a prophylactic approach in which the C‐arm was rotated between small opposing left and right anterior oblique angles was effective in dividing the skin dose between two distinct skin sites. Conclusions: Rotating the C‐arm reduces PSD in IC procedures when used as either a procedural modification or a prophylactic dose reduction strategy. Tight collimation increases the benefit of C‐arm rotation. Conflict of Interest: A. S. Pasciak and A. K. Jones are founders of Fluoroscopic Safety, LLC. Fluoroscopic Safety, LLC provides educational instruction on the safe use of fluoroscopy to physicians.

SU-E-I-08: Do CTDI Measurements Approximate Peak Skin Dose for Wide-Beam Volumetric Scans?

Purpose: To investigate the relationship between peak skin dose and CTDI measurements for wide‐beam volumetric (stationary table) CT scanning. Methods: Air‐kerma (AK) measurements were performed in head and body CTDI phantoms using conventional CTDI, extended CTDI (CTDIe), and AAPM TG‐111 protocols. These measurements were compared to skin dose estimates obtained using a small volume (0.1 ml) ion chamber (IC) mounted on the anterior surface of the phantoms. Measurements were made on a volumetric CT scanner (Toshiba Aquilion ONE) for collimations of 40, 80, 120 and 160 mm and at kVp settings of 80, 100, and 120. Anterior and lateral surface dose measurements were also made on anthropomorphic phantoms at the same fixed techniques. Results: In the CTDI body phantom, peripheral CTDIe nearly equals surface dose while CTDIevol underestimates surface dose by 10–30% over the collimation range. In the CTDI head phantom, either the peripheral or the volume CTDIe values fall within approximately 5% of the surface dose for collimations greater than 80 mm. At smaller collimation, CTDIe values overestimate surface dose in the head phantom. TG‐111 f(0) measurements in the anterior peripheral location slightly overestimate anterior surface dose measurement results for both head and body CTDI phantoms. Surface measurements on the anthropomorphic phantoms exhibit variations between anterior and lateral locations, with lateral doses being smaller. Conclusion: Values derived from CTDIe measurements are useful indicators of peak skin dose for cylindrical phantoms at beam widths in excess of 80 mm. In patients, geometrical correction factors similar to the Size Specific Dose Estimate (SSDE) methodology might be used to account for actual body habitus. Toshiba America Medical Systems is supporting an associated research project on the scanner used for this work. Dr Di Zhang is an employee of Toshiba America Medical Systems.

Development of an innovative approach to predict and reduce the patient radiation dose risk in interventional cardiology

Introduction This study aims at identifying the high-dose procedures in a cardiology department and to find correlation factors to predict the risk of occurrence of deterministic effects in terms of relevant indicators. Materials and methods A working group composed of medical physicists, interventional cardiologists and Radiation Safety Officer was created. DOSITRACE platform, allowing automated data collection and historical patient dosimetry was installed. A couple of approaches have been implemented: a risk management approach that is oriented toward a prevention-based perspective and another risk management approach that is oriented toward a curative-based perspective. Results The use of DOSITRACE in clinical routine has enabled us to identify the recanalization of Chronic Total Occlusion (CTO) as the one which may deliver the highest patient radiation dose. Subsequently, the working group has become interested in this procedure to figure out the factors that determine the escalation of the radiation dose delivered to the patient. The results are as follows: ● An average reduction of 15% of the radiation dose delivered to the patient through a process of optimization of the dose was obtained. ● A correlation between the BMI, the beam angulation and patient radiation dose was found. ● For the procedure for recanalization of CTO, an increase in dose in terms of the complexity factor J-CTO score was highlighted: Score = [0, 1, 2, 3, 4]: Average Dose Area Product (DAP) = [152,160,244,299,418 Gy cm2]. In parallel, the group has worked on the equivalent dose effect of the entrance skin doses delivered for the repeated interventions in order to predict the occurrence of deterministic effects due to cumulative dose. A method, published by the team Balter et al. in 2010 was implemented in DOSITRACE. For the case of the repeated recanalization of CTO, we have implemented an innovative predictive risk method depending on the J-CTO score and BMI. A radiochromic film dosimetry was implemented in a systematic manner for CTO procedures to measure precisely the maximum skin dose delivered to the patient (Peak Skin Dose PSD), a real risk indicator. Conclusion This project has enabled us to identify the high-dose procedures and to implement methods to predict the risk of deterministic effects occurring, both based on the cumulating PSD for the repeated recanalization of CTO interventions, and the J-CTO Score.