Comparison of Dosimetry Approaches in Interventional RadiologyDocument Transcript
Comparison of Dosimetry Approaches in Interventional RadiologyAuthor: R. Padovani, E. QuaiLead Partner: Ospedale S. Maria della Misericordia, Udine, ItalyPart 1 Publishable Final Report1.1 Executive publishable summaryPatient dosimetry methods currently used in interventional radiology may be dividedin three categories according to dosimetry purposes: (i) dosimetry for stochastic riskevaluation, (ii) dosimetry for quality assurance, (iii) dosimetry to preventdeterministic effects of radiation(i) Dosimetry for stochastic risk evaluationDosimetry quantities able to measure the stochastic risk from body irradiation are: (a)the organ equivalent dose to selected organs and tissues, (b) effective dose. Thesequantities represent convenient indicators of overall exposure in the assessment ofdiagnostic practice and population exposure and they estimate the risks to the healthfrom the stochastic effects of radiation.The quantities are able to compare exposures from different types of procedures,irradiation geometries and radiation type and quality.(ii) Dosimetry for quality assuranceDosimetry for quality assurance is addressed to evaluate the optimization level of theradiological practice, compare performance of equipment and operator skill orcompare the practice among different centres. Dose and technical factor quantities areuseful indicators for fluoroscopy guided procedures: (a) fluoroscopy time and/ornumber of acquired images, (b) total dose-area product, dose-area product for imageacquisition and dose-area product for the fluoroscopy part of the procedure.(iii) Dosimetry to prevent deterministic effectsFor intensive image procedures in complex interventions, the knowledge of thelocalized dose to skin is important to assess the potential of deterministic effects ofirradiation on the skin. Such quantity, expressed in term of Maximum EntranceSurface Dose (MESD), can be assessed with different methodologies: (a) by directcalculation, with off or on-line techniques, (b) direct measurements on the patientwith point detectors (TLDs or other solid state detectors), (c) direct measurements onthe patient with large area detectors (films and TLDs array), and (d) by portalmonitoring with area or point/area detectors (DAP, DAP+K).The dosimetric methods for the evaluation of stochastic effects and for the purposesof quality assurance are well defined and, usually, simple to apply. They allow to
obtain comparable results among different institution. In the case of the assessment oflocalised skin dose, the methods are complex and difficult to apply in the routinepractice. Usually they are adopted for research purposes on a reduced sample ofpatients and procedures. The development of on-line methods, based on calculation ofskin dose distribution on the patient’s skin, is in our opinion, the best solution to alertpractitioners when the localised skin dose is approaching the threshold fordeterministic injuries.1. Detailed Final Report2.1 Objective and strategic aspectsInterventional radiology contributes with a significant proportion of the collectiveeffective dose to the population from medical exposures. Its frequency is increasingyear on year as knowledge of its benefits becomes more wide spread and moredifficult/complicated procedures are technically feasible.Interventional radiology procedures are usually fluoroscopy guided diagnostic andtherapeutic interventions; less frequent are the interventions where ultrasound and CTor CTfluoro and MR equipment are used.When complex procedures are performed or procedures are repeated for the samepatient high radiation dose levels occur. In particular, reasons for high patient dosesare: - the procedures may be complicated and require even hours of fluoroscopic guidance in some cases - the procedures may require high-quality, low-noise images - operators may not have sufficient training in radiology imaging, quality assurance and radiation protection.The most complicated interventional procedures are typically performed for patientswho have been diagnosed with severe medical problems. The literature of case reportsdescribing deterministic effects is growing and the potential for deterministic effectson the skin may be of more concern than stochastic long term risks.The Food and Drug Administration (FDA, 1994), World Health Organisation (WHO,2000) and International Commission on Radiological Protection (ICRP, 2000) haverequested attention to the skin dose problems of complicated radiologicalinterventions, giving advices to optimise the techniques.In this context, patient dosimetry approaches are an important issue. Frequentlypublished dose data are expressed in terms of not particularly well defined dosequantities and without clear objective for the measurements performed.This workpackage aims to report and compare dosimetry approaches and propose aclassification of the different dosimetry objectives.
2.2 Scientific and technical description of the resultsAnalysis of different approachesPatient dosimetry methods currently used in interventional radiology, derived fromthe enclosed literature survey (Annex), may be divided in three categories accordingto dosimetry purposes: (i) dosimetry for stochastic risk evaluation (ii) dosimetry for quality assurance (iii) dosimetry to prevent deterministic effects of radiation (skin dose assessment)Dosimetry for stochastic risk evaluationModels, methods for adult and pediatric patient are well developed and practical toolsare available for routine evaluation with an accuracy sufficient for the scope of theevaluation. Assessment of variability of E with patient size in respect to DAPmeasurements is described in the workpackage WP 5.5.Dosimetry for quality assuranceMethods, technical and dosimetry quantities are defined for the purpose to assess theoptimization level of procedures, compare practices performed in different centers orcompare operator skill. For such quantities DIMOND has explored the possibility tointroduce reference levels in interventional radiology for selected and commonprocedures.Dosimetry to prevent deterministic effects of radiation (skin dose assessment)Different approaches to evaluate maximum (localised) entrance surface dose havebeen developed and experienced but a final conclusion has not been reached.Dosimetry methods for off-line evaluation are developed and they allow theestimation of MESD: methods using area detectors are the choice methodology.Dosimetry methods for on-line evaluation are necessary to prevent deterministiceffects in single long and complex procedures, but are not available for routine work. A two level approach is proposed: 1. A first level able to prevent deterministic effects with an indirect assessment of MESD: i. A threshold (or trigger) of technical (fluoro time) and/or simple measurable dosimetry quantities (DAP) is selected for each procedure type and able to alert the operator that a certain value of ESD, corresponding to a threshold for deterministic effects, can be reached 2. A second level with techniques able to assess MESD requires the development of specific methods: i. Electronic point detectors are useful when procedures are using almost stationary fileds (e.g. in interventional cardiology: electrophysiology, RF cardiac ablation)
ii. Computational methods able to asses skin dose distribution from technical data on-line supplied by the x-ray equipment (tube output, field sizes, geometry of irradiation, etc.)1. Dosimetry for stochastic risk evaluationDosimetry quantities able to estimate the stochastic risk from body irradiation are: a. organ equivalent dose to each organ and tissue b. effective dose 1, 2, 5, 8, 10, 11, 13, 17, 18, 19, 22, 29, 30, 31These quantities represent convenient indicators of overall exposure in the assessmentof diagnostic practice and population exposure and reflect the risks from thestochastic effects of radiation exposure. These quantities are able to compareexposures from different types of procedures, irradiation geometries and radiationtype and quality.ICRP (Report No. 60) recommends that effective dose is not used to estimatedetriment (to individuals or population) from medical exposure. This assessment canbe inappropriate because of the uncertainties arising from potential demographicdifferences (status, age, sex, etc.) between population in the study and population forwhich the risk coefficients have been assessed. For example, when applied to youngor pediatric patients, effective dose can underestimate the detriment by a factor of 2or, in the case of old patient, the detriment can be overestimated by a factor of 5(NRPB 4, 1993).2. Dosimetry for quality assuranceDosimetry for quality assurance is addressed to evaluate the optimization level of thepractice, to compare performance of equipment and operator skill and to compareradiological practice among different centres.Useful dose quantities, for fluoroscopy guided procedures, are: a. Dose-area product: the total dose-area product (DAP) for the whole procedure, the dose-area product DAPfluoro for the fluoroscopy part of a procedure and the dose-area product DAPcine for the imaging acquisition part of a proceudre 2, 5, 7, 9, 14, 18, 21But also technical quantities, characterising the procedure protocol are proposed bydifferent authors: b. the total fluoroscopy time of a procedure, the total number of acquired images, the number of series of acquired images, the mean number of images per series in a procedure.3. Dosimetry to prevent deterministic effects (skin dose assessment)For the intensive image procedures used in interventional radiology, the knowledge ofthe localized dose to skin is important with respect to the potential for deterministiceffects of irradiation.
Such exposure, expressed in term of Maximum Entrance Surface Dose (MESD), canbe assessed with different methodologies: a. calculation (off-line or on-line) 3, 8, 16, 33 b. direct measurements on the patient with point detectors (TLDs or solid state detectors) 5, 24, 27, 29 c. direct measurements on the patient with area detectors (film and TLD array) 6, 7, 20, 25, 27 d. by portal monitoring (Wagner BJR 1999) with point or area detectors (DAP, DAP+K) 4, 12, 15, 16, 23, 26, 27
Bibliography1. Alaei P, Gerbi Bj, Geise Ra. Evaluation of a Model-Based Treatment Planning System for Dose Computations in the Kilovoltage Energy Range, Med. Phys. (2000); 27(12): 2821-28262. Chapple Cl, Broadhead Da, Faulkner K. A Phantom Based Method for Deriving Typical Patient Doses from Measurements of Dose-Area Product on Populations of Patients, Br. J. Radiol. (1995); 68:1083-10863. Cotelo E, Pouso J, Reyes W. Radiofrequency Catheter Ablation: Relationship Between Fluoroscopic Time And Skin Doses According to Diagnoses. Basis to Establish a Quality Assurance Programme, Iaea-Cn-85/168 Radiological Protection of Patients in Diagnostic And Interventional Radiology, Nuclear Medicine And Radioterapy4. Cusma Jt, Bell Mr, Wondrow A Et Al. Real Time Measurement of Radiation Exposure to Patients During Diagnostic Coronary Angiography and Percutaneous Interventional Procedures J. Am. Coll. Cardiol (1999); 33:427- 4355. Garcia-Roman Mj, Prada-Martinez E, Abreu-Luis J, Hernandez-Armas J. Patient Radiation Doses from Neuroradiology Procedures, Iaea-Cn-85/112 Radiological Protection of Patients in Diagnostic and Interventional6. Geise Ra, Ansel Hj. Radiotherapy Verification Film for Estimating Cumulative Entrance Skin Exposure for Fluoroscopic Examinations Healt Phys. (1990); 59(3):295-2987. Hernando I, Torres R. Comparison Between Termoluminiscence Dosimetry and Transmission Ionization Chamber Measurements, Iaea-Cn-85/177 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radioterapy8. Huda W, Phadke K, Ogden Km, Roskopf Ml. Patient Doses in Digital Cardiac Imaging Iaea-Cn-85/64 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radioterapy9. Huyskens Cj, Hummel Wa. Data Analysis on Patient Exposures in Cardiac Angiography Rad. Prot. Dosim. (1995); 57(1-4):475-48010. Le Heron Jc. Estimation of Effective Dose to the Patient During Medical X-Ray Examinations from Measurements of the Dose-Area Product, Phys. Med. Biol. (1992); 37(11):2117-212611. Leung Kc, Martin Cj., Effective Doses for Coronary Angiography, Br. J. Radiol. (1996); 69:426-43112. Marsden Pj, Washington Y, Diskin J. Estimation of Skin Dose in Interventional Neuro and Cardiac Procedures, Iaea-Cn-85/62 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radioterapy13. Marshall Nw, Noble J, Faulkner K. Patient and Staff Dosimetry in Neurological Procedures, Br. J. Radiol. (1995); 68:495-50114. Mcparland Bj., A Study of Patient Radiation Doses in Interventional Radiological Procedures, Br. J. Radiol. (1998); 71:175-185
15. Mcparland Bj., Entrance Skin Dose Estimates Derived from Dose-Area Product Measurements in Interventional Radiological Procedures, Br. J. Radiol. (1998); 71:1288-129516. Mooney Rb, Mckinstry Cs, Kamel Ham., Absorbed Dose and Deterministic Effects to Patients from Interventional Neuroradiology, Br. J. Radiol. (2000); 73:745-75117. Rodriguez-Romero R, Diaz-Romero F, Hernandez-Armas J., Absorbed Doses to Patients from Angioradiology, Iaea-Cn-85/111 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radioterapy18. Ruiz-Cruces R, Pérez-Martinez M, Martin-Palanca A, Flores A, Cristofol J, Martinez-Morillo M, Diez De Los Rios A., Patient Dose in Radiologically Guided Interventional Vascular Procedures: Conventional Versus Digital Systems, Radiology (1997); 205:385-39319. Ruiz-Cruces R, Garcìa-Granados J, Diaz-Romero Fj, Hernandez-Armas J., Estimation of Effective Dose in Some Digital Angiographic and Interventional Procedures, Br. J. Radiol. (1998); 71:42-4720. Theodorakou C, Butler P, Horrocks Ja., Radiation Doses in Interventional Neuroradiology, Iaea-Cn-85/68 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radioterapy21. Toivonen M., Patient Dosimetry Protocols in Digital and Interventional Radiology, Rad. Prot. Dosim. (2001); 94(1-2):105-10822. Tort I, Ruiz-Cruces R, Pérez-Martìnez M, Carrera F, Ojeda C, Dìez De Los Rìos A., Organ Doses in Interventional Radiology Procedures: Evaluation of Software, Iaea-Cn-85/226 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radioterapy23. Van De Putte S, Verhaegen F, Taeymans Y., Correlation of Patient Skin Doses in Cardiac Interventional Radiology With Dose-Area Product, Br. J. Radiol. (2000); 73:504-51324. Vaño E, Gonzalez L, Fernandez Jm, Guibelalde E., Patient Dose Values in Interventional Radiology, Br. J. Radiol. (1995); 68:1215-122025. Vano E, Guibelalde E, Fernandez Jm, Ten Ji., Patient Dosimetry in Interventional Radiology Using Slow Films, Br. J. Radiol. (1997); 70:195-20026. Wagner Lk, Pollock Jj., Real-Time Portal Monitoring to Estimate Dose to Skin of Patients from High Dose Fluoroscopy, Br. J. Radiol. (1999); 72:846-85527. Waite Jc, Fitzgerald M., An Assessment of Methods for Monitoring Entrance Surface Dose in Fluoroscopically Guided Interventional Procedures, Rad. Prot. Dosim. (2001); 94(1-2):89-9228. Waite Jc, Fitzgerald M., An Assessment of Methods for Monitoring Entrance Surface Dose in Fluoroscopically Guided Interventional Procedures, Iaea-Cn- 85/61 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radiotherapy29. Webster Cm, Hayes D, Horrocks J., Investigation of Radiation Skin Dose in Interventional Cardiology, Iaea-Cn-85/71 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radioterapy30. Wise Kn, Sandborg M, Persliden J, Alm Carlsson G., Sensitivity of Coefficients for Converting Entrance Surface Dose and Kerma-Area Product to Effective
Dose and Energy Imparted to the Patient, Phys. Med. Biol. (1999); 44:1937- 195431. Zweers D, Geleijns J, Aarts Njm, Hardam Lj, Laméris Js, Schultz Fw, Schultze Kool Lj., Patient and Staff Radiation Dose in Fluoroscopy-Guided Tips Procedures and Dose Reduction, Using Dedicated Fluoroscopy Exposure Settings, Br. J. Radiol. (1998); 71:672-67632. Recording Information in the Patients Medical Record that Identifies the Potential for Serious X-Ray-Induced Skin Injuries. Fda. 15th September 1995.33. Geise Ra, Peters Ne, Dunnigan A, Milstein S. Pacing, Radiation Doses During Pediatric Radiofrequency Catheter Ablation Procedures, Clin Electrophysiol 1996; 19: 1605-1134. Nawfel Rd, Judy Pf, Silverman Sg, Hooton S, Tuncali K, Adams Df, Patient and Personnel Exposure During CT Fluoroscopy-Guided Interventional Procedures, Radiology 2000; 216: 180-4.
Annex: Literature summary of methods for patient dosimetry in interventional radiology1. Alaei P, Gerbi BJ, Geise RA. EVALUATION OF A MODEL-BASED TREATMENT PLANNING SYSTEM FOR DOSE COMPUTATIONS IN THE KILOVOLTAGE ENERGY RANGE Med. Phys. (2000); 27(12): 2821-2826The authors use a commercial treatment planning system (ADAC, Pinnacle) tocompute the dose within phantoms from kilovoltage x-rays and to compare thecalculation with measurements made using TLD dosimeters placed in severalphantoms. The planning system’s capabilities have been extended to lower energiesby the addition of energy deposition kernels in the 20-110 keV range and modellingof beams.Phantoms are: - a cubic solid water phantom; - a solid water phantom with lung-equivalent heterogeneity; - a solid water phantom with bone-equivalent heterogeneity; - an Alderson Rando anthropomorphic phantom.The comparison between measured and computed values shows that the treatmentplanning system can be used with reasonable accuracy to determine the dosedistribution. The system’s limitations introduce inaccuracies for calculations throughmoderately high atomic number materials such as bone. These inaccuracies can begreatly reduced by a modification of existing tools to more accurately describe theinteractions of radiation for lower-energy photon beams.2. Chapple CL, Broadhead DA, Faulkner K. A PHANTOM BASED METHOD FOR DERIVING TYPICAL PATIENT DOSES FROM MEASUREMENTS OF DOSE-AREA PRODUCT ON POPULATIONS OF PATIENTS Br. J. Radiol. (1995); 68:1083-1086One of the chief sources of uncertainty in the comparison of dosimetry data is theinfluence of patient size on dose. The purpose of this work is to develop a method fordetermining size correction factors.Energy imparted correlates better with the ‘equivalent cilindrical diameter’: de=2(sqrt(W/πH))than with weight or patient thickness.If an exponential relationship is assumed between dose and size, size correction factorresult: F=ek(deref – de meas)The factor k must be determined experimentally.
Measurements were carried out using different thickness of tissue equivalent phantommaterial. Values of k have been determined and ranged from 0.13 to 0.18 cm-1, allwith correlation coefficients greater than 0.997.The use of size correction factor allows the inclusion of all patients within a surveyand should improve the accuracy of the results of a small sample size.Data are available for converting DAP to effective dose for reference size man andmay be applied to size corrected DAP values.3. Cotelo E, Pouso J, Reyes W. RADIOFREQUENCY CATHETER ABLATION: RELATIONSHIP BETWEEN FLUOROSCOPIC TIME AND SKIN DOSES ACCORDING TO DIAGNOSES. BASIS TO ESTABLISH A QUALITY ASSURANCE PROGRAMME IAEA-CN-85/168 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadioterapyThe authors determinate the fluoroscopy time and skin doses in relation to pathologyto treat. Authors evaluate fluoroscopic time and estimate skin doses in 233procedures. Significant differences among the medians of fluoroscopic time are foundin those procedures depending on diagnosis and results.Skin doses were evaluated as: D(Gy)=BF Output(distance corrected) mA Fluoroscopy TimeThis method gives dose evaluation affected by significant errors and overestimatesskin doses.4. Cusma JT, Bell MR, Wondrow A et al. REAL TIME MEASUREMENT OF RADIATION EXPOSURE TO PATIENTS DURING DIAGNOSTIC CORONARY ANGIOGRAPHY AND PERCUTANEOUS INTERVENTIONAL PROCEDURES J. Am. Coll. Cardiol (1999); 33:427-4355. Garcia-Roman MJ, Prada-Martinez E, Abreu-Luis J, Hernandez-Armas J. PATIENT RADIATION DOSES FROM NEURORADIOLOGY PROCEDURES IAEA-CN-85/112 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadioterapyThe objective of the work is to establish typical values of effective dose and DAP forsome neuroradiological procedures. The measurements on patients were: - DAP measurements both for fluoroscopy and radiography with relative projection; - Skin dose measurements with TLD placed at the zones thought to be at major exposure.
Some procedures were also performed with a phantom with TLDs into it to measuredose released to organs. Dose released to organs and effective dose were alsocalculated with Monte Carlo simulation.The comparison between measured and calculated doses gave rise major values tothose measured.6. Geise RA, Ansel HJ. RADIOTHERAPY VERIFICATION FILM FOR ESTIMATING CUMULATIVE ENTRANCE SKIN EXPOSURE FOR FLUOROSCOPIC EXAMINATIONS Healt Phys. (1990); 59(3):295-298In this study the exposure was measured using an ion chamber system placed in frontof pre-packaged film and was corrected for the inverse square distance dependence.The verification film was used to measure patient exposure during air contrast bariumenema examinations. TLDs were placed in appropriate locations on several films tocheck the agreement of film exposures to those determined with the TLDs. The TLDswere calibrated against the same ion chamber system used to perform thesensitometry measurements of the film. TLD reading were converted to exposure forcomparing with film exposure values.The average difference between exposures determined by film and exposuresdetermined by TLD was 9%. The maximum difference was 21%.If the TLD happens to be placed near the edge of a field, the dose estimation may besignificantly different than that in the centre of the field. The use of an area detector,such as film, allows for locating the centre of each spot film field and correlating thefields with the anatomical regions being examined.7. Hernando I, Torres R. COMPARISON BETWEEN TERMOLUMINISCENCE DOSIMETRY AND TRANSMISSION IONIZATION CHAMBER MEASUREMENTS IAEA-CN-85/177 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadiotherapyThe authors compare simultaneous measurements of skin dose made with TLDs andwith a DAPmeter. TLD are positioned on the patient’s back in an array made by 2x10chips and 18x2 cm2. DAP-meter: is positioned at the tube exit. The determination offield size at the patient’s skin is made by a radiographic film positioned at thepatient’s back.Calculation of skin dose results from: Dcalc=(F(p,T) Fr Ft L)/Swere: F(p,T) = correction factor for pressure and temperature; Fr = backscattering factor; Ft = transmission factor of operating table; S = field size; L = measurement from DAP-meter.
The calculation does not take into account tube movements, overestimating skindoses.Direct measurements of skin doses with TLDs are more accurate, but do not allowimmediate feedback to the operator. On the other hand, the DAP-meter giveinstantaneous results but all the parameters entering in the dose calculation areaffected by significant errors.8. Huda W, Phadke K, Ogden KM, Roskopf ML. PATIENT DOSES IN DIGITAL CARDIAC IMAGING IAEA-CN-85/64 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadiotherapyThe authors estimate entrance skin doses and the corresponding effective doses topatients undergoing digital cardiac imaging procedures.The x-ray output is determined in terms of air kerma per unit of mAs. Data for the x-ray parameters are recorded for each separate projection. From this informationmaximum skin doses are estimated by taking into account any overlap of the x-rayprojection used for each patient.9. Huyskens CJ, Hummel WA. DATA ANALYSIS ON PATIENT EXPOSURES IN CARDIAC ANGIOGRAPHY Rad. Prot. Dosim. (1995); 57(1-4):475-480In this study an empirical formula has been derived to estimate the kerma-exposureproduct as a function of fluoroscopy time and film length, providing an useful methodto evaluate exposures in interventional radiology (the variability in film length andfluoroscopy time is generally far more important than variations in technicalparameters).The kerma-area product is a direct measure for the patient dose. The kerma-areaproduct can be approximated by the function: KAP = α FT + β CLWhere:FT = fluoroscopy time (min) CL = film length (m)Using a self-made phantom and instruments calibrated in terms of Gycm2, for alldifferent types of projections and usual image intensifier field sizes, differentialvalues for the kerma-area product per unit fluoroscopy time have been measured aswell as the differential values of the kerma-area product per unit film length.For a full interventional procedure, the contribution to the kerma-area product fromfluoroscopy and from cinematography were calculated.It is concluded that the kerma-area product per patient (Gy cm2) in the course of aninterventional procedure can be approximated by:
KAP = 2.5 FT + 0.7 CLUncertainties in the coefficients α and β are estimated to be approximately 40%.10. Le Heron JC. ESTIMATION OF EFFECTIVE DOSE TO THE PATIENT DURING MEDICAL X-RAY EXAMINATIONS FROM MEASUREMENTS OF THE DOSE-AREA PRODUCT Phys. Med. Biol. (1992); 37(11):2117-2126Calculation of effective dose requires the evaluation of doses to many organs. In theabsence of such data it would be useful to directly estimate effective dose from aquantity that can be easily measured in an x-ray room. Relationship between effectivedose and entrance surface dose, entrance air kerma and DAP were studied forcommon radiographic projections using the organ dose data from Monte Carlomodelling. DAP proved to be the best quantity for estimating effective dose.Groups of projections have similar conversion coefficients and then can be grouped.Within these groupings it is possible to assign a limited number of conversioncoefficients to enable an estimate of effective dose from DAP measurements,provided a given level of uncertainty.Use of the conversion coefficients for asymmetrical fields may lead to additionaluncertainties. Caution must be exercised with small fields. Finally, the conversioncoefficients will provide estimates of effective dose for average patients.11. Leung KC, Martin CJ. EFFECTIVE DOSES FOR CORONARY ANGIOGRAPHY Br. J. Radiol. (1996); 69:426-431The calculation of dose conversion coefficients for a wide variety of radiographicprojections has enabled effective doses to be evaluated for procedures where DAP andexposure factor data were available. Effective doses have been derived for coronaryangiography examinations.Data were recorded for 100 coronary angiographies. Data from 10 patients, wherefluoroscopy and radiography were similar to the mean for the group, were consideredto representative of a standard examination. These procedures were used to deriveconversion factors. For every examination the chronological sequence of patientpositions and projections was recorded for all periods of radiography and fluoroscopy.A DAP calibration factor was applied to each period related to projection employedand a size correction factor was applied to give the equivalent DAP for a standardman.Because of the similarities in the patterns of exposure, a standard conversion factorbetween DAP and effective dose was derived for application to data for wholeexaminations.
12. Marsden PJ, Washington Y, Diskin J. ESTIMATION OF SKIN DOSE IN INTERVENTIONAL NEURO AND CARDIAC PROCEDURES IAEA-CN-85/62 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadiotherapyThis paper presents measurements made on antropomorphic phantoms which can beused to link DAP values to skin doses for situations typically encountered in bothinterventional neuroradiology and cardiac procedures.Skin doses were measured directly using a Skin Dose Monitor placed on the entrancesurface at the centre of the field of view. DAP readings were obtained simultaneouslyfrom pre-installed DAP-meter. Conversion factors of DAP to Skin Dose ConversionFactors in Cardiac Fluoroscopy for seven projections are reported.13. Marshall NW, Noble J, Faulkner K. PATIENT AND STAFF DOSIMETRY IN NEUROLOGICAL PROCEDURES Br. J. Radiol. (1995); 68:495-501The aim of the study was to monitor staff doses and to estimate patient organ dosesdue to cerebral angiography and evaluate patient effective dose.Examinations were usually performed under automatic exposure-rate control. Patientthyroid doses were measured with TLDs and general patient dosimetry performedusing a DAP-meter.Estimation of effective dose, requiring the equivalent dose to 12 organs, was madewith TLDs inside a Rando phantom undergoing a typical vessel angiogram. The DAPfor the typical angiogram was recorded and from this a DAP to effective doseconversion factor calculated. In order to estimate the contribution to DAP andeffective dose from the fluoroscopy component of the examination, this entireprocedure was repeated without taking any digital subtraction radiographs.An effective dose/DAP conversion factor for cerebral angiography of 0.087mSvGy-1 cm-2 is reported.14. McParland BJ. A STUDY OF PATIENT RADIATION DOSES IN INTERVENTIONAL RADIOLOGICAL PROCEDURES Br. J. Radiol. (1998); 71:175-185A dose survey of interventional radiology procedures performed on a digitalangiography unit, its analysis and comparison with other data in the literature, arereported.Owing to the complexity of IR procedures, accurate assessment of patient doses isdifficult and averaging over varying beam qualities and anatomical projections istherefore necessary.
DAP values were recorded separately, for fluoroscopy and digital radiography. Withknowledge of beam quality, anatomical region imaged and radiographic projection,the effective dose can be estimated from the DAP using factor for converting DAPmeasurements to effective dose derived from Monte Carlo simulations.The hypothesis that therapeutic procedures have significantly higher DAPs thandiagnostic procedures was tested for five sets of pairs of procedures, each in the sameanatomical region, so that the DAP to ESD conversion factor for each pair was equal.Even though there may appear to be a large difference in mean DAPs between the twocategories, only one pair showed a statistically significant increase in mean DAP forthe therapeutic procedure over the diagnostic procedure.There is evidence of a wide variation in patient radiation dose due to clinicaltechnique differences, statistical sampling and type of x-ray equipment used.15. McParland BJ. ENTRANCE SKIN DOSE ESTIMATES DERIVED FROM DOSE-AREA PRODUCT MEASUREMENTS IN INTERVENTIONAL RADIOLOGICAL PROCEDURES Br. J. Radiol. (1998); 71:1288-1295A method of estimating ESD from measured DAP data for a number of IR proceduresby assuming that each procedure is conducted under a fixed nominal geometryspecific to it, is presented.The uncertainties due to the use of a single nominal geometry for a procedure areanalysed. Finally, ESD estimates are provided for a number of non-coronaryprocedures using DAP data accrued for an IR dose survey at the institution.Changes in ESD caused by deviations in the focus-to-skin and focus-to-imageintensifier distances from the nominal value are well modelled; the dependence of thedose error upon the image intensifier field-of-view is significant, due to the field areadependence of the denominator in the model. Even for the nominal geometry, there isa difference between the calculated and measured doses due to the measurementsperformed on an homogeneous phantom. The ESD uncertainty is also due to theadditional collimation and image intensifier field-of-view used.The overall uncertainty can be comparable to that of other methods commonlyadopted to estimate ESD; moreover, the ease of proposed method allows largenumbers of patients to be surveyed.16. Mooney RB, McKinstry CS, Kamel HAM. ABSORBED DOSE AND DETERMINISTIC EFFECTS TO PATIENTS FROM INTERVENTIONAL NEURORADIOLOGY Br. J. Radiol. (2000); 73:745-751Measurements of absorbed dose to the patient skin undergoing interventionalneurological procedures, involving long fluoroscopy time, were made. From dosemeasurements and records of fluoroscopy time and number of digital runs acquired,estimates of the maximum absorbed skin dose and the maximum absorbed dose to theskull were made.
TLD dosimeters were placed over the areas considered most likely to receive theheaviest irradiation. “Effective” fluoroscopy time can be introduced, which is acombination of the actual fluoroscopy time and the number of DSA runs acquired, togive an indication of the procedure length.Early clinical experience with kilovoltage beams suggests that clinically significantbone damage is not likely to occur without accompanying skin effects.17. Rodriguez-Romero R, Diaz-Romero F, Hernandez-Armas J. ABSORBED DOSES TO PATIENTS FROM ANGIORADIOLOGY IAEA-CN-85/111 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadiotherapyThe aim of the study was to know the patient doses when three different procedures ofangioradiology were carried out. DAP measurements and TLDs were used in ananthropomorphic phantom to obtain values of organ doses when the phantom wassubmitted to the same procedure than the actual patients.The Eff-Dose program was used to estimate the effective doses in the proceduresconditions. The organ doses estimated from TLDs measurements were higher than thecorresponding values estimated by Monte Carlo simulation.18. Ruiz-Cruces R, Pérez-Martinez M, Martin-Palanca A, Flores A, Cristofol J, Martinez-Morillo M, Diez de los Rios A. PATIENT DOSE IN RADIOLOGICALLY GUIDED INTERVENTIONAL VASCULAR PROCEDURES: CONVENTIONAL VERSUS DIGITAL SYSTEMS Radiology (1997); 205:385-393The work includes: evaluations of DAP value differences between conventional anddigital systems and, evaluation of organ and effective dose in procedures performedwith digital systems.For interventional vascular procedures, which involve considerably long fluoroscopytime and variation in beam direction and size, the entrance dose cannot beconveniently measured with TLD dosimeters. The dose measured in five organs whitthe Padovani’s method with TLDs placed on the surface of the patient’s skin wascompared with the organ dose calculated with Eff-Dose. In addition Eff-Dose wasused to calculate the effective equivalent dose. It is reported that, DAP was higherwith the digital system in 13 of the 15 groups analysed.19. Ruiz-Cruces R, Garcìa-Granados J, Diaz-Romero FJ, Hernandez-Armas J. ESTIMATION OF EFFECTIVE DOSE IN SOME DIGITAL ANGIOGRAPHIC AND INTERVENTIONAL PROCEDURES Br. J. Radiol. (1998); 71:42-47Effective dose is an indicator of radiological risk, but its magnitude cannot bemeasured directly, conversion factors from measurable quantities, like DAP, andeffective dose are necessary. In this study, who objective is to provide dose data for
some digital angiographic and interventional procedures, effective dose has beenestimated using Monte Carlo method.For each procedure, technical parameters for both fluoroscopy and radiography, fieldsize, fluoroscopy time and number of radiographic films were acquired. DAP valueswere corrected for the attenuation of the patient table.Effective dose, calculated independently for radiography and fluoroscopy, wasestimated by comparing the actual procedure with simple radiographic projectionspublished. The fluoroscopy component makes a large contribution to the total DAPvalues and a similar influence is observed on the average values of the effective dose.Effective dose values per minute of fluoroscopy and per radiographic film for the fivetypes of procedure analysed can be adopted as conversion factors to estimate thepatient effective dose.20. Theodorakou C, Butler P, Horrocks JA. RADIATION DOSES IN INTERVENTIONAL NEURORADIOLOGY IAEA-CN-85/68 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadiotherapyA preliminary study, performed on 13 patients that underwent to celebralembolization, is reported. Images are taken after injection of contrast medium withtwo imaging modalities: fluoroscopy and Digital Subtraction Angiography (DSA).The study investigates: Entrance Skin Dose TLDs Radiotherapy verification films System calculated values. DAP Organ Dose Operators doseTLD100 chips array 15x15cm2 (6x6 chips) were used. The chips were placed on theradiographic films: one under the patient’s head and one on the right side of the head.For doses above 1Gy, correction factors have been applied to TLD readings in orderto account for supralinearity. Radiotherapy verification films has been used tovisualise the radiation field. Software calculated doses from DAP-metermeasurements, for each plane and for each mode separately and from technicalparameters of radiation beam.Isodose curves are obtained superimposing TLD measurements and images takenfrom the films.Comparing the ESDcalc and the ESDmes for both planes, it may be seen that the ESDcalcin most cases are higher than ESDmes, overestimating the actual dose.Comparing the dose rates for fluoroscopy and DSA it may be seen that the doses fromDSA are much higher than that from fluoroscopy.
21. Toivonen M. PATIENT DOSIMETRY PROTOCOLS IN DIGITAL AND INTERVENTIONAL RADIOLOGY Rad. Prot. Dosim. (2001); 94(1-2):105-108In this paper the quantities proposed to express reference values for IR are reviewed,and methods to collect data required for estimation of their values are compared.Exposure indicators are manufacturer-specific and depend on several technicalfactors. The indicators must be calibrated to a particular air kerma at the imagereceptor periodically.Both the ESD and the DAP, multiplied by their related conversion factors E/ESD orE/DAP, provide an evaluation of the effective dose. The accuracy of the factorsE/DAP is better than those of E/ESD.22. Tort I, Ruiz-Cruces R, Pérez-Martìnez M, Carrera F, Ojeda C, Dìez de los Rìos A. ORGAN DOSES IN INTERVENTIONAL RADIOLOGY PROCEDURES: EVALUATION OF SOFTWARE IAEA-CN-85/226 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadiotherapyThe objective is to estimate organ doses and to make a comparison between theresults given by different software available to carry out the calculation of organdoses in complex interventional radiology procedures. Organ doses and effective dosehave been calculated, for each projection used in the procedures, with differentcommercially available software based on Monte Carlo simulation: Eff-dose, PCXMCand DiaSoft.Eff-dose and DiaSoft provide results practically equal; on the other hand, PCXMCgives very different results. The latter gives the advantage to adjust beam geometryand patient size.23. Van de Putte S, Verhaegen F, Taeymans Y. CORRELATION OF PATIENT SKIN DOSES IN CARDIAC INTERVENTIONAL RADIOLOGY WITH DOSE-AREA PRODUCT Br. J. Radiol. (2000); 73:504-513For a standardized coronary catheterization procedure and a left ventricle angiographyinvestigation, an average skin dose distribution was calculated from the measuredDAP of the different x-ray projections used in the procedure, using Monte Carloderived conversion factors. Attempts have been made to calculate individual skin dosedistributions, based on individual DAP measurements.Skin dose measurements were made using eight TLDs attached to the patient’s skin.To determine the optimal TLD position, an antrophomorphic phantom was coveredwith radiographic film and irradiated using the geometries and irradiation times used
in a standard procedure. The densitometric information obtained was used to calculateskin dose distribution and the area of the skin receiving the highest dose.Using Monte Carlo derived conversion factors, skin dose distributions were calculatedfor two average procedures.The study investigates whether DAP is representative of the skin dose ininterventional cardiology and whether the DAP can be used as an indicator for localoverexposure.Based on the average DAP values, the skin dose distribution, typical for a standardprocedure, was calculated. Good agreement was observed between the calculatedvalues and the TLD measurements.When applying the conversion factors to calculate the individual skin doses, theagreement between the calculated skin dose and the measured dose was rather poor.The study shows that the total DAP per procedure can give only an approximateindication of the skin dose, and support the view that total DAP cannot be used as anindicator of local overexposure.24. Vaño E, Gonzalez L, Fernandez JM, Guibelalde E. PATIENT DOSE VALUES IN INTERVENTIONAL RADIOLOGY Br. J. Radiol. (1995); 68:1215-1220Dose-area product can be used for patient stochastic risk evaluations, where thesurface dose provides an indication of possible deterministic effects.In this study: - DAP was measured using a transmission ionization chamber - surface dose was measured using four TLDs placed over, under and on both sides of the perimeter of the most irradiated patient region; the sum of the four values is used as a Surface Dose Indicator (SDI) for comparative purposes.The suitability of this method has been checked by comparing the results with thoseobtained using TLD arrays based on larger chip numbers. No noticeable loss ofinformation was observed when using four dosimeters.The transmission ionization chamber and TLD measurements were periodicallychecked.SDI values in cardiology are lower than for the rest of IR in nearly all instances,despite the higher DAP values.25. Vano E, Guibelalde E, Fernandez JM, Ten JI. PATIENT DOSIMETRY IN INTERVENTIONAL RADIOLOGY USING SLOW FILMS Br. J. Radiol. (1997); 70:195-200Patient dosimetry in IR and IC is extremely complex, due to the irradiation ofdifferent anatomical areas, with the x-ray beam changing to various projections, fieldsizes, radiation qualities, focus-to-skin distances and focus-to-image intensifierdistances. Typical measurement systems will not provide enough information forbody areas receiving higher doses.
The method proposed allows the simultaneous estimation of DAP, skin dose anddistribution of the irradiated fields, together with their corresponding dose levels.Kodak X-Omat V film has been used to visualize and estimate doses from thedifferent irradiation fields. X-ray sensitometry was carried out to calibrate the film forthe x-ray spectrum and filtration employed in IR and IC.Doses and reproduction of technical parameters were checked by using a calibratedchamber. Doses were also measured with TLD placed in contact with the film.The main source of error is due to the propagation of the error when the characteristicfunction is reversed to calculate doses.26. Wagner LK, Pollock JJ. REAL-TIME PORTAL MONITORING TO ESTIMATE DOSE TO SKIN OF PATIENTS FROM HIGH DOSE FLUOROSCOPY Br. J. Radiol. (1999); 72:846-855The author investigates advantages and disadvantages of a scintillation dosimeter(SD) as a portal monitor used to estimate skin dose during fluoroscopically-guidedprocedures. Uncertainties associated with the use of a portal monitor are discussed.Several methods have been proposed to perform real-time monitoring of skin dose: - direct monitoring: conceptually the simplest method, but the dosimeter, prior the procedure, must be placed at the site on the skin that will receive the highest dose; - indirect monitoring: infer skin doses from measurements made remotely from the skin; will overestimate the maximum dose because it cannot distinguish which area of the skin is being exposed at any time.In portal monitoring the detector is attached to the x-ray collimator beam at theposition of the central axis. A calibration factor was generated to convert the portalmonitor reading into tissue dose.Errors in the real time measurements of absorbed dose to the skin have severalsources here categorized as those related to the monitor and those related to themonitoring technique. SD has a reasonably accurate response over the range ofenergies, doses and operating conditions encountered in interventional work.27. Waite JC, Fitzgerald M. AN ASSESSMENT OF METHODS FOR MONITORING ENTRANCE SURFACE DOSE IN FLUOROSCOPICALLY GUIDED INTERVENTIONAL PROCEDURES Rad. Prot. Dosim. (2001); 94(1-2):89-9228. Waite JC, Fitzgerald M. AN ASSESSMENT OF METHODS FOR MONITORING ENTRANCE SURFACE DOSE IN FLUOROSCOPICALLY GUIDED INTERVENTIONAL PROCEDURES IAEA-CN-85/61 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and Radiotherapy
The authors compare three methods of monitoring Entrance Surface Dose (ESD) influoroscopically guided interventional procedures: - array of 35 TLDs - Skin Dose Monitor (SDM): a small detector in a reflecting plastic housing, linked by a fibre optic to a meter - DAPmeter+KTLD arrays are the most accurate means of measuring ESD but suffer from thesubstantial drawback of requiring post-exposure processing.A more simple method of monitoring ESD would be to establish a relationshipbetween ESD and DAP reading, but no correlation between the two sets ofmeasurements for cardiac procedures was obtained due, maybe, to great irradiationgeometry variation.The SDM compared favourably with a calibrated ionisation chamber in thelaboratory, is easy to use and gives a real time running total of the ESD, but: - the sensor has a small surface area, monitoring a limited area of the skin, that may not be the more irradiated - the system is too bulky - the optic cables are fragile and should be often replaced.29. Webster CM, Hayes D, Horrocks J. INVESTIGATION OF RADIATION SKIN DOSE IN INTERVENTIONAL CARDIOLOGY IAEA-CN-85/71 Radiological Protection of Patients in Diagnostic and Interventional Radiology, Nuclear Medicine and RadiotherapyIn the study, for 56 patients randomly selected (23 undergoing RadiofrequencyCatheter Ablation (RFCA); 33 undergoing Percutaneous Transluminal CoronaryAngioplasty (PTCA)), skin doses have been investigated: - radiation skin doses DAP-meter - TLD - possible skin damages resulting from the procedure (follow-up for a three month period).Measurements: - TLD gives point value of skin dose; the chips are placed directly on the patient’s back in 7 standard positions - DAPmeter gives an average value of dose, does not take into account dose distribution due to x-ray tube movements.Skin dose for each projection is achieved by dividing the DAP by the field size at thepatient’s skin and by multiplying for the backscatter factor.Results: RFCA: not significant correlation between calculated and TLD measuredskin doses (Correlation=0.76; p=0.08ns); PTCA: no correlation between calculatedand TLD measured skin doses (Correlation=0.15).
30. Wise KN, Sandborg M, Persliden J, Alm Carlsson G. SENSITIVITY OF COEFFICIENTS FOR CONVERTING ENTRANCE SURFACE DOSE AND KERMA-AREA PRODUCT TO EFFECTIVE DOSE AND ENERGY IMPARTED TO THE PATIENT Phys. Med. Biol. (1999); 44:1937-1954The estimation of the conversion coefficients from ESD or KAP to effective dose Erequires computer-intensive Monte Carlo methods. Tables are available for a widerange of tube potentials and filtrations but, field size, film-focus distance and positionof the centre of the field are fixed for each combination of phantom age andexamination. Again, there is limited information on the sensitivity of the conversioncoefficients to a number of variations seen in clinical work.The authors investigate the effect on E/DAP and E/ESD for variations of up to fivefactors of: tube potential, field size, field position, phantom size and sex.The method adopted a factorial analysis procedure in which each factor being studiedis varied over all combinations of two values, one low and the other high, chosenfrom observed variations in a single x-ray room. The question to be addressed is:which of the conversion coefficients is the least sensitive to variations which naturallyoccur within a given practice? The work confirms that substantial variations in theconversion coefficients can occur due to variation in field size, field position, patientsize and sex.Whether effective dose or energy imparted to the patient is best estimated using ESDor KAP? The study shows no strong preference for KAP over ESD for estimation of Ewhen all parameters are varied. A practical argument for the use of KAP over ESDcan be based on the observation that use of KAP automatically allows for variations infield size. In general KAP provides a good measure of energy imparted and is to bepreferred for its determination.31. Zweers D, Geleijns J, Aarts NJM, Hardam LJ, Laméris JS, Schultz FW, Schultze Kool LJ. PATIENT AND STAFF RADIATION DOSE IN FLUOROSCOPY-GUIDED TIPS PROCEDURES AND DOSE REDUCTION, USING DEDICATED FLUOROSCOPY EXPOSURE SETTINGS Br. J. Radiol. (1998); 71:672-676The DAP from fluoroscopy and imaging, displayed separately on the operator’sviewing console, were recorded after each procedure. DAP figures were calculatedfrom technical parameters by software. Comparison of calculated DAP tomeasurements by means of calibrated flat ionization chamber showed consistentdeviations throughout a range of different beam sizes with low, medium and high airkerma rates. Patient entrance doses were calculated by the measured DAP, averageentrance beam diameters and application of appropriate backscatter factor.
32. RECORDING INFORMATION IN THE PATIENTS MEDICAL RECORD THAT IDENTIFIES THE POTENTIAL FOR SERIOUS X-RAY-INDUCED SKIN INJURIES. FDA. 15th September 1995.The agency has been requested to clarify the recommendations given in the FDAPublic Health Advisory document of 9th September 1994 regarding ‘which patientsshould have such information recorded’ and ‘what information should be recorded’.The document presents the Agencys advice on these questions. Medical facilities areencouraged to implement these or similar procedures in order to reduce the likelihoodof radiation-related complications. (WP3.7)33. Geise RA, Peters NE, Dunnigan A, Milstein S. Pacing RADIATION DOSES DURING PEDIATRIC RADIOFREQUENCY CATHETER ABLATION PROCEDURES Clin Electrophysiol 1996; 19: 1605-11Radiofrequency catheter ablation procedures may be lengthy and are commonlyperformed in young patients and therefore, concern has arisen about radiation dose inthis group of patients.The authors investigate radiation doses in pediatric patients undergoing RF catheterablation. Standard fluoroscopic equipment used for diagnostic electrophysiologicalcatheterization studies is technologically capable of dose rates as high as 90 mGy/minto skin and adjacent lung and 260 mGy/min to vertebral bone. Dose rates of thismagnitude when used for extended periods of time have been known to causeerythema, pneumonitis, and retardation of bone growth.Skin dose rates of nine paediatric patients undergoing RF catheter ablation fortachycardia and calculated doses to the skin using standard dosimetric methods (fromexposure factors, gantry angle, X-ray field size and SSD) are reported. Fluoroscopictechniques and equipment were studied using a patient simulating phantom. Overlapof fluoroscopic fields was checked using radiotherapy portal verification film, andregions in which doses overlapped from multiple angle exposures were verified usinga treatment planning computer.Patient skin dose rates ranged from 6.2-49 mGy/min for patients ranging in age from2-20 years. Maximum skin doses ranged from 0.09-2.35 Gy. Actual skin dose ratesmay exceed 400 mGy/min. Some bone could receive a dose 2 or 3 times the thresholdset up for dry desquamation of the skin and so there is a potential for seriousimmediate effects (retardation of bone grow or even complete cessation of growthoccurs in young people at 30 Gy).The paper also highlights that TLD measurements of other authors do not account thefact that TLD readings do not reflect the maximum skin dose if the dosimeter is not inthe exact position of the fluoroscopic beam (see reference 12: Radiation exposure topatients undergoing percutaneous transluminal coronary angioplasty. Cascade PN ;Peterson LE ; Wajszczuk WJ ; Mantel J. Am J Cardiol, 59(9):996-7 1987 Apr 15).On average, the patient’s skin is getting about 1 thousand times the dose a personwould receive from secondary radiation at a distance of 1 m without wearing
protective lead apparel. Data demonstrate the need to directly measure dose rates forindividual fluoroscopic equipment and procedural techniques in order to determinewhether limitations need to be set for procedural times. (WP 3.7)34. Nawfel RD, Judy PF, Silverman SG, Hooton S, Tuncali K, Adams DF PATIENT AND PERSONNEL EXPOSURE DURING CT FLUOROSCOPY- GUIDED INTERVENTIONAL PROCEDURES Radiology 2000; 216: 180-4.Surface dose was estimated on a CT dosimetric phantom by using thermoluminescentdosimetric (TLD) and CT pencil chamber measurements. Scatter exposure wasestimated from scattered radiation measured at distances of 10 cm to 1 m from thephantom. Scatter exposures measured with and without placement of a lead drape onthe phantom surface adjacent to the scanning plane were compared. Phantom surfacedose rates ranged from 2.3 to 10.4 mGy/sec.Scattered exposure rates for a commonly used CT fluoroscopic technique (120 kVp,50 mA, 10-mm section thickness) were 27 and 1.2 µGy/sec at 10 cm and 1 m,respectively, from the phantom. Lead drapes reduced the scattered exposure byapproximately 71% and 14% at distances of 10 and 60 cm from the scanning plane,respectively.As a conclusion, high exposures to patients and personnel may occur during CTfluoroscopy–guided interventions. Radiation exposure to patients and personnel maybe reduced by modifying CT scanning techniques and by limiting fluoroscopic time.In addition, scatter exposure to personnel may be substantially reduced by placing alead drape adjacent to the scanning plane. (Vano 3.7)