PATIENT RADIATION DOSES IN DIAGNOSTIC RADIOLOGY

1 1 PATIENT RADIATION DOSES IN DIAGNOSTIC RADIOLOGY PATIENT RADIATION DOSES IN DIAGNOSTIC RADIOLOGY EDWARD L. NICKOLOFF, ZHENG FENG LU, OF RADIOLOGYCOLUMBIA UNIVERSITY& NEW YORK-PRESBYTERIAN HOSPTIALNEW YORK, NYORGANIZATION OF THE PRESENTATIONS PART 1: INTRODUCTION & REVIEW REVIEW OF DIFFERENT UNITS OF RADIATION MEASUREMENTS FACTORS THAT INFLUENCE PATIENT RADIATION DOSE PRACTICAL METHODS FOR ESTIMATING PATIENT RADIATION DOSES WITH REFERENCES2 ORGANIZATION OF THE PRESENTATIONS PART 2: TYPICAL RADIATION DOSE VALUES, RISKS & DEALING WITH PUBLIC SURVEYS REFERENCE VALUES FETAL DOSE CALCULATION GUIDES REVIEW OF SOME BIOLOGICAL RISKS DEALING WITH THE PUBLIC-WITH REFERENCESPATIENT RADIATION DOSES IN DIAGNOSTIC part 1 PATIENT RADIATION DOSES IN DIAGNOSTIC part 1 ZHENG FENG LU, DEPARTMENT OF RADIOLOGYCOLUMBIA UNIVERSITY& NEW YORK-PRESBYTERIAN HOSPTIALNEW YORK, NY3 RADIATION Quantity and Unit EXPOSURE (X):Amount of ion pairs created in air by x-ray or gamma RADIATION .

2 Unit is Roentgen. 1 R = (C/kg)4 RADIATION Quantity and Unit ABSORBED DOSE (D):Energy absorbed from ionizing RADIATION per unit mass. SI Unit is J/kg or Gray (Gy). Conventional unit is Gy = 100 rad or 1 rad = 10 mGy Soft tissue f-factor: for Quantity and Unit Equivalent Dose (H):Converts absorbed dose to equivalent tissue damage for different types of RADIATION . ICRP 92: RADIATION -weighted dose For X-ray, the weighting factor WRis 1. SI unit is Sievert (Sv). Conventional unit is Sv = 100 rem or 1 rem = 10 mSv5 RADIATION Quantity and Unit Effective Dose (E): =TTRTDWWE Concerns different tissue radiosensitivity Tissue weighting factors were established Assigned the proportion of the risk of stochastic effects (Includes fatal + non-fatal cancer risks + serious hereditary effects to all generations)resulting from irradiation of that tissue compared to a uniform whole body irradiation.

3 Weighting individual tissue dose to derive the whole body Tissue-Weighting Bone 60 (1991)ICRP 26 (1977)Tissue Bone Draft (proposed in 2005)ICRP 60 (1991)Tissue I2. FACTORS THAT INFLUENCE PATIENT RADIATION DOSER adiographyFluoroscopyMammographyComputed Tomography 7 Dose Affecting Factors X-RAY BEAM ENERGY (KVP):higher kVp results in lower dose. ADDED FILTRATION:Higher added filtration results in lower dose. COLLIMATION:Aggressive collimation reduces the irradiated area as well as scatter RADIATION . GRIDS:Grids reduce scatter RADIATION but increase PATIENT dose. IMAGE RECEPTOR:Faster speed image receptor reduces PATIENT dose. TUBE CURRENT AND EXPOSURE TIME (mAs):The PATIENT dose is proportional to mAs.

4 PATIENT SIZE:It is beneficial to optimize the technique chart for various PATIENT size and anatomic Dose Affecting Factors8CR: CR plates have lower speed, typically speed 200; Data manipulation tools available for digital image processing; More added filtration and higher kVpmay be used to reduce PATIENT : Usually, DR speed is faster. DR speed can be programmed according to the acceptable image noise Affecting Factors in Mammography Target materials: Molybdenum/Rhodium. Filter materials: filter target combination. Grids: The Bucky factor for mammography grids is usually in the range of 2-3. Mag mode: magnification increases dose. Compression Breast size and tissue composition kVp is 24-30 kVp.

5 RBE for such low energy x-ray photons is higher (BJR 79(2006):195-200).9 Dose Affecting Factors in Fluoroscopy Pulsed fluoroscopy vs. continuous fluoroscopy; Modern fluoroscopy systems are entirely automated. Various programmable features are Fluoro Vs. Pulsed Fluoro22 cm FOV, mm Cu Thickness (cm)ESER (R/min)continuous15 p/s3 p/s 10 ESER Reduction With Added Filtration22 cm FOV, continuous Phantom Thickness (cm)ESER (R/min) Cu 11 ! " ## $% ADULT DIAGNOSTIC CORONARY ANGIOGRAPHY (BASELINE: 16cm FoV, C PLUS, 30pps, GRID, 25cm PMMA)0102030405060708090100 SELECTABLE VARIABLESPERCENT RADIATION DOSE (%)C PLUS, 16cm Fov,30ppsC+ --> C NORMAL30pps --> 15pps16cm FoV --> 25cmFoVC- FLUORO & CNORMAL RECORDSID & SSDOPTIMIZEDAUTOCOLLIMATIONAUTO POSITION12 Factors Affecting CTDI X-RAY BEAM ENERGY (KVP):higher kVpresults in higher CTDI values.

6 X-RAY TUBE CURRENT (mA):dose is proportional to mAs. TUBE ROTATION TIME:dose is proportional to mAs. PITCH:inversely proportional to dose. X-RAY BEAM COLLIMATION:thinner collimation results in higher CTDI Affecting CTDI (..continued) PATIENT SIZE:smaller PATIENT size results in higher CTDI values. DOSE REDUCTION TECHNIQUE, , mAmodulation technique DETECTOR CONFIGURATION SLICE THICKNESS ADDED FILTRATION GEOMETRIC EFFICIENCY13 Take a guessIf the body size is reduced from 32 cm in diameter to 16 cm in diameter, the CTDI will be. A. the same B. increased by 50% C. doubled D. more than doubled05101520253035401015202530 Body Phantom Diameter (cm)Measured CTDIvol (mGy/100mAs)measured CTDIvol at 80 kVpmeasured CTDIvol at 100 kVpmeasured CTDIvol at 120 kVpmeasured CTDIvol at 140 kVp 14 Solid State Integrating DosimeterCOMPARISON OF BODY CT RADIATION DOSE PER 100 mAs vs.

7 WEIGHT024681012141618050100150200250 PATIENT WEIGHT (lbs.) RADIATION DOSE (mGy / 100 mAs)CTvol / 100 mAsMEAS. / 100 mAsLinear (MEAS. / 100 mAs)Linear (CTvol / 100 mAs)15 OUTLINEPart I3. PRACTICAL METHODS FOR ESTIMATING PATIENT RADIATION DOSES WITH REFERENCESP hantoms Acrylic phantoms Anthropomorphic phantoms: Mathematical phantoms: Reference Man 16 !" # $ #% $& ' # ( $ ( ' # ( $ =TTRTDWWE& ' ( )! * ) + ) , -. /!0 ! % 12 # ) 3 Limitations of Tabular Conversion Factors The reference person (male 154lb, female 128lb) has a fixed size. The number of exam types is limited. The number of exam settings is limited: field size, SID, etc. The number of organ types is limited.

8 The data were based upon cancer detriment index published earlier (need updated).17& ' % ") * ) "+,, (, ), ) ", ) -&4!) 4 ,' " ! ) , # 0 4! 4 ') ' , , ) ) , !)) ) ' ) !0 , - )!0 ! --)! # 0 5# 0 -/. !#! 6 0 , 7 !.0 8 # ) , 00 . 9 ! ) : ./00 ! " + 1) - !" %, 234 ) ) 5- * ) ) 6 # 3" $ ) " 5- 1 " !" # $ - 4 " ) ) 7 " ( Steps for Tissue Dose Estimation18 ! " + 1) ' % * " * ) "+,, (, ), ) ", ) .// Section 11 - RADIATION Dosimetry ( Adult Body)Use the TAB key to move between data entry cells in the column named Body Phantom (32-cm diameter PMMA Phantom)MeasuredkVp120mA480 Exposure time per rotation (s) axis collimation T (mm)13# data channels used (N)16 Axial (A): Table Increment (mm) = (I)1 OR Helical (H).

9 Table Speed (mm/rot) = (I)124 Active Chamber length (mm)100 Chamber correction CT ACCREDITATION FORM20 CTDI voland DLPwvolCTDI pitchCTDI1= ) " ) ) 7 " 7 ( 7 !8 7 ) lengthscanCTDIDLPvol =Effective Dose in CT European Guidelines on Quality Criteria for Effective Dose (mSv/mGy-cm)Region of body( )21 Software ResoursesSoftware programs to calculate organ dose using Monte Carlo Techniques: (NRPB):XDOSE, CHILDOSE, CTDOSE (company for CT ):ImpactDosePATIENT RADIATION DOSES IN DIAGNOSTIC part 2 PATIENT RADIATION DOSES IN DIAGNOSTIC part 2 EDWARD L. NICKOLOFF, DEPARTMENT OF RADIOLOGYCOLUMBIA UNIVERSITY& NEW YORK-PRESBYTERIAN HOSPTIALNEW YORK, NY22 TYPICAL PATIENT RADIATION DOSESNATIONAL EVALUATION OF X-RAY TRENDS ( ) SURVEY SPOT (1)191511 CTDIvol FLUORO / SPINE PA3 RDQUARTILE(mGy)MEDIAN (mGy)1stQUARTILE(mGy)EXAMINATION& PROJECTION* FROM.

10 & ACR MAMMO23 DIAGNOSTIC RADIOLOGY DOSE REFERENCE LEVELS (DRL) DIAGNOSTIC RADIOLOGY DOSE REFERENCE LEVELS (DRL) DIAGNOSTIC REFERENCE LEVELS VOLUNTARYFOR COMPARISON BASED UPON NATIONWIDE SURVEYS NOT FOR REGULATORY PURPOSES GUIDANCE LEVELFOR IF ABOVE MAY BE APPROPRIATE BECAUSE OF PATIENT SIZE OR CLINICAL COMPLEXITY MAY BE SUBOPTIMAL USAGE OF EQUIPMENT MAY BE EQUIPMENT PROBLEMS TYPICALLY REFERENCE LEVEL IS THIRD QUARTILE OR ABOUT 80% OF SURVEY MEAN + 0. 70 75 % MEAN + 84 % DIRECTED TOWARDS RADIATION DOSE REDUCTION24 ACR / AAPM REFERENCE VALUES FOR FLUORO / (MQSA) SPINE SPINE PAREFERENCE VALUE( mGy / IMAGE )EXAMINATION& PROJECTIONACRIN MAMMOGRAPHY mGyMEAN + 1 DOSE mGy1 DOSE mGyMEAN DOSE cm1 cmMEAN Drs.