Radiology Review Course Hotel del Coronado Coronado, California

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1 37 th Annual Radiology Review Course Hotel del Coronado Coronado, California Saturday, April 22, AM

2 TABLE OF CONTENTS Saturday, April 22, AM 7:00 AM 7:30 AM Coffee and Pastries for Registrants 7:30 AM 8:35 AM Physics - Radiobiology Daniel E. Wessell, M.D., Ph.D. 8:35 AM 9:25 AM Case Review Session: Neuroradiology James Y. Chen, M.D. 9:25 AM 9:40 AM Coffee Break SAM Session - CT Physics 9:40 AM 10:45 AM Physics - Computed Tomography I Daniel E. Wessell, M.D., Ph.D. 10:45 AM 11:15 AM Case Review Session: Gastrointestinal Cynthia S. Santillan, M.D., FSAR 11:15 AM 12:20 PM Physics - Computed Tomography II Daniel E. Wessell, M.D., Ph.D. 12:20 PM 1:35 PM Lunch On Your Own SAVE THE DATE UCSD Radiology Review Course

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6 + & - Bragg Ionization Peak + & - + & - +/- + & - + & - + & - + & - +/- + & - + & - + & - + & - + & - + & - + & - + & - + & - + & - + & - + & - + & - Low LET: Path length > range High LET: Path length = range 1366

7 Characteristic x-ray of 3.6 kev Energetic photon (x-ray) 70 kev e- e- e- e- e- p+ n p+ n k-shell n k-shell binding energy = 4.04 kev l-shell binding energy = 0.44 kev p+ l-shell p+ n n e- p+ p+ 20 p+ 20 n n n p+ n p+ e- e- e- e kev photoelectron 20 Ca40 Compton Scattered photon of kev Energetic photon 100 kev e- e- e- e- e- k-shell binding energy = 0.54 kev l-shell binding energy = 0.04 kev l-shell k-shell p+ n p+ n n p+ p+ 8 p+ n n p+ 8 n p+ n p+ n n p+ e- e- e- e- e- 5 kev Compton electron 8 O & - + & - + & - + & - + & - + & - + & - + & - + & - + & - + & - + & - + & - Low LET: Path length > range 1367

8 Exposure Exposure is the amount of charge liberated per kilogram of air by the x-ray beam SI unit: C/kg Conventional Unit: roentgen (R), 1 R = 2.58 x 10-4 C/kg Defined only for photons with energy less than 3 MeV Not used for electrons, neutrons, protons or alpha particles. Obeys the inverse square law Useful for measuring film exposure but is a poor assessment of radiation risk Exposure Air X-ray source + - e - e - e - e - e - Ionization Chamber Exposure X-ray source Exposure Tells us nothing about how much energy is absorbed by the tissue being irradiated. Limited utility for evaluating the biologic effects of radiation. Patient Ionization Chamber Film/Screen Cassette Kerma Kinetic Energy Released in MediA (Kerma) measures the energy released into the media by the photon beam SI unit: gray (Gy) = J/kg Conventional Unit: none Air Kerma, J/kg in air, may replace exposure, C/ kg, as a measure of exposure We are interested in the soft tissue Kerma Absorbed Dose Absorbed dose is a measure of the amount of radiation energy absorbed per unit mass of a medium. SI unit: gray (Gy) = J/kg Non SI unit: rad = 10 mgy (i.e. Gy = 100 rad) At diagnostic energies an air Kerma of 1 mgy results in an absorbed dose of approximately 1 mgy in soft tissue 1368

f-factor The f-factor is a conversion factor between exposure, X (C/kg), and absorbed dose, D (Gy or J/kg) D = f x X At diagnostic x-ray energies f is approximately 1.

9 f-factor The f-factor is a conversion factor between exposure, X (C/kg), and absorbed dose, D (Gy or J/kg) D = f x X At diagnostic x-ray energies f is approximately 1. D X Perez and Brady s Principles and Practice of Radiation Oncology 6th edition, by Edward C. Halperin, David E. Wazer, Ca Absorbed Dose X-ray source Absorbed Dose X-ray source X-ray source Scatter Patient s right hand Scatter Patient s left hand Scatter e - Patient e - e - Ionization Chamber Film/Screen Cassette Same absorbed dose whether a single or both hands are imaged. Absorbed dose is calculated per kilogram! Absorbed Dose The absorbed dose is a better measure of the radiation risk Absorbed dose is useful in evaluating the deterministic effects of radiation (e.g. skin injury, cataract formation, etc.) Absorbed dose does not take into account where in the body the radiation dose is absorbed or the relative radiosensitivity of the tissue being irradiated Equivalent Dose Equivalent dose, H, takes into account the type of radiation Different types of radiation (e.g. high LET, low LET and ionizing EM radiation) have different weighting factors, W R The units of equivalent dose SI Unit is the seivert: 1 Sv = 1 J/kg The non-si unit is the rem (radiation equivalent man): 1 rem = 10 msv or 1 Sv = 100 rem 1369

Weighting Factors, W R Equivalent Dose The radiation weighting factors, W R, are conversion factors between absorbed dose, D (Gy) and equivalent dose, H (Sv) H = W R x D For diagnostic x-ray energies

H = D Effective Dose Effective dose takes into account where the radiation dose is being absorbed The effective dose attempts to reflect the equivalent whole-body dose that would result in an

10 Weighting Factors, W R Equivalent Dose The radiation weighting factors, W R, are conversion factors between absorbed dose, D (Gy) and equivalent dose, H (Sv) H = W R x D For diagnostic x-ray energies W R is 1. H = D Effective Dose Effective dose takes into account where the radiation dose is being absorbed The effective dose attempts to reflect the equivalent whole-body dose that would result in an equivalent stochastic risk (e.g. cancer or genetic risk) from the actual absorbed dose to those tissues irradiated in a non-uniform, partial body irradiation The unit of effective dose SI Unit is the seivert: 1 Sv = 1 J/kg The non-si unit is the rem (radiation equivalent man): 1 rem = 10 msv or 1 Sv = 100 rem Effective Dose Effective dose (E) is given by the following E = Σ T (w T x H T,R ) where, w T is the tissue weighting factor for tissue T and H T is the equivalent dose of tissue T Tissue Weighting Factors Effective Doses from Radiation Protection 118: Referral Guidelines for Imaging, Published by the European Commission, 2001 Ref: Estimating Effective Dose in CT, AJR 2010; 194:

Review Exposure ability of radiation to ionize air. Units are the roentgen (non-si). Absorbed Dose energy imparted to the irradiated tissue per unit mass.

Equivalent Dose takes into account the radiation type Effective Dose measure of the population risk posed by radiation.

11 Review Exposure ability of radiation to ionize air. Units are the roentgen (non-si). Absorbed Dose energy imparted to the irradiated tissue per unit mass. Units are the gray (SI) or rad (non-si). Deterministic effects! Equivalent Dose takes into account the radiation type Effective Dose measure of the population risk posed by radiation. Units are the sievert (SI) or rem (non-si). Stochastic effects! Tissue Weighting Factors Ref: Estimating Effective Dose in CT, AJR 2010; 194: DNAstrand11.gif 1371

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13 6 weeks 20 weeks 18 months MedicalImaging/MedicalX-Rays/ucm pdf Radiation-induced Skin Injuries from FluoroscopyThomas B. Shope, Ph.D. 1373

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Film Dosimetry Thermoluminescent Dosimetry Bushberg, The

com/wp-content/uploads/ 2013/05/Thermoluminescence-Dosimetry.

Chambers Measure the charge liberated when photons interact with

phototimers in automatic exposure control units and as dose

Geiger counters are ionization chambers operating in avalanche

17 Film Dosimetry Thermoluminescent Dosimetry Bushberg, The Essential Physics of Medical Imaging /05/Thermoluminescence-Dosimetry.gif Optically Stimulated Luminescence Dosimetry Ionization Chambers Measure the charge liberated when photons interact with the gas in the chamber. That is, they measure exposure directly. Very accurate. They can be used to measure the output of x-ray tubes, as phototimers in automatic exposure control units and as dose calibrators in nuclear medicine. Geiger counters are ionization chambers operating in avalanche mode. Ionization Chamber Pocket Ionization Chambers X-ray Gas Molecules Gas Filled Chamber ma

18 Geiger-Mueller Counter Patient X-ray Tube II or Flat panel detector Scatter Table Patient X-ray Tube Scatter II or Flat panel detector Patient Scatter X-ray Tube Table Table II or Flat panel detector 1378

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30 $* 1390 %# (* %$ )) %% &' $ %& Table of Contents

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37 Routine Chest 1397

38 "Wilhelm Conrad Röntgen - Photo Gallery". Nobelprize.org. 9 Jan /rontgen-photo.html "Wilhelm Conrad Röntgen - Photo Gallery". Nobelprize.org. 9 Jan /rontgen-photo.html "Wilhelm Conrad Röntgen - Photo Gallery". Nobelprize.org. 9 Jan

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41 from RadonTransformOfSheppLoganWeb.mov Nobelprize.org 1401

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43 from I 0 μ 1,1 μ 1,2 I D,1 I 0 μ 1,1 μ 1,2 I D,1 I 0 I D,2 I 0 I D,2 μ 2,1 μ 2,2 μ 2,1 μ 2,2 d = pixel width I D,1 = I 0 e-d(μ1,1+μ1,2) 1403

44 I 0 μ 1,1 μ 1,2 I D,1 I 0 μ 1,1 μ 1,2 I D,1 I 0 I D,2 I 0 I D,2 μ 2,1 μ 2,2 μ 2,1 μ 2,2 ln(i D,1 / I 0 ) = -dμ 1,1 -dμ 1,2 (-1/d)ln(I D,1 / I 0 ) = μ 1,1 + μ 1,2 I 0 μ 1,1 μ 1,2 I D,1 I 0 μ 1,1 μ 1,2 I D,1 I 0 I D,2 I 0 I D,2 μ 2,1 μ 2,2 μ 2,1 μ 2,2 Let C 1,1 = (-1/d)ln(I D,1 / I 0 ) then C 1,1 = μ 1,1 + μ 1,2 C 1,1 = μ 1,1 + μ 1,2 C 1,2 = μ 2,1 + μ 2,2 μ 1404

45 New Image = Old Image x Correction Factor 1405

46 Scanner Computer

Filtration Filtration Tungsten Anode Tube

Filtered 10 20 30 40 50 60 70 80 90 Energy

48 Filtration Filtration Tungsten Anode Tube voltage 90 kvp Relative Output Unfiltered Filtered Energy (kev) Bow-Tie Filter collimator+ct+scan.jpg 1408

49 X-ray Xenon Gas ma CT Xenon Detector CT Scintillator Detector Gas Filled Chamber + - X-ray photon First Generation CT 1409

http://www.bioclinica.com/sites/default/files/u1/prototype-ct-scanner.

50 Second Generation CT

51 Third Generation CT Fourth Generation CT Fifth Generation CT 1411

Sixth Generation CT Slip rings used to bring power to x-ray tube on

acquire information from the detector array.

Radiological Society of North America Slip rings used to bring

52 Sixth Generation CT Slip rings used to bring power to x-ray tube on rotating gantry of a helical CT machine and, for some designs, to acquire information from the detector array. Wolbarst A B, and Hendee W R Radiology 2006;238: by Radiological Society of North America Slip rings used to bring power to x-ray tube on rotating gantry of a helical CT machine and, for some designs, to acquire information from the detector array. Wolbarst A B, and Hendee W R Radiology 2006;238: by Radiological Society of North America 1412

53 Seventh Generation Siemens Volume Zoom (4 rows) Cone-Beam CT 1413

54 Dual Source CT Dual Source CT A B Body A = Slice Thickness B= Reconstruction Intervals B-A= Gap Images 1414

55 Tungsten anode with tube voltage of at least kvp Tube voltage 90 kvp Relative Output Unfiltered Bremsstrahlung Relative Output L-shell K-shell Filtered Bremsstrahlung Energy (kev) Energy (kev) 1415

Relative Output Tube current doubled 10 20 30 40 50 60 70 80 90 Energy (kev)

X-ray Production Processes Relative Output Tube voltage increased from 75 to

56 Relative Output Tube current doubled Energy (kev) X-ray Production Processes Tube voltage 90 kvp X-ray Production Processes X-ray Production Processes Relative Output Tube voltage increased from 75 to 90 kvp with tube current unchanged Energy (kev) 1416

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58 μ μ 1418

59 μ μ μ 400/ / /30 120/

60 1 mm width 6 lp/mm 8 lp/mm 12 lp/mm 15 lp/mm 22 lp/mm 34 lp/mm Ideal Resolution Good vs Poor Resolution Image of line-pair phantom Optical Density Position along line A-A Optical Density Position along line A-A 1420

61 Matrix size 512x512 Pixel size = DFOV/Matrix size DFOV = 50cm DFOV = 36cm DFOV = 25cm 800 mas 400 mas 5 mm 2.5 mm 200 mas 100 mas 1.25 mm mm 1421

62 Matrix size = 512x512 DFOV = 50cm DFOV = 25cm B20 Smooth B40 B60 Sharp FBP 30% ASIR 50% ASIR 70% ASIR 100% ASIR ASIR = Adaptive Statistical Iterative Reconstruction 1422

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From the Department of Health and Human Service s 11

Quote from, Medical X-rays Added to Government

65 From the Department of Health and Human Service s 11 th Report on Carcinogens released in January, From the Department of Health and Human Service s 11 th Report on Carcinogens released in January, Quote from, Medical X-rays Added to Government Carcinogen List. RSNA News, March 2005, Vol. 15, No. 3, pp Quote from, Medical X-rays Added to Government Carcinogen List. RSNA News, March 2005, Vol. 15, No. 3, pp

Ref: Diagnostic CT scans: assessment of patient, physician, and radiologist awareness of radiation dose and possible risks. Radiology 2004; 231:393-398.

Why Perform CT When MRI Is Safer -- and Perhaps Better MRI is an imaging modality that is considerably safer than CT on the basis of a number of factors, of which radiation exposure is perhaps the

66 Ref: Diagnostic CT scans: assessment of patient, physician, and radiologist awareness of radiation dose and possible risks. Radiology 2004; 231: Ref: Diagnostic CT scans: assessment of patient, physician, and radiologist awareness of radiation dose and possible risks. Radiology 2004; 231: Understand the biases of the sources of information you use to make these decisions. Why Perform CT When MRI Is Safer -- and Perhaps Better MRI is an imaging modality that is considerably safer than CT on the basis of a number of factors, of which radiation exposure is perhaps the most serious. In addition, MRI may actually be much more accurate in describing disease. Richard C. Semelka, MD, Director of MR Services; Professor of Radiology; Vice Chairman of Clinical Research, Department of Radiology, The University of North Carolina at Chapel Hill excerpt from Radiation Risk from CT Scans: A Call for Patient-Focused Imaging, Medscape Radiology 6(1),

from Radiation Protection 118: Referral Guidelines for

Estimated risk of radiation induced fatal cancer from

176, Feb, 2001 Ref: 176, Feb, 2001 Image of article

67 from Radiation Protection 118: Referral Guidelines for Imaging, Published by the European Commission, 2001 Ref: Estimated risk of radiation induced fatal cancer from pediatric CT, AJR, Vol. 176, Feb, 2001 Ref: Estimated risk of radiation induced fatal cancer from pediatric CT, AJR, Vol. 176, Feb, 2001 Image of article obtained from

68 Ref: Risk of Cancer from diagnostic X-rays: estimates for the UK and 14 other countries, The Lancet, Vol 363, Jan 31, 2004 Image of article obtained from Ref: Effect of low doses of ionizing radiation in infancy on cognitive function in adulthood: Swedish population based cohort study, BMJ, Vol 328, Jan 3,

69 X-ray source X-ray source + - e - e - e - e - Air e - Ionization Chamber Ionization Chamber Patient Film/Screen Cassette X-ray source X-ray source X-ray source Scatter Patient s right hand Scatter Patient s left hand Scatter e - Patient e - e - Ionization Chamber Film/Screen Cassette 1429

1977 1991 2007 Σ Ref: Estimating Effective Dose

Routine Head Ref: AAPM/RSNA Physics Tutorial for

70 Σ Ref: Estimating Effective Dose in CT, AJR 2010; 194: from Radiation Protection 118: Referral Guidelines for Imaging, Published by the European Commission, 2001 Routine Head Ref: AAPM/RSNA Physics Tutorial for Residents: Topics in CT, Radiographics 2002; 22:

X-ray Tube Main X-ray beam Scatter Detector Ref: AAPM/RSNA Physics Tutorial for

Physics Tutorial for Physics Tutorial for Physics Tutorial for Residents:

71 X-ray Tube Main X-ray beam Scatter Detector Ref: AAPM/RSNA Physics Tutorial for Residents: Topics in CT, Radiographics 2002; 22: Ref: AAPM/RSNA Physics Tutorial for Residents: Topics in CT, Radiographics 2002; 22: Ref: AAPM/RSNA Physics Tutorial for Residents: Topics in CT, Radiographics 2002; 22: Ref: AAPM/RSNA Physics Tutorial for Residents: Topics in CT, Radiographics 2002; 22: Radiation Dose Routine Head Fig from impactscan.org 1431

72 Radiation Dose Radiation Dose Routine Head Fig from impactscan.org Routine Chest 1432

73 Fig from impactscan.org Effective dose for various studies can be approximated via measurements with TLD anthropomorphic phantoms Effective dose for various studies can be approximated via computer simulations Ref: Estimating Effective Dose in CT, AJR 2010; 194:

74 AAPM Report no

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76 Ref: AAPM/RSNA Physics Tutorial for Residents: Topics in CT, Radiographics 2002; 22: Ref: Radiation dose and image quality in pediatric CT: effect of technical factors and phantom size and shape, Radiology 2004; 233:

, AJR 2002; 179: 31-49 Future Advances original 50% dose

77 from from Ref: CT and Computed Radiography: The Pictures are Great, but is the Radiation Dose Greater than Required?, AJR 2002; 179: Future Advances original 50% dose reduction 75% dose reduction 87.5% dose reduction 96% dose reduction 99% dose reduction Images courtesy Bruce Whiting, PhD 1437

78 McNitt-Gray 2011 AAPM Summit on CT dose 180 Ref MA 280 Ref MA 1438

79 Total Dose: 17 msv 1439

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83 GI Case Quiz Cynthia S Santillan How do you classify this finding? A Superficial B Intersphincteric C Transphincteric D Extrasphincteric 1443

84 Most appropriate next step? A Colonoscopy B Check AFP C Start IV antibiotics D Follow-up CT in 3 months 1444

85 What is the most likely provided history? A History of colon cancer B Elevated IgE C History of OCP D HCV, initial imaging 1445

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95 SAVE THE DATE 38 th Annual Radiology Review Course Hotel del Coronado Coronado, California April 1-7, 2018

Dosimetric Consideration in Diagnostic Radiology

Dosimetric Consideration in Diagnostic Radiology Prof. Ng Kwan-Hoong Department of Biomedical Imaging University of Malaya ngkh@um.edu.my Radiation Dosimetry Workshop, 28-29 March 2014 2 Why do we measure