Dawn Banghart, thursday Session II

PET/CT, Cardiac CT, PET/CT, Cardiac CT, Colonography CT : Colonography CT :

A New IAEA Safety Report A New IAEA Safety Report

SeriesSeries Dawn Banghart, CHP Dawn Banghart, CHP

Sr. Health Physicist/Alternate Radiation Sr. Health Physicist/Alternate Radiation Safety Officer Safety Officer

Stanford University Stanford University

IntroductionIntroduction The IAEA Safety Report Series recently published The IAEA Safety Report Series recently published

No. 58, 60 and 61 to address safety issues in:No. 58, 60 and 61 to address safety issues in: PET/CT (58)PET/CT (58) Cardiac CT (60)Cardiac CT (60) Virtual Colonography (61)Virtual Colonography (61)

This talk will encapsulate key principals and This talk will encapsulate key principals and standards highlighted in these reports and raise standards highlighted in these reports and raise the question:the question: Is it possible to write a comprehensive Is it possible to write a comprehensive

document in this changing technological document in this changing technological environment?environment?

Learning objectives:Learning objectives:

After this talk you will be able to: After this talk you will be able to: Site the average effective dose for CT Site the average effective dose for CT

Colonography, Cardiac CT and whole body Colonography, Cardiac CT and whole body PET/CT PET/CT

AskAsk three very good PET/CT dose three very good PET/CT dose optimization questions to raise awareness in optimization questions to raise awareness in the clinical setting the clinical setting

List dose reduction strategies for PET/CT List dose reduction strategies for PET/CT staffstaff

Compare CT Colonography to conventional Compare CT Colonography to conventional endoscopyendoscopy

IAEA Safety Reports IAEA Safety Reports SeriesSeries

Four international organizations collaborated Four international organizations collaborated to produce reports 58, 60 & 61 : to produce reports 58, 60 & 61 : The International Atomic Energy Authority The International Atomic Energy Authority The World Health OrganizationThe World Health Organization The International Society of Radiology The International Society of Radiology The International Commission on Radiological The International Commission on Radiological

Protection Protection The reports provide The reports provide guidanceguidance and and adviceadvice for for

those involved in some of the more dose-those involved in some of the more dose-intensive areas emerging in radiology and intensive areas emerging in radiology and cardiology todaycardiology today

Report General Report General CommentsComments

Pet/CT (No. 58) directed towards patient AND Pet/CT (No. 58) directed towards patient AND staff radiation protectionstaff radiation protection

Cardiac CT (No. 60) and Virtual Colonography Cardiac CT (No. 60) and Virtual Colonography (No. 61) directed towards patient radiation (No. 61) directed towards patient radiation protection ONLYprotection ONLY

All three identifyAll three identify Rapid industry growthRapid industry growth Sharp increase in patient effective dose since the Sharp increase in patient effective dose since the

emergence of CT technology (1970s) and PET emergence of CT technology (1970s) and PET technology (2001)technology (2001)

Expanded applications (e.g., in psychiatry, infection Expanded applications (e.g., in psychiatry, infection imaging)imaging)

Rapid industry growth?Rapid industry growth?Improvements in Improvements in TechnologyTechnology

Circa 1975

Present-day, shows six-fold increase in detail

(images courtesy Siemens Medical Systems and Imaginis.com)

CT use has increased from 3 million scans in 1980 to 62 million a year currently (including 4 million kids)

Beyond new Technology Beyond new Technology what’s up with dose?what’s up with dose?

Increasing Obesity 1960 - Increasing Obesity 1960 - 20002000

From CDC's Diabetes Systems Modeling Project

What’s up with increased What’s up with increased applications?applications?

Over the 20th century, the older population grew from 3 million to 35 million

Increased CT Scans in Increased CT Scans in Children Children

CT scans in children significantly increased between CT scans in children significantly increased between 2004 and 2006 and comprised approximately 8–10 2004 and 2006 and comprised approximately 8–10 % of the total number of CT scans in the USA(1) % of the total number of CT scans in the USA(1)

According to a Duke study from 2000 to 2006, According to a Duke study from 2000 to 2006, pediatric ED patient volume increased by 2%, triage pediatric ED patient volume increased by 2%, triage acuity remained stable (2) acuity remained stable (2)

From the same study, pediatric ED number of From the same study, pediatric ED number of scans increased increased Chest by 435%Chest by 435% Cervical spine Cervical spine CT by 366 % (2)by 366 % (2)

Children are at greater risk from a given dose of Children are at greater risk from a given dose of radiation compared with adults due to increased radiation compared with adults due to increased radiosensitivity of their bodies and a greater period radiosensitivity of their bodies and a greater period of time in which to manifest these changes(1). of time in which to manifest these changes(1).

What All 3 Reports ShareWhat All 3 Reports Share Primary concern – Primary concern –

Cancer induction from PET/CT and CT imaging Cancer induction from PET/CT and CT imaging Patient benefits from PET/CT and CT imaging will Patient benefits from PET/CT and CT imaging will

have to be balanced against “have to be balanced against “the cost of the the cost of the radiation burden to the individual patient, and radiation burden to the individual patient, and possibly to the communitypossibly to the community””

General Aspects of PatientGeneral Aspects of Patient Radiation Protection are Radiation Protection are directed by identifying the practice, justifying and directed by identifying the practice, justifying and optimizing the practice. The “must dos”:optimizing the practice. The “must dos”: Use of radiation in medicine must do more good than Use of radiation in medicine must do more good than

harm (i.e., harm (i.e., The procedure should improve diagnosis)The procedure should improve diagnosis) Reasonable measures must be employed to improve Reasonable measures must be employed to improve

protection and decrease exposureprotection and decrease exposure Individual cancer risk seems low compared to Individual cancer risk seems low compared to

spontaneous incidence, however, there is room for spontaneous incidence, however, there is room for improvement with respect to radiation dose improvement with respect to radiation dose exposures to the patientexposures to the patient

IAEA Safety Report Series No. 58 IAEA Safety Report Series No. 58 Radiation Protection in Newer Radiation Protection in Newer Medical Imaging Technologies: Medical Imaging Technologies:

PET/CT - Extracted GemsPET/CT - Extracted Gems Cautions against using effective dose (whole body Cautions against using effective dose (whole body

dose) to estimate cancer detriment dose) to estimate cancer detriment The effective dose intent was to estimate detriment to a The effective dose intent was to estimate detriment to a

population (specifically workers exposed to radiation)population (specifically workers exposed to radiation) Effective dose intended for whole body exposure, not Effective dose intended for whole body exposure, not

partial exposure (e.g., cardiac scan, head scan)partial exposure (e.g., cardiac scan, head scan) Note: Both effective dose and organ dose are Note: Both effective dose and organ dose are

estimated using phantoms or via Monte Carlo estimated using phantoms or via Monte Carlo calculationscalculations

Pediatric patient effective dose may be Pediatric patient effective dose may be underestimatedunderestimated

Patient-specific dose information can not be Patient-specific dose information can not be obtained due to height, weight and age obtained due to height, weight and age considerations considerations

Safety Report Series No. 58 Safety Report Series No. 58 Extracted Gems continuedExtracted Gems continued

““Dose assessment in CT is challenging” !!Dose assessment in CT is challenging” !! On a practical level for patient dose On a practical level for patient dose

management Report Series No. 58 provides management Report Series No. 58 provides three very good questions to help raise three very good questions to help raise awareness of dose in the clinical setting: awareness of dose in the clinical setting:

1)1) Is a high quality CT scan for PET/CT needed for Is a high quality CT scan for PET/CT needed for diagnosis or therapy management?diagnosis or therapy management?

2)2) Can previously acquired anatomical data be Can previously acquired anatomical data be used for correlative interpretation of PET?used for correlative interpretation of PET?

3)3) Can the low dose CT scan be replaced by the Can the low dose CT scan be replaced by the contrast enhanced diagnostic CT scan?contrast enhanced diagnostic CT scan?

Quoting from the report’s page 20, “image Quoting from the report’s page 20, “image quality in CT quality in CT often exceeds the clinical often exceeds the clinical requirementsrequirements” ”

Case in Point - Cedars-Case in Point - Cedars-Sinai Sinai

Cedars-Sinai error attributed to a Cedars-Sinai error attributed to a "misunderstanding" about an incorrectly "misunderstanding" about an incorrectly programmed CT machine, remained programmed CT machine, remained unchecked for 18 months, involved 206 people unchecked for 18 months, involved 206 people

Exacerbated nationwide concerns that Exacerbated nationwide concerns that patients are exposed to excess radiation patients are exposed to excess radiation during medical testingduring medical testing

It appears as though Cedars-Sinai group It appears as though Cedars-Sinai group lowered the noise ratio which automatically lowered the noise ratio which automatically increased mA settingincreased mA setting

The chief executive said The chief executive said manufacturersmanufacturers could helpcould help prevent future errors by prevent future errors by Improving internal settings and by Improving internal settings and by Installing more safeguardsInstalling more safeguards

Typical effective dosesTypical effective dosesWhole body w/10 mCi FDGWhole body w/10 mCi FDG

Attenuation correction  

CT w/Contrast

Topo

LD-CT FDG-PET D-CT  

0.2 - 0.8

1 - 4 mSv

5.7 - 7.0 mSv

14 - 19  

mSv                   mSv  Figure 5. Safety Report Series No. 58Safety Report Series No. 58

Note: Effective dose refers to the detriment to the whole body

Staff PET Radiation Staff PET Radiation ProtectionProtection

Nuclear medicine technicians receive about Nuclear medicine technicians receive about 0.3 – 0.4 mSv whole body per month 0.3 – 0.4 mSv whole body per month performing the usual nuclear medicine performing the usual nuclear medicine protocols minus PET (Note: Radiology protocols minus PET (Note: Radiology Technicians receive “minimal” exposures)Technicians receive “minimal” exposures)

Technicians dedicated to PET patients will see Technicians dedicated to PET patients will see as high as 3 times the above averageas high as 3 times the above average

Main Sources of RadiationMain Sources of Radiation Patient handlingPatient handling Unshielded radiopharmaceuticalsUnshielded radiopharmaceuticals The patient toilet (you know its true!)The patient toilet (you know its true!)

Tasks with greater radiation exposure: Tasks with greater radiation exposure: Drawing the doseDrawing the dose Patient positioning on the scanner bedPatient positioning on the scanner bed

Staff Dose Reduction Staff Dose Reduction StrategiesStrategies Exposures to PET radiopharmaceuticals can Exposures to PET radiopharmaceuticals can

be minimized through:be minimized through: Good facility designGood facility design Good practice (e.g., conduct patient interviews Good practice (e.g., conduct patient interviews

before injection, use shield carrier to transfer before injection, use shield carrier to transfer dose)dose)

Use unit dose syringes (bulk doses lead to higher Use unit dose syringes (bulk doses lead to higher hand exposures)hand exposures)

Provide patient instructions/ensure patient Provide patient instructions/ensure patient cooperation (e.g., remind to bring warm clothing, cooperation (e.g., remind to bring warm clothing, any prescribed pain medication, to leave PET any prescribed pain medication, to leave PET center when done)center when done)

Minimize time and increase distance by using Minimize time and increase distance by using remote video cameras and audio communicationremote video cameras and audio communication

Question 1Question 1

Of the below dose reduction strategies Of the below dose reduction strategies which task might most reduce a nuclear which task might most reduce a nuclear medicine technician’s exposure? medicine technician’s exposure? a. Using a shield carrier to transfer dosea. Using a shield carrier to transfer dose b. Conduct patient interviews before lunchb. Conduct patient interviews before lunch c. Patient positioning on the scanner bedc. Patient positioning on the scanner bed d. Shielded radiopharmaceuticalsd. Shielded radiopharmaceuticals

Question 1Question 1

The Correct Answer isThe Correct Answer is

c. Patient positioning on the c. Patient positioning on the scanner bedscanner bed

IAEA Safety Series Report Series: IAEA Safety Series Report Series: No. 60 - Radiation Protection in No. 60 - Radiation Protection in Newer Newer Medical Imaging Techniques: Medical Imaging Techniques: Cardiac CTCardiac CT For several reasons it seems likely that For several reasons it seems likely that

pressures will develop to apply new Cardiac pressures will develop to apply new Cardiac CT technologies:CT technologies: Coronary disease is major of cause death in many Coronary disease is major of cause death in many

countriescountries Accumulation of calcium in coronary arteries Accumulation of calcium in coronary arteries

may predict a future heart attack or other heart may predict a future heart attack or other heart diseasedisease

Technologies (cardiac CT) are now available to Technologies (cardiac CT) are now available to monitor the calcification of the coronary arteries monitor the calcification of the coronary arteries

Aging populations for western countries is Aging populations for western countries is increasingincreasing

The Score on The Score on Cardiac CTCardiac CT

Some authors suggest the use of CT calcium Some authors suggest the use of CT calcium scoring in healthy 40-50 year old subjectsscoring in healthy 40-50 year old subjects

Calcium scoring may be helpful in behavior Calcium scoring may be helpful in behavior modification programs (i.e., routine follow-up modification programs (i.e., routine follow-up CT scans) CT scans)

Applications of CT coronary angiographyApplications of CT coronary angiography Can obviate need for invasive catheterization (and Can obviate need for invasive catheterization (and

its risks)its risks) Evaluation of artery abnormalitiesEvaluation of artery abnormalities Bypass graft condition Bypass graft condition Surgical planningSurgical planning

Effective Doses (mSv)Effective Doses (mSv)

IAEA Safety Series Report

Series: No. 60

Table 1.

CT CT CalciumCalciumScoringScoring

CT CT ProspectiProspecti

vevetriggertrigger

CT CT retrospectretrospect

ive ive gatinggating

CT CT AngiographAngiograph

yy

CardiacCardiacCatheterizatCatheterizat

ionion

1.5 - 5.2 (m) 1.9 (m) 3.0 (m)

6.7 - 10.9 (m) 2.1 (m)

1.8 - 6.2 (f) 2.5 (f) 4.0 (f) 8.1 - 13.0 (f) 2.5 (f)

Effective dose (mSv) Effective dose (mSv) compared compared

to other common to other common proceduresprocedures

SourceSource Approximate eff. Approximate eff. DoseDose

CT Calcium ScoringCT Calcium Scoring 1-61-6CT coronary angiographyCT coronary angiography 5-135-13CT scan of thoraxCT scan of thorax 1010Conventional coronary Conventional coronary angiographyangiography

2-62-6

Chest X-rayChest X-ray 0.020.02Annual Natural BackgroundAnnual Natural Background 2.42.4Annual transatlantic pilot Annual transatlantic pilot dosedose

4.04.0

Table 2.

Risk to the patient from Risk to the patient from Cardiac CT scanningCardiac CT scanning

Induction of cancerInduction of cancer Note: epidemiological studies have not demonstrated Note: epidemiological studies have not demonstrated

excess risk of cancer induction at doses less than 100 mSvexcess risk of cancer induction at doses less than 100 mSv However as the number of procedures per individual However as the number of procedures per individual

increases the closer that individual gets to the 100 mSv increases the closer that individual gets to the 100 mSv dosedose

Authors (3) consider the cumulative effective dose of 50 Authors (3) consider the cumulative effective dose of 50 cardiology patients. “On average, each patient underwent cardiology patients. “On average, each patient underwent a median of 36 examinations … Three types of procedures a median of 36 examinations … Three types of procedures were responsible for 86% of the total collective effective were responsible for 86% of the total collective effective dose: dose: Arteriography and interventional cardiology (12% of examinations, Arteriography and interventional cardiology (12% of examinations,

48% of average dose per patient); 48% of average dose per patient); Nuclear medicine (5% of examinations, 21% of average dose per Nuclear medicine (5% of examinations, 21% of average dose per

patientpatient CT (4% of examinations, 17% of average dose per patient).” CT (4% of examinations, 17% of average dose per patient).” Median cumulative effective dose was 60.6 mSv Median cumulative effective dose was 60.6 mSv

Cardiac CTCardiac CTPatient Safety Patient Safety ConsiderationsConsiderations

Based on cumulative exposures and Based on cumulative exposures and higher dose techniques professional higher dose techniques professional societies view the level of detriment societies view the level of detriment set against benefits is too tenuous to set against benefits is too tenuous to warrant use of cardiac CT in mass warrant use of cardiac CT in mass screening programsscreening programs

Less frequent referrals with identified Less frequent referrals with identified risk profiles (combined with dose risk profiles (combined with dose reduction methodology) provides a reduction methodology) provides a more favorable risk-benefit profilemore favorable risk-benefit profile

Safety Series Report 61: Radiation Safety Series Report 61: Radiation Protection Protection in Newer Medical Imaging Techniques: in Newer Medical Imaging Techniques: CT Colonography (CTC)CT Colonography (CTC)

The report proposes that CTC might be applied for The report proposes that CTC might be applied for the screening of symptom free patients (but is this the screening of symptom free patients (but is this “justified” - does CTC benefit outweigh harm?)“justified” - does CTC benefit outweigh harm?)

Colorectal cancer is the second leading cause of Colorectal cancer is the second leading cause of deaths from cancer (Europe and USA)deaths from cancer (Europe and USA)

Screening programs may decrease fatality by 15-Screening programs may decrease fatality by 15-30% 30%

80% of colorectal cancers arise in persons with no 80% of colorectal cancers arise in persons with no known risk factorsknown risk factors

Most carcinomas arise from polyps but the vast Most carcinomas arise from polyps but the vast majority of polyps do not become carcinomas majority of polyps do not become carcinomas

There is a direct relationship polyp size and its There is a direct relationship polyp size and its propensity to become malignantpropensity to become malignant

CTC discussionCTC discussion

Conventional endoscopy Conventional endoscopy regarded as the “gold regarded as the “gold standard” against which all standard” against which all other procedures are other procedures are compared compared

There are substantial There are substantial variations in the scientific variations in the scientific literature in estimates of CTC literature in estimates of CTC accuracy accuracy

10% of polyps greater than 1 10% of polyps greater than 1 cm become malignant in ten cm become malignant in ten yearsyears

Polyp size has a great Polyp size has a great influence on detection influence on detection sensitivitysensitivity

TestTestSensitiviSensitivity ty

Polyp Polyp

>10 mm>10 mm

SensitiviSensitivityty

Polyp 6-Polyp 6-9 mm9 mm

CTCCTC 59%59% 51%51%ConventioConventional nal endoscopyendoscopy

98%98% 99%99%

From Table 1.

Procedure RisksProcedure Risks

Large intestine wall perforation may occur Large intestine wall perforation may occur during CTC, barium enema, fiberoptic during CTC, barium enema, fiberoptic colonoscopycolonoscopy

The risks for CTC perforation (<1/2000) are The risks for CTC perforation (<1/2000) are higher than the rate quoted for barium higher than the rate quoted for barium enemas and lower than that for conventional enemas and lower than that for conventional colonoscocpy colonoscocpy

40% of patients have CTC abnormalities 40% of patients have CTC abnormalities which may be of no clinical interestwhich may be of no clinical interest

CTC positive findingsCTC positive findings Polyps found should be removedPolyps found should be removed

Radiation DoseRadiation Dose

SourceSource Approx. Eff. Approx. Eff. Dose (mSv)Dose (mSv)

CTCCTC 1-181-18

CT pelvisCT pelvis 6-106-10

Barium EnemaBarium Enema 4-74-7

Annual Background Annual Background RadiationRadiation

2.42.4

Chest x-rayChest x-ray 0.020.02

Lumbar spine x-rayLumbar spine x-ray 1.31.3

Table 3.

CTC ConclusionsCTC Conclusions Cancer risk low compared to spontaneous Cancer risk low compared to spontaneous

incidenceincidence As CTC screening increases the number of extra As CTC screening increases the number of extra

cancers from the procedure may also increasecancers from the procedure may also increase Proposed CTC screening interval is five yearsProposed CTC screening interval is five years Implementation of low dose techniques are Implementation of low dose techniques are

likelylikely A number of authors have developed innovative A number of authors have developed innovative

colonic phantoms to optimize CTC protocolscolonic phantoms to optimize CTC protocols Ultra-low dose protocols result in an effective dose of Ultra-low dose protocols result in an effective dose of

1-2 mSv (even 0.05 mSv shown to be feasible!) with 1-2 mSv (even 0.05 mSv shown to be feasible!) with polyp detection sensitivity of over 80% for polyps polyp detection sensitivity of over 80% for polyps greater than 5mmgreater than 5mm

Low dose options optimize the procedure, Low dose options optimize the procedure, reduces risk and perhaps justifies routine use of reduces risk and perhaps justifies routine use of CTCCTC

In conclusion …In conclusion …

The dilemmaThe dilemma

The dilemma expressed to some degree in all The dilemma expressed to some degree in all three reports. three reports. When sophisticated but expensive equipment is When sophisticated but expensive equipment is

available there are inevitable pressures to expand available there are inevitable pressures to expand applications applications

New technologies associated with computed New technologies associated with computed tomography are changing rapidly with time, tomography are changing rapidly with time, providing improved images and, possibly, providing improved images and, possibly, better diagnoses of disease BUT due to better diagnoses of disease BUT due to radiation dose, different considerations need to radiation dose, different considerations need to apply to symptomatic and to asymptomatic apply to symptomatic and to asymptomatic patients.patients.

In conclusionIn conclusion

IAEA Safety Report Series No. 58 , No. 60, No. IAEA Safety Report Series No. 58 , No. 60, No. 61 61 are a nice compact introduction to the are a nice compact introduction to the primary and basic challenges with patient and primary and basic challenges with patient and occupational radiation exposure from PET/CT occupational radiation exposure from PET/CT and CT procedures. and CT procedures.

They are reports to keep in your pocket but They are reports to keep in your pocket but technologic advances leave a few questions technologic advances leave a few questions unanswered. unanswered.

Being one step behind may be the perpetual Being one step behind may be the perpetual dilemma of all comprehensive reportsdilemma of all comprehensive reports

We are still in the wild west …We are still in the wild west …

Thank you …Thank you …

ReferencesReferences 1) Brenner D. J., Hall E. J. Computed 1) Brenner D. J., Hall E. J. Computed

tomography—an increasing source of radiation tomography—an increasing source of radiation exposure. N. Engl. J. Med (2007) 357:2277–exposure. N. Engl. J. Med (2007) 357:2277–2284.[2284.[

2) Broder J., Fordham L. A., Warshauer D. M. 2) Broder J., Fordham L. A., Warshauer D. M. Increasing utilization of computed tomography Increasing utilization of computed tomography in the pediatric emergency department, 2000–in the pediatric emergency department, 2000–2006. Emerg. Radiol (2007) 14:227–232 2006. Emerg. Radiol (2007) 14:227–232

3) Bedetti et al., Cumulative patient effective 3) Bedetti et al., Cumulative patient effective dose in Cardiology, dose in Cardiology, Br Inst Radiology 81 Br Inst Radiology 81 (2008),699-705 (2008),699-705