Quan%ta%ve Tools for Benefit/Risk Op%miza%on in Medical Imaging
MIRD CommiAee Pamphlet
Wesley Bolch, PhD, PE, DABHP, FHPS, FAAPM Medical Physics Program
Department of Biomedical Engineering University of Florida, Gainesville, FL
Fall 2013 Mee%ng of the Florida AAPM / Florida HPS West Palm Beach MarrioA Hotel
October 2013
Presenta%on Outline
1. Mo%va%on for imaging dose reduc%on and op%miza%on 2. Effec%ve dose for quan%fying the risk – what is it and where
does it come from?
3. Alterna%ves to the Effec%ve Dose – organ specific cancer risks
4. Methods of quan%fying the benefits of medical imaging
5. Upcoming MIRD Pamphlet and Book on this topic
NCRP Report 160 Ionizing Radia%on Exposure of the US Popula%on
Early 1980s 2006 ~15% medical ~48% medical
Smith-‐Bindman et al -‐ JAMA 2010 (1996 to 2010)
Smith-‐Bindman et al -‐ JAMA 2010 (1996 to 2010)
Smith-‐Bindman et al -‐ JAMA 2010 (1996 to 2010)
Smith-‐Bindman et al -‐ JAMA 2010 (1996 to 2010)
Poten%al Stochas%c Effects from CT
RBM Dose from pediatric head CT
Brain Dose from pediatric head CT
Demonstrated Determinis%c Effects from CT
Cedars-‐Sinai Medical Center – Overexposure of 206 stroke pa%ents
undergoing brain perfusion studies – Modifica%on of imaging protocols without
understanding or considera%on of radia%on exposure
– Epila%on
Mad River Community Hospital 2-‐year-‐old male scanned 151 %mes over 65 min Erythema shown and cataracts expected Doses es%mated to be from 2.8 to 11 Gy Life%me fatal cancer risk – es%mated at 39%
Effec%ve Dose The effec%ve dose is a dosimetry quan%ty defined by the Interna%onal Commission on Radiological Protec%on (ICRP) and is widely used as a dose metric for stochas%c risk following ionizing radia%on exposure. It is widely used in medical imaging to compare and contrast radia%on risks associated with radiography, computed tomography, fluoroscopy, and nuclear medicine imaging. Ques%ons: What is the history of its development?
What are the proper uses of this quan%ty? What are the alterna%ves when used improperly?
ICRP System of Radia%on Protec%on Three tenets of the ICRP system… Jus%fica%on
No prac%ce shall be adopted unless its introduc%on produces a net posi%ve benefit Very applicable to pa%ent exposures!
Op%miza%on
All exposures shall be kept as low as reasonably achievable, economic and social factors being taken into account Good use of effec%ve dose (or alterna%ves) in medical imaging
Limita%on
Doses to the individual shall not exceed the limits recommended for the appropriate circumstances by the ICRP Pa%ent exposures are not regulated – defer to op%miza%on!
History of the Effec%ve Dose
Radiat Env Biophys 1975
ICRP Publica%on 14 (1969)*
ICRP Pub 26 (1977) ICRP Pub 60 (1991) ICRP Pub 103 (2007) *Radiosensi%vity and spa%al distribu%on of dose
History of the Effec%ve Dose
Radiat Env Biophys 1975
ICRP Publica%on 14 (1969)
ICRP Pub 26 (1977)
ICRP Publica%on 26 -‐ 1977 Absorbed Dose ( D ) and Dose Equivalent ( H )
Absorbed Dose 𝑫= 𝒅𝜺 /𝒅𝒎 where 𝒅𝜺 is the mean energy imparted by ionizing
radia%on to maAer of mass dm (unit – Gy = J/kg )
Dose Equivalent 𝑯=𝑫𝑸𝑵 where Q is the quality factor and N is the product of where Q is the quality factor and N is the product of
all other modifying factors (unit – Sv) Q based upon RBE values for stochas%c effects in humans. Qphotons = Qelectrons
= 1 and Qalphas = 20 func%on of L∞ in water
N could account for factors such as the absorbed dose rate or frac%ona%on scheme, but it was assigned a value of 1 in ICRP 26
ICRP Publica%on 26 -‐ 1977 Effec%ve Dose Equivalent ( HE )
Under condi%ons of non-‐uniform irradia%on, where various organ and %ssues each receive a dose equivalent HT , the effec%ve dose equivalent is defined as the hypothe%cal, uniform, whole-‐body dose equivalent which, if delivered to the individual, would result in the same total detriment (fatal cancer risk / gene%c damage to offspring). Define RT -‐ Life%me risk of fatal cancer or gene%c damage per
unit dose equivalent to %ssue T (unit – Sv -‐1) These values of RT used in ICRP 26 were derived from our understanding of radia%on cancer risks as of the early 1970s. Note – implicit assump%on is the linear no-‐threshold model (LNT)
ICRP Publica%on 26 -‐ 1977 Effec%ve Dose Equivalent ( HE )
Consider a radiopharmaceu%cal that localized in the liver Components of “risk” are thus es%mated from both the self-‐dose to the liver: and the photon cross-‐dose to other organs:
𝑹𝒊𝒔𝒌↓𝑳𝒊𝒗𝒆𝒓 𝑪𝒂𝒏𝒄𝒆𝒓 = 𝑯↓𝑳𝒊𝒗𝒆𝒓 (𝒎𝑺𝒗)∙ 𝑹↓𝑳𝒊𝒗𝒆𝒓 ( 𝒎𝑺𝒗↑−𝟏 )
𝑹𝒊𝒔𝒌↓𝑳𝒆𝒖𝒌𝒆𝒎𝒊𝒂 = 𝑯↓𝑹𝑩𝑴 ∙ 𝑹↓𝑹𝑩𝑴
𝑹𝒊𝒔𝒌↓𝑲𝒊𝒅𝒏𝒆𝒚𝒔 = 𝑯↓𝑲𝒊𝒅𝒏𝒆𝒚𝒔 ∙ 𝑹↓𝑲𝒊𝒅𝒏𝒆𝒚𝒔
𝑹𝒊𝒔𝒌↓𝑳𝒖𝒏𝒈𝒔 = 𝑯↓𝑳𝒖𝒏𝒈𝒔 ∙ 𝑹↓𝑳𝒖𝒏𝒈𝒔
𝑹𝒊𝒔𝒌↓𝑻𝒐𝒕𝒂𝒍 = 𝑹𝒊𝒔𝒌↓𝑳𝒊𝒗𝒆𝒓 + 𝑹𝒊𝒔𝒌↓𝑹𝑩𝑴 + 𝑹𝒊𝒔𝒌↓𝑲𝒊𝒅𝒏𝒆𝒚𝒔 + 𝑹𝒊𝒔𝒌↓𝑳𝒖𝒏𝒈𝒔
ICRP Publica%on 26 -‐ 1977 What then is the effec%ve dose equivalent HE ?
“Real” non-‐uniform exposure of the pa%ent
“Hypothe%cal” uniform exposure of the reference pa%ent yielding same total risk
This is the pa%ent’s “effec%ve dose equivalent” HE
ICRP Publica%on 26 -‐ 1977 Effec%ve Dose Equivalent ( HE )
(█■𝑻𝒐𝒕𝒂𝒍 𝑹𝒊𝒔𝒌 𝒇𝒓𝒐𝒎 𝒖𝒏𝒊𝒇𝒐𝒓𝒎 𝒊𝒓𝒓𝒂𝒅𝒊𝒂𝒕𝒊𝒐𝒏 )=(█■𝑻𝒐𝒕𝒂𝒍 𝑹𝒊𝒔𝒌 𝒇𝒓𝒐𝒎 𝒏𝒐𝒏𝒖𝒏𝒊𝒇𝒐𝒓𝒎 𝒊𝒓𝒓𝒂𝒅𝒊𝒂𝒕𝒊𝒐𝒏 ) 𝑯 ↓𝑻𝑩 (∑𝒊↑▒𝑹↓𝑻↓𝒊 )= 𝑯↓𝑻↓𝟏 𝑹↓𝑻↓𝟏 + 𝑯↓𝑻↓𝟐 𝑹↓𝑻↓𝟐 + 𝑯↓𝑻↓𝟑 𝑹↓𝑻↓𝟑 +…+ 𝑯↓𝑻↓𝑵 𝑹↓𝑻↓𝑵 𝑯 ↓𝑻𝑩 (∑𝒊↑▒𝑹↓𝑻↓𝒊 )= (∑𝒊↑▒𝑯↓𝑻↓𝒊 𝑹↓𝑻↓𝒊 ) 𝑯↓𝑬 =𝑯 ↓𝑻𝑩 = ∑𝒊↑▒𝑯↓𝑻↓𝒊 (𝑹↓𝑻↓𝒊 /∑𝒊↑▒𝑹↓𝑻↓𝒊 ) = ∑𝒊↑▒𝑯↓𝑻↓𝒊 𝒘↓𝑻↓𝒊 = ∑𝑻↑▒𝑯↓𝑻 𝒘↓𝑻 𝑯↓𝑬 = ∑𝑻↑▒𝒘↓𝑻 𝑯↓𝑻
ICRP Publica%on 26 -‐ 1977 Source of the Tissue Weigh%ng Factors wT
Tissue Risk (mSv-‐1) Biological Effect wT
Gonads 4 x 10 -‐6 Risk to 1st two genera%ons
0.25
Breast 2.5 x 10 -‐6 Cancer 0.15
Red Marrow 2 x 10 -‐6 Leukemia 0.12
Lungs 2 x 10 -‐6 Cancer 0.12
Thyroid 0.5 x 10 -‐6 Cancer 0.03
Bone Endosteum 0.5 x 10 -‐6 Cancer 0.03
Remainder 5 x 10 -‐6 Cancer 0.30
Totals 16.5 x 10 -‐6 1.00
History of the Effec%ve Dose
Radiat Env Biophys 1975
ICRP Publica%on 14 (1969)
ICRP Pub 26 (1977) ICRP Pub 60 (1991)
ICRP Publica%on 60 – 1991 Effec%ve Dose ( E )
Absorbed Dose DT,R is defined as the mean absorbed dose to %ssue T delivered
by radia%on type R
Equivalent Dose HT is defined as the product of the mean absorbed dose and a
radia%on weigh%ng factor wR
𝑯↓𝑻 = ∑𝑹↑▒𝒘↓𝑹 𝑫↓𝑻,𝑹
Value of wR have been selected by the ICRP to be representa%ve of values of RBE of that radia%on for the induc%on of stochas%c effects at low absorbed doses.
They replace the quality factor Q
𝑹𝑩𝑬↓𝒂𝒍𝒑𝒉𝒂 = (𝑫↓𝒙−𝒓𝒂𝒚𝒔 /𝑫↓𝒂𝒍𝒑𝒉𝒂𝒔 )↓𝑺𝒂𝒎𝒆 𝑩𝒊𝒐𝒍 𝑬𝒇𝒇𝒆𝒄𝒕 𝒘↓𝑹
ICRP Publica%on 60 – 1991 Radia%on Weigh%ng Factors wR
Note – These values of wR are appropriate for stochas%c effects only! Values RBE for alphas, for example, are only 5 for determinis%c effects
ICRP Publica%on 60 – 1991 Revised Tissue Factors wT
ICRP Publica%on 26 Values of wT were based upon fatal cancer risks or severe gene%c damage
ICRP Publica%on 60 Values of wT were based upon the concept of “detriment” which included: • Risk of fatal cancer • Allowance for years of life lost due to differences in latency periods • Allowance for cancer induc%on for non-‐fatal cancers • Allowance for the risk of severe hereditary disease
ICRP Publica%on 60 – 1991 Revised Tissue Factors wT
ICRP Publica%on 60 – 1991 Revised Tissue Factors wT
ICRP Publica%on 60 – 1991 Revised Tissue Factors wT
ICRP Publica%on 60 – 1991 Revised Tissue Factors wT
ICRP Publica%on 60 – 1991 Revised Tissue Factors wT
Footnotes to ICRP 60 Table of wT values
Age and sex averaging
Defining the remainder %ssues
ICRP Publica%on 60 – 1991 Revised Tissue Factors wT
Footnotes to ICRP 60 Table of wT values
The “splirng rule”
Note – the “splirng rule” was dropped in ICRP 103
History of the Effec%ve Dose
Radiat Env Biophys 1975
ICRP Publica%on 14 (1969)
ICRP Pub 26 (1977) ICRP Pub 60 (1991) ICRP Pub 103 (2007)
ICRP Publica%on 103 – 2007 Revised Tissue Factors wT
Fast forward from 1991 to the mid-‐2000s… • Some 15 years of addi%onal follow up of the Bomb Survivors • Epidemiological studies of other exposed popula%ons • Cancer-‐specific advances treatment outcomes
Time to once again update %ssue weigh%ng factors…
ICRP Publica%on 103 – 2007
Organ / wT ICRP 26 ICRP 60 ICRP 103
Bladder 0.05 0.04
Bone marrow 0.12 0.12 0.12
Brain 0.01
Breast 0.15 0.05 0.12
Colon 0.12 0.12
Endosteum 0.03 0.01 0.01
Esophagus 0.05 0.04
Liver 0.05 0.04
Lung 0.12 0.12 0.12
Skin 0.01 0.01
Salivary Glands 0.01
Stomach 0.12 0.12
Thyroid 0.03 0.05 0.04
Gonads 0.25 0.20 0.08
Remainder 0.30 0.05 0.12
ICRP Publica%on 103 – 2007 Effec%ve Dose Belongs to the Reference Person Only!
MIRD Statements on HE and E
MIRD Statements on HE and E
What effec%ve dose can be used for…
MIRD Statements on HE and E
What effec%ve dose cannot be used for… Accordingly, the effec%ve dose for medical exposures cannot be assigned as an index of stochas%c risk to a single individual pa%ent (male or female), nor can it be assigned to male or female pa%ents of body morphometries significantly different from those of the ICRP reference individuals. These limita%ons stem from the fact that wT is both sex-‐ and age-‐averaged. As a result, the sex-‐averaged value of wT for the breasts provides no informa%on on the risk of breast cancer in male pa%ents. Similarly, the age-‐averaged value of wT for the thyroid overemphasizes the risk of thyroid cancer in adult pa%ents and conversely underemphasizes that risk in children.
Alterna%ves to the Effec%ve Dose
As presented previously in the MIRD Course on Dose Reduc%on in Pediatric Nuclear Medicine… Age, gender, and organ specific cancer risk models are available from the documents such as the BEIR VII report and EPA Blue Book which require knowledge of the mean absorbed dose to different organs…the very same values needed to es%mate the effec%ve dose.
hAp://www.epa.gov/rpdweb00/docs/bluebook/bbfinalversion.pdf
hAp://www.nap.edu/catalog.php?record_id=11340
History of the BEIR Reports BEIR III (1980): General es%mates of radia%on risk at low doses BEIR V (1990): General es%mates of radia%on risk at low doses BEIR VII (2005): General es%mates of radia%on risk at low doses
In the 15 years since the publica%on of the BEIR V report on low-‐LET radia%on, substan%al new informa%on on radia%on-‐induced cancer had become available from the Hiroshima and Nagasaki atomic bomb survivors (LSS – Life Span Study), where slightly less than half of the original survivors were s%ll alive as of 2000. The commiAee evaluated nearly 13,000 incidences of cancer and approximately 10,000 cancer deaths in contrast to fewer than 6000 cancer deaths available to the BEIR V commiAee. Also, since comple%on of the 1990 report, addi%onal evidence had emerged from the LSS sugges%ng that other health effects, such as cardiovascular disease and stroke, could result from radia%on exposure.
BEIR VII Models
The BEIR VII CommiAee used excess rela%ve risk (ERR) and excess absolute risk (EAR) to project radiogenic cancer risks to the U.S. popula%on for each cancer site. Defini%on – Incidence Rate 𝝀 Incidence refers to new cases of disease occurring among previously unaffected individuals. It is calculated as the number of new cases of the disease occurring in the popula%on in a specified %me interval divided by the sum of observa%on %mes in that interval for all individuals who were disease free at the beginning of each %me interval.
BEIR VII Models
Defini%ons – Model Parameters AAained age of an individual a Age at exposure to radia%on e Time since exposure t = a -‐ e Radia%on organ dose (in Sv) D Sex of individual (1 – female and 0 – male) s Study popula%on specific factors p
BEIR VII Models Excess Rela%ve Risk (ERR) Model 𝝀↓𝑰 (𝒂,𝒆,𝑫,𝒔,𝒑)= 𝝀↓𝑰↑𝟎 (𝒂, 𝒔, 𝒑) [𝟏+𝑫⋅ 𝑬𝑹𝑹 (𝒂, 𝒆, 𝒔)] 𝝀↓𝑴 (𝒂,𝒆,𝑫,𝒔,𝒑)= 𝝀↓𝑴↑𝟎 (𝒂, 𝒔, 𝒑) [𝟏+𝑫⋅ 𝑬𝑹𝑹 (𝒂, 𝒆, 𝒔)] where 𝝀↓𝑰 (𝒂,𝒆,𝑫,𝒔,𝒑) = projected cancer incidence rate in exposed persons 𝝀↓𝑴 (𝒂,𝒆,𝑫,𝒔,𝒑) = projected cancer mortality rate in exposed persons 𝝀↓𝑰↑𝟎 (𝒂, 𝒔, 𝒑) = baseline cancer incidence rate by age and sex
(i.e., rate for an unexposed popula%on) 𝝀↓𝑴↑𝟎 (𝒂, 𝒔, 𝒑) = baseline cancer mortality rate by age and sex
(i.e., rate for an unexposed popula%on) 𝑬𝑹𝑹 (𝒂, 𝒆, 𝒔) = excess rela%ve risk per unit dose (i.e., propor%onal increase in incidence rate)
BEIR VII Models Excess Absolute Risk (EAR) Model 𝝀↓𝑰 (𝒂,𝒆,𝑫,𝒔,𝒑)= 𝝀↓𝑰↑𝟎 (𝒂, 𝒔, 𝒑)+ 𝑫 ⋅ 𝑬𝑨𝑹 (𝒂, 𝒆, 𝒔) 𝝀↓𝑴 (𝒂,𝒆,𝑫,𝒔,𝒑)= 𝝀↓𝑴↑𝟎 (𝒂, 𝒔, 𝒑)+ 𝑫 ⋅ 𝑬𝑨𝑹 (𝒂, 𝒆, 𝒔) ⋅ 𝝀↓𝑴↑𝟎 (𝒂, 𝒔, 𝒑)/𝝀↓𝑰↑𝟎 (𝒂, 𝒔, 𝒑) where 𝑬𝑨𝑹 (𝒂, 𝒆, 𝒔) = excess absolute incidence risk per unit dose
(i.e., addi%onal contribu%on to the incidence rate) 𝝀↓𝑴↑𝟎 (𝒂, 𝒔, 𝒑)/𝝀↓𝑰↑𝟎 (𝒂, 𝒔, 𝒑) = lethality frac%on (ra%o of mortality/incidence rates)
BEIR VII Models
Func%onal Form for ERR and EAR 𝑬𝑹𝑹 (𝒂, 𝒆, 𝒔) 𝒐𝒓 𝑬𝑨𝑹 (𝒂, 𝒆, 𝒔) = 𝜷↓𝒔 ⋅ 𝒆𝒙𝒑(𝜸𝒆↑∗ ) ⋅ (𝒂/𝟔𝟎)↑𝜼 where 𝜷↓𝒔 is the sex-‐dependent model parameter in units of (Sv -‐1) for the rela%ve risk model and in (per 10,000 person-‐Sv) for the absolute risk model γ and η are model constants showing dependences on e and a, respec%vely 𝒆↑∗ = 𝒎𝒊𝒏(𝒆, 𝟑𝟎)− 𝟑𝟎/𝟏𝟎
BEIR VII Models Model Parameter Values
BEIR VII Models Age Dependence for Cancer Incidence
BEIR VII Models Age Dependence for Cancer Mortality
BEIR VII Models
BEIR VII Models The parameter life%me aAributable risk or LAR approximates the probability that a given radia%on exposure at age e will result in a premature cancer incidence or death at age a. This probably can be thought of as weighted sums of the age-‐specific excess probabili%es of radia%on-‐induced cancer incidence or death – given by the func%on M(D, e, a). The dependence on sex is implied. 𝑳𝑨𝑹(𝑫,𝒆)= ∫𝒆+𝑳↑𝟏𝟏𝟎▒𝑴(𝑫,𝒆,𝒂) ⋅ 𝑺(𝒂)/𝑺(𝒆) 𝒅𝒂
where 𝑴(𝑫,𝒆,𝒂) = risk at aAained age a from radia%on dose D at age e
(based on either ERR or EAR models and can be either for cancer incidence or cancer mortality)
𝑺(𝒂) = probability of surviving to age a 𝑺(𝒆) = probability of surviving to age e L = minimum latency period
(2 years for leukemia and 5 years for solids cancers)
BEIR VII Models Baseline rates for Cancer Incidence (blue) and Cancer Mortality (green)
BEIR VII Models
Equa%ons for LAR Calcula%ons Cancer Incidence 𝑴↓𝑰 (𝑫,𝒆,𝒂) = 𝑬𝑹𝑹↓𝑰 (𝑫,𝒆,𝒂) ⋅ 𝝀↓𝑰↑𝟎 (𝒂) ERR Model 𝑴↓𝑰 (𝑫,𝒆,𝒂) = 𝑬𝑨𝑹↓𝑰 (𝑫,𝒆,𝒂) EAR Model Cancer Mortality 𝑴↓𝑴 (𝑫,𝒆,𝒂) = 𝑬𝑹𝑹↓𝑰 (𝑫,𝒆,𝒂) ⋅ 𝝀↓𝑴↑𝟎 (𝒂) ERR Model 𝑴↓𝑴 (𝑫,𝒆,𝒂) = 𝑬𝑨𝑹↓𝑰 (𝑫,𝒆,𝒂)⋅ 𝝀↓𝑴↑𝟎 (𝒂)/𝝀↓𝑰↑𝟎 (𝒂) EAR Model
BEIR VII Models Ques%on Which model to use then in providing final es%mates of LAR – those based upon rela%ve or absolute risk model? Answer BEIR VII commiAee adopted geometric averaging of LAR values 𝑳𝑨𝑹= (𝑳𝑨𝑹↓𝑬𝑹𝑹 )↑𝒘 ⋅ (𝑳𝑨𝑹↓𝑬𝑨𝑹 )↑𝟏−𝒘 Thyroid cancer: w = 1.0 (100%:0% weigh%ng) Breast cancer: w = 0.0 (0%:100% weigh%ng) Lung cancer: w = 0.3 (30%:70% weigh%ng) All other cancers: w = 0.7 (70%:30% weigh%ng) Note – EPA has chosen to use a straight arithme%c weigh%ng
BEIR VII Models LAR Tables for Cancer Incidence
BEIR VII Models LAR Tables for Cancer Mortality
BEIR VII Models Summary
BEIR VII provides LAR incidence and mortality es%mates for all solid cancers, for leukemia, and following specific cancer sites:
• Stomach • Colon • Liver • Lung • Bladder • Thyroid
• Prostate • Breast (Female) • Uterus • Ovary • Other Sites (opera%onally
equivalent to remainder in the effec%ve dose)
2011 EPA Blue Book Updates to BEIR VII Models
• In addi%on to the sites men%oned in BEIR VII, EPA es%mates LARs for the following addi%onal sites: -‐ Kidney -‐ Bone Endosteum -‐ Skin – fatal cancers only
• Different Breast Cancer mortality model is used (complex) -‐ Accounts for long survival %mes between incidence and death
• Different Thyroid model is used (similar to NCRP Report 159) -‐ Explicitly accounts for the dependence of ERR on both age-‐at-‐exposure and %me-‐since-‐exposure
MIRD CommiAee Ac%vi%es In a forthcoming MIRD Pamphlet, LAR es%mates for addi%onal
sites were developed in collabora%on with David Pawel, biosta%s%cian at EPA
-‐ Oral cavity -‐ Pancreas -‐ Gallbladder -‐ Central Nervous System (CNS) -‐ Esophagus -‐ Rectum
Example – Thyroid Cancer Incidence
For thyroid cancer, the modest discon%nui%es evident in LAR at ages 5, 10, and 15 are an ar%fact of the categoriza%on used for age-‐at-‐exposure in the thyroid risk model.
Example – Breast Cancer Incidence
Example – Benefit to Risk Ra%o in NM?
Example – Benefit to Risk Ra%o in NM?
Review by Pat Zanzonico (2010 SNM) • Conventional pre-op work-up → Thoracotomy: 81% (78 / 97)
Thoracotomy futile: 41% (39 / 78) • Conventional pre-op work-up → Thoracotomy: 65% (60 / 92)
w/ PET Thoracotomy futile: 21% (19 / 60) • Surgery (Sx)-related mortality: 6.5% • w/ PET → Avoided futile Sx: 20%
Dat
a Ex
trap
olat
ion
• New lung cancers in US (2006): 174,470 /yr • Conventional pre-op work-up → Futile-Sx deaths: 3,766 /yr • Conventional pre-op work-up → Futile-Sx deaths: 1,547 /yr
+ PET • Gross benefit of pre-op PET - Lives saved w/ PET: 2,219 /yr • 18FDG ED / 10 mCi: 7 mSv • Excess cancer deaths: 61 /yr • Net benefit of pre-op PET - Lives saved w/ PET: 2,158 /yr
B/R Ratio - 36
Van Tinteren et al. Lancet 359: 1388, 2002
Alterna%ves to the Effec%ve Dose
Thus, as a metric for op%miza%on of benefit (e.g., image quality) and risk (cancer induc%on) in medical imaging, direct conversion of mean organ dose to cancer risk is increasingly used as an alterna%ve to the effec%ve dose. One advantage over the effec%ve dose is that one can then compare that risk to other risks (or benefits) in the medical treatment of pa%ents.
MIRD Pamphlet Outline
1. Introduc%on – ongoing efforts to minimize radia%on exposure in imaging
2. Stochas%c effects from ionizing radia%on 3. ICRP dosimetry quan%%es related to stochas%c risk 4. Quan%fica%on of stochas%c risk in medical imaging 5. Quan%fica%on of medical benefit in medical imaging 6. Examples of risks and benefits associated with medical
imaging of pa%ents 7. Conclusions
Forthcoming Book by Hendee & Dauer
Forthcoming Book by Hendee & Dauer Introduc*on Part I. Jus%fica%on in Medical Imaging Part II. Radia%on Dose In Medical Imaging –
Defining, Measuring and Assessing Part III. Radia%on Risks in Medical Imaging Part IV. Op%miza%on and Dose Reduc%on in Medical Imaging Part V. Shared Decision Making in Medical Imaging Part VI. Medical Imaging Safety Approaches Conclusions
This concludes my presenta%on I would be happy to entertain any ques%ons!