1. Management in radiology seminar February 2-3 2013 Tehran-Iran
Safety and protection

2. jalaljalalshokouhi@hotmail.com www.medimage.ir
Jalal Jalal Shokouhi – MD
President of Iranian society of radiology
President of cooperation of Iranian radiologists
Technical manager of Jaam e Jam and koorosh medical imaging centers

3. Safety and Protection in medical imaging

4. Using Ionising Radiation in Medicine

5. There are 3 main uses of ionising radiation in medicine:
Treatment
Diagnosis
Sterilisation
Ask pupils: what would ionising radiation in medicine be used for?

6. Radiotherapy Treatment Planning
Every treatment using radiotherapy has to be rigorously planned. The planning process consists of three phases:
Planning
Simulation
Treatment

7. Radiotherapy Treatment Planning
The cancerous tumour has to be located so that its size and position can be analysed. This information can be obtained from:
X-rays
CT scans
MRI scans
Ultrasound images

8. Radiotherapy Treatment Planning Simulation
Once the amount of radiation to be given has been accurately calculated, the patient then goes to the simulator to determine what settings are to be selected for the actual treatment using a linear accelerator.
The settings are determined by taking a series of x-rays to make sure that the tumour is in the correct position ready to receive the ionising radiation.

9. Tracers
There are many uses of ionising radiation based on the fact that it is easy to detect. In such applications, the radioactive material is used in the form of a tracer.
In nuclear medicine, a tracer is a radioactive substance which is taken into the body either, as an injection, or as a drink. Such a substance is normally a gamma emitter which is detected and monitored.
This gives an indication of any problems that may be present in body organs or tissues by how much, or how little, of the substance has been absorbed.
Stress to the class that most tracers come in the form of an injection.

10. Diagnosis Static Imaging
There is a time delay between injecting the tracer and the build-up of radiation in the organ.
Static studies are performed on the brain, bone or lungs scans.

11. Summary
There are 3 main uses of ionising radiation in medicine: treatment, diagnosis and sterilisation.
Radiotherapy is used to treat cancers by irradiating them with ionising radiation.
Radioactive tracers are used to diagnose and investigate several medical conditions.
Ionising radiation is used to sterilise medical equipment as it kills germs and/or bacteria.
Stress to pupils: ionising radiation is used to treat cancer and to sterilise medical equipment because it destroys cells and that radioactive tracers are used because the ionising radiation it emits is easy to detect.

19. RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
L 9: Medical Exposure - BSS (Potential exposure and investigation of accidental medical exposures)
Part …: (Add part number and title)
Module…: (Add module number and title)
Lesson …: (Add session number and title)
Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.)
Duration: (Add presentation time or duration of the session – hrs)
Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate)
References: (List the references for the session)
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

20. Main International Institutions involved in Regulatory aspects
IAEA (The International Atomic Energy Agency)
IEC (International Electro-technical Commission)
ICRP ( The International Commission on Radiological Protection)
OECD/NEA (The Nuclear Energy Agency)
CEC (The Commission of European Communities)
WHO (The World Health Organization)
ILO (The International Labor Organization)
ISO (International Organization for Standardization)
9: Medical Exposure - BSS

21. Regulatory aspects (II)
Part No...., Module No....Lesson No
Module title
Regulatory aspects (II)
Several revised versions of “The Basic Safety Standards” (BSS) published: 1962, 1967, 1982, 1994, 1996, 2011
The last version “Safety series N° 115” (2011) reflects knowledge and developments in radiation protection and safety and related fields at that time
Several revised versions of “The Basic Safety Standards” (BSS) have been published in the IAEA Safety series (1962, 1967, 1982, 1994)
The last version “Safety series N° 115” (1996) supersedes the previous BSS and reflects knowledge gained subsequently and developments in radiation protection and safety and related fields
9: Medical Exposure - BSS
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

22. Responsibilities Main responsibilities: registrants and licensees
employers
Subsidiary include:
suppliers
workers
radiation protection officers
medical practitioners & health professionals
qualified experts, ethical review committees
9: Medical Exposure - BSS

23. Medical exposure responsibilities (I)
REGISTRANTS AND LICENSEES SHALL ENSURE THAT:
No patient be administrated a diagnostic or therapeutic medical exposure unless the exposure is prescribed by a medical practitioner
Medical practitioners be assigned the primary task and obligation of ensuring overall patient protection and safety in the prescription of, and during the delivery of, medical exposure
9: Medical Exposure - BSS

24. Medical exposure responsibilities (II)
REGISTRANTS AND LICENSEES SHALL ENSURE THAT:
Medical and paramedical personnel be available as needed, and either be health professionals or have appropriate training adequately to discharge assigned tasks
For therapeutic uses of radiation, the calibration, dosimetry and quality assurance requirements of the Standards be conducted by or under the supervision of a qualified expert in radiotherapy physics
9: Medical Exposure - BSS

25. Medical exposure responsibilities (III)
REGISTRANTS AND LICENSEES SHALL ENSURE THAT:
The exposure of individuals incurred knowingly while voluntarily helping in the care, visit, support or comfort of patients undergoing medical diagnosis or treatment be constrained so that it is unlikely that her or his dose will exceed 5 mSv during the period of a patient’s diagnostic examination or treatment.
Training criteria be specified or be subject to approval, as appropriate, by the Regulatory Authority in consultation with relevant professional bodies
9: Medical Exposure - BSS

26. Radiation Protection Requirements - JUSTIFICATION (I)
GENERIC MATTER
No practice or source within a practice should be authorized unless the practice produces sufficient benefit to the exposed individuals or to society to offset the radiation harm that it might cause i.e.: unless the practice is justified, taking into account social, economic and other relevant factors
MEDICAL EXPOSURE
Medical exposure should be justified by weighing the diagnostic or therapeutic benefits they produce against the radiation detriment they might cause, taking into account the benefits and risk of available alternative techniques that not involve medical exposure
9: Medical Exposure - BSS

27. Radiation Protection Requirements - JUSTIFICATION (II)
MEDICAL EXPOSURE
In justifying each type of diagnostic examination by radiography, fluoroscopy or nuclear medicine, relevant guidelines will be taken into account, such as those established by the WHO
Any radiological examination for occupational, legal, or health insurance purposes undertaken without reference to clinical indications is deemed to be not justified unless it is expected to provide useful information on the health of the individual examined or unless the specific type of examination is justified by those requesting it in consultation with relevant professional bodies
9: Medical Exposure - BSS

28. Radiation Protection Requirements - JUSTIFICATION (III)
MEDICAL EXPOSURE
Mass screening of population groups involving medical exposure is deemed to be not justified unless the expected advantages for the individual examined or for the population as a whole are sufficient to compensate for the economic and social costs, including radiation detriment
9: Medical Exposure - BSS

29. Radiation Protection Requirements - JUSTIFICATION (IV)
MEDICAL EXPOSURE
The exposure of humans for medical research is deemed to be not justified unless it is:
in accordance with the provisions of the Helsinki Declaration and follows the guidelines for its application prepared by Council for International Organization of Medical Sciences (CIOMS) and WHO
subject to the advice of an Ethical Review Committee and to applicable national and local regulations
9: Medical Exposure - BSS

30. OPTIMIZATION - DESIGN CONSIDERATIONS (IV)
With regard to equipment consisting of radiation generators, registrants and licensees should ensure that:
Whether imported into or manufactured in the country where it is used, the equipment conform to applicable standards (IEC, ISO)
Performance specifications and operating and maintenance instructions be provided in a major world language understandable to the users and in compliance with the relevant IEC and ISO standards
Radiation beam control mechanisms be provided (devices indicating clearly and in a fail-safe manner whether the beam is “on” or “off”)
9: Medical Exposure - BSS

31. OPTIMIZATION - DESIGN CONSIDERATIONS (V)
With regard to equipment consisting of radiation generators, registrants and licensees should ensure that:
As nearly as practicable, the exposure be limited to the area being examined by using collimating devices aligned with the radiation beam
The radiation field within the examination area without any radiation beam modifiers (wedges) be as uniform as practicable and the non uniformity be stated by the supplier
Exposure rate outside the examination area due to radiation leakage or scattering be kept as low as reasonably achievable
9: Medical Exposure - BSS

32. With regard to equipment consisting of radiation generators...:
OPTIMIZATION OF PROTECTION FOR MEDICAL EXPOSURES - DESIGN CONSIDERATIONS (VI)
With regard to equipment consisting of radiation generators...:
Radiation generators and their accessories be designed and manufactured so as to facilitate the keeping of medical exposures to the minimum necessary to obtain adequate diagnostic information
Operational parameters (kVp, filtration, focal spot position, source-image receptor distance, field size, either tube current and time or their product) be clearly indicated
9: Medical Exposure - BSS

33. OPTIMIZATION - DESIGN CONSIDERATIONS (VII)
With regard to equipment consisting of radiation generators...:
Radiographic equipment be provided with devices that automatically terminate the irradiation after a preset time, current-time product or dose
Fluoroscopic equipment be provided with a device that energizes the X Ray tube only when continuously depressed (such as a “dead-man’s switch” and equipped with indicators of the elapsed time and/or entrance dose monitors
9: Medical Exposure - BSS

34. OPTIMIZATION - OPERATIONAL CONSIDERATIONS (I)
Registrants and licensees should ensure for diagnostic radiology that:
The medical practitioners who prescribe or conduct radiological examinations:
ensure that the appropriate equipment be used
ensure that the exposure of patients be the minimum necessary to achieve the required diagnostic objective, taking into account norms of acceptable image quality
take into account relevant information from previous examinations in order to avoid unnecessary additional examinations
9: Medical Exposure - BSS

35. OPTIMIZATION - OPERATIONAL CONSIDERATIONS (II)
Registrants and licensees shall ensure ... that:
The medical practitioner, the technologist or other imaging staff select the following parameters such that their combination produce the minimum patient exposure consistent with acceptable image quality and the clinical purpose of the examination
the area to be examined, the number and size of views per examination and the fluoroscopy time
the type of image receptor (e.g. high v.s. low speed screens)
the use of anti-scatter grids
9: Medical Exposure - BSS

36. OPTIMIZATION - OPERATIONAL CONSIDERATIONS (III)
proper collimation of the primary X Ray beam to minimize the volume of patient tissue being irradiated and to improve image quality
appropriate values of operational parameters (kVp, mA…)
appropriate image storage techniques in dynamic imaging (number of images per second)
adequate image processing factors (chemicals, developer temperature, …)
9: Medical Exposure - BSS

37. OPTIMIZATION - OPERATIONAL CONSIDERATIONS (IV)
Registrants and licensees should ensure ……. that:
Portable and mobile radiological equipment be used only for examinations where it is impractical or not medically acceptable to transfer patients to a stationary radiological installation
Radiological examinations causing exposure of the abdomen or pelvis of women who are pregnant or likely to be pregnant be avoided unless there are strong clinical reasons for such examination
Whenever feasible, shielding of radiosensitive organs such as gonads, lens of the eye and thyroid be provided as appropriate
9: Medical Exposure - BSS

38. OPTIMIZATION - CLINICAL DOSIMETRY
Registrants and licensees should ensure that in radiological examinations, representative values for typical sized adult patients of entrance surface dose, dose-area products, dose rates and exposure time, or organ doses be determined and documented
9: Medical Exposure - BSS

39. OPTIMIZATION - QUALITY ASSURANCE (I)
Registrants and licensees should establish a comprehensive QA program with the participation of appropriate qualified experts in radiation physics taking into account the principles established by the WHO and the PAHO
9: Medical Exposure - BSS

40. OPTIMIZATION - QUALITY ASSURANCE (II)
Quality Assurance programs should include:
measurements of the physical parameters of the radiation generators, imaging devices at the time of commissioning and periodically thereafter
verification of the appropriate physical and clinical factors used in patient diagnosis or treatment
written records of relevant procedures and results
verification of the appropriate calibration and conditions of operation of dosimetry and monitoring equipment
9: Medical Exposure - BSS

41. GUIDANCE LEVELS
Registrants and licensees should ensure that guidance levels be determined as specified in the Standards, revised as technology improves and used as guidance by medical practitioners, in order that:
corrective action be taken as necessary if doses fall substantially below the guidance levels and the exposures do not provide useful diagnostic information and do not yield the expected medical benefit to patient
reviews be considered if doses exceed the guidance levels as an input to ensuring optimized protection of patients and maintaining appropriate levels of good practices
for diagnostic radiology, including CT and pediatric examinations, the guidance levels be derived from the data from wide scale quality surveys for the most frequent examinations
9: Medical Exposure - BSS

42. Controlling dose to staff
Wear protective apron & glasses, use shielding, monitor doses – hand dose is often important
Correct positioning to machine to minimise dose
If beam horizontal (or near to) operator should stand on image intensifier side, if possible
If beam vertical (or near to) keep the tube under the patient
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43. Plan view of an interventional operating
x-ray unit with isodose curves
In high dose mode – dose rates will be mSv/hr (same numerical values)

44. UNSCEAR 2000
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45. Why increased frequency?
20 years ago, a standard CT of the thorax took several minutes while today similar information can be accumulated in a single breath hold making it attractive, patient & user friendly
Advances in CT technology have made possible CT fluoroscopy and interventional procedures, in some cases replacing ultrasound guided interventions
Recently CT screening is picking up
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46. Why increased dose…
Unlike radiography where over-exposure results in blackening of film, better image quality is obtained with higher exposures in CT
There is a tendency to increase the volume covered in a particular examination
Modern helical CT involves volume scanning with no inter-slice gap and with possibility of overlapping scans
Repeat CT examinations
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47. Why increased dose (cont’d)
Same exposure factors used for children as for adult
Same exposure factors for pelvic (high contrast region) as for abdomen (low contrast region)
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48. What is the dose from CT? How high?
The effective dose in chest CT is in the order of 8 mSv (around 400 times more than chest radiograph dose) and in some CT examinations like that of pelvic region, it may be around 20 mSv
The absorbed dose to tissues from CT can often approach or exceed the levels known to increase the probability of cancer as shown in epidemiological studies
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49. Effective doses in CT and radiographic examinations
CT examination
Effective dose (mSv)
Radiographic examination
Head 2
Skull
0.07
Chest 8
Chest PA
0.02
Abdomen
10-20
1.0
Pelvis
0.7
Ba swallow
1.5
Ba enema 7

50. Organ doses in CT
Breast dose in thorax CT may be as much as mGy, even though breasts are not the target of imaging procedure
Eye lens dose in brain CT, thyroid in brain or in thorax CT and gonads in pelvic CT receive high doses
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51. Tissues in the field although they are not the area of interest for the procedure
Lens of the eye Breast tissue
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52. Typical doses in mGy during CT in adults (Shrimpton et al. 1991)
Examination
Eyes
Thyroid
Breast
Uterus
Ovaries
Testes
Head 50
1.9
0.03 *
Cervical spine
0.62 44
0.09
Thoracic spine
0.04
0.46 28
0.02
Chest
0.14
2.3 21
0.06
0.08
Abdomen
0.05
0.72
8.0
0.7
L. spine
0.01
0.13
2.4
2.7
Pelvis 26 23
1.7
The symbol * indicates that dose is < mGy

53. Does spiral CT give more or less radiation dose?
It depends upon the choice of factors
Even though it is possible to perform a spiral CT with lower radiation dose than slice-by-slice CT, in practice the patient gets higher dose due to the factors chosen (scan volume, mAs, pitch, slice width
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54. Does multi-slice CT impart more or less radiation dose?
An increase by 10-30% may occur with multi-slice detector array
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55. Some observations
Most doctors including many radiologists have a feeling that modern CT scanners which are very fast give lesser radiation dose
Unfortunately ‘time’ and ‘radiation dose’ are not proportional in such a situation
Over the years the x-ray tubes are becoming more and more powerful such that they can give high bursts of x-rays which can give satisfactory image in shorter exposure time
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56. What can be done to manage patient dose in CT?
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57. What can operators do…? Limit the scanned volume Reduce mAs values
Use automatic exposure control by adapting the scanning parameters to the patient cross section % reduction in dose documented, without any loss of image quality
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58. What can operators do (cont’d)
Use of spiral CT with pitch factor>1 and calculation of overlapping images instead of acquiring overlapping single scans
Shielding of superficial organs such as thyroid, breast, eye lens and gonads particularly in children and young adults. This results in 30-60% dose reduction to the organ
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59. What can operators do (cont’d)
Separate factors for children. Can reduce dose by a factor of 5 or more
Use of partial rotation e.g. 270 degree in Head CT (refer figure on next slide)
Adequate selection of image reconstruction parameters
Use of z-filtering with multi-slice CT systems
Record of dose, exposure factors
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60. Actions for manufacturers
Introduce automatic exposure control
Be conscious of high doses in CT
Include safety features to avoid unnecessary dose
Display of dose
Convenience in using low dose protocols
Draw attention of users to selecting separate protocols for paediatric patients
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61. Actions for physician & radiologist…
Justification: Ensure that patients are not irradiated unjustifiably
Request for CT examination should be generated only by properly qualified medical or dental practitioners depending upon national educational and qualification system. The physician is responsible for weighing the benefits against risks
Clinical guidelines advising which examinations are appropriate and acceptable should be available to clinicians and radiologists
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62. Actions for physician & radiologist (cont’d)
Consider whether the required information be obtained by MRI, ultrasonography
Consider value of contrast medium enhancement prior to commencing examination
CT scanning in pregnancy may not be contraindicated, particularly in emergency situations, although examinations of the abdomen or pelvis should be carefully justified
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63. Actions for physician & radiologist (cont’d)
CT examination should not be repeated without clinical justification and should be limited to the area of interest
Clinician has the responsibility to communicate to the radiologist about previous CT examination of the patient
CT examination for research purpose that do not have clinical justification (immediate benefit to the person undergoing the examination) should be subject to critical evaluation by an ethics committee
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64. Actions for physician & radiologist (cont’d)
CT examination of chest in young girls and young females needs to be justified in view of high breast dose
Once the examination has been justified, radiologist has the primary responsibility for ensuring that the examination is carried out with good technique
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65. LD 50
LD 50/60
THE AMOUNT OF RADIATIONTHAT WILL CAUSE 50% OF EXPOSED INDIVIDUALS TO DIE WITHIN 60 DAYS

66. BIOLOGIC ASPECTS OF RADIATION
Dose response curves (Sherer)
Line 1
No level of radiation can be considered safe.
Response to exposure is directly proportional
Line 2
Threshold is assumed, response expected at lower doses
Cataractogenesis

67. BIOLOGIC ASPECTS OF RADIATION
Dose response curves (Sherer)
Line 3
Non linear (sigmoid or hypothetical sigmoid) dose response
DIAGRAM B
Non linear, threshold dose response used in radiation therapy

68. Radiosensitivity based on Wt factors
What is more radiosensitive?
CNS or GI?
Rectum or Small bowel?
Erythoblasts or Myelocytes?
red bone marrow or gonads?
Adult or elderly?
Lung or thyroid?

69. Spontaneous abortions during first 2 weeks of pregnancy-- 25 RAD or higher
2nd week to 10th week – major organogenesis –IF radiation is high enough can cause congenital abnormalities
Principle response after that may be malignant disease in childhood

70. PREVENTING ACCIDENTAL IRRADITATION TO PATIENT
FIRST TWO MONTHS, CRITICAL
10 DAY RULE
ELECTIVE BOOKING
QUESTIONAIRE
POSTING

71. IF A PREGNANT PATIENT MUST BE X-RAYED
TIGHT COLLIMATION
HIGH KVP
SHIELDING
REDUCED # OF IMAGES
MAKE SURE TO CHECK WITH YOUR SUPERVISOR AND BE AWARE OF THE SITE’S PROTOCOL

72. MINIMIZING PATIENT EXPOSUER
SHIELDING
Gonadal shielding females reduces gonad dose by 50%
Gonadal shielding males reduces gonad dose by 95%
Flat, shadow shields
COLLIMATION
DID YOU KNOW THAT THERE ARE A HIGHER SET OF LEAD SHUTTERS PLACED NEAR THE X-RAY TUBE WINDOW TO ABSORB OFF-FOCUS RADIATION?

73. FILTRATION
INCREASED FILTRATION (HVL) INCREASES THE AVERAGE BEAM ENERGY
No filtration on a 70 kVp tube (0-70) would produce an average energy of 35 kVp
However, if you filter out the lower energies (30-70 kVp) is 50 kVp
Inherent
Added
_________is required for machines operating at 70 kVp

74. PERSONNEL PROTECTION
Let’s keep safe!

75. THE ENVIRONMENT CONTROLLED AREA OCCUPANCY FACTOR UNCONTROLLED AREA
USE FACTOR
WORKLOAD
Badged personnel
Who,what is where
Everyone else!
% of time primary beam is directed at a particular wall
# of x-ray exams per week

76. Primary barrier
7 feet, 1/16 inch of lead
Secondary barrier
Extend to ceiling
1/32 inch of lead

77. Which of these regulations are accurate?
DL for eye is 50 mSv?
Cumulative whole body is 10mSv x age?
Leakage radiation – 100 mR/hr at 2 meters?
Lead aprons at mm pB equivalent?
ESE in 10R/min in fluoro?
Exposure cord on portable must be 1 meter long?
Pregnant radiographer DL for fetus is 500 mrem for period of pregnancy?
The public exposure DL is 100 mrem per year?
Bucky slot cover and protective curtain, minimum of 0.5 pB equivalent?

78. Pregnancy and Medical Radiation
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79. Contents Introduction Fetal radiation risks
Informed consent, notices, pregnancy determination
Fetal doses from procedures
Pregnant workers
Research involving radiation during pregnancy
Issues regarding termination of pregnancy
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80. Introduction
Thousands of pregnant women are exposed to ionising radiation each year
Lack of knowledge is responsible for great anxiety and probably unnecessary termination of pregnancies
For most patients, radiation exposure is medically appropriate and the radiation risk to the fetus is minimal
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81. Example: justified use of CT Pregnant female, was in motor vehicle accident
ribs
Fetal skull
Blood outside uterus
Fetal dose 20 mGy

82. 3 minute CT exam and taken to the operating room
3 minute CT exam and taken to the operating room. She and the child survived
Free blood
Kidney torn
off aorta (no contrast in it)
Splenic laceration
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83. Fetal radiation risk
There are radiation-related risks throughout pregnancy that are related to the stage of pregnancy and absorbed dose
Radiation risks are most significant during organogenesis and in the early fetal period, somewhat less in the 2nd trimester, and least in the 3rd trimester
Most risk
Less
Least

84. Radiation-induced malformations
Malformations have a threshold of mGy or higher and are typically associated with central nervous system problems
Fetal doses of 100 mGy are not reached even with 3 pelvic CT scans or 20 conventional diagnostic x-ray examinations
These levels can be reached with fluoroscopically guided interventional procedures of the pelvis and with radiotherapy
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85. Central nervous system effects
During 8-25 weeks post-conception the CNS is particularly sensitive to radiation
Fetal doses in excess of 100 mGy can result in some reduction of IQ (intelligence quotient)
Fetal doses in the range of 1000 mGy can result in severe mental retardation and microcephaly, particularly during 8-15 weeks and to a lesser extent at weeks
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86. Heterotopic gray matter (arrows) near the ventricles in a mentally retarded individual occurring as a result of high dose in-utero radiation exposure

87. Frequency of microcephaly as a function of dose and gestational age occurring as a result of in-utero exposure in atomic bomb survivors (Miller 1976)
Dose (cGy)

88. Leukaemia and cancer…
Radiation has been shown to increase the risk for leukaemia and many types of cancer in adults and children
Throughout most of pregnancy, the embryo/fetus is assumed to be at about the same risk for carcinogenic effects as children
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89. Leukaemia and cancer (cont’d)
The relative risk may be as high as 1.4 (40% increase over normal incidence) due to a fetal dose of 10 mGy
For an individual exposed in utero to 10 mGy, the absolute risk of cancer at ages is about 1 excess cancer death per 1,700
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90. Probability of bearing healthy children as a function of radiation dose
Dose to conceptus (mGy) above natural background
Probability of no malformation
Probability of no cancer (0-19 years) 97
99.7 1 5 10
99.6 50
99.4
100
99.1
>100
Possible, see text
Higher

91. Pre-conception irradiation
Pre-conception irradiation of either parent’s gonads has not been shown to result in increased risk of cancer or malformations in children
This statement is from comprehensive studies of atomic bomb survivors as well as studies of patients who had been treated with radiotherapy when they were children
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92. Higher dose procedures
Radiation therapy and interventional fluoroscopically-guided procedures may give fetal doses in the range of mGy or more depending on the specifics of the procedure
After such higher dose medical procedures have been performed on pregnant patients, fetal dose and potential fetal risk should be estimated by a knowledgeable person
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93. Nuclear medicine and pregnant patients…
Most diagnostic procedures are done with short-lived radionuclides (such as technetium-99m) that do not cause large fetal doses
Often, fetal dose can be reduced through maternal hydration and encouraging voiding of urine
Some radionuclides do cross the placenta and can pose fetal risks (such as iodine-131)
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94. Nuclear medicine and pregnant patient (cont’d)
The fetal thyroid accumulates iodine after about 10 weeks gestational age
High fetal thyroid doses from radioiodine can result in permanent hypothyroidism
If pregnancy is discovered within 12 h of radio-iodine administration, prompt oral administration of stable potassium iodine ( mg) to the mother can reduce fetal thyroid dose. This may need to be repeated several times
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95. Research on pregnant patients
Research involving radiation exposure of pregnant patients should be discouraged
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96. Termination of pregnancy…
High fetal doses ( mGy) during late pregnancy are not likely to result in malformations or birth defects since all the organs have been formed
A fetal dose of 100 mGy has a small individual risk of radiation-induced cancer. There is over a 99% chance that the exposed fetus will NOT develop childhood cancer or leukaemia
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97. Termination of pregnancy (cont’d)
Termination of pregnancy at fetal doses of less than 100 mGy is NOT justified based upon radiation risk
At fetal doses in excess of 500 mGy, there can be significant fetal damage, the magnitude and type of which is a function of dose and stage of pregnancy
At fetal doses between 100 and 500 mGy, decisions should be based upon individual circumstances
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98. Risks in a pregnant population not exposed to radiation
Spontaneous abortion > 15%
Incidence of genetic abnormalities 4-10%
Intrauterine growth retardation 4%
Incidence of major malformation 2-4%
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99. Thank you for your attention