Radiation Safetyand Fetal dose

핵의학과

윤석남

Nuclear Medicine

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방사성동위원소 악물

핵의학 영상

• 생리, 생화학 대사 과정

(해부학적 방사선 영상)

옥소: 요오드

저절로 사라진다

Dose 개념

• Bq:international unit

• Bq=dps = decay per sec

• 통상 1mCi = 37MBq= 37X 106Bq

• = 편하게 이용하기 위해서 mCi단위

• 진단스캔: Tc-99m : 30mCi내외

• Tl-201: 3mCi

• 치료용량 I-131: 30/100/150/200mCi

Radiolabeled Particle

R. gases

R. cheates

R. Tracer as ions

R. cells

Receptor binding

Monoclonal antibody

Metabolic substrate

방사선 노출이란?= 배설 및 분포에 의한 영향

인체 영향과 방사선

• 인체는 여러가지 원자로 구성되어 있으며방사선이 인체를 투과할때 인체를 구성하는 원자에 에너지를 부여하고 에너지가 부여된 원자는 전리와 여기등 물리적인 작용이일어 난다

• 전리와 여기작용은 세포핵에 있는 DNA로구성된 염색체를 절단하거나 돌연변이등의 이상을 일으키며 방사선장애의 근원

방사선

• X ray, 무선통신에 사용되는 microwave, 컴퓨터나 가전제품의 전자파(radiowave),투열요법의 고열(diathermy)에서도 나옴.

• 파장이 길고 적은량의 에너지 조직내 이온화하지 못하므로 해로운 영향이 없다.

• R(roentgen)- amount of ionization produced by a beam of x-ray or gamma rays in air.

• Exposure level- detection such as Geiger counters.

• The amount of radiation energy absorbed by irradiated tissue

• - radiation dose- specified in rads or grays.

Rad란

• 1 rad: 100ergs of energy absorbed per gram of tissue

• 1 gray: 1 joule of energy per killogram of tissue

• = 100 rads.

Biologic effect

• Depends -1, the number of ergs per gram

• 2, linear energy transfer of radiation( density of ionization produced by radiation)

• Alpha and neutron: 10-20 times more ionization than X,gamma or beta

• == 각각다른 ㅡmultiplied by a radiation weighting factor

• -new measurement-equivalent dose.

• Rem( roentgen-equivalent-man) or sieverts.

• X-ray,gamma, beta- factor -1

• = equivalent: roentgen,rads and rem

• Radiation dose-expressed in millirads instead of millirems

• Gray and sieverts –numerically equivalent: 1Sv= 100 rems =1Gy=100rad

• Nuclear medicine: quite low-mrem,mSv

• 1Rad=1Rem=1000mRem

• 1Sv=1Gray=100rad=100rem

• 1000mSv= 100rad=100rem

• 1rad =10mSv=10mGy

Radiation dose to the patient

• Whole body- not receive a uniform radiation throughout body

• Ex> Tc0-99mMAG3 5mci- red marrow: 9mrem, bladder-as high as 850mrem

• 장기별-sensitive or resistant

• Effective radiation dose

• Diagnostic nuclear : 100-100mrem(1-10mSv)- 평균- 330mrem(3mSv)

• 비교: background radiation: 300mrem/yr

Back ground radiationflight radiation

• Due to indoor raon etc

• Another source- human body itself

• Travel : 0.5mrem/hr

• US background radiation- about 300mrem( 3mSv)

선 량 한 도 :50mSv/yr

구 분

선 량 한 도

직업상 피폭 일반인 피폭

유효선량한도100 mSv/5년

(연간 50 mSv를 넘지 않는 한도)1 mSv/1년

등가선량한도수 정 체피 부 150 mSv/1년

500 mSv/1년15 mSv/1년50 mSv/1년

등가선량

증 상 비 고

0.25 Sv 거의 증상이 없음

0.5 Sv 임파구 일시적 감소

1 Sv 구토, 구역질, 전신권태, 임파구 현저한 감소

1.5 Sv 방사선 숙취 50%방사선피폭 결과 2일간 술취한 증상을 방사

선숙취라 함

2 Sv 장기 백혈구 감소

4 Sv 사망 30일 이내에 50%사망률 50%를 반치사선량이라 부르고

LD50/30이라고 씀

6 Sv 사망 14일 이내에 90%

7 Sv 사망 100% 100%는 치사선량임

Genetic effect of low dose radiation

• Hiroshima/nagasaki descents

• - hazard 평가

• -no increase in incidence of prenatal or neonatal death or malformation

• Complete data:not yet available

• : 종사자: 5rem/yr( 50mSv/yr)

Pregnant women

• 10-15 rem(0.1-0.15Sv) to a fetus

• - increased incidence of fetal malformation,death or persistent damage of genetic material

• Fetal dose –nuclear medicine-

=0.1-1rem

• Susceptible to congenital defect-1st T:

• frequent voiding등으로 최소화

Potentially pregnant women

• Ask when she had last mens period

• - postponed

• If patient dose not think she is pregnant,

• Fetal risk can be minimized by limiting the radiation exposure to the first 10 days of mens cycle before ovulation and potential conception.

• 임신초기 1-2주 배아기: 배아가 죽거나 아니면 방사선에 의한 세포파괴가 정상으로복구

• 3-10주 기관형성기에 기형

• 최근의 결론- 5rad 미만은 태아의 기형,성장장애 유산등의 위험은 증가안된다.

• 자궁이나 태아의 방사선량

• - 머리 가슴촬영시 -0.01-0.05mrad

• 복부- 100mrad

• 신장뇨관- 1rad

• 엉덩이 – 200mrad

• CT: 3 rad미만

발암 특히 백혈병확률

• 임신중 모체가 1-2 rad: 유아기 백혈병발생확률 2000-3000:1

• 백혈병 형제자매간 발생율: 700:1

Determinstic

Stochastic

• 확정적 영향(deterministic effects)확정적 영향은 세포사에 따라 일어나며 피폭선량이 클

수록 많은 세포를 잃어버리게 되며 기관이나 조직의 기능에 한층 중한 장해가 일어나는 영향이다. 임상적으로병적상태라고 진단하는 데는 일정한 최소선량(문턱값)이필요하다. 따라서 임상적으로 인정할 수 있는 장해의 발생확률은 문턱값 이하의 선량에서는 영이 된다. 문턱값을 넘으면 선량의 증가에 따라 장해의 중독도가 증가하며, 또, 장해의 발생확률(빈도)도 급격히 증가해서 100%의 환자에 장해가 발생하게 된다(그림-1). 또 방사선 치료의 문턱값은 5년이내에 1-5%의 환자에게 장해를 일으키는 선량으로 하고 있다.

• 확률적 영향(stochastic effects)확률적 영향은 세포사보다 오히려 증식 가능한 하나의

손상 세포로부터 생겨나 선량이 증가하면 손상세포의 빈도도 증가해서 결과로서 발암이나 자손에게 전해지는 유전장해의 빈도를 높이는 것과 같은 영향이다. 손상 세포가 임상적으로 발암 증상을 나타내기까지엔 다단계 과정을 거쳐 10 억개 이상의 세포로 증식할 필요가 있다. 또손상 생식세포도 자손의 유전장해로 되기엔 다단계의 수정 선택과정을 거쳐 140조개의 세포로 증식할 필요가 있다. 따라서 선량이 지나치게 크면 세포사 때문에 확률적영향은 감소한다. 증식 가능한 손상세포는 선량이 낮더라도 생겨날 수 있기 때문에 확률적 영향에는 문턱값 선량이 없다고 가정할 수 있다. 또 선량의 증가에 따라 영향의 정도는 변하지 않으며 영향의 발생확률만 증가한다.

100mSv:ICRP• Ann ICRP. 2000;30(1):iii-viii, 1-43.• Pregnancy and medical radiation.• International Commission on Radiological Protection.• Abstract• Thousands of pregnant patients and radiation workers are exposed to ionising radiation each year. Lack of

knowledge is responsible for great anxiety and probably unnecessary termination of pregnancies. For many patients, the exposure is appropriate, while for others the exposure may be inappropriate, placing the unborn child at increased risk. Prenatal doses from most properly done diagnostic procedures present no measurably increased risk of prenatal death, malformation, or impairment of mental development over the background incidence of these entities. Higher doses, such as those involved in therapeutic procedures, can result in significant fetal harm. The pregnant patient or worker has a right to know the magnitude and type of potential radiation effects that might result from in utero exposure. Almost always, if a diagnostic radiology examination is medically indicated, the risk to the mother of not doing the procedure is greater than is the risk of potential harm to the fetus. Most nuclear medicine procedures do not cause large fetal doses. However, some radiopharmaceuticals that are used in nuclear medicine can pose significant fetal risks. It is important to ascertain whether a female patient is pregnant prior to radiotherapy. In pregnant patients, cancers that are remote from the pelvis usually can be heated with radiotherapy. This however requires careful planning. Cancers in the pelvis cannot be adequately treated during pregnancy without severe or lethal consequences for the fetus. The basis for the control of the occupational exposure of women who are not pregnant is the same as that for men. However, if a woman is, or may be, pregnant, additional controls have to be considered to protect the unborn child. In many countries, radiation exposure of pregnant females in biomedical research is not specifically prohibited. However, their involvement in such research is very rare and should be discouraged. Termination of pregnancy is an individual decision affected by many factors. Fetal doses below 100 mGy should not be considered a reason for terminating a pregnancy. At fetal doses above this level, informed decisions should be made based upon individual circumstances.

Unnecessary termination

• Teratology. 1991 Feb;43(2):109-12.• Exposure to ionizing radiation during pregnancy: perception of teratogenic risk

and outcome.• Bentur Y, Horlatsch N, Koren G.• Motherisk Program, Hospital for Sick Children, Toronto, Ontario, Canada.• Abstract• We quantified the perception of teratogenic risk in women attending the

Motherisk program for counseling about diagnostic radiation in pregnancy (n = 50) and compared it with a control group of women exposed to nonteratogenic drugs and chemicals (n = 48). Before receiving known information about the specific exposure, women exposed to radiation assigned themselves a significantly higher teratogenic risk compared with the control group (25.5 +/-4.3% versus 15.7 +/- 3.0% for major malformations, P less than 0.01). The post-consultation perception of teratogenic risk did not differ between the two groups. Special consideration and attention should be given when counseling pregnant women exposed to low-dose ionizing radiation, as their misperception of teratogenic risk may lead them to unnecessary termination of their pregnancy.

Stochastic effect- as low as possible

• Hell J Nucl Med. 2007 Jan-Apr;10(1):48-55.• [Fetus radiation doses from nuclear medicine and radiology diagnostic procedures. Potential risks and radiation protection

instructions]• [Article in Greek, Modern]• Markou P.• Health Care Unit Management, 9 Melenikou Str., 582 00 Edessa, Macedonia, Greece. markp@otenet.gr• Abstract• Although in pregnancy it is strongly recommended to avoid diagnostic nuclear medicine and radiology procedures, in cases of

clinical necessity or when pregnancy is not known to the physician, these diagnostic procedures are to be applied. In such cases, counseling based on accurate information and comprehensive discussion about the risks of radiation exposure to the fetus should follow. In this article, estimations of the absorbed radiation doses due to nuclear medicine and radiology diagnostic procedures during the pregnancy and their possible risk effects to the fetus are examined and then discussed. Stochastic and detrimental effects are evaluated with respect to other risk factors and related to the fetus absorbed radiation dose and to thepost-conception age. The possible termination of a pregnancy, due to radiation exposure is discussed. Special radiation protection instructions are given for radiation exposures in cases of possible, confirmed or unknown pregnancies.

• It is concluded that nuclear medicine and radiology diagnostic procedures, if not repeated during the pregnancy, are rarely an indication for the termination of pregnancy, because the dose received by the fetus is expected to be less than 100 mSv, which indicates the threshold dose for having deterministic effects. Therefore, the risk for the fetus due to these diagnostic procedures is low. However, stochastic effects are still possible but will be minimized if the radiation absorbed dose to the fetus is kept as low as possible.

Not teratogenic – diagnostic radiation

• J Obstet Gynaecol Can. 2006 Jan;28(1):43-8.• Diagnostic radiation in pregnancy: perception versus true risks.• [Article in English, French]• Cohen-Kerem R, Nulman I, Abramow-Newerly M, Medina D,

Maze R, Brent RL, Koren G.• Motherisk Program, Division of Clinical Pharmacology and

Toxicology, Department of Pediatrics, the Hospital for Sick Children, Toronto, Ontario.

• Abstract• Significant numbers of therapeutic abortions are performed for

radiation-exposed pregnant women because of concerns about the teratogenic risk. However, available data suggest that current diagnostic radiation procedures are not teratogenic.

Total 10mSv:PETCTPET:7 +low dose CT:3full dose CT:2-20mSv

• Radiat Prot Dosimetry. 2010 Feb 18. [Epub ahead of print]• RADIATION EXPOSURE OF PATIENTS AND PERSONNEL FROM A PET/CT PROCEDURE WITH 18F-FDG.• Leide-Svegborn S.• Medical Radiation Physics, Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden.

• Abstract• The positron emission tomography (PET)/computed tomography (CT) camera is a combination of a PET

camera and a CT. The image from the PET camera is based on the detection of radiation that is emitted from a radioactive tracer, which has been given to the patient as an intravenous injection. The radiation that is emitted from the radioactive tracer is more energetic than any other radiation used in medical diagnostic procedures and this requires special radiation protection routines. The CT image is based on the detection of radiation produced from an X-ray tube and transmitted through the patient. The radiation exposure of the personnel during the CT procedure is generally very low. Regarding radiation exposure of the patient, it is important to notice whether a CT scan has been performed prior to the PET/CT in order to avoid any unnecessary irradiation. The total effective dose to the patient from a PET/CT procedure is approximately 10 mSv. The major part comes from internal irradiation due to radiopharmaceuticals within the patients (e.g. (18)F-FDG: approximately 6-7 mSv), and a minor part is due to the CT scan (low-dose CT scan: approximately 2-4 mSv). If a full diagnostic CT investigation is performed, the effective dose may be considerably higher. If the patient is pregnant, a PET/CT procedure should be avoided or postponed, unless it is vital for the patient. An interruption in breastfeeding is not necessary after a PET/CT procedure of the nursing mother. Close contact between the patient and a small child should however be avoided for a couple of hours after the administration of the radiopharmaceutical. The radiation dose to the personnel arises mainly due to handling of the radiopharmaceuticals (syringe withdrawal, injection, waste handling, etc.) and from close contact to the patient. This radiation dose can be limited by using the inverse-square law, i.e. by using the fact that the absorbed dose decreases substantially with increasing distance between the radiation source and the personnel.

• No reason for termination of a pregnancy at fetal whole body dose below 100mGy,

• 100mGy=100mSv

Fetal effect from low-level radiation exposure

Estimated dose

1case- hypothyroidism(100mGy) vs 1case-

dead(700mGy)

False negative test

1년내 임신-abortion증가

Transient alteration in ovarian function -1year.