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Radiation safety in CT. RADIATION DOSES DURING CT EXAMS ARE CLASSIFIED AS:. LOW DOSE RADIATION. AS COMPARED TO DOSES GENERATED FROM NUCLEAR EVENTS. BODY RESPONE TO RADIATION:. SOMATIC EFFECTS GENETIC EFFECTS. SOMATIC EFFECT. MANIFESTED IN THE INDIVIDUAL EXPOSED.

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radiation doses during ct exams are classified as
RADIATION DOSES DURING CT EXAMS ARE CLASSIFIED AS:
  • LOW DOSE RADIATION

AS COMPARED TO DOSES GENERATED FROM NUCLEAR EVENTS

body respone to radiation
BODY RESPONE TO RADIATION:
  • SOMATIC EFFECTS
  • GENETIC EFFECTS
somatic effect
SOMATIC EFFECT
  • MANIFESTED IN THE INDIVIDUAL EXPOSED
acute somatic radiation syndrome stages
ACUTE SOMATIC RADIATION SYNDROME STAGES:
  • PRODROMAL- NAUSEA, VOMITING, DIARRHEA
  • LATENT PERIOD – NO SYMPTOMS
  • MANIFEST – ORGAN DAMAGE, DEATH OR RECOVERY

HEMATOPOIETIC

GI

CNS

most common somatic effects
MOST COMMON SOMATIC EFFECTS
  • CATARACT FORMATION
  • SKIN CANCER
  • THYROID CANCER
  • BREAST CANCER
  • LEUKEMIA
effect on an embryo or fetus
EFFECT ON AN EMBRYO OR FETUS
  • MOST PRONOUNCED DURING THE FIRST TRIMESTER!!!!
genetic effect
GENETIC EFFECT
  • MANIFESTED IN THE FUTURE GENERATIONS!
radiation doses from ct scanners are the highest in diagnostic radiology
RADIATION DOSES FROM CT SCANNERS ARE THE HIGHEST IN DIAGNOSTIC RADIOLOGY!!!!

HOWEVER:

radiation exposure should occur
RADIATION EXPOSURE SHOULD OCCUR :
  • AFTER CONSIDERATION BY THE PHYSICIAN
radiologic units customary
RADIOLOGIC UNITS (CUSTOMARY)
  • EXPOSURE, INTENSITY ------ ROENTGEN (R)
  • ABSORBED DOSE ----------- RADIATION
  • ABSORBED DOSE (rad)
  • DOSE EQUIVALENT ---------RADIATION EQUIVALENT MAN (rem)
radiologic units si
RADIOLOGIC UNITS (SI)
  • EXPOSURE, INTENSITY ------ C/kg
  • ABSORBED DOSE ----------- GRAY (Gy)
  • DOSE EQUIVALENT ---------SIEVERT (Sv)

1 Gy = 100 rad

1 Sv = 100 rem

slide29

THE AMOUNT OF COLLECTED CHARGE IN I.C. IS PROPORTIONAL TO THE AMOUNT OF IONIZATION WHICH IS PROPORTIONAL TO THE AMOUNT OF RADIATION PASSING THROUGH THE CHAMBER. THE TOTAL ELECTRIC CHARGE GENERATED BY AN X-RAY BEAM IS REPRESENTED BY Q AND IS MEASURED IN COULOMBS.

slide30

IN 1981 CENTER FOR DEVICES AND RADIOLOGICAL HEALTH SUGGESTED AN EASY AND ACCURATE METHOD TO MEASURE PATIENT DOSE IN CT. IT RELIED ON ON CTDI AND MSAD (MULTIPLE SCAN AVERAGE DOSE)

slide31
MSAD
  • SERIES OF CT SCANS ARE PERFORMED ON A PATIENT . BETWEEN EACH SCAN PATIENT IS MOVED A BED INDEX (BI) DISTANCE.
factors in patient protection
FACTORS IN PATIENT PROTECTION
  • TIME
  • DISTANCE
  • SHIELDING
shielding
SHIELDING
  • IF PERSONNEL PRESENT IN THE ROOM DURING SCAN MUST BE SHIELDED AND STAND FAR FROM THE SOURCE

( INVERSE SQUARE LAW)

gonadal shields
GONADAL SHIELDS
  • 4-5 CM WITHIN THE X-RAY BEAM
contact shields
CONTACT SHIELDS

360 ° AROUND PATIENT

ct dose in spiral scanning
CT DOSE IN SPIRAL SCANNING
  • CTDI CAN ALSO BE USED

PITCH

MSAD OR CTDI

more useful measurement is
MORE USEFUL MEASUREMENT IS
  • EFFECTIVE DOSE

TAKES INTO ACCOUNT QUALITY

OF RADIATION

AND ORGAN SENSITIVITY

EXPRESSED IN Sv

effective dose msv
HEAD------------ 2

CHEST ---------- 8

ABDOMEN --10-20

PELVIS -------10- 20

SKULL -------- 0.07

CHEST PA ---- 0.02

ABDOMEN --- 1

PELVIS -------- 0.7

EFFECTIVE DOSE (mSv)

CT

CONVENTIONAL

dose reduction in ct
BED INDEX

SPIRAL PITCH

COLLIMATION

(PREPATIENT)

NOISE

DOSE

DOSE

DOSE

DOSE

DOSE REDUCTION IN CT
dose reduction in ct1
SID

OID

kVp (15 % RULE)

mAs

DOSE

DOSE

DOSE

DOSE

DOSE REDUCTION IN CT
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