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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: • 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
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 • CATARACT FORMATION • SKIN CANCER • THYROID CANCER • BREAST CANCER • LEUKEMIA
EFFECT ON AN EMBRYO OR FETUS • MOST PRONOUNCED DURING THE FIRST TRIMESTER!!!!
ALTERNATIVE EXAMS SHOULD BE SCHEDULED IF PATIENT IS PREGNANT CT OR MRI ?
GENETIC EFFECT • MANIFESTED IN THE FUTURE GENERATIONS!
RADIATION DOSES FROM CT SCANNERS ARE THE HIGHEST IN DIAGNOSTIC RADIOLOGY!!!! HOWEVER:
RADIATION EXPOSURE SHOULD OCCUR : • AFTER CONSIDERATION BY THE PHYSICIAN
RADIOLOGIC UNITS (CUSTOMARY) • EXPOSURE, INTENSITY ------ ROENTGEN (R) • ABSORBED DOSE ----------- RADIATION • ABSORBED DOSE (rad) • DOSE EQUIVALENT ---------RADIATION EQUIVALENT MAN (rem)
RADIOLOGIC UNITS (SI) • EXPOSURE, INTENSITY ------ C/kg • ABSORBED DOSE ----------- GRAY (Gy) • DOSE EQUIVALENT ---------SIEVERT (Sv) 1 Gy = 100 rad 1 Sv = 100 rem
PENCIL IONIZATION CHAMBER METHOD OF MEASURING CT DOSE(CT DOSE INDEX---CTDI)
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)
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 • TIME • DISTANCE • SHIELDING
SHIELDING • IF PERSONNEL PRESENT IN THE ROOM DURING SCAN MUST BE SHIELDED AND STAND FAR FROM THE SOURCE ( INVERSE SQUARE LAW)
GONADAL SHIELDS • 4-5 CM WITHIN THE X-RAY BEAM
CONTACT SHIELDS 360 ° AROUND PATIENT
CT DOSE IN SPIRAL SCANNING • CTDI CAN ALSO BE USED PITCH MSAD OR CTDI
MORE USEFUL MEASUREMENT IS • EFFECTIVE DOSE TAKES INTO ACCOUNT QUALITY OF RADIATION AND ORGAN SENSITIVITY EXPRESSED IN Sv
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
BED INDEX SPIRAL PITCH COLLIMATION (PREPATIENT) NOISE DOSE DOSE DOSE DOSE DOSE REDUCTION IN CT
SID OID kVp (15 % RULE) mAs DOSE DOSE DOSE DOSE DOSE REDUCTION IN CT