1 Sensitivity to Radiaiton & Calculating pt dose Stat ch 8 Bush ch 40

2 Tissue and Cell Sensitivity to Radiation

3 Tissue Radiation Sensitivity Most Sensitive: Reproductive organs Blood-forming organs Skin Bone and teeth Least sensitive: Muscle Nervous system

4 Effects of Overdose to Humans

5 Effects of Acute Radiation Exposures in Humans

6 Why cancer risks at low doses are uncertain It has been difficult to estimate cancer induction risks, because most of the radiation exposures that humans receive are very close to background levels. At low dose levels of millirems to tens of rems, the risk of radiation-induced cancers is so low, that if the risk exists, it is not readily distinguishable from normal levels of cancer occurrence. In addition, leukemia or solid tumors induced by radiation are indistinguishable from those that result from other causes.

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8 Relative Risk of a 1 in a million chance of death from activities common to our society: ·Smoking 1.4 cigarettes in a lifetime (lung cancer) Eating 40 tablespoons of peanut butter (aflatoxin) Spending two days in New York City (air pollution) Driving 40 miles in a car (accident) Flying 2500 miles in a jet (accident) Canoeing for 6 minutes (drowning) Receiving a dose of 10 mrem of radiation (cancer)

9 PATIENT DOSE RAD MR/MAS PER EXPOSURE - At each kVp level – there is a determined output for each radiographic room EX 70 kvp = 2.5 mr/mas ABD done 70 kVp, 20 mas 2.5 x 20 = 50 mR for that one exposure. LOOK AT formula: mr/mas Ch 8 Stat CH 40 BUSHONG

10 “AVE” CHEST EXPOSURE - 2 IMAGES (Ave – Pt meas 23cm pa 40cm lat) PA 110 KVP 5 MAS 16:1 GRID 400RS 72” LAT 110 KVP 20 MAS 16:1 GRID 400 RS 72” WHAT IS THE PATIENT’S DOSE?? LOOK AT CHART: mr/mas PG 210 Stat

11 “AVE” CHEST EXPOSURE - 2 IMAGES WHAT IS THE PATIENT’S DOSE?? OUTPUT OF TUBE NEEDED: PA Chest = mr/mas = 9.5 LAT 110 KVP 20 MAS 16:1 GRID 400 RS 72” LOOK AT CHART: mr/mas PG 210 Stat

12 Which of the following technical factors will create the highest skin entrance dose to the patient? A. 80 kvp 300 ma.5s no filter B. 80 kvp 300ma 1/10s no filter C. 80 kvp 1000ma 1/20s 2.5mm al eq. filter D. 80 kvp 800ma 1/60 sec.05mm al eq filter

13 The exposure rate to a tech at 4 feet from the source is 240 m R/hr. What distance would be necessary to reduced the rate below 60 mR/hr? A. 1 foot B. 6 feet C. 2 feet D. 9 feet

14 If the exposure at 2 inches = 9 R/min, what is the exposure at 6 inches from the source? A. 1 R B. 5 R C. 3 R D. 81 R E. 60R

15 If 85 kvp, 400ma 0.12s = 150mR - what is the mr/mas? A B. 3.1 C D. 17.6

16 Primary radiation barriers must be at LEAST how high (in feet)? A. 5 B. 6 C. 7 D. 8

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