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Sensitivity to Radiaiton & Calculating pt dose & more “math” problems

Sensitivity to Radiaiton & Calculating pt dose & more “math” problems. Stat ch 8 Bush ch 40 Rev 2012 - week 7 - day 2. Tissue and Cell Sensitivity to Radiation. Most Sensitive: Reproductive organs Blood-forming organs Thyroid Breast Skin Gastrointestinal. Least sensitive :

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Sensitivity to Radiaiton & Calculating pt dose & more “math” problems

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  1. Sensitivity to Radiaiton&Calculating pt dose& more “math” problems Stat ch 8 Bush ch 40 Rev 2012 - week 7 - day 2

  2. Tissue and Cell Sensitivity to Radiation

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

  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. 

  7. TABLE 3-3 Organ or Tissue Weighting Factors

  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. LOOK AT CHART: mr/mas • “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?? CALCULATION

  11. LOOK AT CHART: mr/mas PG 210 Stat • “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”

  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. 0.32 • B. 3.1 • C. 33.1 • D. 17.6

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

  17. If a barrier separates an x-ray room from a hallway where the general public may occupy, then the shielding is designed to limit the amount of exposure in the hallway to?:

  18. More problems • At 2 foot from a source the output intensity is 300 mR/hr and you were there for 20 minutes. • What is the dose? • What is total exposure received when you move 5 feet away and stay there for 40 minutes?

  19. During fluoro, using 80kVp, the intensity at the table top per mA should not exceed ____ /ma/ minute?

  20. Which of the following would produce the least patient dose? • A. 85 kv 100 ma .12s • B. 74 kv 100ma .12s • C. 74 kv 100 ma .06s • D. 74 kv 200 ma .06s

  21. Using the Nomogram Chart – calculate • the patient’s total skin dose for Port AP Chest @ • 40” SID (12” pt thickness), using 5mas • 100 kVp, • 2.5mm filtration

  22. If during an Nephrostrogram exam using 80 kvp – • the Primary tube current output @1 ft was 2 R/mA/min • the fluoro tube operated at 0.5 ma. • What is the TUBE OUTPUT? _________/min • The RT received 150 mr/hr • of scatter @ 2 foot from the patient for 10 min • then moved 8 feet from the patient for another 10 min. • Answer for the following DOSE & Units • What was the total Fluoro time? _____________ • WHAT WAS THE TOTAL EXPOSURE TO THE • PATIENT ________ • TECHNOLOGIST _________________

  23. STAT: BOX 8-10 Information Needed to Develop the Request for Patient Radiation Dose Patient X-Ray Exam Record Form • 1.The x-ray unit or units used for the study • 2.The projections taken • 3.The number of films associated with each projection • 4.Each projection's technical exposure factors (kVp, mAs, image receptor size) • 5.The SID for each view • 6.The patient's AP or lateral dimensions at the site of each projection • 7.For fluoroscopic irradiation, the approximate kVp, mA, and especially the duration • 8.For spot films, the number taken, the kVp and mA selected, and the approximate exposure time

  24. Two of the most radiosensitive tissues with rapidly dividing cells in the body is ____ tissue. Which one is most SENSITIVE

  25. CELLS MOST SENSITIVE CELLS THAT REPRODUCE THE MOST – SPEND THE MOST TIME IN THEIR REPRODUCTIVE STATE • WHITE BLOOD CELLS – LYMPHOCYTES • RED BLOOD CELLS – ERYTHOROCYTES • BASAL CELLS OF THE SKIN • INTESTINAL CELLS • DEVELOPING NERVE CELLS OF EMBRYO • IMMATURE REPRODUCTIVE CELLS • EPITHELIAL CELLS THAT LINE BLOOD • LYMPHATIC VESSELLS (80% BODY)

  26. LYMPHOCYTE PG.103 • SUBGROUP OF WBC • ONLY LIVE FOR 24 HOURS • ARE MANUFACTURED IN BONE MARROW • MOST RADIOSENSITIVE BLOOD CELL • 25 RADS CAN DEPRESS # OF CELLS • LESS ABILITY TO FIGHT INFECTIONS

  27. RHB – SYLLABUS PG 47MOST – LEAST SENSITIVE • LYMPHOCYTES (WBC) • ETHROCYTES (RBC) • EPITHELIAL CELLS (SKIN) • ENDOTHELIAL CELLS (LINE BLOOD VESSELS • CONNECTIVE TISSUE CELLS • BONE CELLS • MUSCLE CELLS • NERVE CELLS • BRAIN CELLS

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