Chapter 38 Designing for Radiation Protection PDF

CHAPTER 38 DESIGNING FOR RADIATION PROTECTION RADIOGRAPHIC PROTECTION FEATURES Beam Alignment  Each radiographic tube should be provided Protective X-ray Tube Housing...

CHAPTER 38 DESIGNING FOR RADIATION PROTECTION RADIOGRAPHIC PROTECTION FEATURES Beam Alignment  Each radiographic tube should be provided Protective X-ray Tube Housing with a mechanism  It must be contained within protective o Purpose: to ensure proper alignment housing of the x-ray beam & the IR  It reduces leakage radiation Filtration Leakage radiation must be less than 100  Total Filtration: mR/hr at a distance of 1 m from the protective o 2.5 mm Al – operated above 70 kVp housing! o 1.5 mm Al – operated b/n 50-70 kVp o 0.5 mm Al – operated below 50 kVp Control Panel  HVL: it measures filtration  It must indicate the condition of exposure  It must positively indicate when the x-ray Mammography tube is energized  Total Filtration: 30 μm Mo or 60 μm Rh o kVp & mA indicators Reproducibility X-ray beam on must be positively & clearly  For any radiographic technique, the output indicated to the radiologic technologist! radiation intensity should be constant form one exposure to another Source-to-Image Receptor Distance Indicator  It must be provided The variation in x-ray intensity should not o Tape measure attached to the tube exceed 5%! housing o Lasers Linearity  Ability of a radiographic unit to produce The SID indicator must be accurate to within constant radiation output for various 2% of the indicated SID! combinations of mA & exposure time  Radiation Intensity: mR/mAs Collimation  Light-localized, variable-aperture The maximum acceptable variation in rectangular collimators should be provided linearity is 10% from one mA station to an  Cones & Diaphragms: for special adjacent mA station! examination Operator Shield The x-ray beam & the light beam must  RT may be in the exposure room during coincide to within 2% of the SID! exposure, but only if protective apparel is worn Positive-Beam Limitation (PBL)  Exposure Control: fixed, not a long cord 125  Automatic, light-localized, variable-aperture collimators Mobile X-ray Imaging System  Lead Apron: should be assigned Page The PBL must be accurate to within 2% of  Exposure Switch: at least 2 m from x-ray SID! tube during exposure STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 38 DESIGNING FOR RADIATION PROTECTION FLUOROSCOPIC PROTECTION FEATURES Cumulative Timer  It produces an audible sound when the Source-to-Skin Distance fluoroscopic time has exceeded 5 minutes  Increased SSD: reduces entrance skin  Designed to ensure that the radiologist is exposure (ESE) aware of the relative beam-on time during  Stationary Fluoroscopes: not less than 38 each procedure cm  Mobile Fluoroscopes: less than 30 cm Dose Area Product (DAP)  A quantity that reflects not only the dose but Primary Protective Barrier also the volume of tissue irradiated  Fluoroscopic IR Assembly:  Expressed in: R-cm2 o It serves as a primary protective  Better indicator of risk than dose barrier  X-ray Beam Intensity o It must be 2 mm Pb equivalent o Table Top: