Radiographic Technique Sergeo Guilbaud Education Director Long Island College Hospital

S. Guilbaud, Education Director Abstract: Radiographic technics is a combination of settings selected on the control panel by the radiographer to produce a desired effect on the radiographic image. There are two sets of factors to take into consideration when setting radiographic technics: exposure technical factors; Image quality factors. These factors provide the radiographer with a specific and orderly means to produce, evaluate and compare radiographs. Understanding these factors and their usage is essential to the production of high quality diagnostic images.

S. Guilbaud, Education Director Kilovoltage Peak (kVp) Primary controller of beam energy and therefore beam penetrability. kVp has more effect on the image receptor than any other factors. It affects beam energy primarily and affects beam quantity secondarily. An increase in kVp increases the penetrating ability of the beam thus, more x-ray photons are present and more scatter radiation is produced.

S. Guilbaud, Education Director Kilovoltage Peak (kVp) Thus resulting in an increase in the overall density on the radiographic image. Most importantly, kVp controls the scale of contrast on the finished radiographic image.

S. Guilbaud, Education Director Milliamperes and Time (mAs) In radiographic technics, (mA) and time (s) are normally combined and used as one factor (mAs).

S. Guilbaud, Education Director Milliamperes and Time (mAs) The mAs determines the number of x- rays in the primary beam and therefore principally controls radiation quantity and quality. The mAs is the key factor in controlling radiographic density.

S. Guilbaud, Education Director Milliamperes and Time (mAs) mA X Time = mAs Example: A radiographic technic calls for 600mA at 200ms. What is the mAs? 600mA X 200ms=  600mA X 0.2s = 120 mAs  400mA X 0.025sec = 10 mAs  400mA X 1/40sec = 10 mAs

S. Guilbaud, Education Director Milliamperes and Time (mAs) The mA and Time can be used to compensate for one another in a direct relationship. The Reciprocity Law states: The optical density on a radiograph is proportional only to the total energy imparted to the radiographic film. In other words:  A known mAs may be obtained with any combination of mA X seconds.

S. Guilbaud, Education Director Example: A radiograph of the abdomen requires 300mA and 500ms. The patient was unable to hold his/her breath, resulting in unacceptable motion unsharpness. Therefore a second exposure was made with an exposure time of 200ms. Calculate the new mA that was required.

S. Guilbaud, Education Director Time (first exposure) = mA (second exposure) Time (second exposure) mA (first exposure) Answer: 500ms = __X___ 200ms 300mA (200ms) X = (500ms) (300mA) (200ms) X = (0.5 s) (300 mA) (200ms) X = 150mAs X = 150 mAs 200 ms X = 150 mAs 0.2 s X = 750 mA

S. Guilbaud, Education Director Milliamperes and Time (mAs) If the generator is properly calibrated, the same mAs and therefore the same radiographic density can be produced or reproduced with various combinations of mA and time.

S. Guilbaud, Education Director Distance According to the Inverse Square Law, distance affects the exposure of the image receptor however, it has no effect on radiation quality. The Source-to-Image receptor Distance (SID) selected largely determines the intensity of the beam at the image receptor.

S. Guilbaud, Education Director Distance Direct Square Law/Density Maintenance Formula. mAs (first exposure) = (SID) 2 (first exposure) mAs (second exposure)(SID) 2 (second exposure)

S. Guilbaud, Education Director Direct Square Law/Density Maintenance Formula Example: An examination requires 100mAs at 180cm SID. If the distance is changed to 90cm SID, what should be the new mAs?

S. Guilbaud, Education Director Answer: 100 = (180) 2 X (90) 2 100= 32,400 X ,400X = 810, ,000 X = ,400 X = 25mAs

S. Guilbaud, Education Director Distance Most problems relate to density, by the film being “too dark” or “too light”. A film that is too dark has high optical density, resulting in overexposure. This is b/c too much radiation interacted with the intensifying screen and or film. A film that is too light has been insufficiently exposed to radiation, resulting in underexposure and low optical density.

S. Guilbaud, Education Director Characteristics of X-Ray Tubes Most X-Ray tubes are equipped with two focal spot sizes: (small and Large). Both are indicated on the control panel. Small Focal Spot is normally 0.6mm. Large Focal Spot is normally 1.2mm.

S. Guilbaud, Education Director Characteristics of X-Ray Tubes Small Focal Spot Used for detail work. Normally used to image extremities and other thin body parts where power is not important. Used for magnification radiography. Changing focal spots does not change the X- Ray quantity or the Quality.

S. Guilbaud, Education Director Large Focal Spot Used for normal imaging. Provides provides for the shortest possible exposure times. Ensures that a sufficient mAs can be produced to image dense body parts. Principal difference b/w focal spot size is the capacity to produce x-rays. Far more x-rays can be produced w/ large focal spots.

S. Guilbaud, Education Director Added Filtration Most Radiographic equipment contain inherent filtration properties. Glass envelope 0.5mm (Al) Collimator Head1.0mm (Al) Manufacture addition Added filtration1.0mm (Al) Note: When properly used, higher filtration results in Lower patient dosage.

S. Guilbaud, Education Director High-Voltage Generation Three basic types of high-voltage generators: Single phase generator  Half-wave rectification  Full-wave rectification Three phase generator  Six (6) pulse  Twelve (12) pulse High frequency generator

S. Guilbaud, Education Director Half-wave rectification With half-wave rectification, x-radiation is only produced and emitted during half of the time. They exhibit 100% voltage ripple. During the exposure, there is no x-ray emission during the negative half cycle of the power supply. Used in some portable equipment and dental equipment. Note: This is rarely used in radiographic equipment today.

S. Guilbaud, Education Director Full-Wave Rectification With full-wave rectification, there is no dead time which means that x-rays are being emitted in pulses during the exposure. The radiation output doubles thus requiring only half the exposure time of the half-wave rectifiers. The radiation quality does not change from the half-wave rectifier.

S. Guilbaud, Education Director Three-Phase Power Three-Phase six pulse. More efficient than single phase power. More x-rays are produced per mAs and the average energy of the produced x-rays is higher. The resultant effect is higher radiation quantity and quality. The emitted radiation is constant rather than pulsed. Less ripple is produced.

S. Guilbaud, Education Director Three-Phase Power Three-Phase twelve pulse. More efficient than single phase power and more efficient than Three-Phase 6 pulse. More x-rays are produced per mAs and the average energy of the produced x-rays is higher. The resultant effect is higher radiation quantity and quality. The emitted radiation is constant rather than pulsed. Less ripple is produced than the three-phase 6 pulse.

S. Guilbaud, Education Director High-frequency generators Developed in the early 1980’s. Exhibits a nearly monoenergetic waveform. Results in higher radiation quantity and quality. Less ripple is produced than the half-wave, full- wave, three-phase 6 pulse and three-phase 12 pulse generators.

S. Guilbaud, Education Director

Radiographic Technique (part 2) Sergeo Guilbaud Education Director Long Island College Hospital

S. Guilbaud, Education Director General 50% of all repeats are attributed to exposure errors. repeat radiographs cost the health care system $100 million annually.

S. Guilbaud, Education Director A. STANDARDIZATION OF EXPOSURE TECHNICS ENSURES QUALITY RESULTS CONTROLS COSTS REPRODUCIBLE IMAGES

S. Guilbaud, Education Director B. IMAGE CONSISTENCY CONSISTENT QUALITY IMAGES CONTRAST MAINTENANCE APPROPRIATE DENSITY MAINTENANCE

S. Guilbaud, Education Director A. CHOICE OF TECHNIQUE SYSTEMS 1. OPTIMUM kVp/VARIABLE mAs 2. VARIABLE kVp/FIXED mAs 3. AUTOMATED EXPOSURE CONTROL  FIXED kVp

S. Guilbaud, Education Director B. PATIENT MEASUREMENTS 1. ESTABLISHES EXACT SCIENCE 2. SHOWS ACCURACY IN WORK PERFORMANCE

S. Guilbaud, Education Director C. PROCESSING 1. PROCESSOR QUALITY ASSURANCE 2. HIGH TEMPERATURE 3. LOW TEMPERATURE 4. FILM FOG 5. IMPROPER WATER FLOW

S. Guilbaud, Education Director TYPES OF TECHNIC CHARTS A. OPTIMUM kVp / VARIABLE mAs 1. ESTABLISHES A SPECIFIC kVp PER BODY PART. 2. THE mAs VARIES ACCORDING TO CM MEASUREMENT OF PART. 3. PRODUCES A CONTRAST CONSISTENCY FOR THE TECHNOLODIST AND RADIOLOGIST. 4. TRAINS THE TECHNOLOGISTS’ EYES AND THE RADIOLOGISTS’ EYES TO VIEW RADIOGRAPHIC IMAGES.

S. Guilbaud, Education Director TYPES OF TECHNIC CHARTS B. VARIABLE kVp / FIXED mAs 1. kVp VARIES ACCORDING TO CM MEASUREMENT. 2 kVp PER CM 2. RADIOGRAPHIC DENSITY REMAINS CONSTANT WHILE CONTRAST CHANGES. 3. SMALL LUCENCIES APPEAR & DISAPPEAR. 4. CONSTANT CHANGE IN CONTRAST

S. Guilbaud, Education Director TYPES OF TECHNIC CHART C. AUTOMATIC EXPOSURE CONTROL (AEC) “PHOTOTIMERS” 1. FORM OF OPTIMUM kVp TECHNIC 2. kVp IS SET, mAs ADJUSTS ACCORDING TO AMT. OF EXPOSURE RECEIVED BY IONIZATION CHAMBER(S). 3. POSITIONING, PHOTOCELL & BODY PART ALIGNMENT MUST BE EXTREMELY ACCURATE.

S. Guilbaud, Education Director OPTIMUM kVp TECHNICS ABDOMEN PLAIN FILMS 70-80kVp SKULL FILMS 70-80kVp FEMUR 70-80kVp

S. Guilbaud, Education Director C-SPINE kVp T-SPINE kVp LAT. T-SPINE IS BEST IMAGED WITH BREATHING TECHNIC. (auto- tomography) L-SPINE kVp 90 kVp L5-S1

S. Guilbaud, Education Director OPTIMUM kVp TECHNICS HUMERUS, SHOULDER, SCAPULA kVp ELBOW kVp FOREARM kVp

S. Guilbaud, Education Director WRIST kVp HAND kVp FINGERS 50 kVp

S. Guilbaud, Education Director OPTIMUM kVp TECHNIC CHEST X-RAY kVp BARIUM STUDIES SINGLE CONTRAST  110 kVp DOUBLE CONTRAST  90 kVp

S. Guilbaud, Education Director KNEE kVp TIBIA FIBULA kVp ANKLE kVp FOOT kVp

S. Guilbaud, Education Director VARIABLE kVp TECHNICS STANDARD RULE 1. MEASURE BODY PART, MULTIPLY MEASUREMENT BY ONCE MEASUREMENT IS ESTABLISHED, ADD OR SUBTRACT 2 kVp FOR EACH cm. 3. The kVp VARIES ACCORDING TO DESIRED CONTRAST

S. Guilbaud, Education Director Automatic Exposure Control (AEC)/ Phototimer SAME AS OPTIMUM kVp TECHNIC

S. Guilbaud, Education Director EXPOSURE CALCULATIONS 15 % kVp RULE (CONTRAST) NORMALLY TRANSLATES TO 8-12 kVp DIFFERENCE. PRIMARILY USED TO EFFECT CONTRAST. EFFECT IS:  FILM CONTRAST CHANGES PRIMARILY AND ALSO CHANGES DENSITY AS A SECONDARY FACTOR.

S. Guilbaud, Education Director EXPOSURE CALCULATIONS 30 % mAs RULE (DENSITY) NORMALLY TRANSLATES INTO DARKENING OR MAKING FILMS LIGHTER (OPTICAL DENSITY). IF kVp IS ACCURATE, mAs CHANGES TO MAKE RADIOGRAPHS VISIBLY LIGHTER OR DARKER. THE mAs MUST BE DECREASED BY HALF OR DOUBLED WITH ANY 15% CHANGE IN kVp.

S. Guilbaud, Education Director NORMALLY, IF A FILM IS TOO DARK OR TOO LIGHT, THE mAs MUST BE DECREASED BY HALF OR DOUBLED TO DEMONSTRATE A SIGNIFICANT CHANGE IN RADIOGRAPHIC DENSITY. Thus, it is pointless to manipulate the density to make the film a little lighter or a little darker.

S. Guilbaud, Education Director BASIC MATH CALCULATIONS EXAMPLE: MAs TO MODIFY CONTRAST  70 X 15% =  70 x.15 = 10.5  70 kVp + or kVp

S. Guilbaud, Education Director BASIC MATH CALCULATIONS mAs CONVERSION 30 mAs X 30 % = 30 X.30 = 9 mAs 30 mAs + or - 9 mAs

S. Guilbaud, Education Director References Bushberg et al, The Essentials of Physics and Medical Imaging, Williams & Wilkins Publisher. Bushong, S., Radiologic Science for Technologists, Physics, Biology and Protection, 8th Edition, C.V. Mosby Company. Carlton et al, Principles of Radiographic Imaging, An Art and Science, Delmar Publishing. Selman, J., The Fundamentals of X-Ray and Radium Physics, 8th Edition, Charles C. Thomas Publisher. Thompson, T., Cahoon’s Formulating X-Ray Techniques, 9 th Edition, Duke University Press.