BS Radiologic Technology Prelims PDF

BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite Exposure Timer PRINCIPLES OF IMAGING − Serves as to...

BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite Exposure Timer PRINCIPLES OF IMAGING − Serves as to determine the length of time of exposure Different types of Exposure Timers: INTRODUCTION 1. Mechanical Timer Radiography o Simple time, that works in a manner similar to spring-set dial Is an art and science of recording x-ray images when x-ray o Mechanical timers are limited to their shortest passes through an object and recorded on x-ray film. These setting of 1/10 second images of the human body serve to assist physicians in the o Shorter times are more advantageous for diagnose and treatment of disease and disorder radiographic imaging of the body, because of possible motion of the body part to be examined Art 2. Synchronous Timer o Are motor driven devices that take advantages Refers to the production of something that is very well done of the 60 Hertz alternating current used in the The art in radiography implies there is a need for specific skills in United States before performance o Synchronous timers use settings that are intervals related to 1/60second Science Example: Are 1/30 sec., 1/20 sec.,, and 1/10 Radiography requires study and theoretical explanation of seconds natural phenomenon 3. Electronic Timer It implies knowledge, especially knowledge gained through o Is the most common type found in radiography experience equipment today o The most sophisticated type of timer, designed Radiograph with complex circuitry, and considered to be the most accurate exposure timers The image produced using x-radiation o The advantages of electronic timer are exposure A radiograph represents, the image recorded on photosensitive times less than 1/120 seconds, reliability, and material, which is usually called as X-RAY FILM being less prone to malfunction Note: o Latent image – invisible image Automatic exposure control (AEC) o Manifest image – visible image − Devices that measures the quantity of radiation that reaches the Radiographers image receptor − Automatically terminates the exposure when the image receptor has − Are professionals who are responsible for producing high quality received the required radiation intensity images using x-ray Evaluation of Timers Primary Responsibilities of the Radiographers − Evaluation of timers must be done periodically to guarantee accuracy − Proper selection of exposure factors − The evaluation or test can be done by using a device called the − There has been an adequate penetration of the part on interest SPINNING TOP − Sufficient radiographic density and contrast are present − Proper selection of field size Rotor − Motion eliminated during exposure − The rotor switch may be separated control or maybe incorporated as − The anatomic part is properly positioned part of the exposure switch − Proper accessories have been selected − Operation of the rotor switch causes the anode to rotate, turning to its Components of Xray Machine System maximum speed before the exposure is made − Maximum rotation of the anode accomplished in about 1 second 1. Operating console − In addition, activation of the rotor switch permits the full current to flow 2. Autotransformer through the cathode filament, causing the filament to become very hot 3. High voltage generators − The rotor switch must remain engaged during the exposure 4. Xray tube − When the maximum RPM of the anode is reached, the exposure switch is activated Operating console/control panel Exposure − Is a part of radiographic equipment that becomes very familiar to radiographers − The activation of the exposure switch results in the production of − Allows the radiologic to control the x-ray tube current and voltage so x-rays that the useful x-ray beam is of proper quantity and quality − X-ray is produced for a time period selected by the exposure timer The control are the following: − It is extremely important that the rotor and exposure switches be o On/Off Switch utilized only as needed for making an exposure o Kilovoltage Selector o mA Selector o Exposure Time o Rotor/ Exposure Switch Prepared by: Panaligan, Krizel L. RDTC 2-1 1 4ADM-XWTT-L6XD-VXJU BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite Autotransformer − The energy of the x-rays is dependent on the kinetic energy of the electrons − Has a single winding and is designed to supply a precise voltage to − Xray tube nowadays uses Coolidge tube as popularized by W. the filament circuit and to the high voltage circuit of the Xray imaging Coolidge in 1913 system − Works on the principle of electromagnetic induction but is very different from the conventional transformer Xray Tube components High voltage generators 1. Glass envelope ▪ Mage of Pyrex glass (to be able to withstand − Responsible in increasing the output voltage from the autotransformer tremendous heat) to the kVp necessary for x-ray production ▪ Tube maintains a vacuum Consist of 3 primary parts ▪ Tube window 1. High voltage auto transformer  A segment of the glass that is thinner than ▪ A step up transformer the rest of the glass envelope ▪ The secondary voltage is higher  Contributes to inherent filtration than the primary voltage  0.5mm Al equivalent ▪ The number of the secondary 2. Cathode windings is greater than the ▪ Negative charge electrode primary windings Two primarily parts: 2. Filament auto transformer 1. Filament ▪ Filament heating isolation step  Small coil pf thoriated tungsten down transformer (2mm in diameter) ▪ Steps down the voltage to  Modern Xray tubes contains two approximately 12V and provide filaments which corresponds to the current to heat the filament the focal spot size ▪ The secondary windings are  When the current though the heavily insulated from the filament is sufficiently high, the primary outer shell electrons of the 3. Rectifiers filament atoms are boiled off ▪ A device that allows current to and ejected from the filament flow only 1 direction “thermionic emission” ▪ Rectification is the process of 2. Focusing cup converting AC to DC  Metallic shroud containing the Notes: two filaments ▪ The process of  Usually made f nickel (good transition of DC to AC electrical conductivity) is called “inversion”  Contains negative charge ▪ The process of  Designed to repel electrons converting AC to DC is called “rectification” Focusing cup effectiveness ▪ Device that allow − Size and shape current to flow in two − Charge direction is called − Filament size and “inverters” shape ▪ Device that allow − Position of filament current to flow in one within the cup direction is called 3. Anode “rectifiers” ▪ Positively charged electrode 3 Main function 1. Electrical conductor X-Ray Tube 2. Mechanical conductor 3. Heat/Thermal dissipator − Electrical device used for the generation of Xray − This is accomplished by the acceleration of electrons and then suddenly decelerating them Prepared by: Panaligan, Krizel L. RDTC 2-1 2 4ADM-XWTT-L6XD-VXJU BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite Two types Why tungsten? 1. Stationary anode  Made of tungsten target o High atomic number (Z=74) – results in high embedded in a large efficiency x-ray production and in high energy x- copper rays  Usually used in dental x- o Thermal conductivity – has a thermal ray system or sometimes conductivity nearly equal to that of copper portable imaging system making it an efficient metal to dissipate the heat where high power tube or produced system is not required o High melting point – any material, if heated sufficiently, will melt and become liquid. Tungsten has a high melting point of 3410 C (compared to 1100 C of copper) and therefore can stand up under high tube current without pitting or bubbling 4. Induction motor ▪ Responsible for driving the rotating anode ▪ Consist of two parts separated by the glass 2. Rotating anode envelope  Provides greater target ▪ Works on the principle similar to the transformer area and greater heat (Electromagnetic induction) dissipation ▪ Current flowing in the stator develops a  Afford the ability to attain magnetic field grater exposure loads by ▪ Stator windings are sequentially energize so that providing a larger area for the induced magnetic field rotates on the axis of the beam to interact with the stator the target ▪ This causes the rotor to rotate  The heating capacity is further enhance with an increased RPM (3400)  High capacity x-ray tubes rotates at 10,000 RPM 5. Protective housing ▪ Xray tube is always mounted inside a lead protective housing that is designed to: ▪ Target is the area of the anode struck by the  Prevent excessive radiation exposure electrons from the cathode  Prevent electric shock to the patient ▪ In stationary anode tubes, the target consist of a and operator (radtech) tungsten alloy embedded in the copper anode  Serves as both insulator against ▪ High capacity Xray tube have molybdenum and electrical shock and thermal cushion graphite layer under the tungsten target for dissipating heat ▪ Constructed of tungsten target (focal track) high  Provides mechanical support for the melting point 3410 Celsius x-ray tubes and protects it from damage Element Chem Atomic K Xray Melting  Some tube housing contain oil in symbol no. E Lvl Temp which the tube is bathed Tungsten W 74 69 3410  Some tube housing contain a cooling Molybdenum Mo 42 19 2600 fan to air-cool the tube Rhenium Rh 45 23 3200 Molybdenum Radiographic Technique or Technical Factors  Surrounds tungsten tret area  Assist is dissipating heat − Is the systematic procedure used by the radiographer to Graphite accomplish the task of producing high quality radiograph.  Serves as mount for molybdenum − This systematic procedure includes the ability to select and tungsten appropriate factors to produce an x-ray beam that will adequately penetrate the body part and provide the appropriate level of blackening (density) and subject contrast on the radiograph. Prepared by: Panaligan, Krizel L. RDTC 2-1 3 4ADM-XWTT-L6XD-VXJU BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite To produce a radiograph, the radiographer selects and manipulates four ✓ Patient Maria Santiago is subjected to have a PA CXR. The significant factors: given kVp is 76 with the machine constant of 45. What is 1. Kilovoltage peak the thickness of the part being examined? 2. Milliampere 3. Exposure Time (s) 4. Distance Kilo (K) − Means 1000 − 80 kV setting means 80,000 volts Kilovoltage selections are made with two control selectors labeled as: Milliampere (mA) ▪ kV Major selector permits changes approximately 10 kilovolts with each turn. − Responsible for the amount/quantity of radiation. ▪ kV Minor selector allows changes of − Responsible for the blackening of the film. approximately 1 to 2 kilovolts with each turn. − Represents the current flowing through the cathode filament - “fine tunes “ the selected technique. at the time of exposure. − The combination of this two selectors permits easy selections for − Responsible for the density. specific kVp settings. Time (s) Kilovoltage peak (kVp) − Exposure time is the factor that controls the length of exposure. − Is define as the force applied to accelerate (push) the electrons − It is also a quantitative factor that when combined with mA, from the cathode to anode at the time of exposure. determines the exposure rate. − It is the penetrating power of the beam. − Responsible for the quality of the x-ray beam. − Responsible for the production of scattered radiation. − Responsible for the contrast. − Is the crest of the waveform that represents photon energy. − X-ray photon travels through matter in wave-like fashion ✓ An examination requires 50 mA and a time of 5 seconds. What is the mAs? ✓ Patient Juan dela Cruz is subjected to have a PA CXR. The ✓ A chest radiograph requires 75 kVp and 90 mA and a time radiographer measures his chest which is 18cms and with of 0.02 seconds. What is the mAs? the machine constant of 40. What will be the required kVp for the examination? ✓ Patient Pepito San Juan is subjected to have a Lat. CXR. ✓ A Shoulder Y view requires 90 kVp and 90 mA and a time The radiographer measures his chest which is 12 inches of 1/5 seconds. What is the mAs? and with the machine constant of 30. What will be the required kVp for the examination? NOTE: 12 inches needs to be converted in cms. 1 inch = 2.54 centimeters 12 inches x 2.54 cms. = 30.48 cms. ✓ Prepared by: Panaligan, Krizel L. RDTC 2-1 4 4ADM-XWTT-L6XD-VXJU BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite mA and time Relationship because the radiography must be performed with the patient in the supine position. What is the new mAs for the − It refers that the mA is inversely proportional to the time of second exposure? exposure to attain the same densities. − This means that an increase in mA requires a decrease in the exposure time. Reciprocity Law − Any combination of Ma and exposure time that results to same mAs, the resultant density is also the same. ✓ A radiograph is made with the following factors: 200 mA, 0.2 s, 90 kVp. A second radiograph must be made with the same mAs and kVp, but with 500 mA. What will be the new Inverse Square Law exposure time? − The law states that radiation intensity is inversely proportional to the squared of the distance from the source of radiation. − Note: When SID increases, radiation intensity decreases. When SID decreases, radiation intensity increases ✓ A radiographer makes an exposure using the standard SID of 40 inches. An ionization chamber measures the radiation Distance at 40 inches to read 8R. The same exposure is made with the measurement taken at 80 inches from the focal spot. − Represents the length of space from the focal spot to the What is the radiation intensity (R) at 80 inches SID? recording medium, and it is called the FFD (Focal film Distance) − New term is SID (Source to Image-receptor Distance). − In the most diagnostic departments, the SID is standardized for all procedures. − In general radiography, the SID is 40 to 42 inches. − And in radiography of the structures of the chest & thoracic cavity, the SID is usually 72 inches. − Which is called Chest-Teleo Radiography. mAs and Distance Relationship − mAs is directly proportional to the squared of the distance (SID). Radiographic Quality − As the distance (SID) is increased, the mAs must also increase to maintain adequate blackening of the film. − Quality relates to the characteristics of an object and indicates − Direct Square Law or Exposure Maintenance Formula the degree of excellence that the object may exhibit. − A high quality radiograph is a radiograph with all factors at optimum. − Quality identifies the amount of information available for reviewing the radiograph. − Radiographers must able to evaluate the quality of a radiograph by VISUAL INSPECTION. − A high quality radiograph is one that demonstrate the following factors: o Sharp image o Adequate contrast o Adequate density ✓ A radiographer exposes a patient’s chest at bed side in the PA projection using 10 mAs, 75 kVp and 72 – inch SID. A second radiograph is required, but as a result of a change in the patient’s condition, only 36 – inch SID can be used Prepared by: Panaligan, Krizel L. RDTC 2-1 5 4ADM-XWTT-L6XD-VXJU BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite Terminologies 2 Types of Contrast Subject Contrast SID – SOURCE TO IMAGE DISTANCE ( FFD ) o the difference in density of adjacent structures. o is present with bone and its surrounding soft tissue. − The distance measured between the focal spot on the target of o contrast media can be used to increase subject an xray tube and the image receptor contrast SOD – SOURCE TO OBJECT DISTANCE (FOD) − The distance measure between the focal spot on the target of an xray tube and the center mass of the patients anatomical organ OID – OBJECT TO IMAGE-RECEPTOR DISTANCE (OFD) − The distance measured between the anatomical part of the patient and the image receptor Radiographic Contrast − Difference in Density or the degree Film Contrast of grayness between areas of the o contrast refers to those qualities of x-ray film that radiographic image result in the recording of high contrast or low contrast. − Can also be identified as the ratio o qualities are inherent in the preparation of the of the radiation intensity as it exit a emulsion. o Fog and scatter affect film contrast. specific type of tissue to radiation intensity exiting an adjacent type Types of Film Contrast of tissue Long Scale Contrast − Make structural detail visible Has many shades of gray. Contrast and Attenuation Is produced by the use of high kVp. The advantage of long scale contrast is the − Attenuation is a reduction in strength or force as a result of visualization of more structural detail. absorption and interactions. As the x-ray photons travel through Higher the kilovoltage, the more gray tones are body tissue, they are attenuated. The result is an x-ray beam present on the radiograph. Part of the grayness that is no longer uniform. is a result of increased scatter radiation − Contrast is the result of attenuation and the differential produced by the increase in kilovoltage. absorption of tissue. Without beam attenuation, contrast would Referred as LOW CONTRAST not be present because a uniform density level would be Short Scale Contrast present. Has a small amount of gray tones. − Density must be present in order for one to visualize contrast. Is produced by the use of low kVp. A shorter scale contrast is more ideal to examine bone structure. Is present when the density differences in adjacent structures are abrupt or pronounced. Exhibit significant clear areas in radiographs where penetration did not occur. Referred as HIGH CONTRAST Factors Affecting Radiographic Contrast Contrast and Silver Deposits PRIMARY − Another way to describe contrast is the distribution of metallic − kVp silver that is present following the development of the latent image. Areas of greater silver deposits have more density and SECONDARY areas with smaller silver deposits will have less density. − Grid Controlling Factors of Contrast − Beam Restriction − Field Size − The PRIMARY technical factor that controls contrast is kilovoltage. − Film Processing − In order for the radiologist to visualize the desired detail, the part − Filtration must be adequately penetrated. Penetration of the part is − Patient Thickness controlled by the kilovoltage. kVp − Milliampereseconds (mAs) changes the quantity of photons in the beam and cannot be used as a substitute factor to alter − Inversely Proportional Relationship with contrast contrast on radiograph. − High kVp produces long-scale and low kVp produces short-scale contrast. − a factor in the production of scatter radiation Prepared by: Panaligan, Krizel L. RDTC 2-1 6 4ADM-XWTT-L6XD-VXJU BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite − In diagnostic radiology, two predominant interactions Crossed Grids occur-Compton scattering and the photoelectric effect. Crossed grids have lead grid strips that run parallel to − as kVp is increased, the probability of Compton interactions the long and short axes of the grid increases. are fabricated by sandwiching two parallel grids together so their grid strips are perpendicular. 15% kVp Rule fabricated by sandwiching two parallel grids together with their grid strips perpendicular to one another. − When the kvp is lowered by 15%, the mAs needs to be Crossed grids are much more efficient than parallel increased by a factor of 2, and when the kVp is increased by grids in cleaning up scatter radiation. 15%, the mAs needs to be divided by 2. Moving Grids ✓ A radiograph is made using 80 kVp and 100 mAs. A Focused grids usually are moving grids. They are request is made to make a second exposure with lower placed in a holding mechanism that begins moving kVp but to maintain the same overall blackening on the just before x-ray exposure and continues moving after film. the exposure ends. Two basic types of moving grid mechanisms are in use today: reciprocating and oscillating. Reciprocating Grid. A reciprocating grid is a moving grid that is motor-driven back and forth several times during x-ray exposure. The total distance of drive is ✓ A lumbosacral radiograph is made using 95 kVp and 40 approximately 2 cm. mAs setting. A request is made to make a second Oscillating Grid. An oscillating grid is positioned within exposure with higher kVp but to maintain the same overall a frame with a 2- to 3-cm tolerance on all sides blackening on the film. What will be the new exposure between the frame and the grid. Delicate, springlike factors? devices located in the four corners hold the grid centered within the frame. A powerful electromagnet pulls the grid to one side and releases it at the beginning of the exposure. Thereafter, the grid oscillates in a circular fashion around the grid frame, coming to rest after 20 to 30 seconds. Grid Problems Grid Off-Level Grid ▪ A properly functioning grid must lie in a − Grids are devices located between the patient and the film. plane perpendicular to the central ray of − it absorbs scattered x-rays that travel in many directions to the x-ray beam. The central ray x-ray beam prevent hitting the film. Scatter rays that travel nearly parallel is the x-ray that travels along the center of with the remnant primary x-ray photons exiting the body will not the useful x-ray beam be absorbed by the grid. ▪ is usually produced with an improperly − require an increase in exposure factors positioned x-ray tube and not an − Direct Proportional with the contrast improperly positioned grid. − Gustav Bucky (1913) Grid Construction Off-center Grid − Glitterblende ( First checkboard Grid) ▪ The center of a focused grid must be − Grid/Lead Strips (HIGH ATOMIC #) – Absorption of Scatter positioned directly under the x-ray tube Radiation target, so the central ray of the x-ray beam − Interspace Materials (LOW ATOMIC #) passes through the centermost inter space of the grid. ▪ Any lateral shift results in grid cutoff across 2 classification of Grid the entire radiograph, producing lower OD. ▪ Stationary This error in positioning is called lateral ▪ Moving (POTTER BUCKY DIAPHRAGM) decentering  Hollis E. Potter (1920) Off-Focus Grid ▪ happens when a focused grid is not used at the proper focal distance ▪ The farther the grid is from the specified focal distance, the more severe will be the grid cutoff. Grid cutoff is not uniform across the image receptor but instead is more severe at the edges. Upside-Down Grid ▪ The explanation for an upside-down grid is obvious. It need occur only once, and it will be noticed immediately Grid Types ▪ A radiographic image taken with an upside- Parallel Grids down focused grid shows severe grid cutoff Simplest type of Grids on either side of the central ray All lead strips are parallel Easiest to Manufacture Prepared by: Panaligan, Krizel L. RDTC 2-1 7 4ADM-XWTT-L6XD-VXJU BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite Grid Ratio ✓ 25 mAs was used with a 16:1 grid on the first exposure. A secondary exposure is needed using a 8:1 grid. What will − height of the grid divided by the width of the interspace material be the new mAs? − In general grid ratios range from 5:1 to 16:1 − 8:1-10:1 for general purpose imaging system − 5:1 reduces approx. 85% of scattered radiation while 16:1 reduces approx. 97%. ✓ A grid is fabricated of 30um lead grid strips sandwiched between interspace material that is 300um thick. The height of the strips grid strips is 2.4mm. What is the grid ratio? Beam Restriction devices − Used to restrict or limit the radiation field size − Invented by WILLIAM ROLLINS − very important in the recording of good contrast. − As the beam becomes more restricted to the actual size of the part, less scatter radiation is produced, − use of beam restriction will increase contrast and produce Disadvantage of the use of grids is the increased radiographs with a shorter scale of contrast. radiographic technique required − As the size of the primary beam decreases, the amount of When a grid is used, exposure factors must be scatter produced during the exposure will also decrease. increased over what they were for non grid Decreasing the scatter will result in decreased density and examination. increased contrast. Usually, the mAs rather than the kvp is increased. − increased restriction of the beam (field size becomes smaller) will result in decreased density recorded on the film, with a shorter scale of contrast. Grid Conversion Factor Types of beam restriction devices Aperture Diaphragm ▪ the simplest of all beam-restricting devices ▪ basically a lead or lead lined metal diaphragm that is attached to the x-ray tube head. ▪ The opening in the diaphragm usually is designed to cover just less than the size of the image receptor used Cones and Cylinders ▪ considered modifications of the aperture diaphragm. ▪ an extended metal structure restricts the useful beam to the required size. Grid Conversion Formula ▪ The position and size of the distal end act as an aperture and determine field size. ▪ the useful beam produced by an extension cone or cylinder is usually circular Variable Light Localizing Aperture Diaphragm Collimator ▪ most commonly used beam-restricting device in ✓ 10 mAs was used with a 6:1 grid on the first exposure. A radiography. secondary exposure is needed using a 12:1 grid. What will ▪ leaves of the second-stage collimator shutter are be the new mAs ? usually made of lead that is at least 3 mm thick. They work in pairs and are independently controlled, thereby allowing for both rectangular and square fields. ▪ Light localization in a typical variable-aperture col limator is accomplished with a small lamp and mirror. Positive Beam Limiting Device Automatic Collimation − mandated by the U. S. Food and Drug Administration in 1974 − When a film-loaded cassette is inserted into the Bucky tray and is clamped into place, sensing devices in the tray identify the size and alignment of the cassette. A signal transmitted to the collimator housing actuates the synchronous motors that drive Prepared by: Panaligan, Krizel L. RDTC 2-1 8 4ADM-XWTT-L6XD-VXJU BS RADIOLOGIC TECHNOLOGY 1st SEM | PRELIMS | AY 2024-2025 Emilio Aguinaldo College - Cavite the collimator leaves to a precalibrated position, so the x-ray Patient Thickness beam is restricted to the image receptor in use. − composition of the anatomic part of interest is important in Film Processing understanding the characteristics of contrast as recorded on the film − Conversion of latent image into manifest image − understanding the characteristics of contrast as recorded on the − Conversion of invisible image into visible image film. Disease processes that increase water content will result in − Conversion of exposed SHC into black metallic silver radiographs exhibiting longer scale. The same is true for fat − proper time-temperature relationship and chemical mixtures are content. Obese patients with increased fat content will exhibit necessary to build proper contrast during the processing cycle radiographs with longer scale. − Chemical fog will tend to prevent good contrast. Fog may result if − On the other hand, disease processes that cause tissue temperatures are too high. destruction such as osteoporosis will generally exhibit a short − If the temperatures are too low, the density will not be sufficient scale of contrast. The same is true for tissue filled with air or gas to build adequate contrast on the film. shadows—the recorded contrast is greater. − Underdevelopment prevents the film from building adequate − a thick body section attenuates a greater number of x-rays than contrast. does a thin body section − Contrast on a radiograph can be enhanced by the use of Time-Temperature relationship compression. In manual processing, the time-temperature relationship is 5 minutes at 68°F. Factors Affecting Attenuation As the temperature of the solutions increases, the time the film stays in the solution decreases, and vice − Atomic Number versa o No. of Protons In automatic processors, the time-temperature relationship is more precise and controlled by the multiple systems that make up the processor unit. In every 2 degrees increase time must be reduce to 30 secs Filtration − Filtration of the primary beam is accomplished by the use of − Thickness metal devices called filters placed in the path of the primary x-ray − Mass Density beam o Compactness of the tissue − selectively remove the low-energy photons from the beam. o No. of Atoms at a given volume These low-energy photons do not possess sufficient energy to − Increasing A.T.M. Means increasing Absorption penetrate the body parts and reach the film. Total Filtration ▪ Refers to the sum of Inherent and Added Filtration. ▪ Total filtration is 2.5 mm. Al eq. Inherent Filtration ▪ Is the amount of filtration provided by the x- ray tube structure, housing, and collimator ▪ The glass envelope provides approximately 0.5 mm Al. eq. ▪ The window or port in the tube housing, along with the attached collimator is approximately 1.0 mm Al. eq. inherent filtration. Added Filtration ▪ Is the added material placed in the beam. ▪ Filters are placed between the tube and the beam restrictor device. ▪ Added filtration ranges from 1 to 3 mm Al equivalent thickness. Aluminum  Is the most commonly used material for added filtration.  Because aluminum is very easy to work with and serves as an efficient tool in the removal of low-energy photons from the x-ray beam. Prepared by: Panaligan, Krizel L. RDTC 2-1 9 4ADM-XWTT-L6XD-VXJU