Bontrager textbook radiographic positioning pdf download

EMBED for wordpress. Want more? Advanced embedding details, examples, and help! Louis, Mo. Detailed positoning with pictures and graphics make it easy to understand. Simple and Precise By azr All that matters here is simplicity and precision. As the title says, Radiographis Positioning and Related Anatomy. You got what you expected: all radiographic positioning almost all and related anatomy enough for x ray procedures but you really need anatomy book by your side I highly recommend this book for reference but additional facts should be close at hand for further referrals.

I believe many universities do the same. The course accompanies the Bontrager text and workbooks, and is perfect for any radiography program. It offers invaluable application opportunities not found in textbooks, and shows you how to produce diagnostic-quality radiographs.

A new master glossary link embedded in screen navigation gives you easy access to glossary terms at any point in the program. Emphasis on radiation safety practices provides recommendations important for clinical practice. Updated photographs visually demonstrate the latest digital technology used in radiography with new radiographs, positioning, and equipment images.

Erect positions have been added throughout the text to reflect current practice. This indicates a greater focal range for portable grids, but SID limitations still exist to prevent grid cutoff Fig. Each technologist should know which types of portable grids are available and should know the focal range of each. Off-le ve l grid tra ns ve rs e tilte d grid, re s ults in ove ra ll de cre a s e in ima ge de ns ity inch cm S ID inch cm S ID CR Corre ct foca l ra nge Off-focus grid, e xce s s ive S ID re s ults in ove ra ll de cre a s e in ima ge de ns ity Fig.

The lead strips are tilted or focused to allow the x-ray beam to pass through unimpeded if the SID is within the focal range and the grid is correctly placed. If the grid is positioned upside-down, the image will show severe cutoff Fig. A general rule states that the lowest m a s th t yiel suf cie t i gthe highest kV ostic i fo m tio shoul be use o e ch iog phic 13 ex m i tio.

Close collimation and correct use of grids also ensure that the processed radiographic image displays optimal contrast. PaT a r UT n Spatial resolution is de ned as the eco e sh p ess of st uctu es o the im ge.

Resolution on a radiographic image is demonstrated by the clarity or sharpness of ne structural lines and borders of tissues or structures on the image.

Resolution is also et il, im ge sh p ess, or e itio. Lack of visible sharpness or resolution is known as blu or u sh p ess. Corre ctly ce nte re d grid Ups ide -down grid re s ults in grid cutoff or de cre a s e d de ns ity on both s ide s of ima ge Fig.

Resolution with lm-screen imaging is controlled by geom et ic f cto s, the lm sc ee system , and m otio. The effect of OID is explained and illustrated in Fig.

The use of the sm ll foc l spot results in less geom et ic u sh p ess Fig. To illustrate, a point source is used commonly as the source of x-rays in the x-ray tube; however, the actual source of x-rays is an area on the anode known as the ocal spot.

Most x-ray tubes exhibit dual focus; that is, they have two focal spots: large and small. Use of the small focal spot results in less unsharpness of the image, or an image with a decreased penumbra. A penumbra refers to the u sh p e ges of objects i the p ojecte im ge. However, even with the use of the small focal spot, some penumbra is present. A faster lm-screen system allows shorter exposure times, which are helpful in preventing patient motion and reducing dose; however, the image is less sharp than when a slower system is used.

La rge r foca l s pot more pe numbra S ma ll foca l s pot le s s pe numbra Fig. Two types of motion in uence radiographic detail: volu t y and i volu t y. Volu t y m otio is that which the patient can control. Motion from breathing or movement of body parts during exposure can be prevented or at least minimized by co t olle b e thi g and p tie t im m obiliz tio.

Support blocks, sandbags, or other immobilization devices can be used to reduce motion effectively. These devices are most effective for examination of upper or lower limbs, as will be demonstrated throughout this text. Involuntary motion cannot be controlled by the patient at will.

Therefore, involuntary motion, such as peristaltic action of abdominal organs, tremors, or chills, is more dif cult, if not impossible, to control. If motion unsharpness is apparent on the image, the technologist must determine whether this blurring or unsharpness is due to voluntary or involuntary motion. This determination is important because these two types of motion can be controlled in various ways. Voluntary motion can be minimized through the use of high mA and short exposure times.

Increased patient cooperation is another factor that may contribute to decreased voluntary motion; a thorough explanation of the procedure and clear breathing instructions may prove helpful. This type of motion is less obvious but can be visualized on abdominal images as localized blurring of the edges of the bowel, with other bowel outlines appearing sharp gas in the bowel appears as dark areas. Study Fig. The remaining edges of the bowel throughout the abdomen appear sharp.

A clear explanation of the procedure by the technologist may aid in reducing voluntary motion; however, a decrease in exposure time with an associated increase in mA is the best and sometimes the only way to minimize motion unsharpness caused by involuntary motion. Patient motion also affects image quality; sho t exposu e tim es and i c e se p tie t coope tio help to minimize voluntary motion unsharpness.

Involuntary motion unsharpness is controlled only by short exposure times. Two types of distortion have been identi ed: size distortion magni cation and shape distortion. No radiographic image reproduces the exact size of the body part that is being radiographed. This is impossible to do because a degree of magni cation or distortion or both always exists as a result of OID and divergence of the x-ray beam. Nevertheless, distortion can be minimized and controlled if some basic principles are used as a guide.

It occurs because x-rays originate from a small source in the x-ray tube the focal spot and diverge as they travel to the IR Fig. The eld size of the x-ray beam is limited by a collimator that consists of adjustable lead attenuators or shutters.

The collimator and shutters absorb the x-rays on the periphery, controlling the size of the x-ray beam. The ce te poi t of the x- y be m , which is called the central ray CR , theoretically has no divergence; the le st m ou t of isto tio is seen at this point on the image.

All other aspects of the x-ray beam strike the IR at some angle, with the angle of divergence increasing to the outermost portions of the x-ray beam. The potential for distortion at these outer margins is increased. Greater magni cation is demonstrated at the periphery A and B than at the point of the central ray C. Because of the effect of the divergent x-ray beam, combined with at least some OID, this type of size distortion is inevitable.

It is important for technologists to control closely and minimize distortion as much as possible. Source image receptor distance SID 2. Object image receptor distance OID 3. Object image receptor alignment 4. The effect of SID on size distortion magni cation is demonstrated in Fig. This is the reason that chest radiographs are obtained at a minimum SID of 72 inches cm rather than of 40 to 48 inches to cm , which is commonly used for most other examinations.

A inch cm SID results in less magni cation of the heart and other structures within the thorax. P A B Le s s ma gnifica tion Fig. S ID T r n ,P T n n , an d i im um i ch o cm d It has been a long-standing common practice to use 40 inches rounded to cm as the standard SID for most skeletal radiographic examinations.

However, in the interest of improving image resolution by decreasing magnication and distortion, it is becoming more common to increase the standard SID to 44 inches or 48 inches cm or cm. Additionally, it has been shown that increasing the SID from 40 to 48 inches reduces the entrance or skin dose even when the requirement for increased mAs is considered. In this textbook, the suggested SID listed on each skeletal positioning page is a m i im um of 40 i ches, with 44 inches or 48 inches recommended if the equipment and departmental protocol allow.

The effect of OID on magni cation or size distortion is illustrated clearly iog phe is to the in Fig. The close the object bei g r , the less e the m g i c tio sh pe isto tio the bette is the esolutio. This refers to the alignment or plane of the object that is being radiographed in relation to the plane of the image receptor. If the object plane is not parallel to the plane of the IR, distortion occurs. The greater the angle of inclination of the object or the IR, the greater the amount of distortion.

For example, if a nger being radiographed is not parallel to the IR, the interphalangeal joint spaces will not be open because of the overlapping of bones, as is demonstrated in Fig. Note the open joints of the digits in Fig. Additionally, the phalanges will be either foreshortened or elongated. These examples demonstrate the important principle of correct object IR alignment.

The pl e of the bo y p t th t is bei g im ge m ust be s e p llel to the pl e of the r s possible to produce an image of minimal distortion. P Fig. Therefore, the le st possible isto tio occu s t the r. Distortion increases as the angle of divergence increases from the center of the x-ray beam to the outer edges. For this reason, correct centering or correct central ray alignment and placement is important in minimizing image distortion.

The CR passes through the knee joint space with minimal distortion, and the joint space should appear open. However, the knee joint is now exposed to divergent rays as shown by the arrow , and this causes the knee joint to appear closed Fig. For certain body parts, however, a speci c angle of the CR is required, as is indicated by the positioning descriptions in this text as the CR angle.

This means that the CR is angled from the vertical in a cephalic or caudad direction so as to use distortion intentionally without superimposing anatomic structures. Density 2. Contrast 3. Distortion Fig. Dive rge nt ra y CR Fig. Although digital imaging differs from lm-screen imaging in terms of the method of image acquisition, factors that may affect x-ray production, attenuation, and geometry of the x-ray beam still apply.

This section provides a brief practical introduction to a very complex topic. These images are a um e ic ep ese t tio of the x- y i te sities th t e t sm itte th ough the p tie t. Each digital image is twodimensional and is formed by a matrix of picture elements called pixels Fig. In diagnostic imaging, each pixel represents the smallest unit in the image; columns and rows of pixels make up the matrix. For illustrative purposes, consider a sheet of graph paper.

The series of squares on the sheet can be compared with the matrix, and each individual square can be compared with a pixel. Digital imaging requires the use of computer hardware and software applications to view images Fig. Digital processing involves the system tic pplic tio of highly com plex m them tic l fo m ul s called algorithms. Numerous mathematical manipulations are performed on image data to enhance image appearance and to optimize quality.

Algorithms are applied by the computer to every data set obtained before the technologist sees the image. Digital imaging systems are capable of producing a radiographic image across a large range of exposure values and are described as having a wide dynamic range Fig.

Because of this wide dynamic range, it is essential that an institution de ne the exposure latitude for the digital imaging systems within its department. The exposure latitude for a digital imaging system is de ned as the acceptable level of exposure that produces the desired image quality for the department. Note that the increase from 1 to 8 mAs still produces a diagnostic image of the elbow.

P ixe l Fig. It must be remembered, however, that the kV and mAs used for the exposure affect patient dose. The kV selected must be adequate to penetrate the anatomy of interest. As kV increases, beam penetrability increases. A bene t of using a higher kV is that patient dose is reduced as compared with lower kV ranges.

Compared with lm-screen imaging, changes in kV can have less of a direct effect on nal digital image contrast because the resultant contrast is also a function of the digital processing. B, Option 2. In digital imaging, the term brightness replaces the lm-based term density Figs. Brightness is controlled by the processing software through the application of predetermined digital processing algorithms. In contrast to the linear relationship between mAs and density in lm-screen imaging, changes in mAs do not have a controlling effect on digital image brightness.

Although the density of a lm image cannot be altered once it is exposed and chemically processed, the user can adjust the brightness of the digital image after exposure see section on postprocessing later in this chapter. This de nition is similar to the de nition used in lm-based imaging, where contrast is the difference in density of adjacent areas on the lm Figs. Contrast resolution refers to the ability of an imaging system to distinguish between similar tissues. Radiographic contrast is affected by the digital processing computer through the application of predetermined algorithms, in contrast to lm-screen imaging, in which kV is the controlling factor for image contrast.

Although the contrast of a lm image cannot be altered after exposure and processing, the user can manipulate the contrast of the digital image see later section on postprocessing. The ability of the image processing software to display a desired image contrast provides the radiographer with a potential opportunity to reduce entrance skin exposure to the patient through the use of higher kVp levels.

It is critical that the radiographer consult with the interpreting radiologist and medical physicist prior to implementing across-the-board kVp increases in order to ensure that acceptable image quality is maintained.

The range of possible shades of gray demonstrated is related to the bit depth of the pixel, which is determined by the manufacturer. Although a comprehensive description of bit depth is beyond the scope of this text, it is important to note that the g e te the bit epth of system , the g e te the co t st esolutio i. The most common bit depths available are 10, 12, and For example, a digital system for chest imaging should have a bit depth greater than 10 bits 2 10 if it is to capture all required information; the x-ray beam that exits a patient who is having a chest x-ray can have a range of more than intensities.

These are acquisition pixel size, which is the minimum size that is inherent to the acquisition system, and display pixel size, which is the minimum pixel size that can be displayed by a monitor. This is accomplished by the correct use of grids, by close collimation, and by selection of the optimal kV. Grid cut-off occurring with digital image receptors will result in an image that has decreased contrast and has an exposure indicator re ecting a decrease in exposure.

The change in exposure indicator is due to the decrease in amount of exit radiation striking the receptor. T r PaT a r n ,P T n n , an d UT n Spatial resolution in digital imaging is de ned as the eco e sh p ess o et il of st uctu es o the im ge—the same as de ned for lm-screen imaging.

Resolution in a digital image represents a combination of the traditional factors explained previously for lm-screen imaging focal spot size, geometric factors, and motion and, just as important, the cquisitio pixel size. This pixel size is inherent to the digital imaging receptor. The smaller the acquisition pixel size, the greater the spatial resolution. Spatial resolution is measured in line pairs per millimeter.

Current digital imaging systems employed for general radiography have spatial resolution capabilities ranging from approximately 2.

The perceived resolution of the image depends on the display capabilities of the monitor. Monitors with a larger display matrix can display images with higher resolution. Refer to the rst part of this chapter; minimizing distortion is an important image quality factor. XP Ur nd aT r The exposure indicator in digital imaging is a um e ic v lue th t is ep ese t tive of the exposu e th t the r h s eceive. The DI provides feedback to the operator regarding receptor Fig.

A DI value of 0 indicates that the level of exposure was appropriate. A positive DI value indicates overexposure and a negative DI value indicates underexposure. It is a value that is calculated from the effect of mAs, the kV, the total receptor area irradiated, and the objects exposed e.

Depending on the manufacturer and the technique used to calculate this value, the exposure indicator is displayed for each exposure. An exposure indicator, as used by certain manufacturers, is i ve sely el te to the radiation that strikes the receptor.

For example, if the range for an acceptable image for certain examinations is to , a value greater than would indicate underexposure, and a value less than would indicate overexposure. An exposu e i ic to as used by other manufacturers is i ectly el te to the radiation striking the IR, as determined by logarithmic calculations. For example, if an acceptable exposure indicator is typically 2.

This text uses the term exposu e i ic to when referring to this variable. It has been stated previously that digital imaging systems are able to display images that have been obtained through the use of a wide range of exposure factors.

Checking the exposure indicator iog phic is key in verifying that acceptable qu lity igit l im ges h ve bee obt i e with the le st possible ose to the p tie t. In a radiographic image, this translates into a grainy or mottled appearance of the image. A low n r is u esi ble; a low signal low mAs with accompanying high noise obscures soft tissue detail and produces a grainy or mottled image.

Overexposed images are not readily evident with digital processing and display, so checking the exposure indicator as described on the previous page is the best way to determine this.

The technologist may check for noise at the workstation by using the magnify feature and magnifying the image to determine the level of noise present within the image.

In the event that noise is clearly visible in the image without any magni cation, the image should be reviewed by the radiologist to determine if the image needs to be repeated. Scatter radiation leads to a degradation of image contrast that can be controlled by the use of grids and correct collimation, as was described previously. A secondary factor related to noise in a radiographic image is electronic noise.

Although a comprehensive discussion of electronic noise is beyond the scope of this text, electronic noise typically results from inherent noise in the electronic system, nonuniformity of the image receptor, or power uctuations. Postprocessing refers to ch gi g o e h ci g the elect o ic im ge fo the pu pose of im p ovi g its i g ostic qu lity.

In postprocessing, algorithms are applied to the image to modify pixel values. Once viewed, the changes made may be saved, or the image default settings may be reapplied to enhance the diagnostic quality of the image. P TPr n an d XP Ur nd 1 aT r r a n After an acceptable exposure indicator range for the system has been determined, it is important to determine whether the image is inside or outside this range.

Theoretically, if the algorithms are correct, the image should display with the optimal contrast and brightness. However, even if the algorithms used are correct and exposure factors are within an acceptable range, as indicated by the exposure indicator, certain postprocessing options may still be applied for speci c image effects.

The most common of these options include the following: Windowing: The user can adjust image contrast and brightness on the monitor. Two types of adjustment are possible: window width, which controls the co t st of the image within a certain range , and window level, which controls the b ight ess of the image, also within a certain range.

It is important to note that when adjusting the display window for a digital radiograph, the manner in which the values assigned for each characteristic vary is dependent on the viewing system software. In some PACS systems increasing window level results in a darker image, and in others it results in a brighter image.

Sm oothing: Speci c image processing is applied to reduce the display of noise in an image. The process of smoothing the image data does not eliminate the noise present in the image at the time of acquisition. Magnif cation: All or part of an image can be magni ed.

Edge enhancem ent: Speci c image processing that alters pixel values in the image is applied to make the edges of structures appear more prominent compared with images with less or no edge enhancement. The spatial resolution of the image does not change when edge enhancement is applied. Equalization: Speci c image processing that alters the pixel values across the image is applied to present a more uniform image appearance.

The pixel values representing low brightness are made brighter, and pixel values with high brightness are made to appear less bright. Subtraction: Background anatomy can be removed to allow visualization of contrast media— lled vessels used in angiography.

Im age reversal: The dark and light pixel values of an image are reversed—the x-ray image reverses from a negative to a positive.

Annotation: Text may be added to images. This section introduces and brie y describes the digital imaging technology used in general radiography. Each of the systems described start the imaging process using an x-ray beam that is captured and converted into a digital signal. Images also may be printed onto lm by a laser printer. The many acronyms associated with digital imaging have created a plethora of misconceptions regarding digital imaging systems, and these misconceptions have resulted in technologists not having a thorough understanding of how various digital imaging systems work.

The following sections describe the current digital imaging systems, based rst on how the image data are captured and data extracted, and second on their appearance. Regardless of appearance and how the image data are captured and extracted, each of the digital imaging systems described has a wide dynamic range that requires a de ned set of exposure indices to enable the technologist to adhere to the principles of ALARA.

The technologist veri es the patient position and checks the exposure indicator at this workstation. It is most commonly called computed radiography CR. A CR digital imaging system relies on the use of a storage phosphor plate that serves the purpose of capturing and storing the x-ray beam exiting the patient. When the plate is exposed to radiation, electrons migrate to electron traps within the phosphor material.

The greater the exposure to the plate, the more electrons move to the electron traps. The exposed plate containing the latent image undergoes a reading process following the exposure Fig.