HESI V3 Image production

The center of the x-ray beam must be aligned to the center of the bucky tray to within what percent of the source to image receptor distance (SID)?

1%

Assuming that automatic exposure control is to be used, what backup milliampere-seconds (mAs) are sufficient for a large (100 kg) adult anteroposterior (AP) lumbar spine done at 80 kilovolts peak (kVp)?

100 mAs. (The rule of thumb suggests a back up mAs 50% larger than the highest expected mAs. Experience teaches that it is never a bad idea to use extra back up mAs, as it is difficult to predict the influence of musculature and pathology on a lumbar spine image. Thus 100 mAs is the best choice. 40 mAs might reasonably be expected to be the minimum mAs used for the actual exposure, not backup. 60 mAs might reasonably be expected to be needed for muscular or heavily arthritic patients. Thus 50% more than the highest expectation is 90 mAs. So 80 mAs, by that reasoning, is too low.)

Which combination results in an image with the greatest recorded detail?

2 inch object-to-image-receptor-distance (OID), 72 inch source-to-image-receptor-distance (SID), 0.6 mm focal spot size (FSS). Correct (The shortest OID (2 inches), longest SID (72 inches), and smallest FSS (0.6 mm) result in the greatest recorded detail. The other answers have at least one component that would decrease recorded detail.)

The collimator light must be aligned to the radiation field to within what percent of the source to image distance (SID)?

2%

Which milliampere-seconds (mAs) setting is most likely to produce quantum mottle?

2.5 mAs. (Quantum mottle results from inadequate exposure of the image receptor (IR), so the lowest mAs is most likely to cause quantum mottle. The other options are less likely to cause quantum mottle, because more exposure of the IR will occur.)

A radiograph of optimal density is produced at 15 milliampere seconds (mAs) and a source to image receptor distance (SID) of 40 inches. Which mAs value is required to produce the same radiographic density if this exam is repeated at an SID of 48 inches?

22. (The density maintenance formula, mAs1/mAs2 = D1 squared/D2 squared, provides a method of compensating for changes in SID. In this instance, 15/x = (40)2/(48)2; 1600x = 34,560; x = 34,560/1600 = 22 mAs. The other answers result from math errors.)

With all other factors remaining the same, which source-to-image-receptor-distance (SID) results in the greatest exposure to the image receptor (IR)?

40 inches.

Which milliamperage (mA) station will result in a milliampere seconds (mAs) value of 44 if the exposure time is 0.11 seconds?

400 mA. (The formula for calculating mAs is mA x time (seconds) = mAs. An mA of 400 with an exposure time of .11 results in a mAs of 44: 44 / .11 = 400 mA.)

Which milliampere seconds (mAs) value should be selected for a patient measuring 30 centimeters if 22 mAs is optimal for a patient measuring 25 centimeters?

44 mAs. (When using fixed kilovolts peak techniques, an increase in patient thickness of 4 to 5 cm requires that the mAs be increased by a factor of 2. In this example, an increase of 5 cm would require in increase from 22 mAs to 44 mAs. The other values represent increases of 25%, 40%, and 80%, respectively.)

An image of the abdomen demonstrates appropriate density and scale of contrast, but motion blur is present due to peristalsis. If the original image was obtained with a 200 milliampere (mA) station and an exposure time of 0.35 seconds, which set of technical factors will produce a comparable exposure while minimizing motion artifact?

500 mA and 0.14 seconds. Correct

Which set of exposure factors is most likely to provide clear visualization of the upper cervical spine through the mandible when performing an anteroposterior (AP) "wagging jaw" projection (Ottonello Method)?

75 kilovolts peak (kVp), 25 milliamperes (mA), 2.0 seconds. (The Ottonello Method for the cervical spine requires the patient to perform a chewing motion during the exposure. An exposure time of at least 1 to 2 seconds is required to allow for blurring of the mandible and visualization of C1 and C2. The other techniques listed do not allow for sufficient exposure time to produce this effect.)

A fixed kilovolts peak (kVp)-variable milliampere (mA) chart recommends exposure factors of 70 kVp and 32 mAs for an anteroposterior (AP) abdomen projection on an average-size patient. Based on this chart, which fixed kVp technique is most appropriate for an AP projection of a double contrast upper gastrointestinal (UGI) image?

90 kVp, 8 mAs (A kVp range of 90 to 100 is recommended for adequate penetration of the barium-filled AP stomach and small intestines on a double contrast UGI series. According to the 15% kVp rule, a technique of 90 kVp and 8 mAs will provide density that is comparable to the recommended non contrast technique, while affording enough penetration to visualize the barium-coated surfaces. Although digital systems are capable of adjusting contrast levels post-exposure, low kVp techniques will result in under-penetration as well as increased dose.)

This mobile chest image lacks which required image element?

Anatomical markers.

Which post-processing action is always acceptable?

Annotating with an upright marker to show the patient was in an erect position. Correct

Which term refers to the positive electrode of the x-ray tube?

Anode

In cassette-based computed radiography (CR) systems, the photostimulable phosphor plate is made of which material?

Barium fluorohalide. (Barium fluorohalide is commonly used as the phosphor in CR imaging plates. Cesium iodide is used as the phosphor layer for indirect capture digital radiography (DR) systems. Amorphous silicon is used in direct capture DR systems. Calcium tungstate was used in conventional radiographic screens before the development of rare earth screens.)

At which location is the ionization chamber located in an automatic exposure control (AEC) device?

Between the grid and the image receptor (IR). Correct

Which procedure is most effective for reducing localized image blurring caused by involuntary patient motion?

Decrease exposure times.

Which effect will a low signal-to-noise ratio (SNR) have on the appearance of a digital radiographic image?

Decreased contrast resolution. (SNR is largely dependent on the number of photons available for image formation. Fewer available photons results in a low SNR, which in turn results in higher image noise and decreased contrast resolution. Dynamic range refers to the ability of an imaging system to display a range of intensities; the wide dynamic range inherent in digital systems yields superior contrast resolution to that of conventional film-screen systems. Brightness levels are determined automatically, based on a preselected histogram. Spatial resolution is dependent upon detector element size and spacing.)

All other factors remaining the same, how will increasing the source to image receptor distance (SID) from 40 inches to 60 inches affect the appearance of a radiographic image?

Decreased magnification.

How does a wide window width affect an image?

Decreases contrast

Which post-processing techniques may be used with digital imaging? (Select the three that apply.)

Electronic masking is one word for post-exposure collimation. Smoothing refers to low-pass filtering, which removes high-frequency noise. Filtering, which may refer to high- or low-pass filtering, averages pixel strength. ABC is used in fluoroscopy. Quantum noise is seen in digital imaging, but is not a post-processing technique.

Which is the best way for a radiographer to reduce the effects of patient motion during a radiographic procedure on an adult patient?

Explain the procedure prior to beginning. Correct

How are automatic exposure control (AEC) devices for mammography different than those used with diagnostic radiography?

Greater accuracy is required. Correct (AEC devices for mammography differ from those used in diagnostic radiography in that greater accuracy is required. AEC devices in mammography must be capable of maintaining optical density (OD) within +/- 0.15; AEC in diagnostic radiography must hold OD to +/- 0.20. AEC devices in mammography often provide more cells, not fewer, to image varying densities of breast tissue. Detector location can be moved to image nipple and chest wall breast locations with greater accuracy. Exposures are terminated directly by the AEC just as they are in routine diagnostic exams.)

Which term refers to a graphical representation of pixel values?

Histogram.

Opening the collimators wider than necessary using digital radiography has which effect on image quality?

Image noise is increased. (Increasing the size of the collimated field increases the quantity of scatter produced but does not affect the size of the pixels. Pixel size in digital radiography is determined by the CR scanning frequency or the DR DEL size.)

Which effect does switching to the small focal spot size have on the manifest image?

Image unsharpness decreases

Which is an advantage of digital imaging systems compared to traditional film-screen systems?

Improved contrast resolution. (One advantage digital systems have over film-screen receptors is improved contrast resolution, or a greater ability to distinguish between structures of similar densities (this is also termed improved dynamic range). Digital systems are no less susceptible to image noise than traditional film-based systems. Spatial resolution is decreased relative to film-screen imaging due to the size of the pixel. Digital systems are more sensitive to scatter radiation than film-screen receptors.)

Which is the best way to avoid excessive quantum noise when using cassette-based digital systems?

Increase the amount of exposure to the image receptor. Correct

Which advantage is gained by increasing the standard source to image receptor distance (SID) from 40 inches to 48 inches?

Increased image resolution. Correct (Increasing the SID will increase resolution by reducing image magnification and penumbra. Radiographic contrast is primarily controlled by factors other than SID (kilovolts peak in conventional film-screen systems, and automatic rescaling in digital radiography systems). Increasing the standard SID should not affect SNR, since a commensurate increase in exposure factors will accompany this change. Due to the necessary increase in exposure factors, x-ray tube life (D) is adversely affected.)

Which technical factor increases the number of x-ray photons reaching the image receptor (IR)?

Increased milliamperage (mA). Correct

How will raising the window level affect the digital image?

Increases brightness. Correct

Which image, when performed according to normal standards, will demonstrate the greatest magnification of the anatomy of interest?

Lateral cervical spine (Because lateral cervical spine xrays typically have large object-to-image-receptor (OID) distances, the cervical spine anatomy is magnified. The OID for an AP lumbar spine may be minimized by asking the patient to bend his or her knees to bring the spine closer to the image receptor (IR). PA hands and lateral forearms have minimal magnification.)

Which is the primary advantage of a rotating anode?

Less heat is generated at the target. (The primary advantage of a rotating anode is that less heat is generated at the x-ray tube target. More heat is generated with a fixed anode. A rotating anode does not increase or decrease filament temperatures.)

When using digital imaging, which has the greatest influence on contrast?

Lookup table (LUT). (In digital imaging, a LUT (C) assigns predetermined grayscale values. KVp (A) controls contrast in film-screen imaging. MAs (B) does not affect contrast. MTF (D) is related to spatial resolution.)

Which factor will have the greatest impact on decreasing recorded detail or spatial resolution?

Motion.

Which acronym describes a network of computers that manages digital images?

PACS.

Which radiopaque marker is image-appropriate after micturition has taken place?

Post-void. (Because micturition means to urinate, a post-void radiopaque marker should be placed on the image receptor (IR). Upright and decubitus are used for positioning differences. Post-evacuation is used after the patient has had a bowel movement.)

Which device in the x-ray circuit changes alternating current to direct current?

Rectifier.

Which term describes the process by which an overexposed or underexposed image receptor (IR) appears acceptable on a display monitor?

Rescaling

Which factors affect spatial resolution in digital imaging? (Select the two that apply.)

Smaller pixels Greater number of pixels.

Which x-ray tube orientation represents the correct application of the anode heel effect?

The anode end is positioned toward the head for an anteroposterior (AP) thoracic spine projection. (Due to the angle of the target, the x-ray beam has greater intensity at the cathode end. Placing the anode end toward the head for an AP thoracic spine projection results in a more uniform radiographic density. The other examples describe incorrect applications of the anode heel effect.)

Which scenario causes foreshortening of the anatomy on the image?

The humerus in contact with the image receptor (IR), the forearm lifted off the image receptor, and the central ray directed perpendicular to the long axis of the humerus. Correct

A lateral lumbar spine image was obtained with a field size of 11x14 inches at 95 kilovolts peak (kVp) and automatic exposure control (AEC) with the center detector selected. The resulting image demonstrates excessive quantum noise. Which is the most likely cause for this appearance?

The patient was not accurately centered. Correct

Which device is located in the primary section of a general x-ray circuit?

Timer circuit. Correct (The timer circuit is located on the primary section of the x-ray circuit. The mA meter is located on the secondary circuit. The step-down transformer and rheostat are located on the filament circuit.)

Which device provides the required amount of voltage for x-ray production?

Transformer

How does aliasing appear radiographically when using computed radiography (CR)?

Two superimposed images, slightly out of alignment. Correct

Which effect does a step-up transformer have on voltage and current?

Voltage is increased and current is decreased. Correct (According to the transformer law, a step-up transformer increases voltage and decreases current. A step-down transformer decreases voltage and increases current. The other choices provided represent violations of the transformer law.)

Which substance is added to the x-ray tube housing to increase heat dissipation?

oil