Fluoroscopic Interpretation and Radiation Safety

Question 1

1. During a typical fluoroscopically-guided procedure, radiation exposure would be expected to be highest when in close proximity to which structure?
   A. The fluoroscope’s image intensifier.
   B. The fluoroscope’s x-ray tube.
   C. The fluoroscope’s optical coupling chain.
   D. The patient’s body.
   E. The procedure table.

Answer 1

1. Answer: B
   Explanation:
   X-rays are produced within the x-ray tube and their effects are most powerful at and immediately adjacent to the x-ray tube.
   Author: David Schultz, MD

Question 2

2. Which of the following descriptions of electromagnetic radiation photons will be the most penetrating?
   A. Frequency of 103 Hz, wavelength of 10° meters (m), energy of l0-8 eV
   B. Frequency of 1020 Hz, wavelength of 10-9 meters (m), energy of l0-5 keV.
   C. Frequency of 1010 Hz, wavelength of 10-5 meters (m), energy of l0-5 eV.
   D. Frequency of 1014 Hz, wavelength of 10-7 meters (m), energy of l01 eV.
   E. Frequency of 1040 Hz, wavelength of 109 meters (m), energy of l01 eV.

Answer 2

2. Answer: B
   Explanation:
   Frequency, wavelength, and energy are the factors that differentiate one form of electromagnetic radiation from another. In terms of penetrability, the photon with the highest frequency, shortest wavelength, and highest energy will be the most penetrating. This is the reason x-rays penetrate matter while other forms of electromagnetic radiation, such as visible light, radio waves, or microwaves do not.
   Source: Lefave L. Medical Radiography: PreTest® Self-Assessment and Review. McGraw-Hill, New York, 1996.

Question 3

3. Which of the following is a factor that differs between x-rays and gamma rays?
   A. Electrical nature
   B. Particulate nature
   C. Speed in a vacuum
   D. Energy Level
   E. Source of origin

Answer 3

3. Answer: E
   Explanation:
   X-rays and gamma rays are virtually identical with the exception of their source of origin. X-rays are produced via the sudden declaration of high-speed electrons in a device such as an x-ray tube.
   Gamma rays are a naturally occurring form of nuclear radiation arising from the nucleus of radioactive elements. Both types of radiation are nonparticulate (no mass), have a neutral electrical nature, are highly energetic, will travel at the speed of light in a vacuum, and will cause biologic and chemical effects on matter.
   Source: Lefave L. Medical Radiography: PreTest® Self-Assessment and Review. McGraw-Hill, New York, 1996.

Question 4

4. At what speed will electromagnetic waves travel in a vacuum.
   A. 3 x 1010 meters per second (m/s)
   B. 186,000 m/s
   C. 186,000 cm/s
   D. 3 x 108 m/s
   E. 3 x 10**20 m/s

Answer 4

4. Answer: D
   Explanation:
   Electromagnetic waves travel at the speed of light in a vacuum. The speed of light is defined in metric terms as 3 x 108 m/s or 3 x 1010 cm/s and in British terms as 186,000 miles/s. This characteristic is the same for all forms of electromagnetic radiation (visible light, radio waves, microwaves, and so on).
   Source: Lefave L. Medical Radiography: PreTest® Self-Assessment and Review. McGraw-Hill, New York, 1996.

Question 5

5. The typical percentage of X-rays that reach an image intensifier is:
   A. 1% of the X-rays generated.
   B. 10% of the X-rays generated.
   C. 50% of the X-rays generated.
   D. 75% of the X-rays generated.
   E. 90% of the X-rays generated.

Answer 5

5. Answer: A
   Explanation:
   Only 1% of the X-rays generated actually arrive at the image intensifier. 99% of the X-rays are absorbed within the patient or scattered (espalhado) to the room.
   Author: Andrea M. Trescot, MD

Question 6

6. What is the dose equivalent of an absorbed dose of 20 rads of alpha radiation?
   A. 20rads (0.2 Gy)
   B. 20 rem (0.2 Sv)
   C. 20 rem (.4**5v)
   D. 400 rads (4.0 Gy)
   E. 400 rem (4.0 Sv)

Answer 6

6. Answer: E
   Explanation:
   Dose equivalent is the product of absorbed dose and the quality factor (QF) applied to alpha particles. The correct unit of measure to indicate dose equivalent is the rem (sievert). To solve this problem, multiply 20 rads (absorbed dose) by 20 (QF of alpha) to equal 400 rem, which is equivalent to 4.0 Sv. This demonstrates the increased biologic effect of alpha exposure compared with an equal dose equivalence of 20 rem (20 x 1).
   Source: Lefave L. Medical Radiography: PreTest® Self-Assessment and Review. McGraw-Hill, New York, 1996.

Question 7

7. Regarding X-ray exposure, which of the following is true?
   A. A provider 3 feet away from the patient will receive 0.1% of the patient’s Entrance Skin Exposure (ESE).
   B. Typical ESE doses during standard fluoroscopy are about 30 R/min
   C. The greatest exposure to the provider’s eyes is when the image intensifier is on the same side as the provider.
   D. With the image intensifier above the table, the highest amount of radiation is above the table.
   E. The primary beam is the major source of provider radiation.

Answer 7

7. Answer: A
   Explanation:
   Typical ESE is 2 R/min. The greatest exposure is when the image intensifier is on the opposite side from the provider, and the greatest radiation is under the table; scatter is the primary source of provider radiation.
   Author: Andrea M. Trescot, MD

Question 8

8. A patient has had an implanted intrathecal infusion pump for post-laminectomy syndrome for the past 3 years. He has had relatively good pain control with a combination infusion of morphine, bupivacaine, and baclofen. You are asked to evaluate him in the emergency room for increasing low back pain associated with new onset of right leg pain and right leg weakness. Physical examination reveals positive right straight leg raise with loss of right Achilles reflex. Plain x-ray has identified the titanium catheter tip marker at the T8 level in the ventral intrathecal space. Which one of the following statements is false:
   A. Most patients who are diagnosed with catheter tip granuloma present with gradual loss of pain control associated with gradual onset of lower extremity neurological deficits evolving over weeks and months.
   B. When catheter tip granuloma is diagnosed, surgical removal of the catheter is always the treatment of choice.
   C. MRI with and without gadolinium enhancement is the imaging study of choice to assess catheter tip granuloma.
   D. Baclofen when used alone in the pump for spasticity management has not been implicated in catheter tip granuloma.
   E. Right lumbar radiculopathy is a more likely diagnosis than catheter tip granuloma in this patient.

Answer 8

8. Answer: B
   Explanation:
   Inflammatory mass formation at the tip of an implanted intrathecal catheter is a rare but potentially devastating complication of intrathecal drug infusion. Hassenbush et al. reviewed published and unpublished case reports and their own experiences to recommend methods to diagnose and treat catheter-tip infl ammatory masses in the above article.
   After comprehensive review, the Hassenbush consensus panel concluded that:
9. Fluctuations in patients’ subjective symptoms and underlying pain levels are common after the implantation of drug delivery systems, but the occurrence of new or extraordinary complaints that require unexpected analgesic dose changes should alert physicians to consider a catheter-tip mass among other possibilities in the differential diagnosis. Gradual, insidious neurological deterioration weeks or months after the appearance of subjective symptoms was the most common clinical course for catheter tip granulomas before the onset of myelopathy or cauda equina syndrome in cases reported to date.
10. Physicians should have a low threshold for performing an imaging study to conf rm or rule out the presence of a catheter-tip mass in patients with suspicious symptoms or physical findings. Unless medically contraindicated, MRI with and without intravenous gadolinium contrast enhancement is the imaging procedure of choice. CT myelogram is an acceptable alternative and is equally sensitive and reliable. Catheter-tip masses are visualized best on intravenous contrast-enhanced T2-weighted images. The mass appears as an enhancing lesion having the tip of the drug administration catheter embedded within it.
11. Not all patients with catheter tip granuloma require catheter and pump removal. When catheter tip granuloma is diagnosed, optimal management should take into account the patient’s clinical condition, the wishes of the patient and the available options for chronic pain management. Mildly symptomatic patients with small masses that are diagnosed during investigation of diminished analgesic eff cacy or other subjective complaints have been managed safely and successfully without open surgical decompression or removal of the mass. These masses did not signifi cantly compress neural structures, nor compromise neurological function, and were treated with prompt discontinuation of intrathecal drug administration. Shrinkage or disappearance of the mass was documented on follow-up imaging studies after an interval of 2-5 months. Consequently, catheter-tip inflammatory masses that are detected early in the clinical course can be treated safely and effectively by maneuvers directed at modifying rather than removing the drug infusion system. If the decision is made to leave the infusion system in place, the responsible physician eventually must decide whether to continue intrathecal therapy and whether to change the dose, concentration, or the drug(s) being infused. Alternatives to complete removal of the catheter and pump include ceasing or changing drug infusion and:
12. Repositioning of the catheter at a different spinal level.
13. Placing a new catheter to replace the existing catheter.
14. Allowing the catheter and pump to remain dormant for a period of time.
    In contrast, patients presenting with paraplegia or progressive myelopathy or with apparently fixed eurological deficits of short duration may require emergent operative intervention because of concern that delayed treatment could foreclose the possibility of neurological recovery. Surgical intervention to remove the mass and/or de-compress the spinal canal has restored neurological function or prevented further neurological deterioration in several reported cases. The extent of resection was limited in some cases owing to adhesions to the spinal cord or nerve roots or because of the ventral location of a mass beneath the thoracic spinal cord. Because the masses were not neoplastic, in several cases the postoperative residual mass gradually shrank or disappeared over time.
    Reference: Management of Intrathecal Catheter-Tip Infl ammatory Masses: A Consensus Statement. Hassenbusch et. Al. Pain Medicine 2002
    Author: David Schultz, MD

Question 9

9. What unit best measures the biological effects of radiation in human tissue?
   A. Curie (Ci)
   B. Rem
   C. Roentgen
   D. Rad
   E. Gray (Gy)

Answer 9

9. Answer: B
   Explanation:
   The following units are used to measure radiation:
10. Roentgen (R):
    The roentgen is a unit used to measure a quantity called exposure. This can only be used to describe an amount of gamma and X-rays, and only in air. One roentgen is equal to depositing in dry air enough energy to cause 2.58E-4 coulombs per kg. It is a measure of the ionizations of the molecules in a mass of air. The main advantage of this unit is that it is easy to measure directly, but it is limited because it is only for deposition in air, and only for gamma and x rays.
11. Rad (radiation absorbed dose):
    The rad is a unit used to measure a quantity called absorbed dose. This relates to the amount of energy actually absorbed in some material, and is used for any type of radiation and any material. One rad is defined as the absorption of 100 ergs per gram of material. The unit rad can be used for any type of radiation, but it does not describe the biological effects of the different radiations.
12. Rem (roentgen equivalent man)
    The rem is a unit used to derive a quantity called equivalent dose. This relates the absorbed dose in human tissue to the effective biological damage of the radiation. Not all radiation has the same biological effect, even for the same amount of absorbed dose. Equivalent dose is often expressed in terms of thousandths of a rem, or mrem. To determine equivalent dose (rem), you multiply absorbed dose (rad) by a quality factor (Q) that is unique to the type of incident radiation.
13. Curie (Ci)
    The curie is a unit used to measure a radioactivity. One curie is that quantity of a radioactive material that will have 37,000,000,000 transformations in one second. Often radioactivity is expressed in smaller units like: thousandths (mCi), one millionths (uCi) or even billionths (nCi) of a curie. The relationship between becquerels and curies is: 3.7 x 1010 Bq in one curie.

SI Units:
5. Gray (Gy)
The gray is a unit used to measure a quantity called absorbed dose. This relates to the amount of energy actually absorbed in some material, and is used for any type of radiation and any material. One gray is equal to one joule of energy deposited in one kg of a material. The unit gray can be used for any type of radiation, but it does not describe the biological effects of the different radiations. Absorbed dose is often expressed in terms of hundredths of a gray, or centi-grays. One gray is equivalent to 100 rads.
6. Sievert (Sv)
The sievert is a unit used to derive a quantity called equivalent dose. This relates the absorbed dose in human tissue to the effective biological damage of the radiation. Not all radiation has the same biological effect, even for the same amount of absorbed dose. Equivalent dose is often expressed in terms of millionths of a sievert, or micro-sievert. To determine equivalent dose (Sv), you multiply absorbed dose (Gy) by a quality factor (Q) that is unique to the type of incident radiation. One sievert is equivalent to 100 rem.
Author: David Schultz, MD

Question 10

10. The five basic radiological densities include all of the following EXCEPT:
    A. Air
    B. Fat
    C. Cartilage
    D. Bone
    E. Metal

Answer 10

10. Answer: C
    Explanation:
    The basic radiological densities are as follows ranked in order of increasing density and decreasing radiolucency:
11. Air
12. Fat
13. Water (soft tissue)
14. Bone
15. Metal
    Cartilage is considered to be of water (soft tissue) density.
    Author: David Schultz, MD

Question 11

11. A pain clinic employee has assisted with procedures in your fluoroscopy suite for the past 10 years. The total amount of x-ray radiation that this person has received over the course of their employment is called:
    A. Occupational dose.
    B. Acquired dose.
    C. Total dose.
    D. Allowable dose.
    E. Working dose.

Answer 11

11. Answer: A
    Explanation:
    Occupational dose is the term used to describe the total amount of radiation exposure a person has received over the course of their employment.
    Author: David Schultz, MD

Question 12

12. The purpose of thin aluminum or copper plates that are placed between the x-ray source and the patient is to:
    A. Absorb heat
    B. Improve image contrast
    C. Remove poorly penetrating x rays from the beam
    D. Compensate for excessive tube current
    E. Decelerate high-speed electrons

Answer 12

12. Answer: C
    Explanation:
    The x-ray beam produced by bremsstrahlung* initially contains a considerable amount of poorly penetrating x rays that provide no imaging capability. These poorly penetrating x rays would deposit nearly all their energy into the patient’s tissue if they were not removed from the beam before escaping from the x-ray tube housing**. The thin metal filters preferentially absorb these x rays. Thus they are removed from the beam by the filters while most of the higher energetic and more penetrating x rays pass through the filters, saving the patient unnecessary radiation dose.

Question 12

12. The purpose of thin aluminum or copper plates that are placed between the x-ray source and the patient is to:
    A. Absorb heat
    B. Improve image contrast
    C. Remove poorly penetrating x rays from the beam
    D. Compensate for excessive tube current
    E. Decelerate high-speed electrons

Answer 12

12. Answer: C
    Explanation:
    The x-ray beam produced by bremsstrahlung* initially contains a considerable amount of poorly penetrating x rays that provide no imaging capability. These poorly penetrating x rays would deposit nearly all their energy into the patient’s tissue if they were not removed from the beam before escaping from the x-ray tube housing**. The thin metal filters preferentially absorb these x rays. Thus they are removed from the beam by the filters while most of the higher energetic and more penetrating x rays pass through the filters, saving the patient unnecessary radiation dose.
    * bremsstrahlung: radiação produzida quando cargas elétricas sofrem desaceleração. A palavra de origem alemã significa: Bremsen= frear e Strahlung= radiação.
    ** abrigo, encaixe, carcaça, invólucro.
    Author: Louis K. Wagner, PhD

Question 13

13. To reduce dose rate to the patient during fluoroscopy, the operator can adjust a control so that the unit operates at a lower tube current per pulse with the pulse rate remaining the same. The trade-off for this action is:
    A. Less edge enhancement.
    B. Increased contrast.
    C. Increased quantum mottle.
    D. “Sticky” motion (increased jitter).
    E. Increased image lag (ghost images).

Answer 13

13. Answer: C
    Explanation:
    Lowering the tube current decreases x-ray production because fewer electrons are used to produce the bremsstrahlung* beam. The system knows that this will result in a dimmer image and makes adjustments to the optics or other component of the image chain** to account for this change in operation. The end result of this action is that fewer x rays contribute to the image. This increases the prominence of the fine grainy mottle that is characteristic of fluoroscopic images.
    * bremsstrahlung: radiação produzida quando cargas elétricas sofrem desaceleração. A palavra de origem alemã significa: Bremsen= frear e Strahlung= radiação.
    ** Beam: feixe
    ** Dimmer: obscura
    ** Chain: cadeia
    ** grainy mottle: Mancha granulada
    Author: Louis K. Wagner, PhD

Question 14

14. In principle, the average dose rate to the patient can be reduced by applying variable pulsed fluoroscopy because:
    A. Quantum mottle can be less.
    B. The beam becomes more penetrating.
    C. Filtration increases.
    D. kVp increases.
    E. Lower pulse rate can be employed.

Answer 14

14. Answer: E
    Explanation:
    Variable pulsed fluoroscopy saves dose to the patient by taking advantage of the fact that different imaging tasks require different levels of dynamic discrimination. Sometimes 30 images per second are required for the perception of fine movement, but for many medical tasks 15 or even fewer frames per second are all that is needed. By eliminating unnecessary x-ray pulses from the pulse rate, dose to the patient is more appropriately limited. Since this is not an automatic adjustment, the operator must specify the pulse rate for each portion of the procedure.
    Author: Louis K. Wagner, PhD

Question 15

15. Which one of the following has the greatest effect on increasing contrast during fluoroscopy?
    A. Using a grid
    B. Using pulsed fluoroscopy
    C. Moving the patient closer to the image receptor
    D. Increasing kVp
    E. Increasing Ma

Answer 15

15. Answer: A
    Explanation:
    Scatter radiation* from the patient kills contrast. Moving the patient closer to the image receptor would have no beneficial effect on removing scatter. Scatter radiation is to x-ray imaging as fog is to sight seers** – it destroys the view. Grids are designed to block scattered radiation from reaching the image receptor while allowing a good majority of the imaging x rays to pass unimpeded. Grids dramatically improve image contrast. Higher kVp increases beam** energy which generally decreases contrast because higher energy beams are less sensitive to the differences in atomic composition of neighboring tissues. Changing mA or pulse frequency affects image factors like noise and dynamic discrimination, but not contrast.
    Author: Louis K. Wagner, PhD
    * Scatter radiation: radiação de dispersão.
    ** sightseers: turistas, sightseers: videntes.
    ** beam: feixe.

Question 16

16. If kVp, pulse rate, pulse width, and beam filtration are unchanged and only the tube current (mA) is doubled, dose rate to the patient:
    A. Is reduced by a factor of four
    B. Is halved
    C. Remains the same
    D. Is doubled
    E. Is quadrupled

Answer 16

16. Answer: D
    Explanation:
    Since x-ray production is directly proportional to the number of electrons being stopped in the tungsten target, and since dose rate is directly proportional to the rate at which x rays strike the patient, the dose rate is doubled if the tube current is doubled.
    Author: Louis K. Wagner, PhD

Question 17

17. A physician wears x-ray attenuating surgical gloves and has to place his/her hands in the center of the fluoroscopic x-ray field during a procedure. How does the automatic exposure rate control respond?
    A. X-ray pulses decrease in frequency.
    B. Dose rate increases.
    C. kVp decreases.
    D. mA decreases.
    E. No change occurs.

Answer 17

17. Answer: B
    Explanation:
    Since the gloves are designed to attenuate x rays, the gloves effectively block radiation from reaching the image intensifier. This causes a drop in image brightness and the ABC responds to this by signaling the AERC* to increase until the gloves are sufficiently penetrated to overcome the attenuation, bringing the image back to its proper brightness. Thus, dose rate to the patient increases; scatter radiation in the room goes up; and the dose rate to the operator’s fingers and hands remain the same or increases as a result.
    *AERC: the automatic exposure rate control
    Author: Louis K. Wagner, PhD

Question 18

18. When created in the x-ray tube, x rays emanate from an area on the tungsten target that is approximately what dimension in size?
    A. 1 mm
    B. 5 mm
    C. 10 mm (1 cm)
    D. 10 cm
    E. 25 cm

Answer 18

18. Answer: A
    Explanation:
    The area from which the x rays emanate, usually called the focal spot, must be very tiny to maintain image sharpness. The larger the focal spot the worse the image quality. Conversely, the smaller the focal spot the sharper the image. However, there are other physical constraints that limit just how small the focal spot can get. The most important constraint is generation of high-temperatures in the small area. These temperatures can reach levels sufficient to damage the anode. Thus a finite-sized but small focal spot is necessary to render a decent image quality. The size of the focal spot is typically 1-mm in dimension.
    Author: Louis K. Wagner, PhD
    focal spot: ponto focal.
    **Sharpness: nitidez.
    ** constraints: restrições.

Question 19

19. An increase in which one of the following decreases dose rate to the patient?
    A. Image contrast.
    B. Tube current (mA)
    C. Pulse rate
    D. Beam filtration
    E. Edge enhancement

Answer 19

19. Answer: D
    Explanation:
    The use of a polyenergetic beam is a real nuisance*, but has been the only method available to produce sufficiently intense x-ray beams**. The low-energy x rays that accompany the bremsstrahlung beam must be removed from the beam to prevent dangerous doses to the skin of the patient. Beam filtration does this.
    Author: Louis K. Wagner, PhD
    Nuisance: incômodo.
    ** Beams: feixes.
    ** bremsstrahlung: é a radiação produzida quando cargas elétricas sofrem desaceleração. A palavra de origem alemã significa: Bremsen= frear e Strahlung= radiação.

Question 20

20. Which one of the following is true about the machine component that houses medical x-ray tubes?
    A. X-rays that penetrate the housing are the greatest cause of radiation exposure to fluoroscopy personnel.
    B. X-rays that penetrate the walls of the housing may not exceed levels that are set by the FDA.
    C. A variable-speed rotating fan of lead blades is mounted inside to act as a shutter device for pulsed x -rays.
    D. A lead shutter7 is used to block the x-ray beam port when the x-ray switch8 is not engaged9.
    E. It is coated internally with a highly polished silver plating to prevent x rays from escaping (except through the port).

Answer 20

20. Answer: B
    Explanation:
    The greatest source of radiation exposure to personnel is scattered radiation* emanating from the patient, not leakage radiation** through the x-ray tube housing. Pulsed fluoroscopy and the beamoff/beam-on mechanism is achieved through electrical pulsing and switching, it is not mechanical. X rays would penetrate a polished coating** of silver. The FDA sets the maximum “leakage” of radiation through the walls of the x-ray source at 0.87 mGy/hr at 1 meter from the housing when the machine is operated at maximum rated output** for the maximum kVp under continuous operation.
    Author: Louis K. Wagner, PhD
    scattered radiation: radiação espalhada.
    ** leakage radiation: radiação de vazamento
    **Tube housing: carcaça do tubo
    **switching: comutação, troca.
    **coating: revestimento.
    ***output: saída.
    7shutter obturar
    8switch: interruptor
    9Engaged: acionado.

Question 21

161. The automatic brightness control/automatic exposure rate control sensor is located inside which component of the below figure?

A. A
B. B
C. C
D. D
E. E

Answer 21

161. Answer: C
     Explanation:
     A is the video monitor that only displays the electronic signal presented to it from the video camera.
     B is a digital image processor that only processes images once they are converted to digital format.
     C is a combination lens and television camera that captures the light image from component D. The automatic brightness control senses the brightness of this image and then tells the automatic exposure rate control to adjust accordingly to accommodate for any brightness loss or gain.
     Component D is the image intensifier that captures the x-ray image, converts that image into a light image, then to an electron image, then minifies (1) the electron image to be displayed once again as a light image amplified by a factor of thousands.
     E is the x-ray source housing.
     (1)minifies: reduz.
     Author: Louis K. Wagner, PhD

Question 22

162. For the control panel shown, engagement of which control is most likely to result in a lower dose rate at the cost of less fluent appearance of motion?

A. A
B. B
C. C
D. D
E. E

Answer 22

162. Answer: D
     Explanation:
     D is the control that engages pulsed fluoroscopy. In pulsed mode fewer pictures per second are acquired to define the motion, thus making the fluoroscopic motion less fluent.
     Author: Louis K. Wagner, PhD

Question 23

163. Which control has no effect (higher or lower) on radiation dose rate to the patient?
     A. A
     B. B
     C. C
     D. D
     E. E

Answer 23

163. Answer: B
     Explanation:
     All control B does is rotate the image. No radiation is applied for this function.
     Author: Louis K. Wagner, PhD

Question 24

164. For the buttons circled, engaging which one will result in a change in the continuity of perceived motion?

A. A
B. B
C. C
D. D
E. E

Answer 24

164. Answer: D
     Explanation:
     Pulsed fluoroscopy engaged with less than 30 pulses per second will result in a choppier (1) motion.
     (1)choppier: picada.
     Author: Louis K. Wagner, PhD

Question 25

165. Which control reduces both the relative amount of scatter in the image and the scattered or stray radiation levels in the room?

A. A
B. B
C. C
D. D
E. E

Answer 25

165. Answer: C
     Explanation:
     Applying collimation (1) narrows the amount of tissue that produces scattered radiation both in the image and in the room.
     (1) Collimation: A aplicação de colimação reduz a quantidade de tecido que produz radiação espalhada na imagem e na sala.
     Colimação é o nome que se dá ao processo de alinhamento de lentes ou de espelhos em componentes ópticos, principalmente telescópios.