Radiation Therapy Chapter 8

p. 169 16. A shifting field arrangement (feathering) often used in treatment of the brain and spinal cord is used primarily to _______________. a. prevent "hot" spots b. prevent "cold" spots c. increase the dose of the gapped area d. spare overlaying skin tissue

A Abutting field edges produces a "hot" spot where diverging beams overlap immediately below the surface, in spinal cord areas. Feathering (migration of the gap through the treatment course) may be used to blur dose inhomogeneity in gapped areas.

p. 170 20. With high-energy treatment units, compensators may be preferred over bolus because they ________________. a. allow greater skin sparing b. treat the target to a homogeneous dose c. increase the dose to the inferior border d. decrease the exit dose

A Patients rarely have a flat surface parallel with a beam of radiation. Skewing of dose distribution caused by irregular surfaces can be compensated by using bolus material to produce a level treatment area; however, a loss of skin sparing accompanies this technique. To retain this important effect, compensating filters may be positioned in the head of the treatment unit, thus modifying the radiation beam to accommodate the contour of the patient.

p. 157 3. The comprehensive electronic medical record (EMR) in radiation oncology may include all except which of the following? a. Patient's history and physical b. Schedules c. Clinical charting d. Radiation treatment details

A The EMR in radiation oncology may be limited to clinical charting and radiation treatment details. A comprehensive record in radiation oncology may include all medical and administrative aspects of the patient's experience with the radiation treatment center: schedules, communications from referring physicians and external diagnostic facilities, and reimbursement information.

p. 174 24. Where would the radiation therapist find the information regarding the status of the treatment unit? a. Console b. Interlock system of the unit c. Patient record d. Cameras in the room

A The console provides information to the radiation therapist regarding the status of the treatment unit. The use of beam modifiers may require verification of placement to release a safety interlock for treatment.

pp. 166-167 11. Methods of matching abutting fields include all except which of the following? a. Penumbra method b. Gaps c. Feathering d. Use of nondivergent beam edges

A The divergence of a photon beam poses geometrical problems during the alignment of adjacent treatment fields. Matching methods vary with clinical objectives. Common methods include gapping the fields, feathering the fields, and a nondivergent method used with blocks. These blocks are called half-beam blocks, central-axis blocks, or beam splitters.

p. 171 26. The cones used during electron beam therapy extend collimation in order to prevent which of the following? a. Increased electron interactions in air b. Increased dose in the build-up region c. Decreased electron energy away from the virtual target d. Decreased electron frequency away from the virtual target

A The mass and charge of the electron give rise to increased interactions in air compared to those of a photon beam. This scattering of the electron beam necessitates the extension of collimation (field shaping) close to the treatment surface, improving radiation dose distribution by sharpening the dose gradient at the beam edges. Secondary collimation systems for the electron beam take the form of cones attached to the treatment accessory tray of the gantry.

p. 157, box 8-1 9. Individual treatment doses may be defined as which of the following? a. Fractionation b. Protraction c. Treatment field d. Beam modifiers

A The radiation prescription must consist of the anatomic site, total radiation dose to be delivered with its fractionation designated (individual treatment dose), and protraction (period of time over which treatment is given). The prescription also identifies the treatment techniques (number and orientation of treatment fields) to be applied. All of this is accompanied by the physician's signature.

p. 169 19. Which of the following is one of the main advantages of a multileaf collimator (MLC)? a. Correct for tissue inhomogeneity b. Customize treatment volume c. Eliminate skin sparing d. Replace the need for interlock system of holding blocks

B By reducing the need for the position of heavy blocks, an MLC improves customization of treatment volumes and increases safety for patient and radiation therapists.

p. 168, call out 28. Which of the following two-field arrangements is considered parallel opposed? a. Field 1 gantry = 0; Field 2 gantry = 90 b. Field 1 gantry = 310; Field 2 gantry = 130 c. Field 1 gantry = 90; Field 2 gantry = 280 d. Field 1 gantry = 180; Field 2 gantry = 10

B Parallel opposed fields are defined as those with a hinge angle of 180.

1. The radiation therapist is responsible for which of the following? I. Delivering radiation therapy treatments II. Monitoring and operating sophisticated equipment III. Maintaining detailed records of treatment IV. Producing the patient's treatment plan a. I and II b. I, II, and III c. I, III, and IV d. I, II, and IV

B Radiation therapists deliver radiation therapy treatments, monitor and operate sophisticated radiation-producing equipment, and maintain detailed treatment records. Producing the patient's treatment plan is the responsibility of a dosimetrist.

p. 174 17. Which of the following opposing field techniques is specifically designed for treatment of the breast? a. AP/PA arrangement b. Tangential fields c. Box technique d. Right and left laterals

B Superficial volumes on curved surfaces such as the breast or ribs may require opposing fields, which flash off the surface of the patient. These fields are called tangential fields, tangents, or tangs. This is the most commonly used setup treatment for breast cancer.

p. 170 21. Which of the following is the measurement of the angle between central rays of two intersecting treatment beams? a. Wedge angle b. Hinge angle c. Isodose angle d. Central axis angle

B The orientation of multiple fields to one another during treatment may produce inhomogeneous dose distributions over the target volume. The wedge is designed to change the angle of the isodose curve relative to the beam axis at a specified depth within the patient. The hinge angle (measure of the angle between central rays of two intersecting treatment beams) decreases and doses delivered to overlapping areas vary significantly, thus creating areas of high- and low-dose regions in the desired target volume.

p. 175 7. The goal of radiation therapy planning is to deliver an evenly distributed radiation dose to the ________ while minimizing the dose to the normal surrounding tissue. a. isodose lines b. target volume c. hinge angle d. penumbra

B Treatment plans are composed of one or more treatment fields designed to maximize the dose delivered to the tumor while minimizing the dose to normal surrounding structures.

p. 172 15. Based partially on historic studies showing a reduction in treatment error associated with increased portal imaging, ________ portal imaging for radical cases has become an accepted but not universally implemented standard. a. twice-daily b. weekly c. monthly d. initial and final

B Verification portal imaging is usually taken at the initial start of treatment and at regular intervals during the course of treatment. Frequency of portal imaging is based on department policy and professional judgment and varies among institutions. Partially based on historic studies showing a reduction in treatment errors associated with increased portal imaging, weekly portal imaging for radical cases has become an accepted, although not universally implemented, standard.

p. 158 6. Safety and care in the assessment of pain, mobility, and other factors affecting the patient's well-being are the responsibility of which of the following? a. Radiation oncologist b. Patient's family c. Radiation therapist d. Radiation oncology nurse

C As the team member interacting with the patient most frequently, the therapist applies knowledge to the physical and emotional well-being of the patient on a daily basis. When needed, patients are directed to the physician or other professional, as specific needs arise.

p. 174 27. What is the melting point of Cerrobend? a. 74 F b. 100 F c. 165 F d. 212 F

C Cerrobend has a melting point of 165 F (74 C).

p. 157 4. Which of the following is a series of documentation and activities performed with the purpose of optimizing patient care? a. Quality control b. Quality auditing c. Quality assurance (QA) program d. Quality of life

C Regulatory and accrediting agencies establish standards to which a radiation oncology facility must adhere. The QA program consists of activities and documentation performed with the goal of optimizing patient care. The treatment chart is the primary component of an institution's quality assurance program.

p. 170 22. Wedge systems used include which of the following? I. Global II. Universal III. Virtual a. I and II b. I and III c. II and III d. I, II, and III

C Standard wedge systems use externally mounted wedges that must be positioned on a tray above the patient. Treatment units using internal wedging methods allow for customizing the wedge angle for each treatment plan. One system uses a 60-degree universal wedge. Other systems use a virtual wedge system in which a dynamic, or moving, jaw starts at one side of the field and opens to a full field over the course of dose delivery.

p. 171 25. Patients are monitored during treatment delivery with megavoltage treatment units by using which of the following? I. Direct visual II. Closed-circuit television III. Two-way audio a. I and II b. I and III c. II and III d. I, II, and III

C With low-energy treatment, visualization of the patient may be done directly through leaded glass windows. With megavoltage units, an indirect monitoring system must be used. For patient safety and accuracy of treatment, audio and visual contact is maintained at all times, by at least two cameras and an audio system.

p. 175 2. Informed consent consists of which of the following? I. Purpose II. Treatment alternatives III. Benefits and risks IV. Disclaimer a. I and II b. I and III c. I, II, and III d. I, II, III, and IV

D Before receiving treatment, patients must receive an explanation of their status, treatment alternatives, and consequences associated with and without treatment, to provide informed consent to any procedures.

p. 172 18. Bolus comes in many forms and has many applications. Which of the following is not a material that bolus would be made from? a. Vaseline gauze b. Water-filled balloon c. Superflab d. Aluminum covered with paraffin wax

D Common materials for bolus include paraffin wax, Vaseline gauze, wet gauze or towel, and water bags. Commercially available products developed specifically for use in radiation therapy are available in sheets of varying thicknesses and powder forms that can be mixed with water and formed to meet specific needs. Filling a cavity with Vaseline gauze or a water-filled balloon significantly improves the dose distribution in the target volume.

p. 170 23. Which of the following is used in shaping the field of an electron beam treatment? a. MLC b. Bolus c. Aluminum d. Cerrobend cutout

D Electron shielding differs considerably from photon beam treatment. Attenuated much more efficiently, full shielding for electron beams requires lead thicknesses of only several millimeters (general rule: energy in millimeters of lead). Field-defining apertures or "cutouts" can be designed to fit directly inside the electron cone. After completion of a template of the defined treatment area, a model for creation of a Cerrobend cutout is made.

p. 170, call out 13. In radiation therapy, which of the following refers to materials whose interactions with the radiation beam mimic those of tissue? a. Wedge b. Electron cutout c. Internal or external shield d. Bolus

D In radiation therapy, bolus refers to material whose interactions with the radiation beam mimic those of tissue. The purpose of a bolus is to compensate for variation in surface contour or to eliminate air gaps in cavities. Thus, it brings the area of maximum dose deposition to the patient's surface.

p. 173 12. Increased skin doses may be seen on patients caused by the interaction of the photon beam with material used in beam-shaping or modifying devices. Therefore, to prevent electron contamination, all devices must be secured at a minimum of ______ cm from the surface of the patient. a. 3 b. 5 c. 15 d. 20

D Low-energy electrons are absorbed in 15 cm of air; therefore, all beam-shaping and modification devices for photon beams must be secured at a minimum of 20 cm from the surface of the patient.

p. 159 8. Arrange the following tasks involved in delivering a dose of radiation therapy in the proper order. I. Complete the treatment record. II. Initiate the beam-on setting, and monitor the patient and equipment. III. Align the field using lasers, light field, and surface landmarks. IV. Prepare the room. a. I, II, III, IV b. II, I, III, IV c. IV, II, I, III d. IV, III, II, I

D Task analysis for treatment procedures consists of 18 steps, described on page 159, Box 8-1.

p. 169 14. An anterior oblique and posterior oblique treatment field is an example of which of the following? a. Arc therapy b. Four-field box or brick c. Wedge pair d. Parallel opposed portals (POP)

D The most basic multiple-field treatment technique is the POP. Examples of those are anterior/posterior fields, right-and-left laterals, and anterior oblique-posterior oblique.

p. 158 5. Which of the following is not considered a part of the radiation oncology team responsible for the department's quality assurance? a. Radiation therapist b. Dosimetrist c. Radiation oncologist d. Medical oncologist

D The radiation therapist communicates with the radiation oncology team through activities such as weekly chart reviews and through maintaining open lines of communication. The radiation oncology team consists of the radiation oncologist, radiation physicist, dosimetrist, radiation therapist, nurses, support staff members, and clerical staff members.

p. 159 10. Which of the following clinical situations do not lend themselves to the reproducible placement of localization marks? I. Mobile skin surfaces II. Elderly or obese patients III. Areas covered by dressings IV. Sloping surfaces such as the breast a. I and II b. I and III c. I, II, and III d. I, II, III, and IV

D With the patient in the precise treatment position, the isocenter is positioned relative to the localization landmarks. For many clinical situations, this is not practical. Examples include mobile skin surfaces such as those treated with tangential fields, irregular surfaces, and areas covered by dressings.