Dosimetry Midterm Questions for Final

Question 1

The majority of cancers in the head and neck are

Answer 1

d. Squamous Cell Carcinomas

Question 2

A bite block is sometimes inserted between the patients teeth because

Answer 2

b. It helps the patient keep his/her mouth open during treatment so more of the oral mucosa can be excluded from the radiation field

Question 3

In the treatment of head and neck cancer, immobilization is particularly important because

Answer 3

c. The proximity of several radiosensitive organs and often small tumor margins

Question 4

To place a very large patient so that the head is in a neutral position

Answer 4

c. A high support is needed under the head

Question 5

To treat the maxillary Antrum tumor without including the eye

Answer 5

b. the chin is extended and the chin is tilted back

Question 6

Prior to starting treatment to boost fields, it is a good idea to take portal images because

Answer 6

a. skin and seed markers may have shifted and margins are small

Question 7

Retinoblastoma is a tumor of the eye that usually occurs in

Answer 7

c. small children

Question 8

The most common of all intracranial malignancies is

Answer 8

d. metastatic disease

Question 9

The most commonly occurring cancer in the United States is

Answer 9

b. Lung Cancer

Question 10

It is important to reproduce the patient’s position

Answer 10

c. As it was during the simulation procedure

Question 11

Treatment fields in the chest should be designed

Answer 11

c. with respiratory motion in mind

Question 12

The number of US women who develop breast cancer is

Answer 12

a. 1/8

Question 13

Cardiac toxicity from breast irradiation is

Answer 13

a. sometimes a serious problem

Question 14

The most important considerations to avoid radiation induced pneumonitis is

Answer 14

b. Total dose, fractionation schedule, and volume of irradiated lung

Question 15

The abdomen is defined as

Answer 15

c. The portion of the body that lies between the thorax and pelvis and that contains the peritoneal cavity

Question 16

The cephalic field margin in whole abdominal irradiation should be set

Answer 16

b. At the superior aspect of the diaphragm in quiet breathing

Question 17

Generally speaking, the kidney tolerance to irradiation in the adult is

Answer 17

2000 cGy at 180 - 200 per fraction

Question 18

The most common site of pancreatic tumors is

Answer 18

c. The head of the pancreas

Question 19

The organs in which normal tissue tolerance is of concern when treating pancreatic tumors are

Answer 19

a. The kidneys, the liver, and the spinal cord

Question 20

When pelvis irradiation is delivered to an obese patient, the advantage of a prone position is that

Answer 20

b. skin marks are more reliable to set up fields

Question 21

When pelvis irradiation is delivered to an obese patient in the supine position, the concern is that

Answer 21

c. uncertainty of dose due to variations in patient thickness would be caused when attempts were made to eliminate skin folds

Question 22

Methods to reduce the volume of small bowel in the pelvis include

Answer 22

a. surgically implanted expander, placement of a mesh sling and a prone position

Question 23

Patients with carcinoma of the cervix are treated with a combination of external beam and intracavitary irradiation. However

Answer 23

b. In patients w more advanced disease, a larger proportion of the dose is delivered using external beam irradiation

Question 24

Treating the pelvis and paraaortic lymph nodes in separate fields

Answer 24

c. It is not preferred because of concerns regarding field matching

Question 25

When a patient is treated for a rectal carcinoma, it is treated in the prone position as opposed to the supine postition

Answer 25

b. The skin reaction between the buttocks is reduced

Question 26

Of gynecological tumors treated with radiation therapy, the most common type is

Answer 26

c. Squamous cell carcinoma of the cervix

Question 27

When a large patient is treated for a pelvic tumor using a four field box technique

Answer 27

b. secondary scatter off the collimator and block trays may be a problem

Question 28

A central pelvis is sometimes used in the treatment of opposed anterior and posterior fields following intracavitary irradiation

Answer 28

a. to protect the bladder, rectum, and tissues irradiated to a high dose via the intracavitary irradiation

Question 29

To reduce the volume of small bowel within the pelvic field

Answer 29

c. the patient's position should be prone on a belly board

Question 30

7.1 The term gross tumor volume, as defined by ICRU, means

Answer 30

c. The gross palpable or visible/demonstrable tumor extent and location of malignant growth

Question 31

7.2 The term clinical target volume, as defined by ICRU, means

Answer 31

a. A tissue volume that contains a demonstrable GTV and/or subclinical microscopic malignant disease, which has to be eliminated

Question 32

7.4 When parallel opposed fields are used and the isocenter is at mid depth in the chest, the length of the spinal cord is

Answer 32

d. Longer in the anterior field than in the posterior

Question 33

7.6 When parallel opposed fields are used and the isocenter is at mid depth in the chest

Answer 33

the anterior port film should appear

Question 34

7.6 When parallel opposed fields are used and the isocenter is at mid depth in the chest

Answer 34

a. the anterior port film should appear exactly the same as the anterior simulation w respect to anatomy

Question 35

7.7 A circular magnification device, which is 5 cm in diameter, is placed on the patient's anterior surface where the SSD is 100 cm. The simulation film is at 135 cm from the target (TFD). The magnification of the device is

Answer 35

a. 1.35 | 135/100

Question 36

7.13 A treatment-planning CT scan is different from a diagnostic CT scan because

Answer 36

b. In a treatment planning CT scan, the patient is never given contrast

Question 37

7.14 A contour of a patient taken for calculating an isodose distribution

Answer 37

a. must be accurate because it has an effect on the dose

Question 38

7.17 Discrepancies in the patient/beam alignment between the first port film and the simulation film may be due to

Answer 38

b. Differences in laser alignment systems, different couch tops, differences in clothing under the patient,

Question 39

7.18 Uncertainties associated w delivering radiation therapy can be totally avoided by

Answer 39

d. No special means, since there is no method by which all uncertainties can be avoided

Question 40

7.19 When the treatment fields are designed by the radiation oncologist, margins are always added around a tumor because of

Answer 40

a. Uncertainties in determining the tumor extent, penumbra of the beam, and patient motion

Question 41

8.1 When a linear accelerator w one independently moving leaf is used w a wedge in the beam, there is a chance that the independent jaw cannot be used because

Answer 41

d. The collimator may have to be turned in a direction such that the independent jaw cannot be used

Question 42

8.2 The attenuation of cerrobend is

Answer 42

b. about 15 percent less than lead

Question 43

8.4 To reduce the risks of ingestion of small fragments of the alloy in a block cutting room, the following precautions should be taken:

Answer 43

b. Practice good hygiene and wash hands before eating, drinking, and smoking

Question 44

8.5 Multileaf collimators are different from custom-shaped blocks because

Answer 44

a. They produce steplike field edges, leakage can occur between leaves, and they can only be used with limited field sizes

Question 45

8.6 Custom-made electron shields are different from custom-made blocks for photon beams because

Answer 45

d. They have no focused edges and are much thinner; also, the size of the opening is practically the same as the field on the skin surface

Question 46

8.9 When a lip lesion is treated, it is possible to reduce the mucosal reaction by

Answer 46

b. Placing an internal shield distal to the tumor and covering the shield with wax

Question 47

8.12 Bolus material is used to

Answer 47

c. reduce the depth of the maximum dose when photon beams are being used

Question 48

8.14 Departmental weekly chart rounds should include verifying

Answer 48

b. Presence of diagnosis and histology, and stage; presence of consent for treatment; presence of pathology report; presence of dose prescription dated and signed; and weekly port films of each field approved, signed, and dated by the radiation oncologist

Question 49

8.15 The frequency of port films varies, but they

Answer 49

c. should always be taken on the first day of treatment

Question 50

8.17 Various methods of documenting the treatment parameters include

Answer 50

b. Tattoo, photograph of ea treatment field, and a port film of ea field

Question 51

8.18 If a 30 degree wedge is left out of the treatment during two of five treatments,

Answer 51

d. the central axis dose is increased and the isodose distribution is affected

Question 52

8.19 When an error in dose delivery is discovered

Answer 52

a. The attending radiation oncologist should be notified

Question 53

8.20 Treatment field should be labeled in the chart with reference to

Answer 53

b. an anatomic description, and it should have a unique number

Question 54

16.1 Afterloading techniques were developed primarily to reduce

Answer 54

c. Exposure to personnel

Question 55

16.2 Radioactive sources frequently used in tandem and ovoids are in the shape of

Answer 55

a. tubes

Question 56

16.3 Radioactive isotopes used in tandems and ovoids are usually

Answer 56

c. cesium 137

Question 57

16.4 Point A is defined in gynecological implants to be a point located

Answer 57

d. 2 cm cephalad of the cervical os and 2 cm lateral to the uterine tandem

Question 58

Ophthalmic plaques can be constructed for use with

Answer 58

all of the above (cobalt 60, iodine 125, ruthenium 106, iridium 192)

Question 59

isotopes used in permanent implants are most frequently

Answer 59

iodine 125 and gold 198

Question 60

surface molds can be used to treat all of the following tumors except

Answer 60

a deep-seated tumors in the pelvis side wall

Question 61

in handling radioactive sources, long-handled instruments must be used to?

Answer 61

reduce the exposure to the hands of the loader