Dosimetry Midterm Questions for Final Flashcards
The majority of cancers in the head and neck are
d. Squamous Cell Carcinomas
A bite block is sometimes inserted between the patients teeth because
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
In the treatment of head and neck cancer, immobilization is particularly important because
c. The proximity of several radiosensitive organs and often small tumor margins
To place a very large patient so that the head is in a neutral position
c. A high support is needed under the head
To treat the maxillary Antrum tumor without including the eye
b. the chin is extended and the chin is tilted back
Prior to starting treatment to boost fields, it is a good idea to take portal images because
a. skin and seed markers may have shifted and margins are small
Retinoblastoma is a tumor of the eye that usually occurs in
c. small children
The most common of all intracranial malignancies is
d. metastatic disease
The most commonly occurring cancer in the United States is
b. Lung Cancer
It is important to reproduce the patient’s position
c. As it was during the simulation procedure
Treatment fields in the chest should be designed
c. with respiratory motion in mind
The number of US women who develop breast cancer is
a. 1/8
Cardiac toxicity from breast irradiation is
a. sometimes a serious problem
The most important considerations to avoid radiation induced pneumonitis is
b. Total dose, fractionation schedule, and volume of irradiated lung
The abdomen is defined as
c. The portion of the body that lies between the thorax and pelvis and that contains the peritoneal cavity
The cephalic field margin in whole abdominal irradiation should be set
b. At the superior aspect of the diaphragm in quiet breathing
Generally speaking, the kidney tolerance to irradiation in the adult is
2000 cGy at 180 - 200 per fraction
The most common site of pancreatic tumors is
c. The head of the pancreas
The organs in which normal tissue tolerance is of concern when treating pancreatic tumors are
a. The kidneys, the liver, and the spinal cord
When pelvis irradiation is delivered to an obese patient, the advantage of a prone position is that
b. skin marks are more reliable to set up fields
When pelvis irradiation is delivered to an obese patient in the supine position, the concern is that
c. uncertainty of dose due to variations in patient thickness would be caused when attempts were made to eliminate skin folds
Methods to reduce the volume of small bowel in the pelvis include
a. surgically implanted expander, placement of a mesh sling and a prone position
Patients with carcinoma of the cervix are treated with a combination of external beam and intracavitary irradiation. However
b. In patients w more advanced disease, a larger proportion of the dose is delivered using external beam irradiation
Treating the pelvis and paraaortic lymph nodes in separate fields
c. It is not preferred because of concerns regarding field matching
When a patient is treated for a rectal carcinoma, it is treated in the prone position as opposed to the supine postition
b. The skin reaction between the buttocks is reduced
Of gynecological tumors treated with radiation therapy, the most common type is
c. Squamous cell carcinoma of the cervix
When a large patient is treated for a pelvic tumor using a four field box technique
b. secondary scatter off the collimator and block trays may be a problem
A central pelvis is sometimes used in the treatment of opposed anterior and posterior fields following intracavitary irradiation
a. to protect the bladder, rectum, and tissues irradiated to a high dose via the intracavitary irradiation
To reduce the volume of small bowel within the pelvic field
c. the patient’s position should be prone on a belly board
7.1 The term gross tumor volume, as defined by ICRU, means
c. The gross palpable or visible/demonstrable tumor extent and location of malignant growth
7.2 The term clinical target volume, as defined by ICRU, means
a. A tissue volume that contains a demonstrable GTV and/or subclinical microscopic malignant disease, which has to be eliminated
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
d. Longer in the anterior field than in the posterior
7.6 When parallel opposed fields are used and the isocenter is at mid depth in the chest
the anterior port film should appear
7.6 When parallel opposed fields are used and the isocenter is at mid depth in the chest
a. the anterior port film should appear exactly the same as the anterior simulation w respect to anatomy
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
a. 1.35
135/100
7.13 A treatment-planning CT scan is different from a diagnostic CT scan because
b. In a treatment planning CT scan, the patient is never given contrast
7.14 A contour of a patient taken for calculating an isodose distribution
a. must be accurate because it has an effect on the dose
7.17 Discrepancies in the patient/beam alignment between the first port film and the simulation film may be due to
b. Differences in laser alignment systems, different couch tops, differences in clothing under the patient,
7.18 Uncertainties associated w delivering radiation therapy can be totally avoided by
d. No special means, since there is no method by which all uncertainties can be avoided
7.19 When the treatment fields are designed by the radiation oncologist, margins are always added around a tumor because of
a. Uncertainties in determining the tumor extent, penumbra of the beam, and patient motion
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
d. The collimator may have to be turned in a direction such that the independent jaw cannot be used
8.2 The attenuation of cerrobend is
b. about 15 percent less than lead
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:
b. Practice good hygiene and wash hands before eating, drinking, and smoking
8.5 Multileaf collimators are different from custom-shaped blocks because
a. They produce steplike field edges, leakage can occur between leaves, and they can only be used with limited field sizes
8.6 Custom-made electron shields are different from custom-made blocks for photon beams because
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
8.9 When a lip lesion is treated, it is possible to reduce the mucosal reaction by
b. Placing an internal shield distal to the tumor and covering the shield with wax
8.12 Bolus material is used to
c. reduce the depth of the maximum dose when photon beams are being used
8.14 Departmental weekly chart rounds should include verifying
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
8.15 The frequency of port films varies, but they
c. should always be taken on the first day of treatment
8.17 Various methods of documenting the treatment parameters include
b. Tattoo, photograph of ea treatment field, and a port film of ea field
8.18 If a 30 degree wedge is left out of the treatment during two of five treatments,
d. the central axis dose is increased and the isodose distribution is affected
8.19 When an error in dose delivery is discovered
a. The attending radiation oncologist should be notified
8.20 Treatment field should be labeled in the chart with reference to
b. an anatomic description, and it should have a unique number
16.1 Afterloading techniques were developed primarily to reduce
c. Exposure to personnel
16.2 Radioactive sources frequently used in tandem and ovoids are in the shape of
a. tubes
16.3 Radioactive isotopes used in tandems and ovoids are usually
c. cesium 137
16.4 Point A is defined in gynecological implants to be a point located
d. 2 cm cephalad of the cervical os and 2 cm lateral to the uterine tandem
Ophthalmic plaques can be constructed for use with
all of the above (cobalt 60, iodine 125, ruthenium 106, iridium 192)
isotopes used in permanent implants are most frequently
iodine 125 and gold 198
surface molds can be used to treat all of the following tumors except
a deep-seated tumors in the pelvis side wall
in handling radioactive sources, long-handled instruments must be used to?
reduce the exposure to the hands of the loader
