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Two missed treatment days due to linear accelerator malfunction:

(A) may be compensated by adding the same or even more fractions to the treatment

course with weekend treatment if possible.

(B) may allow some tumors with high growth fractions and long cell cycle times to recover

through repopulation.

(C) are of major clinical relevance in most cases.

(D) may be made up by increasing the fraction size for the remainder of the treatment

course.

A

For a 4-field box technique, which of the following will deliver the lowest dose to the femoral

heads?

(A) 100 source-to-surface distance (SSD), equal dmax dose to all fields

(B) 100 source-to-surface distance (SSD), equal target dose to all fields

(C) 100 source-to-axis distance (SAD), equal air dose to all fields

(D) 100 source-to-axis distance (SAD), equal target dose to all fields

A

The expression LD 50/60 refers to a whole-body dose which is lethal to 50% of the irradiated

subjects within 60 days. With regard to the hematopoietic syndrome:

(A) The LD 50/60 for healthy, young adults is approximately 325 cGy.

(B) The application of medical care, such as antibiotic treatment, has no effect on the LD

50/60.

(C) An allogenic marrow transplant is not likely to be life-saving if the exposure was greater

than 2 (two) times the LD 50/60.

(D) In humans, the principal cause of death is anemia.

A

The rationale for using a hyperfractionated course of radiation therapy is:

(A) cancer cells have a lower α/β value.

(B) normal late responding tissue has a lower α/β value.

(C) cancer cells has a curvier slope on tissue survival curves.

(D) normal late responding tissue divide faster, therefore recover faster.

B

An unsealed chamber used as a secondary dosimeter gives a reading of 101.0 for a 100

monitor unit exposure at a field size of 10 cm2. If the ambient temperature is 25 degrees C and

the atmospheric pressure is 770 mm Hg, the corrected reading per monitor unit is:

(A) 0.923.

(B) 0.997.

(C) 1.007.

(D) 1.013.

C

If a testicular seminoma is biopsied through the scrotum, what change(s) in the radiation fields

should occur?

(A) The scrotum on the ipsilateral side should only be treated.

(B) The entire scrotal sac should be treated.

(C) The ipsilateral inguinal nodes should be treated.

(D) The inguinal nodes bilaterally should be treated.

C

When an enface electron beam is used for chest wall irradiation, which of the following

describes the dose at the interface between the chest wall and lung?

(A) decreased due to reduced scatter from the lung

(B) decreased due to irregular surface contour effects

(C) increased due to an increase in the electron fluence

(D) increased due to a larger angle of electron scatter

A

Electron beam output factors are corrected for air gaps by using which of the following?

(A) energy coefficient

(B) equivalent thickness

(C) virtual source distance

(D) electron range

C

Where is dose routinely normalized when using a fixed Source to Surface Distance (SSD)

technique?

(A) At isocenter

(B) A tumor depth

(C) At Dmax

(D) On the surface

C

Which of the following is a disadvantage of an anteriorly directed vertex field if a patient’s head

is in a flexed position?

(A) It exits through the chest

(B) It exits through the pharynx and spinal cord

(C) It exits through the eyes

(D) It exits through the posterior scalp

B

From which location do most pancreatic cancers arise?

(A) Head of the pancreas

(B) Body of the pancreas

(C) Tail of the pancreas

A

The mass attenuation coefficient (um) area/ electron is related to the linear attenuation

coefficient (u) by:

(A) Um = Z-ux

(B) Um =u/p x p

(C) Um =u/p

(D) Um =e-ux

C

The collimator scatter factor for any MV x-rays beam:

(A) Is measured in free space with an ionization chamber.

(B) Decreases with the increase of field size.

(C) Does not depend on the field size.

(D) Does not change with the energy of the beam.

A

Treatment of inoperable, unresectable, or recurrent malignant salivary gland tumors using fast

neutrons compared to the use of photons result in:

(A) improved complete response rates for the primary tumor.

(B) improved partial response rates for cervical lymph nodes containing metastatic tumor.

(C) improved five year survival.

(D) unacceptably high acute complication rates.

A

• fast neutrons have higher RBE and were studied specifically for salivary gland tumors

Although they receive the same dose, some tissues exhibit acute radiation damage earlier than

others because they have a:

(A) smaller number of metabolizing cells.

(B) reduced blood flow.

(C) lower number of hypoxic cells.

(D) higher mitotic index.

D

• cells are more radiosensitive when they have a higher mitotic index

According to the National Council on Radiation Protection and Measurements (NCRP) (#116)

guidelines, the annual effective dose limit for continuous exposure to the whole body for the

general public is:

(A) 0.5 mSv (0.05 rem).

(B) 1.0 mSv (0.10 rem).

(C) 15.0 mSv (1.50 rem).

(D) 75.0 mSv (7.50 rem).

B

An orthovoltage beam is used to deliver 350 cGy to a depth of 5 cm. Calculate the timer setting

for an SSD of 52 cm given the following information:

Exposure rate = 128 R/min at 50 cm source-to-surface distance (SSD)

"cGy/R" factor = 0.95 cGy/R

Backscatter factor = 1.17

% depth dose at 5 cm = 63%

Timer error = 0

(A) 3.61.

(B) 3.71.

(C) 4.06.

(D) 4.22.

D

In the convolution superposition algorithm for photon dose calculation which is true.

(A) Dose is calculated from the convolution of KERMA (Kinetic energy released per unit

mass) and dose spread kernel.

(B) Dose is calculated from the convolution of TERMA (total energy released per unit mass)

and dose spread kernel.

(C) Dose spread kernels can only be determined from measured dose distribution data

B

Dose = TERMA x dose spread kernel

Which of the following factors results in an increase in the percent depth dose (PDD) of a

megavoltage beam?

(A) increase the source to skin distance

(B) decrease in source-to-skin distance

(C) decrease in field size

(D) increase in dose rate

A

The contrast resolution for a treatment planning CT scan can be described as a:

(A) function of scanner geometry, including focal spot size, field of view and detector size.

(B) function of the electron density and the atomic number of the tissue within a pixel.

(C) measure of the modulation transfer function and the algorithm characteristics.

(D) measure of the ability to detect objects with small differences in Hounsfield units.

D

• Contrast resolution is the CT scanner's ability to distinguish between tissues/objects that have small differences in attenuation, which appear as small differences in HU.

Which is the most common morbidity that is seen in the radiation treatment of lung cancer with

radiotherapy?

(A) pneumonitis

(B) esophagitis

(C) pericarditis

(D) transverse myelitis

B

• A is common but is a later toxicity

Which of the following would be considering a characteristic of an acceptable tandem and ovoid

insertion on an AP radiograph.

(A) Tandem midway between ovoids

(B) Tandem deviated toward the site of bulky disease.

(C) Ovoids low in the vaginal fornices

(D) Packing material between the ovoid and vaginal wall

A

TAR=

TMR x BSF

Lipowitz's metal is used in place of lead to make customized shielding blocks for which of the

following reasons?

(A) It provides a sharper beam edge.

(B) It requires less block thickness.

(C) It produces lighter blocks.

(D) It has a lower melting point.

D

The correct source-to-tray distance on the therapy machine is 50 cm. If a block is

constructed with the tray distance set at 40 cm, which of the following will result?

(A) The blocked area will be too small.

(B) The block could be in the wrong position on the tray.

(C) The block divergence will not match the beam divergence.

(D) The block will be too far from the patient.

A

C

The most significant factor effecting calculation of dose with tissue inhomogeneity correction is:

(A) energy of the beam

(B) size of inhomogeneity

(C) depth of inhomogeneity

B

A lung tumor is to be treated utilizing a 90 degree arc. For a target volume centered 6.0 cm

below the skin surface, how far below the skin surface should the isocenter be placed?

(A) 2.5 cm

(B) 6.0 cm

(C) 9.0 cm

(D) 12.0 cm

C

• iso needs to be deeper than target for adequate coverage in this case

Accuracy for radiation therapy treatments require accuracy within:

(A) +/- 2%

(B) +/- 3%

(C) +/- 3.5%

(D) +/- 5%

D

Iodine-125 has an exposure rate constant (specific gamma emission) of 1.1 R/hr/mCi and a half

life of 60.2 days. The milligram hour radium equivalency of a permanent implant of a 1 mCi

Iodine 125 seed is therefore:

(A) 193.

(B) 277.

(C) 650.

(D) 1560.

B

For an individual member of the public, the equivalent dose limit to the lens of the eye is:

(A) 50.0 mSv/year (5.00 rem/year).

(B) 17.0 mSv/year (1.70 rem/year).

(C) 5.0 mSv/year (0.50 rem/year).

(D) 1.7 mSv/year (0.17 rem/year).

A

According to NCRP (#116) guidelines, the annual effective dose limit for continuous exposure to

the whole body for the general public is:

(A) 0.5 mSv (0.05 rem).

(B) 1.0 mSv (0.10 rem).

(C) 15.0 mSv (1.50 rem).

(D) 50.0 mSv (5.00 rem).

B

If the exposure rate constant is 0.87 Rcm2

hr-1mCi-1 and the average patient transmission factor

is 0.20, the exposure rate at 12.5 cm for a patient who has been injected with 20 mCi of Tc99m

is:

(A) 18 mR/hr.

(B) 20 mR/hr.

(C) 22 mR/hr.

(D) 25 mR/hr.

B

For quality assurance of brachytherapy treatment planning computers, the dose rates should

agree with published data tables to which of the following degrees?

(A) +- 1%

(B) +- 2%

(C) +- 3%

(D) +- 5%

B

The CT simulation is performed on a scanner that has 2 mm axial resolution. If the slice width is

5 mm, what is the voxel size of the digitally reconstructed radiograph (DRR)?

(A) 4 mm2

(B) 8 mm3

(C) 10 mm2

(D) 20 mm3

D

• voxel size= pixel area x slice thickness

• width x height x thickness

An ipsilateral fibrotic lung lesion was detected after electron arc for breast cancer. The most

probable cause is:

(A) a new metastatic lesion.

(B) improper dosage.

(C) incorrectly chosen energy.

(D) concentrated bremsstrahlung dose.

D

The surface dose for 6 MeV electron beam, based on a 10x10 cm2

field size, is:

(A) 60%.

(B) 70%.

(C) 80%.

(D) 90%.

C

The five-year survival rate for a pancreatic cancer tumor treated with primary radiation is:

(A) 0% to 5%.

(B) 5% to 10%.

(C) 25% to 30%.

(D) 50% to 70%.

A

Which site has been shown to have the smallest setup and alignment discrepancy?

(A) Brain

(B) Head And Neck

(C) Extremities

(D) Pelvis

B

In the pediatric population, the least likely CNS tumor would be :

(A) Medulloblastoma

(B) Anaplastic astrocystoma

(C) Low grade astrocystoma

(D) Ependymoma

D

In malignant tumors of the nasopharynx that spread directly to the middle cranial fossa, what is

the usual route of invasion?

(A) Directly through base of skull bone

(B) Foramen ovale

(C) Foramen lacerum

(D) Foramen rotundum

D

Nonlinearity in the range of CT numbers in tissue densities is due to:

(A) change in the mass number of the tissue.

(B) change in the attenuation coefficients of the tissue.

(C) change in the photoelectric interactions.

(D) change in the atomic number of the tissues.

D

The measured and computer generated isodose curves should agree within:

(A) +/- 3%, 2mm.

(B) +/- 2%, 3mm.

(C) +/- 2%, 2mm.

(D) +/- 3%, 3mm.

B

Dose variation across the field at a specified depth is referred to as:

(A) medial alignment

(B) dose profile

(C) beam profile

(D) lateral alignment

C

On Monday the Ir-192 HDR source activity is 6.67Ci with a treatment time of 800 seconds.

What would be the approximate expected treatment time on Wednesday with source strength of

6.57Ci?

(A) 788s

(B) 800s

(C) 806s

(D) 812s

D