RTTT 214 midterm 2020

For nonisocentric treatment techniques, ______ is the factor of choice to demonstrate central axis dose at a given depth.

%DD

A wedge pair technique may effectively treat to a tumor depth of:

0-7cm

The use of bolus: 1. compensates for surface irregularities 2. increases the skin dose by eliminating skin sparing 3. corrects for internal heterogeneity

1 & 2

The wedge angle is determined by the tilt of the isodose lines at: 1. The 50% isodose line in low energy beams 2. A depth of 10 cm for high energy beams 3. The depth of the 20% isodose line in high energy beams 4. The depth of 5 cm for low energy beams

1 & 2

Dose volume histograms (DVHs) are useful to: 1. provide a graphic display of dose tot he target 2. optimize the radiation treatment in a reasonable time 3. give a good representation of the dose received by the normal structures 4. indicate precisely the extreme dose (hot spot) in the volume treated

1 & 3

Surface dose: 1. increases with field size 2. increases with beam quality 3. is more for electron beams compared to photon beams 4. can be measured using a Farmer chamber

1 & 3

Tissue-air ratio (TAR) is dependent on: 1. beam energy 2. depth 3. field size 4. source-to-surface distance (SSD)

1, 2, 3

Which factors influencde the construction of a PTV from a CTV? 1. Patient set-up uncertainty 2. Organ motion 3. Proximity of critical structure 4. Extent of microscopic disease

1, 2, 3

Image-guided radiation therapy can be accomplished with: I. Ultrasound units II. CT scanner III. kV imager IV. Cone beam V. Simulator

1, 2, 3, 4

Field weighting: 1. gives the relative contribution of beams to dose at target center or dmax point 2. changes the dose rates at input ports 3. improves dose uniformity across the target 4. reduces dose to normal tissues or critical structures

1, 3, 4

The mean life of a radioactive source is given by:

1.44 T1/2

The depth of the 80% isodose line for a clinical electron beam of energy E (MeV) is approximately given by:

1/3 of E

The therapeutic depth (depth of the 90% depth dose) in cm for a clinical electron beam of most probable energy E (MeV) is approximately given by:

1/4 of E

According to ICRU specifications, the wedge angle is defined at:

10cm depth

The most desirable feature of a wedge pair technique is a __________ beyond the overlap region. I. Rapid dose build-up II. Rapid dose fall-off III. Uniform dose distribution

2 only

During a 4 MV treatment, a sloping skin surface is corrected by a ___________ shift toward the skin surface of the isodose curve.

2/3

According to ICRU-50, the following statement(s) is correct: 1. CTV = PTV 2. Treatment volume <PTV 3. Treatment volume >PTV 4. Treament volume < Irradiated volume

3 & 4

Clinical proton generators consist of: 1. Linacs 2. Microtrons 3. Synchrotrons 4. Betatrons 5. Cyclotrons

3 & 5

The primary transmission for a block used to shield a portion of the field is usually about

3-5%

As a general guideline the appropriate electron energy should be about ______ the maximum depth of the tumor.

3x

The depth dose characteristics of electron and photon beams are similar in which of the following ways? 1. They have a finite range of penetration 2. The percent surface dose in high 3. The percent surface dose increases as the energy increases 4. The percent depth dose increases as the beam energy increases

4 only

A patient is to be treated with a single field of a 16 MeV electron beam. Calculate the depth of the 90% isodose line, along the central axis.

4cm

To produce high quality DRR's CT slice spacing should be no more than:

5mm

The range of penetration of 12 MeV electrons is:

6 cm

The skin dose, in the case of electron beams, is about

80-90%

When planning a GYN implant, which point is dose calculated to?

A

Long forceps are required for direct handling of radioactive sources so that:

Amount of exposure to handler's hands is decreased

Bragg peak is:

An ionization maximum near the end of the range of a heavy charged particle

Which technique is most often used for the treatment of superficial tumors that extend to a depth of 7 centimeters?

Angled fields using wedge-pair technique

At what point does the treatment planning process begin?

CT imaging

The radioactive source inventory room should have a sign that reads:

Caution Radioactive Material

The term image registration applies to a process of:

Comparing and fusing images from one study to those from another

As photon energy INCREASES, surface dose _________ and depth of dmax ___________.

DECREASES, INCREASES

As photon energy increases, surface dose _______ and depth of dmax _______.

DECREASES, INCREASES

The type of radium needles that have a higher activity at both ends are termed:

Dumbbell needles

In stereotactic radiosurgery (SRS):

Geometric accuracy of isocenter localization of +/- 1 mm is acceptable

Which of the following is an advantage of HDR over LDR?

HDR can be given on an outpatient basis

All of the following are true of IMRT except:

IMRT dose distributions are always more inhomogeneous than conventional 3-D plans

As electron energy energy increases, surface dose ___________ and depth of dmax ____________.

INCREASES, INCREASES

The Fletcher's suite application is an example of:

Intracavitary low dose rate brachytherapy

Patients with gynecological malignancies have an increased risk of developing a thrombosis when treated with:

LDR

Why are (125) I and (103) Pd typically used for prostate implants?

Lower energies reduce the dose to surrounding critical structures

What invention allowed IMRT to become a reality?

MLC

Following discharge of a patient who received low dose rate brachytherapy, a room survery should be conducted to:

Make sure that there are no remaining radioactive sources in the room

Target volume delineation for lung tumors may involve cardiac or respiratory gating procedures. The rationale for this is that lung tumors:

Move with cardiac and respiratory motion

Absorbed dose at depth x 100% = absorbed dose at Dmax is the definition of:

PDD

Generally, which term would describe the largest volume of tissue in the patient planning process according to ICRU Report 50?

PTV

The term "step-and-shoot" is sometimes used to describe which IMRT delivery technique?

Segmental MLC - IMRT

Image segmentation refers to:

Slice-by-slice delineation of targets and organs at risk

Absorbed dose at a given depth divided by the dose in air dose at a fixed reference is the definition of:

TAR

The entire right breast will be treated in your patient diagnosed with T1 N1 M0 infiltrating ductal carcinoma. The most likely field arrangement would be:

Tangential fields with subsequent tumor bed boost

In a head and neck treatment where left lateral, right lateral, and anterior fields are commonly used, one of the following statements is not true:

The field junction can be present in the area where the tumor is present

Wedges are used for all of the following except:

To increase the anterior hot spot for a larynx treated with lateral opposed fields

Advantages of intracavitary brachytherapy include: A. preservation of normal anatomy B. sources can be easily placed at the tumor site and removed C. dose is higher to the tumor than adjacent tissues D. all of the above

all

Appropriate disposal of radioactive sources include: A. Transfer to an authorized recipient B. Incineration C. Burial D. All of the above

all

IGRT is useful because it can: 1. result in a more focused treatment 2. account for interfraction and intrafraction motion 3. compare in-room image set with treatment planning image set

all

Organs that can be affected by motion are the: 1. lung 2. liver 3. pancreas

all

The depth of maximum dose for a photon beam is approximately equal to: A. The depth at which dose and kerma are equal B. The maximum range of the secondary electrons C. The depth at which electronic equilibrium occurs D. All of the above E. None of the above

all

The tolerance of normal tissues is related to the: 1. Overall volume irradiated 2. Radiosensitivity of the organ under treatment 3. The time over which the radiation takes place

all

Which of the following factors can be corrected to adjust the isodose lines of beams with oblique incidences? I. PDD II. TAR III. TMR

all

Ultrasound

can be used for localizing tumors and delineating patient contour

Any container in which radionuclides are transported, stored, or used must have a label saying:

caution-radioactive material

Which of the following is most likely to be treated using a remote afterloader?

cervical cancer

Which of the following is not used for brachytherapy treatments?

cobalt

A brachytherapy source is encapsulated to:

contain radioactivity and stop particles other than gamma in delivering tumor dose

A(n) ______________ is a reproduction of an external body shape, usually taken through the transverse plan of the CA of the treatment beam.

contour

One disadvantage of radium is:

decays to radon

Treatment planning and delivery systems are rapidly evolving to accomplish all of the following except:

decrease patient care

As the depth increases, the PDD:

decreases

The therapeutic depth (along beam central axis) for dose prescription is given by (electron beam):

depth of 90% of isodose level

What is(are) spatial representattion(s) of the magnitude of the dose produced by a source of radiation?

dose distributions

Heyman capsules may be used to treat the:

endometrium

The Sterling formula is a method to determine:

equivalent square

The percentage depth dose (PDD) curve is an example of a two-dimensional representation of the variation of dose.

false

A dose-volume histogram

helps in optimizing the treatment plan

"Skin sparing" is reduced in photon beams by all of the following except:

increasing photon energy

Which of the following most significantly effects brachytherapy dose distributions?

inverse square law

A method for correcting an isodose chart for contour irregularities is the:

isodose shift method

What is an advantage of remote afterloading?

limits exposure to patient and personnel

Forced shallow breathing technique is used to control:

motion

During IMRT treatments, how is the intensity of the beam altered?

movement of MLCs

The skin dose can be reduced by using a bolus (of less than the buildup thickenss) for treatment with accelerator photon beams.

no

The shape of the isodose distribution for a tandem and ovid treatment is:

pear shaped

The radiation oncologist should mark on each CT slice:

planning target area

The cyclotron may produce _________ beams.

proton

Which of the following is the most favorable situation for the overall goal of radiation therapy?

radiosensitive tumor and radioresistant normal tissue

Patients can be treated with "mixed beam" - a combination of electrons and low energy photons. The advantage of a mixed beam over electrons alone is to:

reduce skin dose

To beam split means to?

remove divergence

Radioactive sources should be transported around the treatment facility in:

shielded containers

Radiation prescriptions must provide specific information to allow its interpretation by radiotherpay staff. These prescriptions must include:

the anatomical site and total dose to be delivered

When documenting and/or verifying off-axis SSD's, it is important to remember that the ODI is only accurate at?

the central axis

Which of the following represents the ratio of the dose at a given point in a phantom to the dose in free space at the same point?

tissue air ratio (TAR)

Each point along an isodose line has exactly the same dose.

true

TAR is:

used for irregular fields and rotation calculations

An autoradiograph is taken to:

verify uniformity of source

When more than two planes of sources are used, it would be called a:

volume implant

Conformal treatment improves tumor control.

yes

IMRT treatment gives better conformity compared to 3D-CRT treatments.

yes

Organs at risk (OAR) are the critical normal tissues or structures whose irradiation may significantly influence the treatment plan or dose presciption.

yes