Mosby - Tx Planning Qs Flashcards by Brianne Bradford

The anterior margin flashes over the anterior surface of the neck. The posterior margin includes the arytenoids. The superior margin includes the infra-hyoid epiglottis and the inferior margin includes the cricoid cartilage. This describes the target volume for the treatment of the:
A. salivary gland
B. tonsil
C. true vocal cord
D. oral cavity

C. true vocal cord

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Indian club needles have:
A. gold seed
B. one hot end
C. two hot ends
D. even activity

B. one hot end

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A volume that consists of the demonstrated tumor and any other tissue presumed to contain tumor is called the:
A. integral volume
B. treatment volume
C. target volume
D. irradiated volume

C. target volume

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What thickness of cerrobend would be equivalent to 8 cm of lead?
A. 6.7
B. 7
C. 9.6
D. 12

C. 9.6

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The physical size of the treatment field is defined at the interception of the central axis at the specific isocentric distance and which isodose line?
A. 10%
B. 20%
C. 50%
D. 80%

C. 50%

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The attenuation of Cerrobend is less dense than lead by about:
A. 5%
B. 10%
C. 15%
D. 25%

C. 15%

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Which radioisotope is commonly used for permanent, interstitial implants of the prostate gland?
A. Cesium-137
B. Cobalt-60
C. Gold-198
D. Iodine-131

C. Gold-198

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A 6 MV photon beam on the linear accelerator has an output at isocenter of 1.2 cGy/MU. What is the output at an extended distance of 120 cm?
A. 0.8124
B. 0.9876
C. 1.45
D. 1.776

A. 0.8124

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Which of the following radioisotopes is sometimes administered into the peritoneal cavity in the treatment of gynecological malignancies?
A. Cesium-137
B. Iridium-192
C. Iodine-131
D. Phosphorus-32

D. Phosphorus-32

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In the usual orientation of the three planes with respect to the patient:
A. The transverse plane lies across the patient.
B. The sagittal plane lies across the patient.
C. The coronal plane lies parallel with the x axis.
D. The sagittal plane lies parallel with the z axis.

A. The transverse plane lies across the patient.

Rationale:
The transverse plane corresponds to the axial plane and lies across the patient, dividing the patient into upper and lower halves.

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What is the range in soft tissue of a 12 MeV electron beam?
A. 3 cm
B. 4 cm
C. 6 cm
D. 10 cm

6 cm

Rationale:
The range, in centimeters, of an electron beam in tissue/water is 1/2 of the beam energy.

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Surface mold brachytherapy is appropriate for all of the following except:
A. pelvic sidewall tumors
B. hard palate tumors
C. orbit tumors
D. superficial skin cancer

A. pelvic sidewall tumors

Rationale:
Mold therapy is appropriate in superficially located tumors in the oral cavity, skin, or eye.

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One disadvantage of using a vertex field to treat primary brain malignancies is that the field exits through the:
A. brain and mediastinum
B. pharynx and spinal cord
C. orbits
D. chest

B. pharynx and spinal cord

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The tolerance dose (TD 5/5) for the whole brain is:
A. 45 Gy in 25 fractions
B. 60 Gy in 30 fractions
C. 60 Gy in 15 fractions
D. 45 Gy in 15 fractions

A. 45 Gy in 25 fractions

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In the maintenance phase of managing ALL, whole brain irradiation may be given with the inferior border of the treatment field at the:
A. base of skull
B. mastoid tip
C. cervical spine #2
D. cervical spine #7

C. cervical spine #2

Rationale:
In the maintenance phase of ALL, whole brain irradiation may be administered using the helmet technique where the inferior border is at C2.

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Total dose to the lumpectomy site following accelerated partial breast irradiation utilizing high dose rate brachytherapy will be approximately:
A. 20 Gy
B. 35 Gy
C. 45 Gy
D. 60 Gy

45 Gy

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When using rotational arc therapy, monitor units or treatment time should be calculated using which of the following methods?
A. Mayneord’s factor
B. Paterson-Parker
C. tissue air ratio
D. Clarkson’s

TAR

Rationale:
Rotational arc treatment time/monitor units are calculated using the TAR method.

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Hypogastric lymph nodes would likely be included in radiation field for the treatment of the:
A. base of tongue
B. stomach
C. esophagus
D. rectum

D. rectum

Rationale:
The hypogastric lymph nodes are part of external iliac chain of nodes in the pelvis and would likely be included in fields for rectal carcinoma.

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Isodose curves would shift away from the skin surface for underlying:
1. lung
2. air cavities
3. bone

1 & 2

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The energy loss of megavoltage (MeV) electron beams in water is approximately_____MeV/cm.
A. 10
B. 5
C. 2
D. 3

C. 2

Rationale:
Electron beams lose about 2 MeV per centimeter of tissue.

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Dose rates in air express the dose measured:
A. at 10 cm depth in a phantom
B. without a phantom, with a buildup cap at a certain distance
C. with a phantom, without a buildup cap at a certain distance
D. without a build up cap or phantom with a 10 x 10 cm field size

B. without a phantom, with a buildup cap at a certain distance

Rationale:
Dose rates in air are measured without a phantom and with a buildup cap to achieve electronic equilibrium at a certain distance from the source.

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If the cGy/MU is 1.0 at 100 cm SSD, what is the cGy/MU at 200 cm SSD?
A. 0.25 cGy/MU
B. 2.0 cGy/MU
C. 0.5 cGy/MU
D. 4.0 cGy/MU

A. 0.25 cGy/MU
Inv. sq

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If a patient has a large pelvic tumor involving the bladder and prostate, and there is a presacral mass, the best arrangement would be:
A. opposed anterior and posterior fields
B. opposed lateral fields
C. four-field box technique
D. 90 degree wedged pair

A. opposed anterior and posterior fields

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The depth of electronic equilibrium for a 10 MV photon beam is:
A. 0.5 cm
B. 1.0 cm
C. 1.5 cm
D. 2.0 cm

D. 2.0 cm

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Electron beams are useful in radiation therapy primary because they: A. have a greater biological effect that X-rays B. provide more skin sparing than gamma rays C. have a definite range in tissue D. have maximum LET at electronic equilibrium

C. have a definite range in tissue Rationale: Electrons have a definite range in tissue, making them useful in the treatment of superficial lesions with critical tissues beyond.

The shape of the isodose curves depends largely upon: 1. field size 2. depth dose 3. flattening filters 4. SSD

2 & 3 Rationale: The shape of the isodose curve depends on the field size, filters and accessories such as blocks, wedges, cones and multi-leaf collimators.

The focus-to-film distance on a conventional simulator is 140 cm. A 5 cm wire is placed on the patient's skin. The focus-to-skin distance is 100 cm. The magnification factor is given by: A. 100/5 B. 140/100 C. 100/140 D. 5/100

B. 140/100

#612 The tumor lethal dose of 50 cGy will need to be given to a midline abdominal tumor through a single anterior port using the SSD technique. The abdominal tumor is located at the depth of the 80% dose line, and the spinal cord is at the depth of the 75% dose line. Dose to the cord will be: A. 66 Gy B. 50 Gy C. 47 Gy D. 37.5 Gy

66 Gy Rationale: The spinal cord will receive 47 Gy. You can compute the applied dose by using TD/%DD. 50/.80 = 62.5 Gy and then taking 75% of the applied dose- 62.5(0.75) = 47 Gy. Or use direct proportion; 50 Gy:80% as x:75%.

The field size of an X-ray or gamma ray beam is defined as the area enclosed within the boundary of the __________% depth dose line. A. 50 B. 60 C. 80 D. 100

A. 50

In radiation therapy planning, the x, y, z coordinate system is used to: A. align patients daily for treatment B. describe a point in space relative to isocenter C. describe the location of isocenter D. assure all planes are parallel

B. describe a point in space relative to isocenter

The actual physical dimensions of the tumor, including regions of presumed occult spread, is the: A. absorbed dose volume B. irradiation volume C. treatment volume D. tumor volume

D. tumor volume

The skin dose, in the case of electron beams, is about: A. 80% to 90% B. 30% to 40% C. 100% D. 10%

A. 80% to 90%

Calculate the magnification factor for an object measuring 6 cm on a film. The SOD was 70 cm and the SFD was 100 cm. A. 1.43 B. 0.7 C. 0.08 D. 4.6

A. 1.43

The posterior surface of the patient should be flat when treating the entire spine so that: A. Skin gaps are smaller. B. Dose is more uniform. C. Position is reproducible. D. Patients are most comfortable.

B. Dose is more uniform.

While treating lateral fields in the treatment of the craniospinal axis, to avoid having the caudal margin of the lateral fields diverge into the posterior spine field, the couch should be rotated: A. way from the collimator B. toward the collimator C. until the table is at 5 degrees D. until the table is at 10 degrees

B. toward the collimator

An advantage of using the wedged pair technique is that beyond the point of beam intersection, there is: A. rapid dose buildup B. rapid dose falloff C. isodose uniformity D. heel-effect dose

B. rapid dose falloff

The expected total dose to point A for treatment of the cervix from both external radiation and brachytherapy is approximately: A. 35 Gy B. 70 Gy C. 90 Gy D. 140 Gy

C. 90 Gy

The volume of lung within an anterior supraclavicular field can be reduced when treating breast carcinoma by: A. elevating the arm B. treating the supraclavicular field every other day C. placing the angle board under the chest D. moving the breast down on the chest wall and making the match line as superior as possible

D. moving the breast down on the chest wall and making the match line as superior as possible

The dDmax dose for a 250 cGy tumor dose if the depth dose percentage is 96% would be: A. 240 B. 260 C. 300 D. 350

B. 260 Rationale: Using the applied dose formula. Applied dose = TD/%DD. 250/96% = 260.

When treating the whole brain with opposing laterals, one way to minimize beam divergence into the eye opposite the entrance port would be to: A. rotate the collimator B. center the axis near the lateral canthus C. turn the patient's head slightly away from the beam D. rotate the couch away from the gantry

B. center the axis near the lateral canthus Rationale: Since there is no beam divergence at the central axis, placing the central axis near the lateral canthus and then using beam shaping would minimize beam divergence to the opposite eye.

Partial breast irradiation may involve treatment techniques that employ all of the following except: A. 5-field breast technique B. brachytherapy C. 3-D conformal IMRT D. intraoperative radiation therapy

A. 5-field breast technique

The backscatter factor depends on (select two): 1. field size 2. distance 3. energy 4. time

FS & Energy

The factors that determine the number of treatment fields to be used includes: 1. beam quality 2. adjacent normal tissue 3. tumor depth 4. tumor shape

All

In order to reduce the potential for electron contamination, the preferred material for custom block and compensator holders is: A. foil B. Lucite C. aluminum D. tungsten

B. Lucite

During verification placement imaging for radioactive needles, the image receptor is located 120 cm from the source. The 3-inch needles measure 4.0 cm on the film. How far away were the needles from the image receptor? A. 130 cm B. 120 cm C. 90 cm D. 30 cm

D. 30 cm

A 200-degree rotational arc will be used to treat a pituitary adenoma. The prescribed dose is 180 cGy/day. The daily cGy/degree setting will be: A. 1.11 B. 1.23 C. 0.9 D. 0.81

C. 0.9

The percent depth dose is 91.8% for a 10 MV beam with a field size of 12 x 12 at 5 cm depth and 80 cm SSD. Calculate the percent depth dose for the same field size and depth for 100 cm SSD. A. 81.5 B. 83.8 C. 87.4 D. 92.9

D. 92.9

The shape of the isodose curves depends largely upon: 1. field size 2. depth dose 3. flattening filters 4. SSD

D. 2, 3 Rationale: The shape of the isodose curve depends on the field size, filters and accessories such as blocks, wedges, cones and multi-leaf collimators.

When treating an extremity, the limb should be positioned: A. parallel to the horizontal axis of the beam B. perpendicular to the table C. resting on a sponge D. parallel to the torso

A. parallel to the horizontal axis of the beam

The equivalent square field size must be determined in order to calculate the: A. dose to be delivered to the central axis of an irregular field B. relative dose values from a reference beam C. spread of the beam from a certain distance from the target D. air gap on the patient's external contour

A. dose to be delivered to the central axis of an irregular field

Anatomical data for CT imaging and reconstruction is acquired through the: A. coronal plane B. transverse plane C. sagittal plane D. none of the above

B. transverse plane

A source of I131 has an activity of 2.5 mCi. What is the activity after 12 days? A. 0.9 mCi B. 30 mCi C. 0.21 mCi D. 2.5 mCi

A. 0.9 mCi Rationale: Recall that the half-life of iodine 131 is 8 days. Use the activity formula.

In order to make custom Cerrobend blocks, the following information is needed: 1. target-to-film distance 2. beam energy 3. patient thickness

1. target-to-film distance 2. beam energy Rationale: In order to make custom blocks, the cutter must know the energy of the machine, the target-to-film distance, and the target-to-tray distance.

When using film for portal imaging, the size of the enlarged image or shadow on the film is dependent on: 1. target-to-object distance 2. object-to-table distance 3. target-to-film distance

1 & 3 Rationale: Magnification of objects on film depends on target-to-object distance, target-to-film distance, and object-to-film distance.

A method of radiation therapy in which the source is moved around the patient, but only through certain sectors of a circle is called: A. step and shoot B. arc therapy C. adjacent field technique D. feathering technique

B. arc therapy

A representation of the dose in an irradiated volume, as a function of spatial position along a single line is known as a/an: A. isodose curve B. percent depth dose line C. dose profile D. dose volume histogram Look up in Tx Planning Book

C. dose profile

The natural slope of the chest may cause high dose regions in the upper mediastinum. This area of increased dose may be managed by the use of a: A. bolus B. custom compensator C. bite block D. wing board

B. custom compensator Rationale: The slope of the chest causes uneven dose distribution leading to higher dose regions in the upper mediastinum, where the anatomy is thinner. Custom compensators, standard wedges, or dynamic wedges may be used to produce more even dose distribution.

The width of penumbra increases with increasing: A. SSD B. source to collimator distance C. energy D. SAD

SSD

As SSD increases, depth dose: A. does not change B. increases C. decreases

increases

For patients with bladder cancer, the preoperative radiation treatment fields should be large enough to include the bladder and regional nodes such as: A. obturator and inguinal B. obturator, external iliac, and internal iliac C. hypogastric and external iliac D. external iliac, hypogastric, and inguinal

A. obturator and inguinal

Which radioisotope is commonly used for permanent, interstitial implants of the prostate gland? A. Cesium-137 B. Cobalt-60 C. Gold-198 D. Iodine-131

C. Gold-198 Rationale: Gold-198, Iodine-125, or Palladium-103 seeds are commonly used for permanent prostate implants.

Positron Emission Tomography (PET) is based on imaging with photons produced in: A. pair production B. annihilation of positrons by electrons C. fluorescence caused by positrons in certain screens D. Compton scattering of photons

B. annihilation of positrons by electrons

For a sloping skin surface, even dose distribution and maintenance of skin sparing using a high energy beam can be achieved by using a: A. wedge B. bolus C. laser D. wider beam

A. wedge

Tissue inhomogeneites that may alter dose distribution would include: 1. air cavities 2. lung 3. fat 4. bone

All Rationale: During treatment planning, any tissues without the same density as water may alter dose distribution.

Percent depth dose varies with: 1. depth 2. fractionation 3. field size 4. radiation quality

1, 3 & 4 Rationale: Percent depth dose varies with the depth in tissue, the field size, and beam energy.

The ratio of dose at depth in tissue to the dose at electronic equilibrium on the beam axis is known as the: A. tissue air ratio B. percent depth dose C. scatter air ratio D. field size correction factor

B. percent depth dose Rationale: The percent depth dose is the ratio of dose at Dmax to dose at a certain depth in tissue.

When using lateral and anterior supraclavicular fields to treat a tumor in the oropharynx, the field junction should be placed: A. cephalad of the thyroid notch B. caudal of the thyroid notch C. caudal of the larynx D. cephalad of the mandible

A. cephalad of the thyroid notch Rationale: If field matching is done while treating the oropharynx, the junction can reasonably be placed cephalad, or superior to, the thyroid notch to avoid overdosing the larynx.

A 6 MV photon beam on the linear accelerator has an output at isocenter of 1.2 cGy/MU. What is the output at an extended distance of 120 cm? A. 0.8124 B. 0.9876 C. 1.45 D. 1.776

A. 0.8124 Rationale: The new output can be found by multiplying the old output by the inverse square factor 0.677. Use the inverse square formula.

#436 For a field treated with the isocenter at a depth of 12.5 cm on a 100 cm SAD linear accelerator, the collimator setting is 20 x 25. The field would measure ______ on the patient's skin surface. A. 20 x 25 B. 7.5 x 12.5 C. 17.5 x 21.9 D. 22.9 x 28.6

C. 17.5 x 21.9 Rationale: Use direct proportion. Figure the SSD: 100-12.5 = 87.5 cm. The collimator setting is the measured field size at isocenter. 20:100 as x:87.5. Do the same for the length.

#530 The isodose chart shown is for an electron beam energy of approximately: A. 5 MeV B. 7 MeV C. 9 MeV D. 12 MeV

9 Rationale: Using the rules for electron energy and isodose depths, you can apply the 80% rule: E/3 = 3 cm (depth of the 80% dose line).

#531 The 50% isodose line for a 12 MeV electron beam would be at an approximate depth of: A. 3 cm B. 4 cm C. 5 cm D. 6 cm

5 Rationale: Use the rules for electron beam therapy: 4(E) = depth of 50% isodose in millimeters. 4(12) = 48 mm or E = 2.5 x depth of 50% isodose in centimeters. 12 = 2.5(x).

External beam radiation for cancers of the midesophagus is best delivered using: A. anterior field only B. right and left lateral fields C. posterior and two posterior obliques D. anterior and two posterior obliques

D. anterior and two posterior obliques Rationale: Feedback: The middle section of the esophagus is best treated with an anterior and two posterior obliques to adequately deliver dose to the volume while sparing the dose-limiting spinal cord.

The volume larger than the treatment volume receiving some significant dose is the: A. tumor volume B. target volume C. irradiated volume D. clinical volume

B. target volume

What would be the finishing angle for a clockwise rotational arc starting at 280 degrees with an MU setting of 205 and MU/degree of 1.21? A. 94 degrees B. 101 degrees C. 89 degrees D. 132 degrees

C. 89 degrees Rationale: Draw the gantry dial. Compute the number of degrees rotated when administering 205 MU. 205/1.21 Mu/dgree = 169 degrees. Then, count degrees from the starting angle.

Radiation therapy to treat medullary thyroid cancer requires large treatment portals that include: 1. the lesion 2. bilateral supraclavicular nodes 3. superior mediastinum

All Rationale: If medullary thyroid cancer is treated with radiation, the field will include the lesion, bilateral supraclavicular nodes, and superior mediastinal nodes.

All thermoplastic materials need some kind of base plate support on the couch top. It is preferable to have these plates made of: A. high-density material B. nontissue equivalent material C. carbon fiber material D. Lucite

C. carbon fiber material Rationale: The base plate support for thermoplastic immobilization devices should preferably be made of carbon fiber due to its low attenuation.

When comparing an isodose profile from a linear accelerator with one from an orthovoltage machine, the linear accelerator isodose will have the following characteristics: 1. greater penetration 2. greater side scatter 3. higher % DD at depth 4. flatter isodose lines

1, 3 & 4 Rationale: The linear accelerator beam will be of greater energy so it will show greater penetration, less side scatter, higher percent depth dose and flatter isodose lines.

A patient is treated on a linear accelerator. The treatment distance is 94 cm SSD. The TAR at the treatment depth is 0.888 and the output is 1.02 cGy/monitor unit. How many monitor units are required to deliver 100 cGy? A. 98 MU B. 110 MU C. 113 MU D. 100 MU

B. 110 MU Rationale: Use the monitor unit formula. TD/output x TAR. Use the factors given.

The linear accelerator dose rate is 250 MU/minute. What will be the treatment time for a treatment field receiving 100 MU? A. 0.4 seconds B. 2.5 seconds C. 4.0 seconds D. 24 seconds

D. 24 seconds Rationale: At 250 MU/minute. Using a direct proportion, it will take 0.4 minutes to deliver 100 MU. Convert the 0.4 minutes to 24 seconds also using direct proportion.

#471 A patient is treated using the SAD technique on a 100 cm isocentric linear accelerator. The field size is 24 x 20. The isocenter is located 5 cm below the patient's skin surface. What does the field measure on the patient's skin? A. 24 x 20 B. 19 x 15 C. 23 x 19 D. 22 x 22

C. 23 x 19

#606 If a tumor receives 225 cGy at a point where the percent depth dose is 75%, the dose at maximum buildup is: A. 150 cGy B. 170 cGy C. 250 cGy D. 300 cGy

D. 300 cGy Rationale: Using the applied dose formula. Applied dose = TD/%DD. 225/75% = 300.

Clarkson's method is used to determine the scatter produced in: A. irregular fields B. rectangular fields C. square fields D. extended fields

A. irregular fields

A large area must be treated measuring 45 x 60 cm. On a 100 cm SAD linac with a limited collimator setting of 40 x 40, a distance of ______ would be required to accommodate this field size. A. 145 cm B. 160 cm C. 95 cm D. 150 cm

D. 150 cm

A good surface landmark to approximate the apex of the lung is the: A. clavicle B. sternal angle C. thyroid notch D. cricoid notch

A. clavicle

For breast irradiation, internal mammary lymphatics would be best treated using: A. an anterior 10 MV photon field B. widened tangential fields C. an anterior electron field D. a posterior electron field

C. an anterior electron field Rationale: Internal mammary lymphatics may be included in tangential fields; however this would increase lung volume. An anterior field could be matched to tangential fields using low-energy photons or electron beam. The electron beam would be best so that dose to limit dose to the mediastinum. Internal mammary nodes are located approximately 3 cm below the anterior surface in patients of normal body habitus.

Where is the depth of the 80% isodose line for 12 MeV electron beam through water?

4cm

In preparation for Fletcher's suite brachytherapy, an orthogonal set of films was acquired on the conventional simulator. The hinge angle for the set of films was: A. 45 degrees B. 90 degrees C. 180 degrees D. not enough information given

B. 90 degrees Rationale: An orthogonal set of films are films taken 90 degrees apart.

When it is determined that an immobilization device is needed, the therapist should: A. make the device, then determine beam orientation B. determine beam orientation, then make the device C. determine device, patient position, and then beam orientation D. make the device, then determine patient position

B. determine beam orientation, then make the device Rationale: Before fabricating a device, the therapist should consider the most appropriate patient position, likely beam orientation, and then which device.

The best position for treating the vertex field is: A. chin extended as much as possible B. chin flexed C. chin turned to one side D. chin extension at 12 cm

B. chin flexed Rationale: The vertex is best treated with the chin flexed. This position makes the field easy to image.

A patient is receiving 3000 cGy total dose to a spine port using the SSD technique. The total given dose is 3636 cGy. What is the percent depth dose? A. 100% B. 120% C. 82.5% D. 75%

C. 82.5% Rationale: Use the applied dose formula. Given dose = TD/%DD. 3636 = 3000/x; 3000/3636 = 0.825.

Diagnostic CT machines are often not suitable for therapy planning because (select two): 1. The table top is concave. 2. The bore is not large enough to accommodate various positions and devices. 3. The slice thickness cannot be varied. 4. The mode can not be switched from axial to helical.

1. The table top is concave. 2. The bore is not large enough to accommodate various positions and devices

When preparing to assist with the administration of iodine based contrast, the therapist should inspect the contrast container and use only when the content is: A. expired B. clear C. viscous D. warm

B. clear Rationale: Before use, contrast should be inspected and be confirmed as clear, not discolored or cloudy, and having a current date.

The range of a 10 MeV electron beam in tissue is approximately:

5 cm

When a missing tissue compensator is used, it should be placed: A. directly on the skin surface B. at some distance from the skin surface C. on the end of an electron cone D. on top of a bolus material at isocenter

B. at some distance from the skin surface Rationale: To preserve the skin-sparing effect, tissue compensators should be placed at least 15 cm from the patient's skin surface.

In one month, the output of a cobalt machine would reduce by about: A. 0.1% B. 1% C. 2% D. 5%

B. 1% Memorize or do math.

If the pituitary gland is treated using a three-field technique, including laterals and vertex fields, wedges will be used in: A. the lateral fields B. all three fields C. the vertex field D. none of the fields

A. the lateral fields Rationale: Due to the contour of the skull in the coronal plane, wedges would be used in the lateral fields only for a midline tumor such as one located in the pituitary gland.