Breast

Question 1

Why are breasts not treated with parallel opposed AP/PA fields?

Answer 1

The body isn’t symmetrical front to back, which means that the AP/PA dose would be uneven using basic treatment techniques

Other reasons include lung dose concerns and unnecessary spine exposure.

Question 2

What is the maximum allowable amount of tissue from the opposite breast that can be in the treatment field when treating one breast?

Answer 2

2 cm - Two fingers width of contralateral breast tissue is often acceptable

It’s important to avoid healthy tissue in the radiation field to reduce cancer risk.

Question 3

Is it true that common breast treatment techniques include placing the patient in the prone position?

Answer 3

True

The prone position helps reduce radiation dose to the lungs and heart.

Question 4

How many light borders can be traced when drawing the breast treatment field borders?

Answer 4

3

Three borders are present on both the medial and lateral tangential fields.

Question 5

What is one reason patients are traditionally placed on a slant or breast board for radiation treatments?

Answer 5

To compensate for the slope of the chest

Other considerations include preventing the breast from falling superiorly.

Question 6

Which radiation treatment technique is not used after breast-conserving surgery?

Answer 6

Radiation with wide-field electrons

Techniques like supine whole breast irradiation and partial breast irradiation to the lumpectomy cavity are common.

Question 7

True or False: The femoral head is blocked from receiving radiation because it produces blood cells.

Answer 7

False

It is blocked due to concerns with synovial fluid drying out.

Question 8

Which of the following is not considered a critical structure when treating a supraclavicular field?

Answer 8

Eyes

The eyes should be sufficiently superior to the treatment field.

Question 9

What does ‘en face’ mean in the context of electron treatments?

Answer 9

The surface to be treated should be perpendicular to the central axis of the radiation beam

‘En face’ essentially means facing forwards.

Question 10

Why should the radiation therapist be in the room when moving the gantry between field positions?

Answer 10

1, 2, and 3

Reasons include potential collision with the patient’s arm, insufficient camera angles, and the patient panicking.

Question 11

What are the standard tattoos a patient typically receives prior to breast cancer radiation treatment?

Answer 11

One at midline anterior (AP) and two at midline opposing laterals (Lats)

These tattoos serve as permanent reference points for accurately aligning the patient during each treatment session.

Question 12

Why is it crucial to verbally inform a patient before lowering their gown or sheet during breast cancer radiation treatment setup?

Answer 12

To avoid the legal issue of assault

Lowering the gown without explanation could be perceived as unwanted touching and violates patient autonomy.

Question 13

What is the significance of instructing a patient not to scratch, adjust their body, or talk during the leveling process?

Answer 13

To maintain the accuracy and consistency of the treatment setup

Any movement can compromise the precision of radiation delivery.

Question 14

List the four borders needed to establish the breast treatment fields.

Answer 14

• Superior: First costal interspace or just below the clavicular head
• Inferior: 1.5 cm below the inframammary fold
• Medial: Midline of sternum
• Lateral: Mid-axilla line

These borders define the treatment area and ensure adequate coverage while minimizing exposure to healthy tissues.

Question 15

What is the purpose of rotating the gantry to specific angles (300-315 and 120-130 degrees) during the breast treatment setup process?

Answer 15

To visually inspect and adjust the medial and lateral field borders using the field light

This ensures treatment fields align correctly with the intended target volume.

Question 16

Explain the concept of ‘Respondent Superior’ in relation to radiation therapists.

Answer 16

‘Let the master answer’; implies that an employer is liable for the actions of their employees

This doctrine explains the necessity for radiation therapists to follow a doctor’s orders.

Question 17

Describe the purpose of the Supra Clavicular (Sclav) field in breast cancer radiation therapy.

Answer 17

To irradiate the supraclavicular lymph nodes at risk for metastasis

It ensures treatment of any cancer cells that may have spread to these nodes.

Question 18

Why is the Posterior Axillary Boost (PAB) field falling out of favor in clinics?

Answer 18

Due to improvements in technology allowing better targeting of axillary lymph nodes

More precise imaging and treatment planning reduce the need for a separate PAB field.

Question 19

Explain why bolus is often used during scar boost treatments.

Answer 19

To bring the maximum dose closer to the skin surface

Bolus ensures effective treatment of superficial scar tissue.

Question 20

Why are parallel opposed tangential fields used instead of AP/PA fields?

Answer 20

They offer better sparing of the heart and lungs

This reduces the risk of long-term side effects compared to AP/PA fields.

Question 21

What does Sclav refer to?

Answer 21

The supraclavicular lymph nodes

Sclav is an abbreviation commonly used in medical contexts.

Question 22

What is PAB in the context of radiation therapy?

Answer 22

An additional radiation field used to target the posterior axillary lymph nodes

PAB stands for Posterior Axillary Boost.

Question 23

Define Inframammary Fold.

Answer 23

The crease where the breast meets the chest wall

This anatomical feature is significant in breast surgery and radiotherapy.

Question 24

What is the purpose of using a breast board with a slant or incline for treatment?

Answer 24

To help flatten out the angle of the chest for an even radiation beam dose distribution.

Remember that the preference is always to treat a flat surface and get an even dose distribution.

Question 25

Which of the following fields are not generally considered part of a primary breast treatment, and often not calculated in the initial treatment plan dose?

Answer 25

Photon or electron scar/tumor bed boost field ## Footnote Boost fields like scar/tumor bed are usually smaller and planned separately; PAB is typically calculated with the initial dose.

Question 26

What is the correct name for the line where two fields meet in a dual isocenter breast setup?

Answer 26

Match line

Question 27

In a dual isocenter breast setup, what direction is the couch typically adjusted to align the supraclavicular field after tangents are treated?

Answer 27

Vertically

Question 28

What can happen if the couch is adjusted incorrectly in a dual isocenter setup?

Answer 28

A hot spot and a cold spot

Question 29

Why do you adjust the table vertically in a dual isocenter setup?

Answer 29

To correct for a change in depth dose

Question 30

Where do the two isocenter fields (SCLAV and tangents) meet?

Answer 30

On the border between the clavicle and breast tangential areas The tangential area will have on iso-center mark and the sclav another iso-center mark in a two isocenter field treatment. They are two separate treatment areas with abutting fields. When treating a breast mono or singles iso-center breast, you would place the iso-center mark on the match line between the two areas. One of the two opposed jaws (collimators) would close to that line, while the other remained open to treat. they would then do the opposite for the other treatment area.

Question 31

Where do you place the isocenter mark for a single isocenter breast treatment?

Answer 31

On the border between the clavicle and breast tangential areas The tangential area will have on iso-center mark and the sclav another iso-center mark in a two isocenter breast treatment. They are two separate treatment areas with abutting fields. You could draw a match line between the fields, but you would not place your isocenter mark at the intersection. When treating a breast mono or singles iso-center breast, you would place the iso-center mark on the match line between the two areas. One of the two opposed jaws (collimators) would close to that line, while the other remained open to treat. they would then do the opposite for the other treatment area.

Question 32

Which couch adjustments help align tangents with the supraclavicular field in a dual isocenter setup?

Answer 32

Kick the couch and Insert a wedge Unlike a mono isocenter breast treatment field, a dual isocenter requires a straight match line. Due to divergence on the tangential fields, kicking the couch helps their superior border remain parallel to the inferior border of the sclav field where the match line is located.

Question 33

What angle is typically used when kicking the couch in a dual isocenter breast setup?

Answer 33

5 to 15 degrees

Question 34

Which direction do you kick the couch in a dual isocenter setup?

Answer 34

Patient’s feet away from the gantry Patient's feet towards the gantry would actually increase the angle in relation to the sclav field, not make it parallel.

Question 35

What is the most likely situation requiring bolus on tangents?

Answer 35

The patient had a radical mastectomy and you need to keep the dose close to the surface because all of the tissue and muscle is gone. The only reason you would use bolus on a full breast is because the cancer is on, or very close to, the skin's surface. This also means that no breast surgery was likely used. This is rare and an unlikely situation. A lumpectomy means that the remaining breast needs to be irradiated. Unless the lumpectomy surgery left the breast completely misshapen, you wouldn't worry or compensate for a minor indentation. After all breasts are irregular shapes in general. A radical mastectomy leaves little tissue, but a worry concerning microscopic cancer remaining. This is common and practical use of bolus.

Question 36

What is the most important advantage of prone breast positioning?

Answer 36

Little to no lung tissue is in the tangential breast fields Avoiding the erythema and dose buildup caused by the breast tissue touching the chest wall tissue is also a good answer. however reducing unnecessary dose to the lungs, and potential secondary radiation induced malignancy in the future, is more important than reducing side effects of dose buildup caused by skin on skin. The inframammary fold area was going to get some dose regardless of positioning, while it may be possible to completely avoid the lungs.

Question 37

Which patient benefits most from prone positioning during breast treatment?

Answer 37

A patient with pendulous breasts The correct answer is a patient with pendulous breasts because in the prone position they will fall away from the chest wall. The other patients listed, probably have breasts that would remain close to the chest wall and negate the prone position advantage. In addition, a patient with back problems might find the prone position to be very uncomfortable. It is not uncommon for women with large breasts to suffer from back problems.

Question 38

What anatomical landmark is typically used for the superior border of the left breast tangential field?

Answer 38

First intercostal space

Question 39

What anatomical marker is used for the inferior field border of a left breast tangential field?

Answer 39

1.5 cm inferior to the inframammary fold

Question 40

What is the maximum amount of contralateral breast tissue that is permissible in a tangential field?

Answer 40

2 cm is generally considered the maximum permissible of contralateral tissue The generally acceptable answer is that 2 cm of contralateral breast tissue is permissible. Increasing the angle on the medial treatment field would greatly increase lung and possibly heart dose.

Question 41

You are setting up a left breast tangential field. The lateral border can be considered to be approximately mid-axillary or 2 cm beyond the breast tissue. How do you check lateral border positioning with the Linac field light for breast setup?

Answer 41

Set the lateral field tangential field and use the field light to visually observe You can only see the lateral field border using the light field with the gantry in the lateral treatment position. Just because the ribs align using the DRR and KV imaging does not mean you have correct lateral positioning. Patients can be rotated or have breasts that, in reality, do not conform to the plan. You need to check positioning based on the plan before starting the treatment.

Question 42

When treating breast cancer, the gantry is often rotated on the supraclavicular field to avoid what structure(s)?

Answer 42

Esophagus and spinal cord

Question 43

What is the typical degree of gantry rotation for a supraclavicular breast field?

Answer 43

10 to 15 degrees

Question 44

What condition usually justifies the addition of a supraclavicular field in a breast treatment plan?

Answer 44

4 or more positive lymph nodes See " Portal design in Radiation Therapy" page 71; "A supraclavicular field is generally treated in patients with four or more positive lymph nodes or extracapsular extension".