MIXED BEAM MODALITY FOR TREATING SCALP LESIONS: HEAD/NECK SUPPORT AND ALPHA CRADLE® BRAND FOAM

Donland Dea, CMD, RTT
University of California at San Francisco
San Francisco, California

Scalp lesions are actually skin lesions. The most common source of metastases to the scalp in men are due to neoplasm of the lung and kidney. For women the most common source of metastases to the scalp is breast carcinoma.
Finding a technique for treating the superficial malignancies along the entire scalp is not an easy task. When irradiating the scalp, the goal is to deliver a uniform dose throughout the entire scalp while minimizing dose to the brain tissue. This is difficult to achieve due to the surface geometry of the head and the close proximity of the scalp to the adjacent normal brain tissue. Some techniques will irradiate too much of the underlying brain tissue. While other techniques that are highly complex may create field junction problems. A Mixed Beam Modality technique that utilizes lateral opposed photon and electron fields will give sufficient dose coverage throughout the entire scalp. With this technique the normal brain tissue receives minimal dosages. Also, the complexities of simulation and treatment are greatly eased.
The Mixed Beam Modality technique will alleviate the irradiating of the normal brain tissues, optic nerve and chiasm as described by Akazawa (1989). The initial simulation and treatment set up are easier and less time consuming. This technique will provide a more uniform dose distribution, too (Fig. 1).

Fig. 1 Dose distribution for opposed lateral photon electron beams.

MIXED BEAM MODALITY FOR TREATING SCALP LESION
The Mixed Beam Modality technique consisted of opposed lateral beams only. Each side is treated with a low MV photon beam and a low MeV electron beam that are aligned to the same center point on the patient. This makes the set up easier, less time consuming and more reproducible. A custom-made wax bolus that follows the surface dose and reduces the dose to the normal brain tissue, optic nerve and chiasm.
The photon fields are used to cover only the outer areas of the scalp. The electron fields are used to cover the inner areas of the scalp. When treating the outer areas with the photon fields the inner areas are blocked out. When treating the inner areas with the electron fields the outer areas are blocked out (Fig. 2).

Fig. 2 Outer area; photon: Inner area; electron.

For a more accurate and easier set up the patient is placed in a supine position. This position is most comfortable for the patient, therefore, making it easier to align the reference marks that are on the patient. The patient is more likely to remain still for the actual treatment, too.
Because this technique utilizes abutting fields a good immobilizing system is needed to ensure an accurate set up from the first day to the last day of treatment. A problem with abutting fields is that when there is an overlap or separation between fields the dose distribution will be greatly affected. Therefore, a good head/neck supports such as a Timo which is used along with the Smithers Medical Products, Inc. ALPHA CRADLE® brand Patient Repositioning System provides a good, comfortable support for the patient at the same time immobilizes the patient’s head, neck and shoulder regions (Fig. 11). This combination of support and immobilization system makes the set up more accurate, easier, less time consuming and reproducible from the first day to the last day of treatment. The ALPHA CRADLE® foam is used to mold the Timo, and the lower neck and shoulder regions of the patient. It provides a permanent seat for the Timo head/neck support. This enables the patient to lie in the same comfortable position from the first day to the last day of treatment.
The key to any successful treatment with or without a treatment plan is the immobilization of the patient. Patient positioning and comfort are the key in making any type of immobilization system, like the Smithers Medical Products, Inc. ALPHA CRADLE® brand Patient Repositioning System, successful. When the patient is well supported, comfortable and with the help of an immobilization device, the patient can remain motionless for the actual treatment. This helps to ensure an accurate, less time consuming and reproducible treatment.
For this technique a Timo B head/neck support is most often used. The ALPHA CRADLE® form was made using the ALPHA CRADLE® MOLD MAKER II system along with the ACMM Foaming Agents (see making the ALPHA CRADLE® form). A piece of Styrofoam® 5”x 9”x 1” thick is used to elevate the Timo. The Styrofoam® is placed on the bottom of the ALPHA CRADLE® form (the ALPHA CRADLE® form is made on top of the Styrofoam®, Fig. 4). This is to ensure that there is enough clearance for the electron cone. Also, the ALPHA CRADLE® form is made with the Timo B on top (Fig. 5). This provides a seat for the Timo B head/neck support and allows for easy removal of the Timo so that it can be used for other patient’s set up.
After having made the ALPHA CRADLE® form, a wax bolus is made to cover the entire scalp (Fig. 12). It is best to shave the patient’s head. Shaving the head allows the wax bolus to fit better and allows for a more accurate and easier set up on the reference marks that are on the scalp. The wax bolus is used to increase surface dose and to help reduce dose to the normal brain tissues (see the wax bolus).
Once the ALPHA CRADLE® form and wax bolus has been fabricated the actual simulation procedure can be started. With the patient in a supine treatment position (wax bolus in place) set up a lateral field that will cover the involved areas plus a minimum of 1.0 cm of flash around the entire scalp (wax bolus in place). The combination of wax bolus plus flash will provide a more uniform dose distribution around the entire scalp. These patients are set up with the standard treatment distance on the skin (SSD or TSD set up).
Once the field set up has been approved, the wax bolus is removed so as to allow for the marking of the location of the lateral field centers onto the patient’s skin (Fig. 14). Also, for alignment purposes an anterior mark located at mid separation is marked on the patient’s skin (Fig. 15). From the lateral marks, transfer the short axis (anterior to posterior) onto the ALPHA CRADLE® form and from the anterior mark transfer the long axis (superior to inferior) to the ALPHA CRADLE® form.
These three marks on the patient and ALPHA CRADLE® form are used daily to align the patient to the ALPHA CRADLE® form and field centers. These three marks are very important in the alignment of the patient. When used it will make the set up easier, accurate, less time consuming and reproducible from the first day to the last day of treatment.
Place the wax bolus back on the patient and take and X-ray film of the field set up. This X-ray film of the field set up is used to check if the bolus is seated properly on the skin of the patient’s scalp (remold if needed). Also, this X-ray film will be used for the fabrication of the shielding blocks.
Treatment planning is used for selecting the photon and electron energy, the beam weighting, and the blocking that will provide a uniform dose distribution at the same time minimizing the dose to the normal brain tissue, optic nerve, and chiasm.
The Mixed Beam Modality for treating scalp lesions is a very sophisticated technique. It will be a total waste if this treatment cannot be delivered with precision. To assure an accurate and precise treatment of this kind some type of immobilization device is readily needed. It was found that the ALPHA CRADLE® PATIENT REPOSITIONING SYSTEM by Smithers Medical Products, Inc. was the solution in providing excellent immobilization for the patient. This system was easy to use and very, very, very inexpensive. Smithers Medical Products has spent a lot of time and funds in producing a product that is safe and inexpensive to use.
When comparing the amount of time required to make an ALPHA CRADLE® form to that of generating a sophisticated treatment plan, making an ALPHA CRADLE® form is no big thing. An ALPHA CRADLE® Patient Repositioning System is a must when providing a hi-tech state-of-the-art care to a patient. It assures us that sophisticated techniques can be used with accuracy and precision therefore helps give us an ease of mind.

ALPHA CRADLE® FORM PROCEDURE

Place the ALPHA CRADLE® MOLD MAKER II board at the top end of the simulation couch (short end of board toward patient’s head).
Open and remove the two bottles of chemical and polyform bag from the AC325 kit.
Snap open the polyform bag.
Place the polyform bag on top of the ALPHA CRADLE® MOLD MAKER II board (open end toward the right or left side of the patient since it is the widest).
Fold the sealed end (end toward patient’s head) underneath to obtain the desired width (Fig. 3).
Place the 5” x 9” x 1” thick Styrofoam® piece underneath the polyform bag at upper-middle end of the polyform bag (leave a 2” margin at the top end of the polyform bag, Fig.4).
Place a Timo B on top of the polyform bag at the location of the 5” x 9” 1” thick Styrofoam piece (Fig. 5).
Explain the procedure for making and ALPHA CRADLE® form to the patient.
With patient in the supine position, position the patient’s head onto the Timo B head/neck support.
Check to see if patient is comfortable and the polyform bag is wide enough in all directions.
Make adjustment if needed.
Have patient sit up-right without moving in any direction.
Mark the location of the Timo and Styrofoam piece.
Remove and set aside the Timo and Styrofoam piece.
Put on protective gloves, goggles and smock.
Open polyform bag wide at opening so the mixture can easily be poured deep inside.
Grab the top and bottom of the large expandable bottle and expand the bottom portion up to the indicated line (Fig.6).
Pour the entire contents of the non-expandable bottle and expand the bottom portion up to the indicated line (Fig. 6).
With the bottle cap secured, pointed down and away from everyone shake the combined mixture vigorously for 15 seconds (Fig. 8).
Remove the lid slowly (do not re-cap).
Pour the entire mixture into polyform bag (Fig. 9).
When the mixture begins to foam, wait another minute before carefully smoothing as much air out of the poly-form bag as possible (Fig. 10).
Fold the open end of the polyform bag underneath and spread mixture evenly with your hands.
Reposition and align the Styrofoam piece and Timo B to the marked location.
Position the patient onto the polyform bag and Timo head/neck support.
Lift and hold the polyform bag against patient as the foam begins to rise.
Place the dividers into slots on the MOLD MAKER board to help press the rising foam securely against patient to create a customized repositioning mold.
Have patient lie motionless for 15 minutes before removing the ALPHA CRADLE® MOLD MAKER II board from underneath the patient. (Fig. 11).

Fig. 3 Sealed end of polyform bag folded underneath to obtain the desired width.

Fig. 4 Styrofoam® piece placed underneath polyform bag.

Fig. 5 Timo on top.

Fig. 6 Expanding of large expandable bottle

Fig. 7 Pour content of non-expandable bottle into expandable bottle.

Fig. 8 Shake combined mixture vigorously.

Fig. 9 Pour mixture into polyform bag.

Fig. 10 Smooth air out of polyform bag.

Fig. 11 Finished Alpha Cradle® form.

Fig. 12 Wax bolus over scalp.

Fig. 13 Lateral field.

Fig. 14 Lateral field center marked on patient and Alpha Cradle® form.

(diagram)

Fig. 15 Anterior midline mark on patient and Alpha Cradle® form.