MEDULLOBLASTOMA IMMOBILIZATION AND TREATMENT CONSIDERATIONS

Edward J. Goldschmidt, Jr.
Cooper Hospital/University Medical Center
Camden, New Jersey

MATERIALS NEEDED:
ALPHA CRADLE®(trademark of Smithers Medical Products, Inc.) brand Mold Maker [includes: slotted board, dividers, chemical set (bottles 1 and 2), plastic bag, protective head cap, protective gloves). Small piece of Styrofoam® for head rest, additional board (12.5 ft. x 1-2 ft. wide x .5-1 inch thick) Spirit level, marker, masking tape, centimeter ruler, and lateral isoline lasers (for optional technique]

INTRODUCTION
For treatment considerations with medulloblastoma immobilization, Alpha Cradle forms accommodate variations in anatomy. The plastic bag enclosed with the Smithers Medical Products, Inc. ALPHA CRADLE® brand foaming agents must be tapered to accommodate there variations in each patients anatomy. The following modified fabrication procedure will suggest approximate measurements. They are included as a benchmark reference only and it should be understood that inherent latitude exists. The latitude is given because of expected differences in patient cooperation and body size.
Since most medulloblastoma patients are children, it becomes advantageous to have more than one person available at the time of the form fabrication and adjustment. Where additional healthcare personnel problems exists, ancillary medical or civilian personnel can be utilized to guarantee the child’s peace of mind. Having the child’s parent or guardian present during form fitting can in most cases expedite the fabrication process without incident. Ancillary personnel will be required only for the form assemble process and will be asked to leave just prior to the simulation procedure. The fabrication guidelines suggested below are easy to follow, accomplish, and show marked reproducibility if done carefully. However, we strongly suggest that any institution wishing to use this procedure first carry out a practice modified ALPHA CRADLE® form on its own before attempting on actual patient.

FABRICATION PROCEDURE
Part One – Tapering the plastic bag for individual patient size.
The intent of tapering the supplied bag is to distribute the SMP ALPHA CRADLE®* form’s foaming agents, to achieve uniform form thickness. Optimum immobilization is achieved through the SMP system when the supplied foaming agents are distributed over a minimally defined surface area. This creates a sturdy immobilization shell which will easily endure through out an entire course of radiotherapy treatments which is typically three to five weeks.

*Registered by Smithers Medical Products, Inc.

Step 1 – To determine the required length of the form bag, have the patient stand erect with neck flexed such that his/her chin can rest in the suprasternal notch area. Next, remove the plastic bag from the ALPHA CRADLE® kit and hold the edge of the open end such that it extends two centimeters superior to the patients lower lip. Hold the edge in place with one hand, and let the bag hang down touching the anterior surface of the patient. Then mark (use marker pen) a small line on the bag at the level of the iliac crest of the pelvis.
Step 2 – To determine necessary bag width, keep the patient in the erect position and carefully wrap the bag around the front of the patient. Be sure the sides of the bags are symmetric with respect to the spinous processes (i.e. sides of bag will touch patients back). Hold bag in place with one hand and with the other palpate the medial edge of the scapula. Mark an additional line corresponding to the medial edge of the scapula. Repeat process for other scapula.
Step 3 – Now fold the sides of the plastic bag to the lines that were just made and tape the folded portion with masking tape lengthwise. The resulting taped creases will now serve as the width of the bag. Next, fold the bottom of the bag to its corresponding marked line and tape the folded portion crosswise. This taped crease will serve as the bottom of the cradle bag.
Step 4 – Place the slotted ALPHA CRADLE® MOLD MAKER on the simulation table lengthwise. The additional board (see materials needed) is placed on top of the slotted board at a midplane patient position. The protective head cap should now be placed on the patient’s head. This will prevent any accidental contact of the foam with the patient’s hair. The supplied gloves should be placed on the fabricators hands before attempting use of the foaming agents, as this will afford the fabricator maximum skin protection. Note that it is imperative that the following steps be performed in an expeditious manner so that the foaming agents do no harden before required. The SMP ALPHA CRADLE® MOLD MAKER kit is equipped with a set of divider boards that fit within the large slotted board. They should be in close proximity to the simulation table at this time.
Step 5 – The SMP ALPHA CRADLE®* MOLD MAKER instruction sheet included with the fabrication kit should be previously read and shall now be readily available during the procedure for reference. During the form construction process, steps 1 through 7 (on sheet) should be done at this time, omitting step 3 (on sheet) as it has already been accomplished (see attached sheet).
Step 6 – After the foam has been poured into the bag, the open end of the bag will be folded over slightly. This creates a crease which must be taped to prevent bag leakage. Next, the additional board is lifted up being careful to keep it as level as possible. This will prevent any uneven rise of the foam. Place it on a previously determined level surface near the simulator table.
Step 7 – With the patient sitting on the end of the slotted board with his/her buttocks completely on the board, have the patient lie back on the board. Place folded sheets underneath the patients occipital region, this will compensate for the patients chin flexion into his/her suprasternal notch. The folded sheets should be adjusted to proved adequate support under the occipital region. The patient’s arms should be straight down at their sides with palms touching the lateral pelvis. The entire spine as well as the patients legs must be straight before attempting to place bag in position. With the patient correctly positioned, the additional board is lifted directly above the patients chest. Next, it is turned over placing the bag on the patients chest, here you will notice a non-uniform distribution of foaming agents in the region of the shoulders and neck. Also, there will be a tendency for these regions to become thicker then the others, but, this you will see is advantageous for the patients immobilization.
Step 8 – Lift the superior end of the bag so that the edge of the bag is at the level of the lower lip. Adjust the bag side to side until the bag is symmetric to the patients width. Make sure the patients chin is resting in the suprasternal notch area, and superior edge of the bag should be at the lower lip. Press the bag slightly against the anterior portion of the mentum with one hand. With the other hand, wrap the excess bag under the patients neck (do this one side of neck at a time). Small dividers should be placed on each side of the neck making sure the bag is kept as close to the skin as possible. The dividers are to be placed in the vertical slots as shown in Diagram 1.
Step 9 – Wrap each side of the plastic bag around each arm and tuck under the posterior surface of each upper extremity. Place the longest divider boards beside the patients arms that are enclosed by the bag. The closest slot should be used to assure a tight fit around the upper arms. The area of the plastic bag around the shoulders should be wrapped under the shoulders with dividers placed parallel to the clavicles in the horizontal slots of the slotted board. The smallest dividers should now be placed around the periphery of the bag and patient as illustrated in Diagram 1.

Diagram 1

Step 10 – The additional board and spirit level are now used to verify the flatness of the anterior ALPHA CRADLE® form. Place the additional board on top of the anterior segment of the bag, keeping the board at rest on the shoulder and anterior chest area. This area should now exhibit some excess foam volume, but the board should not lay over this area. Instead, the board should lie directly underneath the patients chin (The chin will rise with the foaming agents). Next place the spirit level on the additional board keeping its long axis parallel across the patient from right to left (i.e. crosswise). Keep one hand on one side of the additional board, and the other hand on the opposite side of the additional board. Balance the additional board on the patients chest until assurance that the level surface condition is demonstrated. The level surface is critical after the patient is turned prone for simulation and daily treatment.
Step 11 – (OPTION) If a level is not available, then lateral isoline lasers in the simulator room can be used to demonstrate a level condition. Instead of the level, simply raise the simulator table until the lateral isoline lasers skin the top of the additional board from both sides of patient. Adjust the additional board and table height until the isoline lasers are coincident with the boards surface as illustrated in Diagram 2. Caution, before attempting to use the isoline method, be sure to verify that the laser lines are directed parallel with the long axis of the simulation table.

Diagram 2

Step 12 – The patient will be required to stay still in the level position for at least ten minutes. During this time it will be necessary to hold or support the additional board in the level condition throughout this time period until the form is hardened. After it has sufficiently hardened the form is ready for removal.
Step 13 – Next turn both the ALPHA CRADLE® form and additional board over so that the flat surface is in direct contact with the simulator table surface. The form is now ready to receive the patient in the prone position.

Part Two – Patient Forehead Immobilization
The need to flex the chin down into the suprasternal notch of each patient creates a different distance between the simulator table surface and the patients occipital while the patient is in the supine form fabrication position. Once the form with additional board is used for prone treatment a gap between table surface and forehead exists. To immobilize the head region and compensate for the distance from forehead to table, an individual forehead rest is designed in Styrofoam® for each new patient. Styrofoam® is inexpensive and readily available in the majority of radiotherapy centers where low melting allow beam restrictors are used.
Step 1 – Place the child prone into the modified form. Be sure the patients arms are by the child’s sides and that the palms of their hands are touching the lateral pelvis. The child’s chin must be tucked into the groove created during fabrication flexion. In addition, place a 45° angle support sponge under the patient’s ankles for comfort and support during simulation, port filming, and daily treatment. If an angle sponge is unavailable at your facility, several wrapped sheets can be used instead.
Step 2 – The Styrofoam® piece mentioned in the supplies needed section earlier should now be placed directly in front of the patient forehead. Using a magic marker, outline the contour of the patients forehead on the side of the Styrofoam®. This will establish a beginning reference for shaping the Styrofoam® to each patients particular shape. Once the Styrofoam® is appropriately shaped and accurate, line the headrests/patient interface with masking tape and adjust until the patient is comfortable with it.
Step 3 – Place the customized forehead rest on the table and have the child tuck his/her chin down to fit the ALPHA CRADLE® chin saddle resting his/her forehead on the rest. There should not be any space between the forehead and the custom forehead rest at this point. If the child is uncooperative, there may be the need to secure the head and forehead rest attaching a piece of masking tape to the simulator or treatment unit table.
Step 4 – At this point you are ready to ask the parent or guardian to leave the room, make any adjustments to the form that might be necessary, and begin the simulation process.

SUMMARY
We have modified and refined the ALPHA CRADLE® Patient Repositioning System to enhance patient comfort and treatment, as well as alleviate anxiety by allowing the initial form construction process to take place in the supine rather than the final prone treatment position. Using only a few additional readily available tools such as an additional board, a level or lateral isoline lasers, we have been able to produce a modified immobilization device which after fabrication will: 1) guarantee a flat table/patient treatment surface, 2) be light weight and easily moved from one treatment room to another, 3) fills the immobilization requirement by sealing the patient tightly within the form’s grip, 4) demonstrates minimal anterior to posterior spine displacement, and 5) assure on a daily basis geometric dosimetric reproducibility.