This figure shows a patient lying on the robotic bed in one of the two gantry treatment rooms. The gantries are used to treat lesions throughout the body. See enlarged image

Pediatric protocols for proton stereotactic radiotherapy include tumors such as:

• Astrocytoma
• Craniopharyngioma
• Ependymoma
• Ewing sarcoma
• Rhabdomyosarcoma
• Tumors of the central nervous system (CNS) such as Medulloblastoma
• Tumors of the eye such as Retinoblastoma

Special care is provided for young children, as they often require administration of general anesthesia for each PSRT treatment session. Board certified anesthesiologist provides this service as a regular part of the pediatric care. Pediatric nurses help the transition for parents and child in the induction and recovery process.

Two-year-old patient, Mary Conroy and her mom Mari-Beth with pediatric nurse Rachel Bolton. Pediatric nurses provide extensive care during the induction and recovery process.

Mary and mom say hello to colorful monkeys as they enter the treatment room. The treatment delivery team includes an anesthesiologist who monitors vital signs during sedation and radiation therapists who align the patient and deliver the radiation.

Adult proton stereotactic radiotherapy protocols include:

• Base of skull tumors such as Chordoma and Chondrosarcoma
• Bone and soft tissue sarcomas including sacral, spinal and paraspinal sarcomas
• Nasopharyngeal and Paranasal Sinus Carcinoma
• Prostate Adenocarcinoma

The series of images that follow demonstrate the radiation dose conformality obtained with proton stereotactic radiotherapy in many areas of the body. In all cases the red area designates the high dose region and the blue area designates the low dose region. Some of the cases have two targets; the first target includes the area of obvious disease and is prescribed to receive a high dose of radiation; the second target with a lower prescription dose includes regions that are at risk of disease.

	Adenocystic Carcinoma of the Lacrimal Gland Proton radiation minimizes the dose to the adjacent brain, brainstem and spares some of the orbit. See Enlarged Image
	Paranasal Sinus Tumor Proton radiation minimizes the dose to the adjacent brain as well as some of the optic structures including the eyes. See Enlarged Image
		Skull Base Chordoma Proton radiation minimizes the dose to the adjacent brain, brainstem and some of the auditory structures. Click on image to see enlarged
		Lumbar Spine Chordoma Proton radiation minimizes the dose to the adjacent kidneys and bowel. Click on image to see enlarged
		Hepatoma Proton radiation minimizes the dose to the adjacent liver and bowel. Click on image to see enlarged

PSRT Planning & Treatment Process

Once a patient is accepted for proton stereotactic radiotherapy they will need to go through a planning process prior to undergoing treatment.

Pictured Above: Immobilization devices minimize motion of the diseased target ensuring that the treatment margins are reduced as much as possible. Different approaches are required depending on the treatment area being considered. These include masks, bite molds, body casts, arm and leg rests…

One of the first PSRT steps is the fabrication of a custom immobilization device. The purpose of the device is to ensure that patients remain as still as possible during the proton therapy treatment enabling us to aim the protons to a targeted area that has very little motion, thereby minimizing the need to treat a larger area which encompasses both the planned target and its motion.

Using the patient specific immobilization device a CT imaging study is obtained. A CT scanner obtains images as if it were slicing through the body like sliced bread. It allows physicians to see internal as well as external anatomy. Contrast material that makes internal body parts more visible is often administered during the study.

The planning process involves outlining the targeted area as well as those normal body structures, which might be of concern if irradiated. An example might be a lesion located near the eyes. In such a case the lesion and any other suspicious tissue would be outlined as a target and the optic structures would also be outlined as critical structures. Once physicians have outlined all structures of interest they define the radiation doses to be delivered. Using the above example the plan would involve delivering the prescribed dose to the target while keeping the dose to the optic structures below a predefined value. At this stage dosimetrists or physicists generate a 3D treatment plan, which models the radiation onto the planning CT according to the dose prescription. Plans are customized to the specific shape and location of the targets being considered. Plan reflects the various directions from which the radiation is aimed.

Once a PSRT plan is finalized and reviewed by physicians special hardware is fabricated for each treatment direction to be used. A thorough quality assurance process ensures that every device being made adheres to the intended specifications. Before devices are used for treatment, measurements ensure that the computer plan is properly modeled.

The whole pre-planning process from immobilization to the first proton stereotactic radiotreatment typically takes a few days to a week.

Depending on the complexity of the cases, PSRT treatment sessions usually last between 20 and 40 minutes. As the treatment session starts the patient is greeted by radiation therapists. The therapists assist the patients onto the treatment bed and into their immobilization device. Once in position the therapists verify the patient’s position by taking x-ray images or using a 3D ultrasound machine. Adjustments are made based on the images and when necessary new images are acquired to confirm the final treatment position. With the patient in the treatment position the therapists request for radiation from the delivery system. Radiation is delivered to one of three treatment rooms sequentially therefore small delays are possible from the time radiation is requested to the time it is ready to be delivered. Only when the delivery system is ready to deliver radiation will the therapists leave the treatment room. Final radiation parameters are confirmed and the radiation is delivered while the therapists monitor the patient via closed circuit video cameras.

Each proton stereotactic radiotherapy treatment session may be slightly different since the proton radiation may be delivered from different directions. X-ray treatments may also be incorporated into the treatment plan. In such cases a different machine called a linear accelerator is used to deliver the radiation. Receiving a limited number of high-energy x-ray treatments in combination with proton therapy does not compromise the overall treatment plan and is sometimes advantageous. X-ray treatments are provided within the same department and are generally quicker than proton treatments.

Physicians and nurses regularly examine patients throughout the treatment course to monitor progress and address any concerns patient may have. Follow-up instructions are provided to monitor patient progress following the treatment course.