Radiotherapy Immobilization PDF

IMMOBILIZATION • Immobilization means “Incapable of movement”. • Radiotherapy is designed very precisely to treat exactly the right area, so it is important to keep that part of the body as still as possible during treatment. • Immobilization device is used to make sure the patient stays in the tre...

IMMOBILIZATION • Immobilization means “Incapable of movement”. • Radiotherapy is designed very precisely to treat exactly the right area, so it is important to keep that part of the body as still as possible during treatment. • Immobilization device is used to make sure the patient stays in the treatment position during the course of treatment. ROLE OF IMMOBILIZATION • Patient positioning and immobilization are said to be the most crucial parts of Radiotherapy Treatment. • For accurate delivery of a prescribed radiation dose to a target volume, while sparing surrounding normal and critical structures. • Without proper immobilization, the patient is at risk for improper treatment and unwanted side effects. • Immobilization such as moulds, casts, headrests and other devices are constructed to reduce setup errors and patient movement during the treatment. • Although the primary goal of immobilization system is to limit patient motion and reduce the probability of major positioning errors. • A well constructed immobilizing system can reduce the time of daily patient setup. • It can make the patient feel more secure and less apprehensive. • To stabilize the relationship between the external skin marks and internal structures. DESIRABLE CHARACTERISTICS OF IMMOBILIZATION DEVICES • Should be transparent to allow visibility of beam light and optical distance indicator. • Should be light weight, strong and durable. • Ease to use. • Ease of making the device. • Comfort for the patient. • Minimal place requirement for the storage. • Resistance of bending and stretching. • Minimal altered of the beam so as not to produce any artifacts in the image acquisitions. • Device be useable on simulator, CT/MRI and other treatment planning imaging system. • Surface dose should not be altered. • Rigid & holds its shape over time. • Laser. • Base plate. • Indexer. • Head supports. • Acrylic mould. • Thermoplastic mould. • Vacuum mould. EARLY 1980 AND ONWARDS NEED FOR A POSITIONING DEVICES • Set up the patient in a special position designed to improve the therapeutic ratio and patient comfort. • Proximity of the target (PTV) to the surrounding radiosensitive structures. • Optimal beam access is limited by external anatomic features such as the extremities, a large belly or a pendulous breast. MATERIALS USED FOR IMMOBILIZATION • Variety of materials and methods are available for immobilization. Selection of the immobilization depends on the comfort of the patient and preferred by the Radiation Oncologist. • Plaster of Paris. • Thermoplastics. • Vacuum bags. • Bite blocks. THERMOPLASTIC MOULD PREPARATION • The most common immobilization device used to treat cancers is Thermoplastic. • Available in different sizes and shapes. • It is rigid in room temperature. • When it heated in water ( for temperature 60 to 65 degree) the material softens and become malleable. • When it is wet, it is placed over the patient body and conforms to the contour of the treatment area. Impressions • Head cast :- Ear impression & Nasal impression. • Head & neck cast :- Ear impression, and sternal notch impression. • Chest cast :- Sternal notch impression. • Abdomen cast :- Sternal notch, umbilicus impression. • Pelvic cast :- Umbilicus impression. ADVANTAGES :Thermoplastic provide great reproducibility in daily treatment, lightweight and easy to use. Additionally modification can be made to mask if the patient experienced with swelling or weight loss during the course of treatment. DISADVANTAGES :Windows cut can not be reused and when old it becomes very soft when activated. TYPES OF IMMOBILIZATION • Head & neck immobilization. • Immobilization in Brain tumors. • Thorax and Breast immobilization. • Pelvic and abdominal immobilization. • Immobilization for the Body extremities. • SBRT solution with AIO Board. HEAD & NECK IMMOBILIZATION • Initial construction and selection of proper immobilization for H&N cancer is one of the most important parts of confirming proper treatment of the patient. • Current methods for the H&N tumors include a variety of masks ,molds, and frame systems. • In some instances, shoulder Retractors are used to pull the shoulders out of the treatment field for the neck. FIXATION BASE PLATE FOR H&N • The plate onto which the head immobilization system is secured is referred to as a base plate. • It is usually made of Perspex or carbon fiber. • It should be low z material and should attenuate the radiation minimally when the beam passes through it. IMMOBILIZATION IN BRAIN For the general brain tumor and whole brain cases the mostly common immobilization device is the 3 clamp thermoplastic orfit. Maxillary antrum tumors :- Pituitary or small brain tumors :- Patient Head positioned with the chin hyper extended to include the superior extent of maxillary antrum in the anterior field without including the eye. Head positioned with neck in extreme flexion. Anterior beam can avoid the dose-limiting structures such as the optic chiasm, the retina, and much of the brain tissue. THORAX AND BREAST IMMOBILIZATION There are 3 common immobilization devices used when treating the tumors in the chest cavity. • VACLOK. • BREAST BOARD. • 2 CALMP OR 4 CLAMP THORACIC MOULD. VACLOK • Consists of light weight plastic mattress filled with radiolucent polystyrene (Styrofoam) beads. • The air is then vacuumed out of the bag for a custom fit and sealed in order to retain the shape. • Advantage: Radio translucent, after treatment the bag is recycle and used for other. BREAST BOARD • It is used specifically for the treatment of breast cancer. • It has several adjustable features to allow for the manipulation of patient arms, wrists, head and shoulders. • Allows the patient to be positioned with the chest wall horizontal avoiding angulation of the collimator. • Breast boards are generally constructed of carbon fiber, thermocol allowing the device to be light weight and durable. • Carbon fiber breast boards have lower attenuation levels, which permit maximum beam penetration. • Takes advantages of gravity to pull the large breast down into better treatment position. BREAST AND LUNG AIO BOARD CARBON FIBER BREAST BOARD 2 CALMP & 4 CLAMP THORACIC MOULD PRONE BREAST PLATFORM SUPPORT • Patient lies in prone position. • Rigid supporting device mounted on the top of the treatment couch. • Involved breast hangs under its own weight through a window in the bottom of the through. • Provides improved separation between the target and the normal tissues. • Lateral tangential beams used for the treatment. • Reduces pulmonary cardiac skin complications. BELLY BOARD IMMOBILIZATION • Belly boards are used when the patient is treated in prone position, it is allow the small bowl to drop below the lateral field to avoid severe side effect. • Use of the belly board minimizes the average volume of small bowel that would otherwise be within the lateral field during the standard box field technique treatment. PELVIC IMMOBILIZATION • There are two important aspects to be followed in the case of Pelvic Immobilization. • Properly maintain patients outer contour during treatment with respect to the iso center. • Other is related to the variation of internal structures during the daily treatment. • Immobilization system such as vac lok, belly board, and thermoplastic masks are commonly used during treatment of pelvic region. • A mould from the patients mid-thorax to upper thigh is made by thermoplastic over the patient and then securing that mask to the pelvic board by a locking system. • Window on either side can be cut, so that the skin tattoos are visible. • Vaclok are popular choice for the hip and pelvic positioning due to the patient comfort and setup reproducibility. IMMOBILIZATION FOR EXTREMITIES • Immobilization for the body extremities is a quite challenge for us, but with this special thermoplastic solution we can perform it easily. • The system consists of a low density carbon fiber base plate with a leg support, two comfort cushions and dedicated masks. The base plate can be indexed to any couch top on 2-pin bars and has multiple holes to offer a maximum of possibilities for positioning and immobilizing both upper and lower extremities. SBRT IMMOBILIZATION SOLUTION • The SBRT Solution provides a precise, stable and easy to use set-up that allows to apply the most effective radiation treatment method for thoracic and abdominal tumors. The SBRT Solution is MR safe. • The long SBRT base plate can be combined with two sets of The AIO Solution, The Breast- and Lung Board Solution The Belly and Pelvic Board Solution. (except the Leg Separator) OTHER ACCESSORIES IN USE HEAD RESTS & WEDGES • Which helps to maintain the position without strain. • The curvature of the patient cervical spine can be altered by changing the support under the head. • Materials Used: Acrylic / Rubber / Polyurethane. INDEXING BAR & SHOULDER RETRACTION • The two pin indexing bar is designed for reproducible positioning and stable fixation of the base plate. • The indexing bar can be placed at the desired indexing indents the couch and can be locked. • Shoulder retraction in patients with short neck or the patients where opp lateral fields are used to treat the neck, The shoulders need to be retracted caudally to avoid entrance and exit doses, and most probably reduce unwanted dose passes through head of the humerus. KNEE REST & FOOT REST • Used to maintain the patient position during pelvis irradiation. • It avoids patient tilt (Rotational error). ORAL PROSTHESIS (MOUTH BITE) • Helps in reproducing the opening of the mouth during the treatment. • Used to minimize the volume of oral mucosa within the treatment field. • The patients mouth kept open by inserting a mouth bite made from dental impression material. • An impression of the patient teeth or gum is made in the soften dental material and within approximately 5 minutes the material becomes hard. CONCLUSION • Throughout this introduction about the immobilization device, it is hoped that the patient understands the importance and its requirement in radiotherapy treatment. • It also hoped that the patient should prepare to give their best possible co-operation and effort during this non painful device fabrication process to give the best outcome. • Proper immobilization will minimize the setup errors considerably in day to day patient setup.