Intensity Modulated Radiotherapy (IMRT)
Intensity-modulated radiation therapy (IMRT) is an advanced form of three-dimensional conformal radiotherapy (3DCRT). It uses sophisticated software and hardware to vary the shape and intensity of radiation delivered to different parts of the treatment area. It is one of the most precise forms of external beam radiation therapy available. Currently, IMRT is used to treat select patients with prostate cancer, head and neck cancer, gynaecologic cancers, some brain tumors, pediatric and bone & soft tissue tumors. In IMRT, the physician designates specific doses of radiation (constraints) that the tumor and normal surrounding tissues should receive. The physics team then uses a sophisticated computer program to develop an individualized plan to meet the constraints. This process is termed "inverse treatment planning". The treatment plan is then evaluated and finalized before the precise implementation and delivery of the planned radiation using sophisticated linear accelerators under strict quality assurance. Optimal delivery of IMRT is a team effort that includes the radiation oncologist, medical radiation physicist and radiation therapy technologist.
Stereotactic Radiosurgery (SRS)
It is a highly precise technique used to treat brain tumors and other intracranial cancers. Stereotactic radiosurgery involves a single, high-dose application of radiation to the tumor, instead of the many smaller doses given in standard radiation treatment. This technique, which is accurate to one millimeter or less, does not require surgery. Stereotactic radiosurgery includes the participation of the radiation oncology, radiology and surgical team who work together to evaluate and treat each patient. Radiosurgery is limited to lesions that are well-defined and no larger than three to four centimeters. The location of the lesion is also important. For example, lesions too close to radiosensitive structures, such as the optic nerve, are not good targets for radiosurgery. Through the use of three-dimensional computer-aided planning and the high degree of immobilization, the treatment can minimize the amount of radiation to healthy brain tissue. Stereotactic radiosurgery is routinely used for brain tumors and lesions. It may be the primary treatment; utilized where a tumor is inaccessible by surgical means; or as a boost or adjunct to other treatments. Stereotactic radiosurgery is an important treatment option for many patients with abnormal blood vessels in the brain (for example, arterio-venous malformations), solitary metastatic brain tumors, meningiomas and other special tumors of the head and neck regions, such as acoustic schwannomas. Radiation is delivered using a framed system. Several radiation beams are precisely aimed to converge upon a small tumor. The patient lies on a couch that rotates 180 degrees for maximum targeting, without harming surrounding tissues.
Stereotactic Radiotherapy (SRT)
SRT accurately delivers lower doses of radiation over a series of treatment sessions. The overall total dose is higher than with an SRS treatment. Each treatment is called a "fraction" therefore this type of therapy is sometimes called "fractionated" therapy. SRT combines the advanced precision of radiosurgery with fractionated radiation and hence improves delivery compared to standard radiation therapy. Fractionated therapy can be particularly important when the tumor is adjacent to or involving vital neurological structures such as the optic nerve. It can be used in situations where single dose radiosurgery cannot be applied safely. Patients who have larger lesions that are not appropriate for radiosurgery may benefit from the advanced precision and focal radiation applied with SRT. SRT also has ideal application for pediatric patients because compared to conventional radiation it treats a much smaller area of a normal brain. Children are more sensitive to many of the side effects from radiation. SRT utilizes a frame system with a mouth bite which is a painless dental impression that fixes to the upper teeth. . This allows the patient to be precisely positioned on a repeat basis.
Stereotactic Body Frame (SBF) Radiotherapy
Stereotactic body radiotherapy is also called as extra-cranial stereotaxy. This specialized technique of radiotherapy allows very precise delivery of radiation doses to relatively small target volumes situated at sites outside the cranium. Owing to the high degree of precision in radiation delivery and the small volumes of tissue generally treated, it is possible to deliver higher doses of radiation per sitting and thus resulting in shorter duration of total treatment time. For accurate delivery and reproducibility of patients' treatment position, a special device called the stereotactic body frame is used for positioning and immobilizing the patient. The treatment is completely non-invasive requiring no needle sticks or anesthesia for treatment. It is an out-patient procedure requiring no hospitalization. It is also convenient in that it is usually delivered in one to five treatments sessions.
Total Body Irradiation ( TBI )
Conventionally radiation therapy is considered to be a form of localized treatment with the radiation beam directed to the diseased area sparing the surrounding normal tissues as far as possible. In certain conditions like low grade lymphomas radiation can also be delivered to the entire body in low doses either used alone or in combination with chemotherapy to achieve disease control. Low and high dose total body irradiation is also used as a part of the conditioning regimen for bone marrow transplant.
Total Skin Electron Beam Therapy (TSET)
Disease conditions like Mycosis Fungoides primarily involve the skin all over the body. As mycosis fungoides responds very well to radiation, radiotherapy remains the mainstay of treatment of this disease. Total skin electron beam therapy is a specialized technique of radiotherapy which allows the delivery of a relatively uniform dose of radiation (electrons) to the skin all over the body while sparing the underlying structures.
Electron Arc Therapy
This specialized technique of radiation therapy allows delivery of the radiation to flat or curved superficial surface structures like skin, chest wall, abdominal wall, and scalp/ skull while minimizing radiation doses to the underlying structures.
TomoTherapy, or Helical TomoTherapy, is a new way to deliver radiation treatment for cancer, and is the latest in radiation therapy delivery systems. TomoTherapy literally means "slice therapy," and gets its name from tomography, or cross-sectional imaging. The TomoTherapy Hi·Art System delivers a very sophisticated form of intensity-modulated radiotherapy (IMRT), and combines treatment planning, CT image-guided patient positioning, and treatment delivery into one integrated system. The equipment used for TomoTherapy looks much like a CT scanner. The patient lies on a couch that moves continuously through a rotating ring gantry. The gantry houses a small megavoltage linear accelerator, which delivers radiation in the shape of a fan beam as the ring is turning. With the couch moving at the same time the gantry is rotating, the radiation beam makes a spiral (or helical) pattern around the patient, targeting tumors with optimal levels of radiation while minimizing the dose to healthy normal organs and tissues in the region.
The advantage of TomoTherapy is having a radiation treatment beam projected into the tumor continuously as it rotates, rather than having a limited number of fixed beams, each providing only a fraction of the dose necessary to irradiate the tumor. With the TomoTherapy Hi·Art System, it is now possible to adjust the size, shape, and intensity of the radiation beam to target the radiation to the size, shape, and location of the patient's tumor.
Additionally, this unit provides the opportunity to obtain CT images of the body in the treatment setup position, and is hence one of the first devices capable of providing modern image-guided radiation therapy (IGRT). These CT scan images also can be used to precisely place the radiation beam and allow the operator to modify the treatment should the patient’s anatomy change due to weight loss or tumor shrinkage (adaptive radiotherapy).
Image Guided Radiation Therapy
IGRT, or Image Guided Radiation Therapy, is currently one of the most sophisticated methods of radiation therapy delivery in the world. IGRT is the process of frequent two and three-dimensional imaging, during a course of radiation treatment, used to direct radiation therapy utilizing the imaging coordinates of the actual radiation treatment plan. An example of Three-dimensional (3D) IGRT would include localization of a cone-beam computed tomography (CBCT) dataset with the planning computed tomography (CT) dataset from planning. Similarly Two-dimensional (2D) IGRT would include matching planar kilovoltage (kV) radiographs fluoroscopy or megavoltage (MV) images with digital reconstructed radiographs (DRRs) from the planning CT.
Tata Memorial Hospital has just recently acquired the state-of-art Varian Trilogy 3D IGRT system. This linear accelerator has an on-board kv imager that obtains cone beam CT (CBCT) images of the patient daily, at the time of treatment set-up and positioning. This integrated imaging system allows the radiation technologists to verify the position of the tumor before each treatment session, so adjustments can be made online and on the spot to make sure that radiation is delivered exactly where it should be. CBCT based IGRT can result in sub-millimeter accuracy in treatment delivery, and this allows doctors to safely reduce the treatment margins thus increasing dose to the tumor and at the same time significantly reducing radaition dose to critical normal organs near the tumor. Pediatric malignancies, Lung cancer, head and neck tumors, breast cancer, prostate cancer, stereotactic radiosurgery and stereotactic body radiotherapy are just some examples of the treatments commonly performed using IGRT.