Three-Dimensional Conformal Radiation Therapy (3D-CRT)
Tumours are not regular; they come in different shapes and sizes. Three-dimensional conformal radiation therapy, or 3D-CRT, uses computers and special imaging techniques such as CT, MR or PET scans to show the size, shape and location of the tumour as well as surrounding organs. Your radiation therapist can then precisely tailor the radiation beams to the size and shape of your tumour with shielding called multileaf collimators. Because the radiation beams are very precisely directed, nearby normal tissue received less radiation and is able to heal more quickly.
Intensity Modulated Radiation Therapy (IMRT)
Intensity modulated radiation therapy, or IMRT, is a specialized form of 3D-CRT that allows radiation to be more exactly shaped to fit the tumour. With IMRT, the radiation beam can be broken up into many “beamlets”, and the intensity of each beamlet can be adjusted individually. Using IMRT, it may be possible to further limit the amount of radiation received by healthy tissue near the tumour. In some situations, this may also safely allow a higher dose of radiation to be delivered to the tumour, potentially increasing the chance of a cure.
Volumetric Modulated Arc Therapy (VMAT)
Volumetric modulated arc therapy, or VMAT, is a form of IMRT which is a volumetric arc therapy that delivers a precisely sculpted 3D dose distribution with 360° rotations of the linear accelerator. It improves dose conformity, while significantly shortens treatment time and increases precision.
Electron therapy is a type of radiation therapy using electrons that is directed at the surface of the body. This type of radiation goes into the outer layers of the skin, but does not go deeper into tissues and organs below the skin. Using electron beams allows disease within approximately 6 cm of the surface to be treated effectively, sparing deeper normal tissues.
Image Guided Radiation Therapy (IGRT)
Radiation therapists use image guided radiation therapy, or IGRT, to help better deliver the radiation to the cancer since tumours can move between treatments due to differences in organ filling or movements while breathing. IGRT involves conformal radiation treatment guided by imaging such as CT, ultrasound or x-rays taken in the treatment room just before the patient is given the radiation treatment on a daily basis. All patients first undergo a CT scan as part of the planning process. The information from the CT scan is then transmitted to a computer in the treatment room to allow radiation therapists to compare the earlier image with the images taken just before treatment. During IGRT, radiation therapists compare these images to see if the treatment needs to be adjusted. This allows radiation therapists to better target the cancer while avoiding nearby healthy tissue. In some cases, doctors will implant a tiny marker in or near the tumour to pinpoint it for IGRT. This helps to account for organ/tumour motion even if the body is immobilized by a casting device.
Stereotactic Body Radiation Therapy (SBRT)
Treatment outside the brain is called stereotactic body radiation therapy (SBRT), given in a few treatments (typically three to eight). Often used for the lung, spine or liver, it may allow radiation to be given in a way that is safer and more effective than other radiation techniques. Because specialized treatments with stereotactic radiation are often much higher doses than daily radiation treatment, additional precision and quality assurance is necessary. By using a very secure immobilization of the head or body or by using techniques that allow the radiation beam to follow organ motion during treatment, stereotactic radiation offers new ways for your doctor to treat cancer.
Stereotactic Radiation Therapy (Stereotactic Radiosurgery – SRS)
Stereotactic radiotherapy is a specialized technique that allows your radiation oncologist to use extremely focused beams of radiation to destroy certain types of tumours using higher doses than with daily radiation treatments. Since the beam is so precise, your radiation oncologist may be able to spare more healthy tissue. In selected cases, stereotactic treatments can be used to retreat tumours that have received radiation before. Stereotactic radiotherapy originally developed first to treat brain tumours in a single dose. In addition to treating some cancers or benign tumours, radiosurgery can also be used to treat malformations in the brain’s blood vessels and certain noncancerous (benign) neurologic conditions. In some cases, using more than a single dose may help decrease the risk of side effects with stereotactic radiation therapy.
In radiation therapy, a very precisely targeted radiation beam is aimed at a tumor. The goal is to kill cancerous cells while sparing normal, surrounding tissue. This becomes more complicated when treating tumors of the chest and abdomen, which move each time a patient breathes. Respiratory gating is a process for continuously monitoring the movement of tumors during normal breathing. Radiation is only delivered when the tumor is exactly in the right place, and the treatment beam automatically turns off when the tumor moves outside of the target field. This technique is used as part of some radiation therapy treatment plans.
Deep Inspiration Breath Hold
Deep inspiration breath hold (DIBH) is a radiation therapy technique where patients take a deep breath during treatment, and hold this breath while the radiation is delivered. By taking a deep breath in, your lungs fill with air and your heart will move away from your chest. DIBH can be useful in situations where radiation therapy is necessary in the chest region, and it is desired to avoid radiation dose to the heart.
Prone Breast Radiation Therapy
Prone breast radiation therapy is a unique approach to treating breast cancer. Radiation is administered on a specially-designed table with a breast board to help a woman lay comfortably in the prone position, on her stomach with the breast hanging away from the body. The healthy breast is kept close to the body, better isolating the area for treatment. With the breast away from the body, radiation exposure to the surrounding organs and tissues like the heart and lungs, is minimized. This lowers the risk of complications such as future heart disease, lung damage and poor cosmesis.