Radiation therapy or radiotherapy is therapy using ionizing radiation, generally as part of cancer treatment to cure cancer. These high-energy radiations destroy fast-growing cancer cells by damaging the DNA within these cells. Although normal cells will also be damaged during the process, they possess better self-repairing capability while these damages are way beyond the capabilities of the cancer cells' repair systems.
VMAT is volumetric-arc radiotherapy which delivers a sculpted 3D-dose distribution precisely with a 360-degree rotation of the linear accelerator gantry. With tomosynthesis guidiance and as the gantry rotates, the planned algorithm is able to modulate the speed of the gantry rotation, the shape of the multi-leaf collimator and the dose rate of the beam continuously. This allows for the delivery of high dose radiation to the target while reducing dose to surrounding organs. Literature has shown that arc therapy is effective for a multitude of cancers, including cranial, head and neck, prostate and cervical tumors.
Oncologists can use complete or partial arcs to reduce treatment delivery times up to 50-80% comparing to conventional radiotherapy. For unstable patients (for example patients with irregular breathing pattern), VMAT also allows for increased patient throughput which shortens waiting lists.
As breathings cause movement of tumors, the patient needs to hold his/her breathe during simulation and external beam radiotherapy to increase the operation accuracy. The ABC is therefore used not only to minimize the anatomical movement in the chest and abdomen due to breathing and cardiac motion but also minimizes the radiation dose to the critical organs or normal tissue surrounding the tumor.
In order to achieve an efficient active breathing radiation therapy, the medical specialists will tailor-make a mold for fixation of each patient and connect the mold to the ABC device. The breath-hold periods, therapy type and dose can be calculated and monitored through a computer system after the therapy plan is further verified by the doctor.
During a course of radiotherapy, patients may lose appetite and result in weight loss. The contour and shape of the patient may change. Adaptive Radiotherapy and verification scans are used to scan the inter-fractional contour change and monitor tumor evolution. It is used to quantitatively measure the tumor response during radiotherapy.
Tomotherapy is an advanced type of radiation therapy delivery system that combines positioning, image-guided and intensity-modulated radiation therapy (IMRT), resulting in greater precision and accuracy in radiation treatment. By using this technology, radiation therapists are able to create optimal plans, locate the location and monitor the change in shape of the tumor for each individual patient. The radiation dose is directed to the tumor while minimizing exposure to healthy tissue.
In general, if the cancer cells disperse and spread to a large area, radiotherapy is not recommended for its strong side effects. Radiation is produced by a device called the linear accelerator (linac). The linac is mounted to a CT scanner-like ring gantry in the Tomotherapy treatment machine. This unique ring gantry design enables the system to deliver radiation in a helical (continuous 360°) delivery pattern up to 51 angles ((Helical Intensity Modulated Radiation Therapy, IMRT). It also uses a patented multi-leaf collimator (MLC) that divides the radiation beam into many smaller, narrow "beamlets". With three-dimensional view of a patient's anatomy and the Adaptive Image Guided Radiotherapy (IGRT), more angles and more beam modulation result in a more precise dose distribution.
For patients with wide tumors dispersion where radiotherapy for large area is needed, Tomotherapy is able to cover up to 160 cm and the therapy duration is therefore greatly reduced.
The exact location of a tumor can vary everyday depending on factors such as internal organ movement between treatments and the patient's relative positioning at the time of each treatment. This system allows us to take a CT scan just prior to each treatment in order to obtain a three-dimensional view of a patient's anatomy for that day.
Integrating these images with the CT images taken beforehand, the time consumed will increase 1 to 4 times comparing to conventional therapy. However, medical specialists can adjust the patient's position to make sure radiation is directed right where it should be. The daily pre-treatment CT scan can also be used for dose guidance, allowing therapist to visualize the dose that will actually be delivered to the patient while reducing the risk of side effects.
SRS is a type of therapy that requires precise and accurate positioning. It reduces the damage to the surrounding tissues by using special equipment to position the patient that precisely gives a single large dose of radiation to a tumor. SRS is mainly used to treat brain and neck tumors.
SRS requires shorter duration comparing to conventional low dose therapy and therefore is the optimal therapy plan for elderly or patient with severe conditions. Before the SRS, doctor usually uses TomoTherapy to obtain the internal images of the patient in order to accurately locate the tumor. TomoTherapy is also considered an efficient therapy as it can simultaneously locate various tumors. Last but not least, the special equipments used in Radionics can assist to accurately position the tumor, thus lowering the risk of other normal tissues.
Intensity Modulated Radiation Therapy (IMRT) is an advanced radiation treatment technique that allows us to deliver radiation to a tumour with more precision, resulting in potentially fewer side effects and higher cure rates. IMRT utilizes thousands of tiny radiation beams entering into the body from different angles to intersect on the tumor. The therapy will adjust the dose according to the shape of the tumor and locations of other surround tissues.
Image-guided radiation therapy assists in improving the precision and accuracy of daily radiation treatments. The location of the tumor can vary from day to day depending on factors such as internal organ movements between treatments and variations in patient’s relative position at the time of treatment. Orthogonal X-ray images and CT scans will be taken prior to each treatment and then compared to the CT images. By integrating these images, we are able to adjust the patient’s position accordingly to ensure that the radiation is administered as planned.
Three-dimensional (3D) conformal radiotherapy uses 3D images on a computer to shape beams of radiation around the shape and size of the tumor. The radiation beams are highly focused (conformed) on the tumor and this precise nature allows high doses of radiation to be given, while reducing the amount of radiation damage to the surrounding healthy tissue. However, 3DCRT is still under improvement. Anatomical structures, such as the nasopharynx, have a special "C shape" which wraps around the spinal cord. Minimal dose to the spinal cord and other surrounding organs such as the parotid glands cannot be achieved using 3DCRT. IMRT is an advanced type of 3DCRT that uses even more sophisticated software (advanced computer planning programs) and hardware (dynamic multi-leaf collimators) to control the shape and intensity of radiation delivered to the desired parts of the treatment area.
Using CT images, the oncologist and radiation therapists visualize the tumor and the surrounding region in three dimensions. The oncologist designates specific doses of radiation that the tumor and surrounding normal tissues should receive. With the help of an advanced computer program, the radiation therapist develops an optimal plan to meet the specified requirements. This process is called "inverse treatment planning". The resulting radiation dose distribution is consistent with the shape of the tumor by modulating the intensity of the radiation beam. The ultimate goal of this inverse treatment planning is to maximize tumor dose while simultaneously protecting the surrounding normal tissue.
In addition to the sophisticated computer program, IMRT also involves the use of dynamic multi-leaf collimators located in the radiation treatment machine. They are computer-controlled devices made up of individual "leaves" that can move independently in and out of the radiation beam. They vary radiation beam intensity across the treatment area. With IMRT, the patient is treated with numerous small beams from various angles with different intensity. The resulting radiation beams are conformed to the shape of the tumor according to the optimal plan established by the oncologist and radiation therapist, resulting into a better tumor targeting, lessened side effects and improved treatment outcomes.
Superficial radiation therapy is an effective treatment for skin cancer including basal cell carcinoma, squamous cell carcinoma and Kaposi's sarcoma.
It is treatment using a low energy radiation beam (x-ray) within the range of 50-150 kV (kilovolts). The beam energy penetrates only the top layer of the skin. Therefore, the treatment avoids deeper tissues, thus reducing scars. The treatment is also used in cases where surgical excision is difficult to reconstruct or where the risk of disfiguring is high. In certain skin cancers, if the pathology report following surgery suggests a high risk of recurrence, adjuvant superficial radiation therapy can further improve the cure rate.
In radiotherapy, reproducible setup and comfortable patient positioning are critical. For breast cancer patients, a new alternative to supine treatment is to plan and treat in the prone position. The patient is irradiated in the prone position while the treated breast hangs down away from the chest wall and brings about the benefit of minimizing the radiation dose to normal tissues.
The dose-volume histograms demonstrate that lung tissue irradiation is significantly lower with the patient in the prone position than that of the supine position. On top of that, large-breasted women appear to benefit most from irradiation in the prone position.
In one of the largest published studies of prone breast radiotherapy that included 245 women with early-stage breast cancer, the prone technique was well tolerated, with only a few patients (~ 4.9 %) complaining of chest wall or rib pain during treatment. None of these cases necessitated a treatment break. With the added advantage of improved dose homogeneity throughout the breast as well as decreased hot spots in the apex and base, prone breast irradiation is an effective alternative in fighting against breast cancer.
With the Flexitron Afterloading Brachytherapy delivery system, radioactive sources (Ir192) are used to deliver radiation at a short distance by interstitial, intracavitary, or intraluminal application. With this mode of therapy, a high radiation dose can be delivered locally to the tumor with rapid dose fall-off, thus minimizing dose to the surrounding normal tissues.
Suitable cases for Brachytherapy include: