Targeting Cancer with Precision
A new image-guided radiation therapy targets cancersmore accurately to help safeguard surrounding healthy tissue
Cancer is a scary disease. Thankfully, arduous efforts made by researchers in recent years have resulted in new innovative technologies being made available to improve cancer treatments and their outcome.
One good example is Helical TomoTherapy; a treatment which combines various innovative radiotherapy technologies.
Radiotherapy is one of the most common forms of cancer treatment. It can be used alone, combined with other treatments such as Chemotherapy, or as palliative therapy for different conditions.
Radiation beams are accurately delivered from the radiotherapy machine to the human body, making use of its direct damaging effect to kill cancer cells.
Marking tumors: Computed Tomographyversus skin marking
Before a patient begins radiotherapy treatment, a well-trained radiotherapy team will delineate the patient’s “targeted zone” where the planned radiation beams will be delivered.
In conventional radiotherapy, the patient is marked with lines and symbols on their skin to indicate the target area for the therapy after computer analysis. Every subsequent treatment is carried out based on these indicators.
By way of a contrast, TomoTherapy is installed with an inner computed scanning system called “Megavoltage Computed Tomography” (MVCT) which carries out image-guided targeting.
Before every daily treatment, MVCT is used to scan the patient for locating the target area. A computer simulation and calculation are then carried out to make sure the treatment area is correct before the treatment starts.
This true imaged-guidance technology allows image fusion comparison using Image-Guided Radiation Therapy (IGRT) and the planned computed tomography technique, so a higher degree of accuracy is achieved.
Why is it necessary for a comparison to take place before every treatment? If a patient needs radiotherapy, different radiological imaging will be used to locate the tumor in order to formulate the best possible treatment plan in terms of dosage and the angle of the radiation beams. However, the tumor location may change during the treatment course.
The course of radiotherapy treatment can range from several to tens of sessions. For example, the position of the patient lying on the treatment couch may not be exactly the same every time. Also during a course of treatment, body shape, the size and location of tumor may also change. For instance, the normal duration of a treatment course for Nasopharyngeal Carcinoma is seven weeks. However, the tumor may shrink to a rather great extent within 2 to 3 weeks after starting treatment.
By making regular comparisons, any discrepancy can be corrected immediately. A second re-plan is sometime needed in the middle of a course for adjustment if great changes are detected. The advantage of this is to minimize error as much as possible so that the radiation beam can accurately target the tumor while minimizing normal tissue damage.
Source: Dr Donna Chow Lee, Specialist in Clinical Oncology at Hong Kong Adventist Hospital