Simulation is a procedure by which site of treatment is viewed through fluoroscopy and adjustments done to obtain the desired treatment field. This is done using a Conventional Simulator. The staff place the patient in the desired position for treatment with the necessary immobilization aids, which are custom made for each patient. In addition, oral or IV contrast material may be administered as indicated, for better identification of organs and the tumor. After the necessary adjustments are made, the field borders are defined and X rays taken for post planning verification.

 

 


Conventional Simulator Team

 

 


CT Simulator Team


CT Simulator is a Computed Tomography scanner to do the simulation so that target volumes can be reproduced in a 3 Dimensional format for better target volume delineation, normal organ sparing and treatment planning. In 2008, a large bore 64 slice CT Simulator (SOMATOM Open Sensation- Siemens) was installed for planning cases for 3DCRT, forward planning and IMRT. The large bore enables patients to be scanned with the immobilization device in place, e.g. Breast Board. The 64 slice scans offer better resolution during voluming thus allowing better soft tissue identification. CT simulation may be done with or without intravenous contrast according to the request of the treating physician. Contrast enables better visualization of structures like lymph nodes, enhancing tumor tissue, but also carries the risk of hypersensitivity and the limitation of use in patients with abnormal renal function. The whole process of simulation may take around 30-40 minutes depending on whether contrast is used or not.

 

Immobilization devices are those used to maintain good immobilisation of the treatment areas during radiotherapy. The most common one used is the Thermoplastic head and neck shell, usually used for nasopharyngeal carcinoma patients. These are placed in a hot water bath, where they become more pliable, and then positioned on the area of the patient. After the shell cools, it sets into the shape of the contour and can be used for the treatment. There are also Orfit moulds for application over abdomen and pelvic region for conformal radiotherapy in that area.

 


Thermoplastic shell


Breast board on CT Sim couch

 

Other devices used are the breast board (Medtec) for positioning breast cancer patients with their arms abducted and extended into a measurable and reproducible position for every treatment involving tangential oblique beams. The Vacloc is a device working on the principle of foam beads fixing into position in a vaccum and is mainly used for thoracic and pelvis malignancies mainly for smaller children.

 

External Beam Therapy Radiation therapy is delivered using 3 LINAC (Linear accelerators), one of which is equipped with Multi Leaf Collimator for delivering IMRT. About 120 patients are treated daily for a variety of solid tumors including nasopharyngeal, breast, rectum, cervix, head and neck cancers. LINAC comprises of an automated couch situated in the center of a rotating treatment head which delivers radiation from predetermined angles as shown in the picture.

 

Radiotherapy involves the use high energy X rays delivered through a fixed rectangular or conformal field for the purpose of treatment.  In 1985 the department started with 2 Linear Accelerators (LINAC- Siemens Mevatron 74, Mevatron 77). In 1996 we acquired a Cobalt 60 (Theratron-T1000). Subsequently the 2 LINACs were replaced with updated versions in 1997 (Siemens KD2) and 2005 (Siemens PRIMUS with MLC) respectively and the Cobalt unit was replaced with another LINAC (Siemens PRIMUS) which was installed and commissioned in 2007. These 3 LINACs are manned by 30 radiographers working in 2 shifts, treating approximately 120 patients a day.

 


LINAC with MLC: PRIMUS 1


LINAC: PRIMUS 2


LINAC: KD 2

 

Brachytherapy is a form of radiotherapy involving insertion of radiation sources (Iridium-192) in close proximity to the organ with tumor so that normal organs can be spared better. This gives good tumor control with least normal tissue complications. This form of radiotherapy is used in cancer of the cervix, nasopharynx and esophagus. The procedure is done using short sedation in the brachytherapy suite which comprises of a specialised table with a C-arm, display console and the HDR brachytherapy system. The applicator is positioned and verified by X-rays which are transferred to the PLATO TPS, where the dosage calculations are done and then treatment is administered from the control room.

 


HDR Brachytherapy in NPC

HDR Brachytherapy in Cervix

 

Intensity Modulated Radiotherapy (IMRT) service was started since February, 2009. IMRT

is a modern and highly sophisticated technique of radiation delivery. Contrary to conventional radiotherapy treatment where two or more fields where multiple segments of fields are used to deliver varying intensities of radiation for radiotherapy. Clinically, this improves on 3D Conformal Radiotherapy in further reducing radiation toxicities to normal organs like parotid gland, skin, spinal cord and small intestine; thus better reduction of radiation morbidity in patients. In patients with nasopharyngeal cancer, this form of treatment reduces the incidence of dry mouth, swallowing difficulties, hearing loss, skin and subcutaneous fibrosis that accompanies conventialanl radiotherapy.

 

Brachytherapy service was started in this hospital from as early as 1985 using the MDR-Buchler Remote After loader.  This was replaced in 2000 by the High Dose radiotherapy unit (Nucletron-HDR) which is the current standard of brachytherapy world wide and currently more than 300 patients are treated annually at our hospital using this technique.

 

Medical Physics service is a crucial cog in the planning and delivery of radiotherapy. This team is led by Dr Tang Tieng Swee, Senior Physicist and includes 5 junior physicists. After the post planning verification is done in Conventional planning, the films and the contours are transferred using a digitizer into a computerized image where dose calculations in the form of Monitoring Units are transferred to the treatment machine.

 

This dedicated physics team has been instrumental in bringing the modern technology of Intensity Modulated Radiotherapy to reality in this department. Almost a year of hard work in the form of multiple verification tests, Q.A, dose quantification and monitoring was required, to ensure that this complicated treatment is delivered accurately and effectively. Since Feb 2009 this service has been made available in Sarawak General Hospital in the treatment of nasopharyngeal cancer, prostate cancer and re-irradiation of head and neck and pelvic cancers.

 

Intensity Modulated Radiotherapy service was started since February 2009. IMRT is a modern and highly sophisticated technique of radiation delivery. Contrary to conventional radiotherapy treatment where two or more fields where multiple segments of fields are used to deliver varying intensities of radiation for radiotherapy. Clinically, this improves on 3D Conformal Radiotherapy in further reducing radiation toxicities to normal organs like parotid gland, skin, spinal cord and small intestine; thus better reduction of radiation morbidity in patients. In patients with nasopharyngeal cancer, this form of treatment reduces the incidence of dry mouth, swallowing difficulties, hearing loss, skin and subcutaneous fibrosis that accompanies conventional radiotherapy.

 



Differences between conventional radiotherapy (left) and IMRT (right). The red area signifies the area of high dose and how it is confined to the area of disease in the IMRT plan. Also note the multiple beams employed, hence the increased time of treatment.

 

Such kind of treatment requires imaging done via CT simulator and the images are transferred to the post planning section where voluming of the tumor and the clinically involved area is done by the Oncologist using the ONCENTRA treatment planning software. This data is then transferred to the planning system where the beams are designed and the IMRT plan produced. Once the plan is ready, IMRT QA measurement is done and the dose distributions are compared to that obtained on a phantom to assure that they have a good degree of agreement. Due to the number of steps involved in this form of radiation delivery, it takes about two weeks from planning simulation to execution of treatment compared to 1 week duration for conventional radiotherapy.

 


Dr. Rajiv voluming on TPS

CT simulator with Alderson Rando Phantom