IMPOTRANCE OF CT- SIMULATOR IN RADIOTHERAPY

Vipin singh palB.Sc-Radiotherapy Technology Student

Aim

• The purpose of this study is to develop a general strategy that allows for design the best and more precise treatment plan and specific ct-simulation protocol based on radiotherapy goal

What is ct simulator

• Dedicated CT scanner for use in Radiotherapy treatment simulator and planning are known as CT Simulator.

• The CT scanner is used to acquire a volumetric CT-Scan of a patients which represents the “virtual “or digital patients

• The ct-simulation software provides virtual representation of the geometric capabilities of a treatment machine

Ct-simulator components

• X-ray tube• Large bore ct-scanner with an opening of up to

85cm• Detectors systems• Collimators and attenuator• Patients couch• Laser• Computer and work station• Control console

patients positioning and immobilization accessories used during ct-simulation and

treatments

• Thermoplastic orfit cast• Vac- lok• AIO base plate• Knee rest• Head rest• Shoulder traction tube• Foam wedges

CT-simulation procedure

1.PATIENT POSITIONING AND IMMOBLISATION

• The precision required for beam delivery

• Patient may or may not required an external immoblisation device for their treatment

• Immoblisation devices improve the reproducibility and rigidity of the set-up

2.REFERENCE MARRKING • During the CT scan a set of reference marks

must be placed on the patient so the patient can be positioned on the treatment machine

• Anatomical landmark

3. SCAN PROTOCOL• Energy select • Slice thickness• Slice spacing • Sprial pitch• Field of view• This protocol depends

upon disease and anotomy

4.CONTRAST • For several treatment sites

contrast can be used to help differentiate between tumour and surrounding healthy tissue

• I.V. fluid is commonly used as contrast

5.Volumetric data aquire from 2 ways 3D volumetric data 4D volumetric data

• 4d imaging is a complete data set that contains images from each portion of the breathing cycle.

• Images used to determine tumor normal organ motion.

3D radiation therapy simulation allows multiple cross sectional CT slices of the patient with a graphic display of the 3D anatomy of both normal tissue and tumour bearing region.

RESULT• The CT images excellent soft tissue contrast allowing for

greatly improved tumor localization and defining in comparison to conventional simulator.

• Patient contour may be obtained easily from CT data in particular the patients skin contains target and any organs of interest.

• Electron density information useful in the calculation of dose inhomogeneity due to the different composition of human tissue.

• The target volume and its position are identified with relative case of each CT slice.