Radiation Therapy is Awesome !

PRESENT: What is used in practice today ???

Currently, Radiotherapy Linear Accelerator (LINAC) are fully controlled by computers and with new technique of dose distributions, such as intensity-modulated RT, volumetric-modulated arc therapy (VMAT) and the image-guided RT (IGRT). Those were measured in millimetres and it is more precise compared to CT.

Use of IMRT

• Use LINAC to safely and painlessly deliver precise radiation doses to a tumour while minimizing the dose to surrounding normal tissue.

• Allows for the radiation dose to conform more precisely to the 3D shape of the tumour by controlling the intensity of the radiation beam in multiple volumes. 

Use of VMAT

•  A novel radiation which can achieve highly conformal doses distribution with high target volume coverage  

• Use of IGRT-machines that deliver radiation that allow the physician to image the tumor immediately before or even during the time radiation is delivered
  - Other methods for IGRT is the use of marker place on the patient’s body surface
  -Use to treat tumors in area of the body that are prone to movement  

Computed Tomography (CT)
ADVANTAGES

• Tumour motion can be accessed.
•  Possible to identify mass attenuation coefficient.
•  Shorter acquisition 

LIMITATIONS

• Suboptimal tissue contrast
• Inability to visualize small groups of cancer cells that are  separated from the gross tumour
• Lack of functional information

Other mobility is magnetic resonance imaging (MRI) and positron emission tomography (PET) can provide additional info in order to more precisely define the tumour localization for treatment plan.

Positron Emission Tomography (PET)
PET involve  imaging the biodistribution of a radiolabeled compound selected based on it biochemical behavior. Used Fluore-2-deoxy-D-glucose known as FDG. Early 2000, PET and CT is combined and known as PET-CT.

ADVANTAGES

• Show metabolic active tissue.
• Used to monitor tumor response, while noting that metabolic changes would precede changes in tumor shape and size.

LIMITATIONS

• High costs of cyclotrons needed to produce the short-lived radionuclides.
• The need for specially adapted on-site chemical synthesis apparatus to produce the radiopharmaceuticals after radioisotope preparation

Magnetic Resonance (MR)

MRI scanners use strong magnetic fields, radio waves and field gradients to form images of the body. Used in various clinical specialties such as orthopedics, neurology and neurosurgery as well as for various anatomies and pathologies including pelvic organs and tumours, soft-tissue visualization is used for diagnosis. MR is still a secondary image modality in role of imaging in radiotherapy.

 

ADVANTAGES

• Better soft tissue contrast
• Greater resolution
• Non-ionizing radiation

LIMITATIONS

• Image artifact
• Lack tissue density information
• Small field of view