Radiotherapy Techniques

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New radiotherapy techniques allow treating the tumour precisely. In radiotherapy two main streams are there one is External beam therapy and another one is Brachytherapy.


In external beam therapy in turn has different techniques they are,


1. Conventional therapy

2. 3D Conformal Radiotherapy (3DCRT)

3. Intensity Modulated Radiotherapy (IMRT)

4. Image Guided Radiotherapy (IGRT)

5. Volumetric Modulated ARC Therapy

6. Stereotactic Radio surgery / Stereotactic radiotherapy (SRS/SRT) Indeed, Brachy therapy also has its own different techniques they are,
 
1. Intracavitary Brachytherapy

2. InterStitial Brachytherapy

3. Surface moulds


Intracavitary therapy is used when applicators containing radioactive sources can be introduced into body cavities like cervix, lumen etc.,  


 Interstitial therapy is indicated when the tumor is well localized (breast, prostrate, cheek etc.,) and can be implanted directly according to accepted rules of distribution.


 Surface molds are used to treat small superficial areas, such as the ear or the lip.


In all these cases, owing to the short treatment distance, the geometry of source distribution is critical.

Three Dimensional Conformal Radiotherapy (3DCRT):


    3DCRT is the superior technique to the conventional radiotherapy, in conventional radiotherapy sparing of normal tissues difficult task and sometimes not possible also.  After the introduction of 3DCRT it make us to conform the irregular shape of the tumor with help of Multileaf collimators, customized etc. Indeed, helped to spare the normal tissues in many cases. For doing this technique we should require three dimensional information of anatomy with good treatment planning system.
    
Intensity modulated radiotherapy (IMRT):


IMRT is a technique which uses linear accelerators to deliver conformal radiation – radiation which is sculpted to the shape of the tumour.  IMRT utilizes the mulch-leaf collimators on a linear accelerator to vary the radiation beam intensity around a target field. The shape of the radiation beams may change hundreds of times during the course of treatment. The intensity of the beams and the direction from which they are delivered also varies. The result is radiation distributed in three dimensions around the tumour, minimizing radiation dose to normal tissue.


Image Guided Radiotherapy (IGRT):


    Image-guided radiation therapy (IGRT) is the use of frequent imaging during a course of radiation therapy to improve the precision and accuracy of the delivery of treatment.
In IGRT, machines that deliver radiation, such as a Linac (for x-ray or photon) or cyclotron/synchrotron (for proton), are equipped with imaging technology so that the physician can image the tumour immediately before or even during the time radiation is delivered, while the patient is positioned on the treatment table. Using specialized computer software, these images are then compared to the images taken during simulation. Any necessary adjustments are then made to the patient's position and/or radiation beams in order to more precisely target radiation at the tumour and avoid healthy surrounding tissue.


IGRT is used to treat tumours in areas of the body that are prone to movement, such as the lungs (affected by breathing), liver, and prostate gland, as well tumours located close to critical organs and tissues. It is often used in conjunction with intensity-modulated radiation therapy (IMRT), proton beam therapy, stereo-tactic radio surgery, or stereo-tactic body radiotherapy (SBRT), which are advanced modes of high-precision radiotherapy that utilize computer-controlled x-ray accelerators to deliver precise radiation doses to a malignant tumour or specific areas within the tumour


Volumetric Modulated Arc Therapy:


RapidArc or VMAT is a volumetric arc therapy that delivers a precisely sculpted 3D dose distribution with a single 360-degree rotation of the linear accelerator gantry. It is made possible by a treatment planning algorithm that simultaneously changes three parameters during treatment:


Rotation speed of the gantry


Shape of the treatment aperture using the movement of multileaf collimator leaves


Delivery dose rate.


Volumetric modulated arc therapy differs from existing techniques like helical IMRT or intensity-modulated arc therapy (IMAT) because it delivers dose to the whole volume, rather than slice by slice. And the treatment planning algorithm ensures the treatment precision, helping to spare normal healthy tissue.



Questions:

1. 3DCRT is the conformal radiation therapy is it true or false?


a) True


b) False



2. IMRT stands for


a) Intensity Modulated Radiotherapy


b) Intensity modulated Arc Therapy


c) Intensity Guided Radiotherapy


d) Imaging Modified Radiotherapy



3. Advantages of IGRT are,


a) Increases the precision delivery


b) Taking into account of motion movements


c) Conform the position of the patient


d) All


Answers:


1. a)True


2. a)Intensity Modulated Radiotherapy


3. d) All





References:


1. http://www.radiologyinfo.org


2. http://www.royalmarsden.nhs.uk


3. http://www.varian.com


4. The Physics of Radiation Therapy by F. M. Khan

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