TELETHERAPY :  Teletherapy refers to radiation therapy given by an external radiation source at a distance from the body The isocentre is the point in space about which the gantry of the linear accelerator, the treatment head of the linear accelerator, and the couch rotate. Beam AXIS - axis around which the collimator rotates  Radiation Field - … Continue reading The Working of a LINAC

ELECTRON BEAMS Electron beams are used for radiotherapy treatments where the dose deposition required is near the surface. Clinically very useful for Basal cell carcinoma, squamous cell carcinoma of skin. While photons penetrate the surface for some distance before achieving Dmax, the Dmax for electrons is much closer to the skin surface. One can define … Continue reading Electron Therapy

Types of dosimetry:  Relative - measure changes in dose rather actual doses (PDD, TMR)  Absolute: Direct measurement of dose  (e.g. calorimetry) Reference: standard set up to use as reference to calibrate other measuring devices  Beam quality index - A measure used to compare the penetrating effect of different radiotherapy beams. For a linac, each beam … Continue reading Radiation Dosimetry

DOSE VOLUME HISTOGRAM:  Graphical representation of dose to volumes of tissue. DVH statistics considers each small voxel (a voxel is essentially like a pixel but in 3D. It's a small volume based division of tissue in the radiation field and derived from a planning CT scan) independently. The treatment planning system mathematically calculates the dose … Continue reading DVH and ICRU (International Commission on Radiation Units) reports summary:

Scatter/ Wedges / Equivalent Square/ Field matching/ Beam Blocking In EBRT, the Radiation beam exits from the linac head in form of high energy photons. Isocentre: The isocentre is the point in space about which the gantry of the linear accelerator, the treatment head of the linear accelerator, and the couch rotate. Beam profile: Transverse … Continue reading Radiation Concepts:

Cell Cycle: The series of stages between one cell division and the next.Four phases: G1 (Gap 1) , S (Synthesis), G2 (Gap 2) and M (Mitosis) Average length of cell cycle is 16 hours (can widely vary)G1 phase is the most variable in duration between cell typesThe passage of the cell through the various stages is … Continue reading CELL CYCLE