intensity 5ch3.pdf

Intensity modulated radiotherapy ❑Radiation beams in standard external beam radiotherapy including 3-D conformal radiotherapy usually have a uniform intensity across the field, fulfilling the linac flat-ness and symmetry specifications. ❑Non-uniform beam intensities (intensity modulation) c...

Intensity modulated radiotherapy ❑Radiation beams in standard external beam radiotherapy including 3-D conformal radiotherapy usually have a uniform intensity across the field, fulfilling the linac flat-ness and symmetry specifications. ❑Non-uniform beam intensities (intensity modulation) can be used to improve dose distributions by: ❑Compensating for contour irregularities ❑Compensating for tissue inhomogeneities ❑Compensating for highly irregular target volumes ❑Sparing organs at risk located in the vicinity of target volume. 37 M.Sc. Medical Physics Dr. Khalid I Hussein  Intensity modulated radiotherapy ❑Physical wedges and compensators have long been used to produce simple intensity modulation to compensate for contour irregularities. Their effects are incorporated into a treatment plan through the use of forward planning algorithms. ❑Modern radiotherapy techniques based on computer-controlled intensity modulation systems have been developed during the past decade and currently represent the most sophisticated 3-D conformal dose delivery process. ❑The 3-D CRT technique which relies on multiple beams with optimized intensity modulated fluence distributions is referred to as intensity modulated radiotherapy (IMRT). ❑Two techniques are currently available for IMRT dose delivery: ❑Tomotherapy unit. ❑Isocentric linac in conjunction with a multileaf collimator 38 M.Sc. Medical Physics Dr. Khalid I Hussein