3-D Treatment Planning Of Chest Wall/Breast, Using Monoisocentric Technique
A Muzaffar*, Shifa International Hospital, Islamabad, Pakistan Capital TerritorySU-E-P-26 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
The purpose of this study is to describe the monoisocentric technique followed in Shifa International Hospital.
More than 30 consecutive patients have been treated from Oct 2011 to May 2012 with monoisocentric technique. Methods for treatment planning and irradiation, the methodology for making the isocenter and fields. With precise treatment planning system, linear accelerator - asymmetric four collimator jaws, the longitudinal(Y) jaws beam-split at the match line namely upper and lower border of fields, transverse (X) jaws defined lateral border of the fields. All patients underwent CT planning in the supine position with the ipsilateral arm overhead. The chest wall/breast was treated with a pair of opposing half beam tangential fields with the blockage of upper half of the field and the upper axillary and supraclavicular nodal region were treated with an anterior photon field with the blockage of lower half of the field.
A monoisocentric technique was used to match the tangential fields with the anterior field at the isocentre. Multi-leaf collimators were utilized for shielding of normal structures.
Various techniques using a half-blocked supraclavicular field with special tangential fields have been introduced to eliminate the junction problem. These are, however complicated involving couch motion & machine isocentre repositioning when changing from the supraclavicular to the tangential fields. Monoisocentric technique is simple and easy to setup; since the same machine's isocentre is used for all treatment fields and no couch movements or patient reposition is required. Another use/advantage of monoisocentric technique is a reduction of treatment time.
Treatment technique takes full advantage of dual asymmetric jaws to achieve a perfect match-line, necessitates only one isocenter and set-up point. In monoisocentric technique reproducibility of positioning is simple and precise. This setup is technician friendly and the match-line is perfect without overdose and underdose at the junction.