A 4-field reclining TSEI technique: an alternative to the Stanford Technique for the frail patient

The classic Stanford technique requires the patient to remain standing, naked and blindfolded in the different treatment positions during the daily fraction, typically 20 minutes. Though most patients can tolerate this, some are too frail to be treated in this mode. As an alternative, we have developed a simple method to treat the reclining patient. With the gantry at 45 deg. and using a low mobile bed on the floor a SSD of 2.5 m is achieved. The body contour is covered by 4 fields with the patient alternating in the prone and in the supine positions. The bed is translated longitudinally to cover the total length and the fields are matched to achieve field uniformity. An acrylic degrader sheet is positioned close to the skin. Relative dosimetry is done with TLD and film, whereas ion chambers with cable shielding, are used for calibration and energy measurements. The total skin dose is determined by measuring the surface dose on a humanoid phantom (Alderson-Rando) with TLD. The doses to the fully exposed areas are averaged and related to the calibration dose by way of a multiple-field factor. We have used this skin-dose calibration technique for the Stanford method as well. Independent in vivo measurements with TLD on 15 patients agree with the calculated dose within the margins of measurement accuracy. This TSEI method developed for reclining patients, though inferior in homogeneity to the classic Stanford method, is an acceptable alternative for patients that are too frail to stand up during treatment