Computerized optimization of 125I implants in brain tumors

Code of practice for brachytherapy physics: Report of the AAPM Radiation Therapy Committee Task Group No. 56

“…Some require interactive reconfiguration by the user, assisted by sophisticated manipulation and display capability, 71 and others involve automatic adjustments of source positions and/or strengths. [72][73][74] In one of the latter, 74 125 I seed positions are iteratively leastsquares optimized, first with only one seed per catheter and then after each of a sequence of maneuvers in which nearestneighbor catheters are combined; the combinations, which continue as long as reasonable goodness-of-fit is maintained, serve both to reduce the number of skull penetrations necessary and to separate individual catheters enough that retainer buttons on the surface do not interfere with one another. For automatic position adjustments in this type of optimization, it is essential ͑for convergence͒ that seeds be constrained not to move outside a three-dimensional bit-map structure conforming either to target contours drawn on the scans or, if desired, to smaller contours ͑e.g., the enhancement margin presumed to indicate tumor͒.…”

<title>Three-dimensional and multiplanar tomographic image processing for neurosurgical planning and automation</title>

“…With two-dimensional 2D multiplanar or 3D imaging processing, the size, shape, and main axis of intracranial lesions can be determined along with the important surrounding anatomical structures. Computer calculations and graphic capabilities contribute to optimized dosimetry for interstitial radiotherapy and convergent beam external radiotherapy (5,10,24,28,33). This information can be transposed into stereotactic space with mathematical accuracy.…”

“…This highly localized treatment requires a 3D configuration of the isodose distribution curves adjusted to tumoral volume and shape. 5 which allows an easy detection of faulty contours. Computer dose calculations for interstitial implants of radioactive seeds are based on the knowledge of the spatial coordinates for each seed.…”

“…To accelerate the trial-and-error method of conventional treatment planning, computers offer the possibility of automatic optimizing procedures (5). Its objective is to change the source configuration in such a way that a selected isodose surface can be adjusted as close as possible to the target volume surface.…”

Stereotactic Brachytherapy for Brain Tumors

“…Inverse treatment planning is used. The desired surface dose, implantation time, and trephination point(s) are selected manually and a seed configuration yielding optimal coverage of the tumor with the prescribed dose is calculated automatically by minimization of an appropriate objective function (Bauer-Kirpes et al, 1988) (Fig. 4).…”