Conformal radiotherapy has brought the capacity to shape dose gradient in an effort to approximate three-dimensional tumors and target structures, such that tumoricidal dose may be delivered to areas at risk for neoplastic involvement, while sparing proximal non-target tissue. The planning process for conformal radiotherapy is predicated on dose calculations derived from the Hounsfield units of given voxels on a simulation DICOM image set (typically CT). Voxels within this dataset are then designated as ROIs and assigned nominal designations as GTV, clinical areas of presumed microscopic spread (CTV), or OARs. Only those volumes defined by the physician end user may be utilized to either prescribe sufficient dose to ensure tumor demise (GTV/CTV) or spare organs (OARs) through dose delivery constraints (International Commission on Radiation Units and Measurements. 1999). The ROIs are then utilized as DICOM-RT structures for dose calculation by the radiotherapy treatment planning software.
Since these ROIs provide the definitions for dose constraints used for treatment planning, accurate target delineation is crucial for precision radiotherapy [6
In the pre-conformal radiotherapy era, standardized fields were utilized to ensure uniformity of treated regions. However, in the era of volume-based delineation, data suggest that considerable operator dependant variation exists in target volume delineation and consequent dose distribution [5
]. This variability complicates clinical trial quality assurance and prevents ready comparison of treatment protocols. Several groups have also sought to account for systematic variability introduced in target delineation in order to optimize volume definition and treatment planning margins.
Recent survey data suggest, that significant numbers of radiation oncologists receive minimal formal training in intensity modulation radiotherapy, and points to a need for greater research into optimum methodologies for user instruction in target delineation, among other aspects of IMRT practice. Furthermore, in recognition of the importance of proper target delineation, a host of didactic educational activities have been created to assist clinicians in developing target delineation skill-sets for clinical practice. While there are software programs allowing interactive instruction (www.educase.edu
], few extant software/devices provide automated/semiautomated real-time instructional feedback regarding target volume delineation skill-development for trainees in radiation oncology. Little extant data exist regarding how to evaluate acceptable levels of user competency in target delineation [8
]. Despite great interest, comparatively little data has to date been presented regarding strategic optimization of target delineation itself, either as a function of standardized practices or as a function of deliberate educational curriculum.
Several series have also established that user variability in target volume delineation may result in potentially significant dosimetric differentials between prescribing radiation oncologists. Additionally, collected data suggest that clinical trial data may be obfuscated by user-dependent differentials in prescription volume determination. While this may be partially ameliorated by modification of study criteria with regard to volume delineation, there remains, at present, no efficient, automated mechanism to evaluate target volumes.
Consequently, there is a great need for tools that allow evaluative measures to be collected and reported regarding inter-and intra-user performance in target delineation in a DICOM-RT enviornment. The purpose of this effort is to develop a software application which will allow users to delineate target structure ROIs in DICOM-RT compatible formats, followed by automated comparison and scoring of user-derived with ROIs defined by reference sets derived from expert users.