Applications of imaging in brachytherapy

Image based treatment planning for brachytherapy is improving treatment quality and increasing treatment options. Computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound (US) are used to aid low dose rate and high dose rate treatments, CT and MRI are used to better define the target and normal organ volumes and to calculate the dose to critical structures. Imaging information is used to optimize source placement to better achieve desired dose constraints. MRI is particularly valuable in better defining the target volume due its versatility in differentiating normal tissue from tumor tissue. Improved dosimetry for intracavitary gynecologic implants has shown increased maximum doses to normal organs than traditionally been reported. Dosimetric criteria for optimal implants are being developed. Interstitial implants benefit from better defined target volumes, needle placement and optimization of source strengths. High dose rate prostate implants using on-line imaging and dosimetry during needle placement has reduced uncertainty of dose delivery by reducing the time interval from imaging study to treatment delivery