Tumours treated with radioactive implants are in most cases small and accessible to clinical examination or endoscopy. Gross tumour volume is consequently mainly determined clinically or with endoscopy. Imaging may also be useful, with classical techniques, as mammography, or with CT-scan or MRI. Clinical target volume includes gross tumour volume and a 5-10 mm margin. Distribution of dose is estimated on the basis of images performed after implantation, classically with two orthogonal films of the implant. It can then be optimised. Dose-volume histogram of gross tumour volume and critical organs can be obtained with a CT-scan or a MRI of the implant, which may be difficult to perform because of implantation material and dummy sources.