6 Modern Imaging in Brachytherapy

126 Modern Imaging

This comprehensive approach is also valid for cervix and vagina, where, in addition to the clinical examination and a vaginal impression by a mould, the depth of infiltration can be investigated accurately by sectional imaging like MRI and intraluminal US. Different applicators are used for specific tumour sites according to specific demands and possibilities at these sites from a clinical and dosimetric point of view. In addition, for an applicator to be useful, certain requirements must be met for a specific imaging technique detailing visibility, reliability and reproducibility of the applicator with as little negative impact as possible on the imaging quality of the tumour and the organs at risk and with no negative impact on the geometrical accuracy of the image. These requirements vary with the imaging technology used and are met to different degrees by specific devices: for ultrasound by echogenic needle tips (for example for prostate); for CT by applicators not producing metallic artifacts; for MRI by non-metallic applicators and needles (for example for gynaecology). In some situations, for example for the vagina and for the anorectal region, it is advisable to introduce image compatible dummy applicators or moulds in provisional treatment planning to provide similar topographic conditions for provisional and definitive treatment planning. Table 5.2: Overview of imaging procedures for delineation of the Gross Tumour Volume and for determination of the Clinical and Planning Target Volume for different sites of brachytherapy; Endoscopy (ES) is added, if indicated 1 st choice 2 nd choice Mobile Tongue MRI CT Floor of mouth MRI CT, US Buccal mucosa MRI, CT, US Oropharynx MRI, ES CT Nasopharynx ES, MRI CT Lip (CT) Cervix MRI CT, US (endo) Endometrium MRI, ES CT, US (endo) Vagina US (endo), MRI CT Breast Mammography, MRI CT, US Bladder ES, MRI, CT US Prostate MRI US (endo), CT Penis MRI US, CT Anorectal ES, MRI, US (endo) CT Oesophagus ES, Oesophagogram (Barium) CT, MRI, US (endo) Bile duct Cholangiogram, ES CT, US, MRI Soft tissue sarcoma MRI CT Bronchus ES, CT, Chest X Ray MRI Skin (US) Brain MRI CT Eye fundoscopy, US, angiography MRI Intravascular Angiography, US (IVUS)

Specific investigation protocols are set up and adapted based on diagnostic imaging for a given tumour site in order to achieve optimal results with regard to high quality simultaneous imaging of the applicator, tumour and the surrounding tissue.