Caren van Roekel

66 Chapter 2 acquired using CT images. Activity vials were ordered assuming a 10% LSF for HCC and 5% LSF for metastatic disease. At the day of treatment, patients underwent the work-up angiographic procedure with administration of 99m Tc-MAA. Within 2 hours, planar scintigraphy was performed and LSF was calculated. Activity was calculated according to the MIRD method and this was done between the scan and the transfer back to the angiography suite, where patients received treatment. Cone-beam CT was used for the evaluation of possible enterohepatic vessels. The mean total procedure time was 2.7 hours. This study shows that single-day treatment is feasible (143). In a letter to the editor, Van den Hoven et al. even advocate to eliminate the LSF calculation in patients with colorectal carcinoma metastases, since these patients seldom have a high LSF (144). However, if one leaves out this work-up procedure, personalized dosimetry based on the distribution of 99m Tc-MAA becomes impossible. Radioembolization with 166 Ho is always performed on a single day in the current clinical trials. Between the work-up procedure and the treatment procedure, the angiography suite is used for other treatments, to increase cost-effectiveness. 9.5. Technical advances Another option to shorten treatment time is to use simultaneous x-ray and nuclear imaging. This would allow the intervention radiologist to directly identify possible extrahepatic deposition of the microspheres and render the possibility of e.g. adjusting the injection position. A prototype was built with a mobile C-arm and a gamma camera with a four-pinhole collimator (Figure 13). The x-ray detector, the x-ray tube and the gamma camera were all placed in one line to enable imaging of the same field-of-view. Measurements with this prototype have demonstrated the feasibility of simultaneous x-ray and nuclear imaging (145, 146). Recently, much effort is being put into the development of different catheter types, such as anti-reflux catheters. Advantages of anti-reflux catheters, such as the Surefire catheters with an expandable tip or the Occlusafe catheters with an expandable balloon tip, are the anti-reflux capacities and the fixed catheter tip in the middle of the lumen(147, 148). The anti-reflux mechanism