S.I.R.T. imaging: Development of acquisition protocols for therapy planning and post-therapy assessment.

Objectives To develop and establish suitable acquisition protocols for SIRT in palliative treatment of primary liver tumors and liver metastases of other tumors.

Methods Diagnostic phase: 150 MBq Tc99m-MAA, are injected selectively into the hepatic artery or its branches. After the procedure a planar partial-body scan and a SPECT/CT of the liver are performed on a dual-head gamma camera . Planar: 100 cm; LEHR collimator, 10 cm/min; 140 keV +- 7.5 %. SPECT/CT : 128x128; 30s/step; 3°/step; H-mode; LEHR; cw; low-dose CT: 256x256; 2.6 RPM; 140 kV; 2.5 mA; 10 mm slices. The investigation visualizes the arterial perfusion of the tumor as well as possible arterial shunts to other organs such as lung, stomach, intestine and pancreas, and allows the calculation of the shunt-fraction to the lung. Therapeutic phase: 14 days later the therapy with selective intra-arterial injection of 2-3 GBq of Y90-microspheres is performed followed by a bremsstrahlen-scan which confirms their correct localization. Planar: 100 cm; 20cm/min; LEHR; 140 keV +- 50%. SPECT/CT: 128x128; 25s/step; zoom 1.0; 3°/step; LEHR; 140 keV +-50%; low-dose CT: 256x256, 2.6 RPM; 140kV; 2.5 mA; 10 mm slices.

Results In the diagnostic phase our imaging technique allows a sensitive assessment of the tumor-perfusion and of shunts from the liver. The post-therapy bremsstrahlen imaging delivers information about tracer distribution in an exceptionally high quality. Major shunts can also be detected.

Conclusions Accurate imaging is an essential component of every S.I.R.-Therapy. Our protocols allow the correct indication for the therapy and provide a high peri-therapeutic safety for the patient.