Hansjoerg Rempp, Presenter: Nothing to Disclose

Joerg Roland, Abstract Co-Author: Nothing to Disclose

Stephan Miller MD, Abstract Co-Author: Nothing to Disclose

Claus Detlef Claussen MD, Abstract Co-Author: Nothing to Disclose

Philippe Lucien Pereira MD, Abstract Co-Author: Support, Terumo Corporation Support, Celon AG medical instruments Support, Siemens AG Support, CeloNova BioSciences, Inc Support, Bayer AG Support, Bracco Group Support,Sirtex Medical Ltd

Stephan Clasen MD, Abstract Co-Author: Nothing to Disclose

Diethard Schmidt MD, Abstract Co-Author: Nothing to Disclose

PRF temperature mapping allows the prediction of the coagulation zone with an acceptable sensitivity and positive predictive value if fast gradient echo images and sequence gating is used. It could thus be used to increase patient safety and may help to reduce the local tumor recurrence rate. 

Proton Resonance Frequency shift (PRF) based temperature mapping can be used in MR-guided thermoablative tumor therapy in order to protect sensitive structures adjacent to the tumor and in order to predict the size and location of the developping ablation zone.

Twenty-five patients with hepatic tumors were treated by MR-guided radiofrequency (RF) ablation using a wide bore 1.5 T MR scanner. Mean lesion size was 22 mm (range 13-42). Two MR-compatible RF probes were placed onto the tumor. Phase images acquired by fast gradient echo sequences were used to calculate temperature maps based on the PRF method. A breathing belt placed on the abdomen of the patient was used for sequence gating; temperature maps were acquired in late expiration phase. In order to evaluate the quality of the temperature data, slices from a 3D dataset of contrast-enhanced images acquired after therapy were registered on the temperature maps and the necrotic, non-enhanced area was segmented and compared to the area with a displayed temperature above a selcected cut-off level of 60°C. Sensitivity and positive predictive value of the temperature maps were calculated, using the control imaging as a gold standard. Temperature mapping reached acceptable image quality in 44/50 slices. Sensitivity, i.e. the rate of correctly detected coagulated tissue was 0.81±0.03. Positive predictive value, i.e. the rate of voxel in the temperature map over 60°C that actually developed necrosis was 0.89±0.06.

The PRF method requires reference images before the start of energy application in order to subsequently generate the temperature maps. These are susceptible to patient movements, needle and breathing artefacts. To increase image quality, sequence gating and the use of fast segmented sequences is necessary. The feasibility of temperature mapping with an acceptable quality could be shown in a small number of patients.

Rempp, H, Roland, J, Miller, S, Claussen, C, Pereira, P, Clasen, S, Schmidt, D, Temperature Mapping in MR-guided Radiofrequency Ablation of Liver Tumors Using the Proton Resonance Frequency Shift Method.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9011846.html