Multi-slice computed tomography: A tool for non-invasive temperature measurement?

Abstract

Purpose: To investigate the potential of multi-slice computed tomography (MSCT) as a tool for non-invasive temperature measurement. Materials and methods: Samples of water, 0.9% saline, sunflower oil and dilutions of (1:32, 1:64, 1:128) contrast agent (Iopromid 370, BayerSchering Pharma, Berlin) were heated in a plexiglass phantom. In a first set-up, samples of 0.9% saline solution were scanned at defined temperatures (25°–75°C; 5°C intervals) using a clinical CT scanner. Scan parameters (tube current–time product, tube voltage, collimation, slice thickness) were systematically varied. In a second set-up samples of the different fluids (water, sunflower oil, contrast agent dilutions) were scanned using the following scan protocol: 250 mAs, 140 kV, 1.2 mm collimation, 9.6 mm slice thickness. CT numbers were measured in reconstructed axial images at the different temperatures. A regression analysis was performed to investigate the relationship between temperature and CT number. Results: Standard deviation of measured CT numbers decreased with increasing tube current–time product, increasing tube voltage, thicker collimation and higher slice thickness. Regression analysis showed an inverse relationship between temperature and CT number for all fluids with regression coefficients of −0.471 (0.9% saline), 0.447 (water), −0.679 (sunflower oil), −0.420 (contrast agent 1:32), −0.414 (contrast agent 1:64) and −0.441 (contrast agent 1:128), respectively. Conclusion: Multi-slice computed tomography can depict thermal density expansion of different fluids. Based on these results the implementation of a temperature discrimination of several degrees C at a high spatial resolution is achievable.