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DOI: 10.1148/rg.276075097
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MR Imaging in Hyperthermia1

James R. MacFall, PhD and Brian J. Soher, PhD

1 From the Department of Radiology, Duke University Medical Center, Box 3808, Erwin Road, Durham, NC 27710. Presented as a refresher course at the 2007 RSNA Annual Meeting. Received May 4, 2007; revision requested May 16 and received June 21; accepted June 25. Supported by grant P01-CA42745 from the National Institutes of Health. All authors have no financial relationships to disclose.

Figure 1
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  		Figure 1.  Photograph shows a gel-filled phantom (large white arrow) inside a cylinder with four radiofrequency antennae on the outside. The small white arrow indicates one of the H-shaped antennae. There is a water-filled space (black arrow) between the antennae and the phantom.

 

Figure 2
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  		Figure 2.  Graph shows the MR image phase as a function of directly measured temperature at six different locations in a gel phantom surrounded by a water bolus, as shown in Figure 1. The inset is a phase image obtained along the axis of the phantom (coronal view); the small white inhomogeneities are the probe locations.

 

Figure 3A
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  		Figure 3a.  (a) Axial MR image of the phantom in Figure 1 shows the positions of the catheters that contain the direct temperature measurement probes (small arrows). The large arrows indicate the locations of the mineral oil–filled tubes that were placed outside the phantom in the water bolus. The lines in the water bolus are the folds of the plastic membrane that contains the water, and the bright inhomogeneities on the outside are due to the conductive antennae for heating placed on the outside of the outer cylinder. (b) Image obtained by summing all of the temperature changes measured with the PRFS method, which are indicated by an orange-toned intensity scale, shows the circularly symmetric heating pattern at the end of the heating.

 

Figure 3B
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  		Figure 3b.  (a) Axial MR image of the phantom in Figure 1 shows the positions of the catheters that contain the direct temperature measurement probes (small arrows). The large arrows indicate the locations of the mineral oil–filled tubes that were placed outside the phantom in the water bolus. The lines in the water bolus are the folds of the plastic membrane that contains the water, and the bright inhomogeneities on the outside are due to the conductive antennae for heating placed on the outside of the outer cylinder. (b) Image obtained by summing all of the temperature changes measured with the PRFS method, which are indicated by an orange-toned intensity scale, shows the circularly symmetric heating pattern at the end of the heating.

 

Figure 4A
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  		Figure 4a.  Graphs of the temperature change at the different regions of interest (ROIs) in Figure 3b calculated with the PRFS method over time. During the 65 minutes shown, the phantom remained unheated and at a constant temperature for the first 35 minutes, followed by 20 minutes of heating and then 10 minutes of cooling. (a) Graph shows data that have not been corrected for phase drift, which is clearly demonstrated by the PRFS measurements in the oil references (the constantly decreasing values). (b) Graph shows the data corrected for drift by using spatial interpolation and the oil references. The data are seen to be comparable with the direct temperature measurements (black lines).

 

Figure 4B
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  		Figure 4b.  Graphs of the temperature change at the different regions of interest (ROIs) in Figure 3b calculated with the PRFS method over time. During the 65 minutes shown, the phantom remained unheated and at a constant temperature for the first 35 minutes, followed by 20 minutes of heating and then 10 minutes of cooling. (a) Graph shows data that have not been corrected for phase drift, which is clearly demonstrated by the PRFS measurements in the oil references (the constantly decreasing values). (b) Graph shows the data corrected for drift by using spatial interpolation and the oil references. The data are seen to be comparable with the direct temperature measurements (black lines).

 

Figure 5A
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  		Figure 5a.  Estimates of temperature change (starting at body temperature) during hyperthermia therapy in a patient with a soft-tissue sarcoma of the lower leg. (a) Axial image of the calf and the tumor shows the anatomy. The leg is surrounded by a water bolus and the heating antennae are on the outside of the cylinder, as shown in Figure 1. (b) Graph shows the temperature changes during the 70 minutes of therapy. The different lines correspond to the ROIs, which are shown as color blocks in c and d. 1 = ROI in the tumor near the invasive fiberoptic temperature probe (black line on graph), 2 = ROI in normal muscle, 3 and 4 = ROIs in the oil references. The drift correction has been applied to the graph, as demonstrated by the near-constant values of the oil references. (c, d) Anatomy images obtained at the beginning (c) and near the end (d) of therapy show the regional temperature changes by means of an overlaid orange-toned temperature scale.

 

Figure 5B
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  		Figure 5b.  Estimates of temperature change (starting at body temperature) during hyperthermia therapy in a patient with a soft-tissue sarcoma of the lower leg. (a) Axial image of the calf and the tumor shows the anatomy. The leg is surrounded by a water bolus and the heating antennae are on the outside of the cylinder, as shown in Figure 1. (b) Graph shows the temperature changes during the 70 minutes of therapy. The different lines correspond to the ROIs, which are shown as color blocks in c and d. 1 = ROI in the tumor near the invasive fiberoptic temperature probe (black line on graph), 2 = ROI in normal muscle, 3 and 4 = ROIs in the oil references. The drift correction has been applied to the graph, as demonstrated by the near-constant values of the oil references. (c, d) Anatomy images obtained at the beginning (c) and near the end (d) of therapy show the regional temperature changes by means of an overlaid orange-toned temperature scale.

 

Figure 5C
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  		Figure 5c.  Estimates of temperature change (starting at body temperature) during hyperthermia therapy in a patient with a soft-tissue sarcoma of the lower leg. (a) Axial image of the calf and the tumor shows the anatomy. The leg is surrounded by a water bolus and the heating antennae are on the outside of the cylinder, as shown in Figure 1. (b) Graph shows the temperature changes during the 70 minutes of therapy. The different lines correspond to the ROIs, which are shown as color blocks in c and d. 1 = ROI in the tumor near the invasive fiberoptic temperature probe (black line on graph), 2 = ROI in normal muscle, 3 and 4 = ROIs in the oil references. The drift correction has been applied to the graph, as demonstrated by the near-constant values of the oil references. (c, d) Anatomy images obtained at the beginning (c) and near the end (d) of therapy show the regional temperature changes by means of an overlaid orange-toned temperature scale.

 

Figure 5D
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  		Figure 5d.  Estimates of temperature change (starting at body temperature) during hyperthermia therapy in a patient with a soft-tissue sarcoma of the lower leg. (a) Axial image of the calf and the tumor shows the anatomy. The leg is surrounded by a water bolus and the heating antennae are on the outside of the cylinder, as shown in Figure 1. (b) Graph shows the temperature changes during the 70 minutes of therapy. The different lines correspond to the ROIs, which are shown as color blocks in c and d. 1 = ROI in the tumor near the invasive fiberoptic temperature probe (black line on graph), 2 = ROI in normal muscle, 3 and 4 = ROIs in the oil references. The drift correction has been applied to the graph, as demonstrated by the near-constant values of the oil references. (c, d) Anatomy images obtained at the beginning (c) and near the end (d) of therapy show the regional temperature changes by means of an overlaid orange-toned temperature scale.

 

Figure 6
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  		Figure 6.  Graph shows the dependence of the fractional change in ADC in canine tissue as a function of temperature change.

 

Figure 7A
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  		Figure 7a.  MR images and temperature maps of two tumors with higher (a, b) and lower (c, d) vascularity. (a, c) Contrast-enhanced MR images show two sarcomas of the leg. (b, d) Corresponding temperature maps show temperature change from the beginning of heating by means of a color scale, which ranges from blue (0°–2°C) to red (>6°C). Note that the image magnification is different between the MR images and the temperature maps.

 

Figure 7B
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  		Figure 7b.  MR images and temperature maps of two tumors with higher (a, b) and lower (c, d) vascularity. (a, c) Contrast-enhanced MR images show two sarcomas of the leg. (b, d) Corresponding temperature maps show temperature change from the beginning of heating by means of a color scale, which ranges from blue (0°–2°C) to red (>6°C). Note that the image magnification is different between the MR images and the temperature maps.

 

Figure 7C
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  		Figure 7c.  MR images and temperature maps of two tumors with higher (a, b) and lower (c, d) vascularity. (a, c) Contrast-enhanced MR images show two sarcomas of the leg. (b, d) Corresponding temperature maps show temperature change from the beginning of heating by means of a color scale, which ranges from blue (0°–2°C) to red (>6°C). Note that the image magnification is different between the MR images and the temperature maps.

 

Figure 7D
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  		Figure 7d.  MR images and temperature maps of two tumors with higher (a, b) and lower (c, d) vascularity. (a, c) Contrast-enhanced MR images show two sarcomas of the leg. (b, d) Corresponding temperature maps show temperature change from the beginning of heating by means of a color scale, which ranges from blue (0°–2°C) to red (>6°C). Note that the image magnification is different between the MR images and the temperature maps.

 




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