Sean Foxley BS, Presenter: Nothing to Disclose

Xiaobing Fan PhD, Abstract Co-Author: Nothing to Disclose

Jonathan River, Abstract Co-Author: Nothing to Disclose

Marta A. Zamora BS, Abstract Co-Author: Nothing to Disclose

Erica Markiewicz BA, Abstract Co-Author: Nothing to Disclose

Sham Sokka PhD, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Gregory Stanislaus Karczmar PhD, Abstract Co-Author: Nothing to Disclose

00030490-DMT et al, Abstract Co-Author: Nothing to Disclose

We propose the use of High Spectral and Spatial resolution (HiSS) MRI to detect changes in blood flow and oxygenation in response to mild hyperthermia (3° – 5° C.) as a new diagnostic tool. Blood flow and blood oxygenation in cancers are expected to respond differently from surrounding normal tissue to a ‘temperature challenge’ due to differences in vascular smooth muscle, vascular and transport inhomogeneity, and metabolic regulation. HiSS MR imaging may be sensitive to changes in T1 and T2*, as well as other spectral changes that reflect these physiologic differences.

Athymic female nude mice (n = 4) with PC3 tumors implanted in a hind limb were imaged when the tumors were approximately 7mmLx6mmWx6mmH in size. A loop of PE tubing (1.2mm ID/2.2mm OD) was wrapped around the base of the tumor and taped in place. MRI was performed at 9.4 Tesla using high-resolution, respiratory gated, echo-planar spectroscopic imaging (EPSI) with an acquisition time of ~150 seconds, spectral resolution of 3Hz, and an in-plane resolution of 0.156mm in a FOV of 20mm. Five control images were obtained, followed by four images as warm water was pumped through the tubing, increasing tumor temperature by 3° – 5° C. Water peak height images were used to evaluate changes in the water resonance lineshape during temperature challenges.

Increases in local temperature caused large heterogeneous changes in image intensity in the tumor but not in muscle. The average increase in water peak height during mild hyperthermia in the tumor was 13.6 ± 6.5% and 0.7 ± 0.5% in normal muscle; the average decrease was -8.2 ± 0.08% in tumor and -1.6 ± 0.6% in muscle. The positive and negative mean changes in tumor tissue were statistically significantly larger than those in the muscle (p < 10-6 for both). These changes reflect changes in T1 and T2* of the water resonance and were independent of the expected temperature shift changes in resonance frequency.

These results demonstrate that a ‘temperature challenge’ may be valuable for improving cancer detection and diagnosis. The observed changes likely reflect temperature dependent variations in blood oxygenation, tissue water content, and metabolism.

A ‘temperature challenge’ could be produced clinically with high intensity focused ultrasound (HIFU), followed by HiSS MRI to detect tumors and characterize anatomy and physiology.

Foxley, S, Fan, X, River, J, Zamora, M, Markiewicz, E, Sokka, S, Karczmar, G, et al, 0, Mild Hyperthermia Produces Significant Contrast Changes in High Spectral and Spatial Resolution (HiSS) MR Images of PC3 Tumors.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8012985.html