Imaging of interstitial cryotherapy--an
in vitro comparison of ultrasound, computed tomography, and magnetic
Tacke J, Speetzen R, Heschel I, Hunter DW, Rau G, Gunther RW.
Department of Diagnostic Radiology, University of Technology, Aachen,
RATIONALE AND OBJECTIVES: To evaluate the imaging
capabilities of ultrasound (US), computed tomography (CT), and magnetic
resonance imaging (MRI) in monitoring interstitial cryotherapy and
to compare them with visual control. METHODS: An experimental MR-compatible,
vacuum-insulated and liquid nitrogen-cooled cryoprobe was inserted
under in vitro conditions into a porcine liver, which was kept at
a temperature of 37 +/- 1 degrees C, in a water bath with continuous
stirring. The freezing procedure was controlled macroscopically,
by US (Toshiba Sonolayer, 7.5-MHz linear array transducer), by CT
(Siemens Somatom Plus, slice thickness 2-8 mm, 165-210 mA at 120
kV), and by MRI (Philips Gyroscan ACS-NT, FFE TR/TE/FA = 15/5.4/25
degrees, T1-SE 550/20, T2-TSE 1800/100) after the iceball reached
its maximum size. RESULTS: The maximum iceball diameter around the
probe tip was 12.0 mm by visual control, 12.4 mm by US, 12.7 mm
by CT, and within 12.8 mm by spin echo sequences and 11 mm by gradient
echo sequence. Due to the nearly signal-free appearance of the frozen
tissue on MR images, the ice/tissue contrast on T1-weighted and
gradient echo images was superior to T2-weighted images and CT images.
Sonographically, the ice formation appeared as a hyperechoic sickle
with nearly complete acoustic shadowing. CONCLUSION: Due to the
better ice/tissue contrast, T1-weighted or gradient echo MR images
were superior to CT and US in monitoring interstitial cryotherapy.
Gradient echo sequences generally underestimated the ice diameter
by 15%. Copyright 1999 Academic Press.
PMID: 10328915 [PubMed - indexed for MEDLINE]