Sonoelastography makes headway in prostate cancer assessment

March 12, 2007

Sonoelastography shows strong performance in prostate cancer detection, but room for improvement remains when it comes to specificity, according to research from the Medical University Innsbruck in Austria, a leading center in prostate imaging research.

Sonoelastography shows strong performance in prostate cancer detection, but room for improvement remains when it comes to specificity, according to research from the Medical University Innsbruck in Austria, a leading center in prostate imaging research.

Sonoelastography has been in research stages for many years but has only recently approached the verge of entering clinical practice. The technique uses ultrasound to measure the elastic properties of tissues, based on the well-established principle that malignant tissue is harder than benign tissue. A color classification system registers tissue as benign (green) or malignant (blue).

Prostate cancer is one of the most common cancers in men. As diagnostic testing with the prostate-specific antigen blood test has increased, so have the number of biopsies, with a high rate of negative results. Typically, biopsies are performed by urologists guided by gray-scale ultrasound, which suffers from low sensitivity.

The release of two new software upgrades in the last year and the availability of more effective probes have enhanced sonoelastography's performance in prostate imaging, according to Dr. Ferdinand Frauscher, director of uroradiology at Medical University Innsbruck.

"We now have tools that provide better imaging information about tissue elasticity and enable better detection of suspicious lesions," said Frauscher in an interview with Diagnostic Imaging.

At the conference on Monday, Innsbruck researchers presented two new papers about the technique's role in prostate imaging, based on results with a Hitachi ultrasound system. In the first study of almost 500 patients, they found a very high correlation between sonoelastography and systematic biopsy results.

Patients involved in the study had a PSA level over 1.5 ng/mL and underwent 10-core systematic biopsy. To overcome the challenge of getting adequate compression of the entire gland, the Austrian researchers use a narrower region of interest, examining the prostate in three sections: base, midgland, and apex.

According to systematic biopsy results, 125 patients had cancer. There were 321 cancerous areas, with Gleason scores ranging from 3 to 10.

Confirmed results on biopsy showed that sonoelastography had very good sensitivity of 86% for the entire prostate organ but lower specificity of 72%. Of 533 findings, the technique identified 275 false positives, due to mistaken assessments of areas with inflammation and atrophy.

Sonoelastography performed best in cancers of the apex, with sensitivity of 79% and specificity of 85% to 93%. Performance was weakest in cancers located in the base of the organ.

"The results are promising, especially in atypical areas," said Dr. Leo Pallwein, who presented results.

Another study from the same institution suggests sonoelastography can help determine whether cancer has spread beyond the capsule of the prostate gland (extracapsular extension). Making such a determination is crucial for selecting the most appropriate treatment for the patient.

Researchers performed sonoelastography and obtained contrast-enhanced T1- and T2-weighted MR images in 15 patients with elevated PSA levels prior to radical prostatectomy. Spectroscopy and image fusion were not performed with MR.

Based on the histopathologic results, all cancers were well visualized with both sonoelastography and MRI. Surgery results indicated extracapsular extension in 11 of 15 cases.

Sonoelastography showed infiltration of the capsule in eight patients and stiffness in seminal vesicles in four cases. MRI showed infiltration in the perioprostatic fat tissue in seven cases and infiltration of the seminal vesicles in five cases.

"Sonoelastography correlated well with MRI and histologic findings. It showed remarkable strength for prediction of extracapsular extension," said Dr. Friedrich Aigner, who presented study results.