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Spatial variations in prostate tissue histology as measured by a tactile resonance sensor
Umeå University, Faculty of Science and Technology, Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics.
Umeå University, Faculty of Science and Technology, Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics.
Umeå University, Faculty of Medicine, Medical Biosciences.
Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences.
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2007 (English)In: Physiological Measurement, ISSN 0967-3334, Vol. 28, no 10, 1267-81 p.Article in journal (Refereed) Published
Abstract [en]

In recent years, tactile sensors based on piezoelectric resonance sensor technology have been used for medical diagnosis where the sensor's stiffness-measuring properties can reflect tissue pathology. The change in the frequency of the resonating system and the change in force when contact is made with tissue are used as a stiffness parameter. Earlier stiffness measurements of prostate tissue in vitro demonstrate variations related to tissue composition. In this study, measured stiffness from two human prostate specimens was compared to histological composition of prostate tissue below and around the measurement points. Tissue stiffness was measured with the resonance sensor system. Tissue composition was measured at four different depths in the tissue specimen using a microscopic-image-based morphometrical method. With this method, the proportion of tissue types was determined at the points of intersections in a circular grid on the images representing each measurement point. Numerical values were used for weighting the tissue proportions at different depths in the tissue specimen. For an impression depth of 1.0 mm, the sensing depth in this study was estimated to be 3.5-5.5 mm. Stiffness variations due to horizontal tissue variations were investigated by studying the dependence of the size of the circular grid area relative to the contact area of the sensor tip. The sensing area (grid radius) was estimated to be larger than the contact area (contact radius) between the sensor tip and the tissue. Thus, the sensor tip registers spatial variations in prostate tissue histology, both directly below and lateral to the tip itself. These findings indicate that tumours around the sensor tip could be detected, which in turn supports the idea of a future resonance-sensor-based clinical device for detecting tumours and for guiding biopsies.

Place, publisher, year, edition, pages
2007. Vol. 28, no 10, 1267-81 p.
Keyword [en]
prostate tissue, tactile sensor
National Category
Biomedical Laboratory Science/Technology
URN: urn:nbn:se:umu:diva-19113DOI: 10.1088/0967-3334/28/10/011PubMedID: 17906393OAI: diva2:201410
Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2009-11-17Bibliographically approved
In thesis
1. Tactile sensing of prostate cancer: a resonance sensor method evaluated using human prostate tissue in vitro
Open this publication in new window or tab >>Tactile sensing of prostate cancer: a resonance sensor method evaluated using human prostate tissue in vitro
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Prostate cancer is the most frequent type of cancer in men in Europe and the USA. The methods presently used to detect and diagnose prostate cancer are inexact, and new techniques are needed. Prostate tumours can be regarded as harder than the surrounding normal healthy glandular tissue, and therefore it is of interest to be able to reliably measure prostate tissue stiffness. In this dissertation the approach was to evaluate tactile resonance sensor technology and its ability to measure mechanical properties and to detect cancer in human prostate tissue.

The tactile resonance sensor is based on a piezoelectric transducer element vibrating at its resonance frequency through a feedback circuit. A change in the resonance frequency is observed when the sensor contacts an object. This feature has been utilized to measure tissue stiffness variations due to various pathophysiological conditions.

An impression-controlled tactile resonance sensor system was first used to quantify stiffness and evaluate performance on silicone. Then the sensor system was used on fresh human prostate tissue in vitro to measure stiffness using a combination of frequency change and force measurements. Significant differences in measured stiffness between malignant and healthy normal tissue were found, but there were large variations within the groups.

Some of the variability was explained by prostate tissue histology using a tissue stiffness model. The tissue content was quantified at four depths in the tissue specimens with a microscope-image-based morphometrical method involving a circular grid. Numerical weights were assigned to the tissue data from the four depths, and the weighted tissue proportions were related to the measured stiffness through a linear model which was solved with a least-squares method. An increase in the proportion of prostate stones, stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Stroma and cancer had the greatest effect and accounted for 90 % of the measured stiffness (45% and 45%, respectively).

The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed. A sensing depth was extrapolated from the numerical weights for the measurements performed at different impression depths. Horizontal surface tissue variations were studied by altering the circular grid size relative to the contact area between the sensor tip and the tissue. The results indicated that the sensing area was greater than the contact area. The sensor registered spatial tissue variations.

Tissue density-related variations, as measured by the frequency change, were weakly significant or non-significant. The measured force registered elastic-related tissue variations, to which stroma and cancer were the most important variables.

A theoretical material-dependent linear relation was found between frequency change and force from theoretical models of frequency change and force. Tactile resonance sensor measurements on prostate tissue verified this at small impression depths. From this model, a physical interpretation was given to the parameters used to describe stiffness.

These results indicate that tactile resonance sensor technology is promising for assessing soft tissue mechanical properties and especially for prostate tissue stiffness measurement with the goal of detecting prostate cancer. However, further studies and development of the sensor design must be performed to determine the full potential of the method and its diagnostic power. Preferably, measurements of tissue mechanical properties should be used in combination with other methods, such as optical methods, to increase the diagnostic power.

Place, publisher, year, edition, pages
Umeå: Tillämpad fysik och elektronik, 2007. 70 p.
Resonance Sensor Lab, ISSN 1653-6789 ; 4
tactile resonance sensor, prostate tissue, prostate cancer, stiffness, density, elastic, variations, tissue histology
National Category
Medical Laboratory and Measurements Technologies
urn:nbn:se:umu:diva-1445 (URN)978-91-7264-461-8 (ISBN)
Public defence
2007-12-14, N430, Naturvetarhuset, Umeå universitet, Umeå, 10:00 (English)
Available from: 2007-11-22 Created: 2007-11-22 Last updated: 2011-03-30Bibliographically approved

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Jalkanen, VilleAndersson, Britt MBergh, AndersLjungberg, Börje
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