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Resonance sensor measurements of stiffness variations in prostate tissue in vitro: a weighted tissue proportion model
Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Centrum för medicinsk teknik och fysik.
Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Centrum för medicinsk teknik och fysik.
Umeå universitet, Medicinsk fakultet, Medicinsk biovetenskap.
Umeå universitet, Medicinsk fakultet, Kirurgisk och perioperativ vetenskap.
Visa övriga samt affilieringar
2006 (Engelska)Ingår i: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 27, nr 12, s. 1373-86Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Prostate cancer is the most common type of cancer in men in Europe and the US. The methods to detect prostate cancer are still precarious and new techniques are needed. A piezoelectric transducer element in a feedback system is set to vibrate with its resonance frequency. When the sensor element contacts an object a change in the resonance frequency is observed, and this feature has been utilized in sensor systems to describe physical properties of different objects. For medical applications it has been used to measure stiffness variations due to various patho-physiological conditions. In this study the sensor's ability to measure the stiffness of prostate tissue, from two excised prostatectomy specimens in vitro, was analysed. The specimens were also subjected to morphometric measurements, and the sensor parameter was compared with the morphology of the tissue with linear regression. In the probe impression interval 0.5-1.7 mm, the maximum R(2) > or = 0.60 (p < 0.05, n = 75). An increase in the proportion of prostate stones (corpora amylacea), stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Cancer and stroma had the greatest effect on the measured stiffness. The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed. Tissue sections deeper in the tissue were assigned a lower mathematical weighting than sections closer to the sensor probe. It is concluded that cancer increases the measured stiffness as compared with healthy glandular tissue, but areas with predominantly stroma or many stones could be more difficult to differ from cancer.

Ort, förlag, år, upplaga, sidor
2006. Vol. 27, nr 12, s. 1373-86
Nyckelord [en]
image analysis, prostate tissue, resonance sensor
Nationell ämneskategori
Medicinsk laboratorie- och mätteknik
Identifikatorer
URN: urn:nbn:se:umu:diva-19116DOI: 10.1088/0967-3334/27/12/009PubMedID: 17135706OAI: oai:DiVA.org:umu-19116DiVA, id: diva2:201414
Tillgänglig från: 2009-03-04 Skapad: 2009-03-04 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Ingår i avhandling
1. Tactile sensing of prostate cancer: a resonance sensor method evaluated using human prostate tissue in vitro
Öppna denna publikation i ny flik eller fönster >>Tactile sensing of prostate cancer: a resonance sensor method evaluated using human prostate tissue in vitro
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Umeå: Tillämpad fysik och elektronik, 2007. s. 70
Serie
Resonance Sensor Lab, ISSN 1653-6789 ; 4
Nyckelord
tactile resonance sensor, prostate tissue, prostate cancer, stiffness, density, elastic, variations, tissue histology
Nationell ämneskategori
Medicinsk laboratorie- och mätteknik
Identifikatorer
urn:nbn:se:umu:diva-1445 (URN)978-91-7264-461-8 (ISBN)
Disputation
2007-12-14, N430, Naturvetarhuset, Umeå universitet, Umeå, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2007-11-22 Skapad: 2007-11-22 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
2. Resonance sensor technology for detection of prostate cancer
Öppna denna publikation i ny flik eller fönster >>Resonance sensor technology for detection of prostate cancer
2006 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Prostate cancer is the most common type of cancer in men in Europe and the USA. Some prostate tumours are regarded as stiffer than the surrounding normal tissue, and therefore it is of interest to be able to reliably measure prostate tissue stiffness. The methods presently used to detect prostate cancer are inexact, and new techniques are needed. In this licentiate thesis resonance sensor technology, with its ability to measure tissue stiffness, was applied to normal and cancerous prostate tissue.

A piezoelectric transducer element in a feedback system can be set to vibrate at its resonance frequency. When the sensor element contacts an object a change in the resonance frequency is observed, and this feature has been utilized in sensor systems to describe physical properties of different objects. For medical applications it has been used to measure stiffness variations due to various pathophysiological conditions.

An impression-controlled resonance sensor system was used to quantify stiffness in human prostate tissue in vitro using a combination of frequency change and force measurements. Measurements on prostate tissue showed statistically significant (p < 0.001) and reproducible differences between normal healthy tissue and tumour tissue when using a multivariate parameter analysis. Measured stiffness varied in both the normal tissue and tumour tissue group. One source of variation was assumed to be related to differences in tissue composition. Other sources of error could be uneven surfaces, different levels of dehydration of the prostates, and actual differences between patients.

The prostate specimens were also subjected to morphometric measurements, and the sensor parameter was compared with the morphology of the tissue with linear regression. In the probe impression interval 0.5–1.7 mm, the maximum coefficient of determination was R2 ≥ 0.60 (p < 0.05, n = 75). An increase in the proportion of prostate stones (corpora amylacea), stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Cancer and stroma had the greatest effect on the measured stiffness. The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed.

It is concluded that prostate cancer increases the measured stiffness as compared with healthy glandular tissue, but areas with predominantly stroma or many stones could be more difficult to differentiate from cancer. Furthermore, the results of this study indicated that the resonance sensor could be used to detect stiffness variations in human prostate tissue in vitro, and especially due to prostate cancer. This is promising for the development of a future diagnostic tool for prostate cancer.

Ort, förlag, år, upplaga, sidor
Umeå: Fysik, 2006. s. 47
Serie
Resonance Sensor Lab, ISSN 1653-6789 ; 2
Nyckelord
resonance sensor, prostate tissue, stiffness, detecting prostate cancer
Nationell ämneskategori
Medicinsk laboratorie- och mätteknik
Identifikatorer
urn:nbn:se:umu:diva-896 (URN)91-7264-153-3 (ISBN)
Presentation
(Engelska)
Handledare
Tillgänglig från: 2006-10-17 Skapad: 2006-10-17 Senast uppdaterad: 2018-06-09Bibliografiskt granskad

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