Tactile imaging is a type of elasticity imaging or elastography that is used to map the elastic properties of soft tissues. The other names for tactile imaging are ’mechanical imaging’, ‘stress imaging’ and ’computerized palpation’. It is a medical imaging technique in which the sense of touch is converted into a digital image. The tactile image works as a pressure map, which requires the specified directions of the tissue deformation. It is a function of P(x,y,z), where P represents the pressure on soft tissue surface when deformation is applied and x,y,z represent the coordinates at which the pressure P is measured.
In tactile imaging technique, a probe consisting of a pressure sensor array is mounted on the face of the device. This probe acts similar to human fingers during clinical examination, which results in the deformation of soft tissue and detects the outcome/changes in the pressure pattern.
This type of imaging provides important information about the tissue or organ anatomy and elasticity structure as it is highly sensitive to the changes in tissue structures because of the different physiological and pathological processes. The elasticity can be measured by special gradients within P(x,y,z) at specified location.
Tactile imaging and other types of elasticity imaging can be differentiated with the use of ultrasound and magnetic resonance imaging. Below mentioned are the major two differences:
- Restructuring of the internal mechanical structure of tissue is done in the tactile imaging with the help of the stress pattern data over the compressed tissue, whereas the ultrasound or magnetic resonance imaging detects the strains induced in the tissue.
- Compared to the ultrasound or magnetic resonance imaging, tactile imaging requires relatively larger tissue deformations under the applied load in order to collect the stress data.
Uses in Medical Science
- Detection of structural changes in the tissue.
- Detection of cancer nodules in the breast or prostate.
- Detection of a mechanical heterogeneity.
Vagina and pelvic floor
The Vaginal Tactile Imager (VTI) can translate the sense of touch into computer image, allowing the visualization of the vagina and pelvic floor support structures in terms of stiffness. Tactile image is able to assess pelvic floor conditions and function in a quantitative, anatomically sensitive and specific manner.
High-definition functional muscle tactile imaging can be performed by the VTI for entire vagina during voluntary muscle contraction, involuntary relaxation and involuntary reflex contraction. There are 8 tests in a full VTI examination protocol. They are all observed in real time on VTI display by an operator. The report of VTI examination is generated and stored automatically in a digital format. The US Food and Drug Administration (FDA) has approved the VTI as an aid in diagnosis and evaluation of vaginal and female pelvic floor conditions.
The Breast Tactile Imager (BTI) is used for analysis, which includes a probe with a pressure sensor array, an electronic unit, and a laptop computer. Various structural and mechanical properties of breast and breast lesions can be evaluated such as Young’s modulus, elasticity contrast, tissue nonlinearity (strain hardening), heterogeneity index, nodule size, shape and mobility. Data has proven the BTI’s capability for characterizing and differentiating benign and malignant breast lesions. It is an efficient technique and has the potential to be used as a cost effective device for cancer diagnostic modality.
Estimations say that the benign biopsy rate could significantly be reduced by the use of BTI after standard screening procedures. SureTouch is a device similar to BTI and has been approved by the FDA as a visual mapping system for documentation of the findings in the clinical breast examination.
Prostate Mechanical Imager (PMI) is used for the analysis of prostate cancer and it consists of various parts like probe with a pressure sensor array and motion tracking system, a movable cart with an electronic unit and a computer. The PMI is useful to detect and locate the abnormalities within the gland. The Digital Rectal Examination (DRE) was used previously, and now the FDA has approved PMI to be used as it documents prostate abnormalities.
The human sense of touch has been the most prevalent and successful medical diagnostic technique. A great variety of diseases were diagnosed through tactile sensing. Nowadays, new tactile imaging machines have been developed which are making it easier to detect and analyses the different types cancers so that they could be acted upon immediately.