A convenient method for testing and calibrating surface perfusion sensors has been developed. A phantom tissue model is used to mimic the non-directional blood flow of tissue perfusion. A computational fluid dynamics (CFD) model was constructed in Fluent to design the phantom tissue and validate the experimental results. The phantom perfusion system was used with a perfusion sensor based on the clearance of thermal energy. A heat flux gage measures the heat flux response of tissue when a thermal event (convective cooling) is applied. The blood perfusion and contact resistance are estimated by a parameter estimation code. From the experimental and analytical results, it was concluded that the probe displayed good measurement repeatability and sensitivity. The experimental perfusion measurements in the tissue were in good agreement with those of the CFD models and demonstrated the value of phantom tissue system. This simple, cost effective, and noninvasive convective blood perfusion system was then tested in animal models. The perfusion system was evaluated for repeatability and sensitivity using isolated rat liver and exposed rat kidney tests. Perfusion in the isolated liver tests was varied by controlling the flow of the perfusate into the liver, and the perfusion in the exposed kidney tests was varied by temporarily occluding blood flow through the renal artery and vein. The perfusion estimated by the convective perfusion probe was in good agreement with that of the metered flow of perfusate into the liver model. The liver tests indicated that the probe can be used to detect small changes in perfusion (0.005 ml/ml/s). The probe qualitatively tracked the changes in the perfusion in kidney model due to occlusion of the renal artery and vein. / Ph. D.

A non-invasive blood perfusion system has been developed and tested in a phantom tissue and an animal model. The system uses a small sensor with a laminated flat thermocouple to measure the heat transfer response to an arbitrary thermal event (convective or conductive) imposed on the tissue surface. Blood perfusion and contact resistance are estimated by comparing heat flux data with a mathematical model of the tissue. The perfusion system was evaluated for repeatability and sensitivity using both a phantom tissue test stand and exposed rat liver tests. Perfusion in the phantom tissue tests was varied by controlling the flow of water into the phantom tissue test section, and the perfusion in the exposed liver tests was varied by temporarily occluding blood flow through the portal vein. The phantom tissue tests indicated that the probe can be used to detect small changes in perfusion (0.009 ml/ml/s). The probe qualitatively tracked the changes in the perfusion of the liver model due to occlusion of the portal vein. / Master of Science

Colonoscopy is the current standard for colorectal cancer screening. This procedure requires improvement since it causes patient pain and can even result in injury. Novel colonoscopy devices have to be evaluated to gain information about their performance. At the preclinical stage of the device development the evaluation is typically performed in laboratory experiments. For these experiments an artificial environment is required which can recreate the anatomical and biomechanical features of the colon. A colonoscopy simulator for the evaluation of colonoscopy devices was developed within the ERC funded CoDIR project (Colonic Disease Investigation by Robotic Hydrocolonoscopy). The here developed simulator had to provide a colon phantom with realistic biomechanical properties as well as a sensor setup to measure signals which can be used to quantify the performance of devices which are tested within the simulator. Related literature was reviewed and possible tissue mimicking materials were selected. The suitability of the selected materials was evaluated by testing the frictional and elastic properties of the materials and subsequently comparing the results to those of colon tissue. PVA cryogel was selected as the most suitable material as it exhibits comparable elasticity and coefficients of friction. The tissue mimicking materials were mould casted into phantoms which were designed to represent the anatomical features of the colon. A simulator environment was developed which integrates the phantom as well as force and pressure sensors into a functional system. The sensors measure mesenteric forces and intraluminal pressures which can be related to the performance of tested devices. The simulator allows the arrangement of the sensors and the phantoms in an adjustable, modular approach. The simulator environment was successfully applied in the evaluation of a novel colonoscopy device. The results indicate that PVA cryogels exhibit unique mechanical properties which can be compared to those of colon tissue. The developed colonoscopy simulator provides a promising tool which can aid the development of novel colonoscopy devices.

Intra-Body Communication (IBC) is a prospective technology where human tissue may be used as a signal medium in order to transmit useful data within the human body. Proposed applica- tions of this technology are prosthetics control or implanted device communication, potentially by establishing an Intra-Body Area Network (IBAN), which could further be enhanced by other IoT applications and 5G radio systems. Previous research at Uppsala University has shown the fat tissue to be a promising medium due to its low permittivity and loss tangent. This form of implementation is named Fat-IBC. This thesis aimed to produce a Fat-IBC enabled device, as a proof of concept. This project successfully produced and characterized phantom tissue, produced a basic demonstrator device in the form of a 3D-printed arm prosthetic, and integrated a wireless communication system into the arm prosthetic. The communication system was implemented using Arduino microcontrollers and XBee RF modules, based on the 802.15.4-based ZigBee protocol at 2.45 GHz. Muscle, fat, and skin phantom tissues were produced, with the muscle tissue being similar to other comparable tissue samples, while the fat and skin tissues deviated from such samples. A signal loss transmission test measured a -67 dB loss over 20 cm of fat tissue. Several potential issues with production and measurement were discussed. The arm demonstrator device was also tested by transmitting the control signal across phantom fat tissue, being fully functional through 10cm of tissue, and of limited function across 20cm of tissue.