Primary breast cancer while increasing in incidence has been successfully treated with a combination of surgery and adjuvant therapies in the majority of patients. Novel treatments for primary breast cancer need to show additional benefits to existing treatments with equivalent or improved efficacy for niche groups. Photodynamic therapy (PDT) is a potential novel treatment and a Phase I/IIA, open label, non-randomised, single site trial of photodynamic therapy for the treatment of primary breast cancer was conducted. The primary aim was to identify the light dose required for 12 mm of tumour necrosis (or a plateau of necrosis) assessed by histopathology. Post-dose MRI correlation with histopathology findings in treated tumours and in normal breast tissue was sought. In addition adverse events were recorded and comparison of outcome made with matched controls. Results of the first human clinical trial with 12 patients with median follow-up of 39 months showed PDT was well tolerated, with no adverse effects and comparable outcome to control populations. Tumour necrosis increased with incremental increases in light dose, however some patients showed a poor response even at the highest light dose. Analysis suggests that there may be predictive factors for good and poor response. PDT in primary breast cancer requires further investigation to identify which patients would most benefit from this therapy.
Direct and continuous measurements of blood flow are of significant interest in many medical specialties. In cardiology, intravascular physiological measurements can be of critical importance to determine whether coronary stenting should be performed. Intravascular pressure is a physiological parameter that is frequently measured in clinical practice. An increasing body of evidence suggests that direct measurements of blood flow, as additional physiological parameters, could improve decision making. In this study, we developed a novel fibre optic intravascular flow sensor, which enabled time-of-flight measurements by upstream thermal tagging of blood. This flow sensor comprised a temperature sensitive polymer dome at the distal end of a single mode optical fibre. The dome was continuously interrogated by low coherence interferometry to measure thermally-induced length changes with nanometre-scale resolution. Flow measurements were performed by delivering heat upstream from the sensor with a separate optical fibre, and monitoring the temperature downstream at the dome with a sample rate of 50 Hz. A fabricated flow sensor was characterized and tested within a benchtop phantom, which comprised vessels with lumen diameters that ranged from 2.5 to 5 mm. Water was used as a blood mimicking fluid. For each vessel diameter, a pump provided constant volumetric flow at rates in the range of 5 to 200 ml/min. This range was chosen to represent flow rates encountered in healthy human vessels. Laser light pulses with a wavelength of 1470 nm and durations of 0.4 s were used to perform upstream thermal tagging. These pulses resulted in downstream temperature profiles that varied with the volumetric flow rate.
Many percutaneous needle-based procedures such as foetal interventions, tumor biopsies, nerve blocks, and central venous catheterizations are guided by ultrasound (US) imaging to identify the procedural target and to visualize the needle. A key challenge associated with ultrasound-guided needle insertions is accurate and efficient identification of the needle tip, as thin needles can readily stray from the imaging plane and can have poor visibility at large insertion angles. Ultrasonic tracking is a method for localising the needle tip relative to the imaging plane in real-time, using an ultrasonic transmitter or receiver integrated into the needle that is in communication with an external ultrasound imaging probe. This study had two foci. The first was to increase the sensitivity with which ultrasound reception was performed, using a custom fiber optic hydrophone with a high-finesse Fabry-Pérot cavity based ultrasound sensor. This sensor, which comprised of a polymer layer sandwiched between dielectric mirrors, was interrogated continuously during insertions into tissue. The second focus of the study was to develop a custom needle stylet into which the fiber optic hydrophone was integrated, which was fully compatible with clinical practice and which could be adapted to different needles. We tested the sensitivity of the sensorized stylet across a wide range of needle angulations, depths and insertion angles in different biological tissues. We demonstrated, for the first time, needle tip localization in ex-vivo tissues at depths beyond 6 cm and insertion angles steeper than 80°. We conclude that ultrasonic tracking with high-finesse Fabry-Pérot fiber optic hydrophone is very promising for use in clinical practice.
Photoacoustic imaging is a powerful and increasingly popular technique for tissue diagnostics. Suitable tissue- equivalent phantoms are in high demand for validating photoacoustic imaging methods and for clinical training. In this work, we describe a method of directly 3D printing a photoacoustic tissue-equivalent phantom of a kidney based on Gel Wax, which is a mix of polymer and mineral oil. A kidney phantom that is compatible with photoacoustic scanning will enable clinicians to evaluate a portable LED-based photoacoustic and ultrasound imaging system as a means of locating tumors and other abnormalities. This represents a significant step towards clinical translation of the compact system. Training using realistic phantoms reduces the risks associated with clinical procedures. Complications during procedures can arise due to the specific structure of the kidney under investigation. Thus the ability to create a 3D printed phantom based on detailed anatomical images of a specific patient enables clinicians to train on a phantom with exactly the same structure as the kidney to be treated. Recently we developed a novel 3D printer based on gel wax. The device combines native gel wax with glass microspheres and titanium dioxide (TiO2) particles to obtain a medium with tissue-like optical and acoustic properties. 3D models created using this printer can be given a range of values of optical absorption reduced scattering coefficients. The ability to 3D patient-specific phantoms at low cost has the potential to revolutionize the production and use of tissue-equivalent phantoms in future, and can be applied to a wide range of organs and imaging modalities.
Small form-factor invasive pressure sensors are widely used in minimally invasive surgery, for example to guide decision making in coronary stenting procedures. Current fiber-optic sensors can have high manufacturing complexities and costs, which severely constrains their adoption outside of niche fields. A particular challenge is the ability to rapidly prototype and iterate upon sensor designs to optimize performance for different applications and medical devices. Here, we present a new sensor fabrication method, which involves two-photon polymerization printing and integration of the printed structure onto the end-face of a single-mode optical fiber. The active elements of the sensor were a pressure-sensitive diaphragm and an intermediate temperature-sensitive spacer that was insensitive to changes in external pressure. Deflection of the diaphragm and thermal expansion the spacer relative to the fiber end-face were monitored using phase-resolved low coherence interferometry. A pressure sensitivity of 0.031 rad/mmHg across the range of 760 to 1060 mmHg (absolute pressure), and a temperature sensitivity of 1.2 mrad/°C across the range 20 to 45°C were observed. This method will enable the fabrication of a wide range of fiber-optic sensors with pressure and temperature sensitivities suitable for guiding minimally invasive surgery.
Sentinel lymph node biopsy is a standard diagnosis procedure to determine whether breast cancer has spread to the lymph glands in the armpit (the axillary nodes). The metastatic status of the sentinel node (the first node in the axillary chain that drains the affected breast) is the determining factor in surgery between conservative lumpectomy and more radical mastectomy including axillary node excision. The traditional assessment of the node requires sample preparation and pathologist interpretation. An automated elastic scattering spectroscopy (ESS) scanning device was constructed to take measurements from the entire cut surface of the excised sentinel node and to produce ESS images for cancer diagnosis. Here, we report on a partially supervised image classification scheme employing a Bayesian multivariate, finite mixture model with a Markov random field (MRF) spatial prior. A reduced dimensional space was applied to represent the scanning data of the node by a statistical image, in which normal, metastatic, and nonnodal-tissue pixels are identified. Our results show that our model enables rapid imaging of lymph nodes. It can be used to recognize nonnodal areas automatically at the same time as diagnosing sentinel node metastases with sensitivity and specificity of 85% and 94%, respectively. ESS images can help surgeons by providing a reliable and rapid intraoperative determination of sentinel nodal metastases in breast cancer.
Medical phantoms with accurate tissue-mimicking properties and anatomical structures are vital for evaluation of imaging system performance, calibration of medical devices, and training medical staff in techniques such as ultrasonography. Tissue-mimicking phantoms based on Agar/gelatin and polyvinyl alcohol (PVA) materials have been developed, however, they are fragile, exhibit dehydration problems and cannot reproduce complex structures. There is an ongoing need for novel tissue-mimicking materials and phantom fabrication methods. Three-dimensional (3D) printing additive technology allows direct formation of the object layer by layer and provides freedom in object design.
Various 3D printing materials have been employed from metal and ceramics to resins and polymers. Unfortunately, commercially available 3D printing materials don’t have suitable physical properties to mimick tissue. In this work, we describe the development of a novel 3D printing technology based on an original soft tissue-mimicking material, Gel Wax, a mixture of polymer and mineral oil. This material is soft, optically and acoustically clear and does not dehydrate. The optical, acoustic and mechanical properties of the material can be tailored to mimic biological tissues by embedding titanium dioxide, dyes, glass microspheres, or paraffin wax. Gel Wax cannot be made into a conventional filament and we designed a novel 3D printing techniques.
We demonstrate hippocampus models directly printed using our proposed Gel Wax 3D printer. This technology holds a great promise for fabricating patient-specific medical phantoms. This opens the door for 3D printing to provide new affordable medical phantoms to enable widespread application in biomedical field.
Percutaneous coronary interventions are widely performed minimally invasive procedures used to treat narrowing (stenosis) of arteries in the heart. Differential blood pressure measurements across a stenosis are invaluable to estimate the prognostic benefit of performing angioplasty and stenting via calculation of the fractional flow reserve. Achieving stable measurements from within pressure microcatheters and guidewires that are compatible with stenosed vessels, and which can be fabricated with low cost manufacturing methods, remains an important challenge. We have developed all-optical pressure and temperature sensors with a single optical fibre and sensing element. This approach provides simultaneous temperature and pressure measurements in a highly miniaturised device, with a simple construction method using low cost materials. Polymeric structures including membranes and domes are applied to the distal ends of single mode optical fibres. Temperature and pressure changes induce time-varying displacements of these structures, which are monitored using phase-resolved low-coherence interferometry. Phase measurements are acquired at 250 Hz with a sensitivity of approximately 0.2 rad/°C for temperature measurements between 20 and 45°C, and approximately 0.08 rad/mmHg for pressure between 760 and 1060 mmHg. In vivo studies in arteries and hearts of sheep and swine indicate that the sensors have sufficient sensitivity and speed for measurement of physiological pressure waveforms in clinical settings. We will discuss the integration of these sensors within medical devices, and the potential for providing additional physiological parameters with the same devices.
High frequency ultrasound probes such as intravascular ultrasound (IVUS) and intracardiac echocardiography (ICE) catheters can be invaluable for guiding minimally invasive medical procedures in cardiology such as coronary stent placement and ablation. With current-generation ultrasound probes, ultrasound is generated and received electrically. The complexities involved with fabricating these electrical probes can result in high costs that limit their clinical applicability. Additionally, it can be challenging to achieve wide transmission bandwidths and adequate wideband reception sensitivity with small piezoelectric elements. Optical methods for transmitting and receiving ultrasound are emerging as alternatives to their electrical counterparts. They offer several distinguishing advantages, including the potential to generate and detect the broadband ultrasound fields (tens of MHz) required for high resolution imaging. In this study, we developed a miniature, side-looking, pulse-echo ultrasound probe for intravascular imaging, with fibre-optic transmission and reception. The axial resolution was better than 70 microns, and the imaging depth in tissue was greater than 1 cm. Ultrasound transmission was performed by photoacoustic excitation of a carbon nanotube/polydimethylsiloxane composite material; ultrasound reception, with a fibre-optic Fabry-Perot cavity. Ex vivo tissue studies, which included healthy swine tissue and diseased human tissue, demonstrated the strong potential of this technique. To our knowledge, this is the first study to achieve an all-optical pulse-echo ultrasound probe for intravascular imaging. The potential for performing all-optical B-mode imaging (2D and 3D) with virtual arrays of transmit/receive elements, and hybrid imaging with pulse-echo ultrasound and photoacoustic sensing are discussed.
In a wide range of clinical procedures, accurate placement of medical devices such as needles and catheters is critical to optimize patient outcomes. Ultrasound imaging is often used to guide minimally invasive procedures, as it can provide real-time visualization of patient anatomy and medical devices. However, this modality can provide low image contrast for soft tissues, and poor visualization of medical devices that are steeply angled with respect to the incoming ultrasound beams. Photoacoustic sensors can provide information about the spatial distributions of tissue chromophores that could be valuable for guiding minimally invasive procedures. In this study, a system for guiding minimally invasive procedures using photoacoustic sensing was developed. This system included a miniature photoacoustic probe with three optical fibers: one with a bare end for photoacoustic excitation of tissue, a second for photoacoustic excitation of an optically absorbing coating at the distal end to transmit ultrasound, and a third with a Fabry-Perot cavity at the distal end for receiving ultrasound. The position of the photoacoustic probe was determined with ultrasonic tracking, which involved transmitting pulses from a linear-array ultrasound imaging probe at the tissue surface, and receiving them with the fiber-optic ultrasound receiver in the photoacoustic probe. The axial resolution of photoacoustic sensing was better than 70 μm, and the tracking accuracy was better than 1 mm in both axial and lateral dimensions. By translating the photoacoustic probe, depth scans were obtained from different spatial positions, and two-dimensional images were reconstructed using a frequency-domain algorithm.
Detection of tissue structures such as nerves and blood vessels is of critical importance during many needle-based minimally invasive procedures. For instance, unintentional injections into arteries can lead to strokes or cardiotoxicity during interventional pain management procedures that involve injections in the vicinity of nerves. Reliable detection with current external imaging systems remains elusive. Optical generation and reception of ultrasound allow for depth-resolved sensing and they can be performed with optical fibers that are positioned within needles used in clinical practice. The needle probe developed in this study comprised separate optical fibers for generating and receiving ultrasound. Photoacoustic generation of ultrasound was performed on the distal end face of an optical fiber by coating it with an optically absorbing material. Ultrasound reception was performed using a high-finesse Fabry-Pérot cavity. The sensor data was displayed as an M-mode image with a real-time interface. Imaging was performed on a biological tissue phantom.
Novel ultrasound transducers were created with a composite of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS) that was dip coated onto the end faces of optical fibers. The CNTs were functionalized with oleylamine to allow for their dissolution in xylene, a solvent of PDMS. Ultrasound pulses were generated by illuminating the composite coating with pulsed laser light. At distances of 2 to 16 mm from the end faces, ultrasound pressures ranged from 0.81 to 0.07 MPa and from 0.27 to 0.03 MPa with 105 and 200 μm core fibers, respectively. Using an optical fiber hydrophone positioned adjacent to the coated 200 µm core optical fiber, ultrasound reflectance measurements were obtained from the outer surface of a sheep heart ventricle. The results of this study suggest that ultrasound transducers that comprise optical fibers with CNT-PDMS composite coatings may be suitable for miniature medical imaging probes.
We undertook a phase I dose-escalation study of verteporfin photodynamic therapy (PDT) in 15 patients with locally advanced pancreatic cancer. Needle placement and laser delivery were technically successful in all patients. Thirteen patients were treated with a single laser fibre. Three treatments were carried out each at 5, 10 and 20 J/cm2; and 5 treatments (4 patients) at 40 J/cm2. A further 2 patients were treated with 2 or 3 laser fibres at 40 J/cm2. Tumour necrosis was measured on CT (computed tomography) by two radiologists 5 days after treatment. There was a clear dosedependent increase in necrosis with a median area of 20 x 16 mm (range 18 x 16 to 35 x 30 mm) at 40 J/cm2. In the 2 patients treated with multiple fibres, necrosis was 40 x 36 mm and 30 x 28 mm, respectively. There were no early complications in patients treated with a single fibre. Both patients treated with multiple fibres had evidence on CT of inflammatory change occurring anterior to the pancreas but without clinical deterioration. These results suggest that single fibre verteporfin PDT is safe in a clinical setting up to 40J/cm2 and produces a dose-dependent area of pancreatic necrosis.
Photodynamic therapy (PDT) mediated with verteporfin is currently being investigated to treat pancreatic cancer in
patients who are not surgical candidates. Clinically, interstitial light delivery is administered through a fiber, via
percutaneous needle implantation guided by ultrasound and/or verified by CT. Tumor response to PDT is based on
photosensitizer (PS) dose, light dose, light dose rate and the timing of light application following PS injection. However,
studies have shown that even when matching administered PDT treatment parameters such as drug dose and light level,
there can be significant inter-patient variation in tissue damage post-PDT, and this has been primarily attributed to
imprecise PS concentration at the target tissue site.
In order to achieve optimal tumor response from PDT without causing major damage to surrounding tissue, it would be
advantageous to measure the PS concentration in the target tissue just prior to light application. From these
measurements, the clinician can adapt the light application dose to the measured target tissue PS concentration (i.e.
insufficient target tissue PS concentrations compensated by higher light doses and vice versa.) in order to provide an
optimal light dose for each patient.
In animal studies, a spectrometer-based in-vivo fluorescence dosimetry system has been used to assess accumulated PS
levels (verteporfin) in situ. Measurements are taken from skin, leg muscle, buccal mucosa and tumor tissue locations one
hour after injection of the photosensitizer. Real-time spectral fitting, subtraction of background autofluorescence and
ratiometric analysis is performed on the raw data to extract out only the photosensitizer fluorescence and therefore
concentration. Using a pre-measured calibration data set of varying concentrations for verteporfin in tissue phantoms
composed of intralipid and whole blood, it was possible detect concentrations of the photosensitizer below 0.5nM.
In the clinical studies being performed at UCL Hospital in which verteporfin-PDT treatment is being given to patients
with pancreatic cancer, the dosimetry system is being used to assess PS concentration the pancreatic tumor tissue prior to
interstitial light dose treatment. The goal of the work here is to determine whether the dosimetry system can accurately
and efficiently be used clinically by evaluating the measured local tissue PS concentration to treatment outcome (area of
necrosis established). The results of this study will partially determine the need for fluorescence dosimetry to
individualize PDT treatment for patients based on local tissue PS concentration.
Photodynamic therapy (PDT) is being investigated as a treatment for localized prostate cancer. Photodynamic therapy uses a photosensitizing drug which is activated by a specific wavelength of light, in the presence of oxygen. The activated drug reacts with tissue oxygen to produce reactive oxygen species which are responsible for localized tissue necrosis. One of the determinants of the PDT effect is the penetration of light in the prostate. This study assesses the penetration depth of 763 nm light throughout the prostate. Eight men undergoing multiple hollow needle insertion for high dose rate brachytherapy were recruited. 763 nm light, produced by a diode laser, was delivered to the prostate using cylindrically diffusing optical fibers within the plastic needles. Light was detected at different distances from the source, using an isotropic detector within nearby needles. Penetration depth was calculated using the Boltzmann approximation to the diffusion equation. Delivery detector fiber separation was measured on computed tomography. The mean penetration depth was 0.57 cm, but there was within patient variation of a mean factor of 4.3. Further work is ongoing to assess the effect of such variability in light penetration, on the PDT effect.
A novel method for rapidly detecting metastatic breast cancer within excised sentinel lymph node(s) of the axilla is presented. Elastic scattering spectroscopy (ESS) is a point-contact technique that collects broadband optical spectra sensitive to absorption and scattering within the tissue. A statistical discrimination algorithm was generated from a training set of nearly 3000 clinical spectra and used to test clinical spectra collected from an independent set of nodes. Freshly excised nodes were bivalved and mounted under a fiber-optic plate. Stepper motors raster-scanned a fiber-optic probe over the plate to interrogate the node's cut surface, creating a 20×20 grid of spectra. These spectra were analyzed to create a map of cancer risk across the node surface. Rules were developed to convert these maps to a prediction for the presence of cancer in the node. Using these analyses, a leave-one-out cross-validation to optimize discrimination parameters on 128 scanned nodes gave a sensitivity of 69% for detection of clinically relevant metastases (71% for macrometastases) and a specificity of 96%, comparable to literature results for touch imprint cytology, a standard technique for intraoperative diagnosis. ESS has the advantage of not requiring a pathologist to review the tissue sample.
Photodynamic therapy (PDT) mediated with Verteporfin is being investigated as a pancreatic cancer treatment in the
cases for non-surgical candidates. Tissue response to PDT is based on a number of parameters including photosensitizer
(PS) dose, light dose and time interval between light application and PS injection.
In this study, PS uptake and distribution in animal leg muscle, oral cavity tissues, pancreas and tumor was measured
in vivo using light-induced fluorescence spectroscopy (LIFS) via an Aurora Optics Inc. PDT fluorescence dosimeter. An
orthotopic pancreatic cancer model (AsPC-1) was implanted in SCID mice and treated with the PS. Probe measurements
were made using a surface probe and an interstitial needle probe before and up to one hour after intravenous tail vein
injection of the PS.
The study demonstrated that it is possible to correlate in-vivo LIFS measurements of the PS uptake in the pancreas
with measurements taken from the oral cavity indicating that light dosimetry of PDT of the pancreas can be ascertained
from the LIFS measurements in the oral cavity. These results emphasize the importance of light dosimetry in improving
the therapeutic outcome of PDT through light dose adaptation to the relative in situ tissue PS concentration.
Background: Methods are required for propulsion of endoscopes through the small bowel and for propelling capsule endoscopes without cables. Aim: To test the hypothesis that electrical stimulation could propel an endoscope by stimulating muscular contraction. Methods: Prototype acrylic devices of ovoid shape were constructed with two stainless steel electrodes mounted on the tapered section. Five devices of 13 to 23 mm diameter with a taper of 16 degree(s) to 20 degree(s) (half angle) were tested. When in contact with the bowel wall electrostimulation was applied causing circular muscle contraction which when applied to the taper of the ovoid resulted in forward propulsion of the device. The method does not induce peristalsis but works by stimulating local contraction. The device was tested in small bowel and oesophagus of anaesthetized pigs. Results: Electrostimulation caused the ovoid to advance rapidly (6 mm/sec) up and down the oesophagus by inducing circular esophageal muscle contraction. When stimulated at 15 Hz with 30 ms pulses the threshold for movement was 12 mA; at 20 mA the device moved reliably in both directions in the small bowel at speeds of up to 4.5 mm/s, negotiating tight curves.
An integrated system for the planning of maxillo-facial and cranial surgery is described. The system is based on the use of computer graphics to simulate surgical operations on the bone and to predict and present the outcome of these on the soft tissue and appearance of the face. The input data consists of a suitable set of contiguous X-ray CT slices. As well as the core system which provides the simulation and modelling an extensive range of support facilities is provided for measuring external and internal anatomy profile plotting and quantitative postsurgical assessment. A system for long term follow up of facial shape change is provide by an optical surface scanner. Facilities are also provided for the downloading of data to a numerically controlled milling machine for the production of customised prostheses.
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