Dynamic physiological temperature and pressure sensing with phase-resolved low-coherence interferometry.

We report the development and characterisation of highly miniaturised fibre-optic sensors for simultaneous pressure and temperature measurement, and a compact interrogation system with a high sampling rate. The sensors, which have a maximum diameter of 250 µm, are based on multiple low-finesse optical cavities formed from polydimethylsiloxane (PDMS), positioned at the distal ends of optical fibres, and interrogated using phase-resolved low-coherence interferometry. At acquisition rates of 250 Hz, temperature and pressure changes of 0.0021 °C and 0.22 mmHg are detectable. An in vivo experiment demonstrated that the sensors had sufficient speed and sensitivity for monitoring dynamic physiological pressure waveforms. These sensors are ideally suited to various applications in minimally invasive surgery, where diminutive lateral dimensions, high sensitivity and low manufacturing complexities are particularly valuable.

Photodynamic therapy: Inception to application in breast cancer.

Photodynamic therapy (PDT) is already being used in the treatment of many cancers. This review examines its components and the new developments in our understanding of its immunological effects as well as pre-clinical and clinical studies, which have investigated its potential use in the treatment of breast cancer.

Music-of-light stethoscope: a demonstration of the photoacoustic effect.

In this paper we present a system aimed at demonstrating the photoacoustic (PA) effect for educational purposes. PA imaging is a hybrid imaging modality that requires no contrast agent and has a great potential for spine and brain lesion characterisation, breast cancer and blood flow monitoring notably in the context of fetal surgery. It relies on combining light excitation with ultrasound reception. Our brief was to present and explain PA imaging in a public-friendly way suitable for a variety of ages and backgrounds. We developed a simple, accessible demonstration unit using readily available materials. We used a modulated light emitting diode (LED) torch and an electronic stethoscope. The output of a music player was used for light modulation and the chest piece of the stethoscope covered by a black tape was used as an absorbing target and an enclosed chamber. This demonstration unit was presented to the public at the Bloomsbury Festival On Light in October 2015. Our stall was visited by over 100 people of varying ages. Twenty families returned in-depth evaluation questionnaires, which show that our explanations of the photoacoustic effect were well understood. Their interest in biomedical engineering was increased.

Minimal residual disease testing after stem cell transplantation for multiple myeloma.

Increased use of novel agents and autologous stem cell transplantation has led to a significant improvement in PFS and overall survival in patients with multiple myeloma. Despite improved treatment strategies, most patients eventually relapse due to persistent low levels of disease in the bone marrow. Increasingly sensitive methods to measure or detect such disease have been evaluated, including multi-parametric flow cytometry, PCR, next-generation sequencing and imaging modalities. The following literature review examines current methods for detecting and monitoring minimal or measurable residual disease (MRD) in the post-transplant setting. Improved methods for detecting MRD will refine the current definitions of remission and could guide treatment approaches.

A randomised controlled trial of ALA vs. Photofrin photodynamic therapy for high-grade dysplasia arising in Barrett's oesophagus.

Photofrin photodynamic therapy (PDT) is a licenced treatment for Barrett's oesophagus (BE) with high-grade dysplasia (HGD) but causes strictures and photosensitivity and complete reversal of dysplasia (CR-HGD) by 50 % at 5 years. 5-Aminolaevulinic acid (ALA) is an alternative treatment with non-randomised data suggesting 85 % CR-HGD and a low risk of side effects. We aimed to compare efficacy and side effect profile between the drugs. A single-centre randomised controlled trial was conducted. Presence of HGD was confirmed on three occasions by two specialist GI pathologists. Stratification was by length of BE and extent of dysplasia. Standard protocols for ALA and Photofrin-PDT were followed. Endoscopic follow-up with 2-cm four-quadrant biopsy was at 6 weeks, 4 months, and then annually. All adverse event data were collected. Sixty four patients were randomised, 34 ALA and 30 Photofrin-PDT. Median follow-up is 24 months. On intention-to-treat analysis, CR-HGD was 16/34 (47 %) with ALA-PDT and 12/30 (40 %) with Photofrin-PDT. The overall cancer incidence was 14 % (9/64). On sub-group log-rank analysis, for BE ≤ 6 cm, CR-HGD was significantly higher with ALA-PDT than Photofrin-PDT (χ(2) =5.39, p=0.02). Strictures and skin photosensitivity were significantly more common after treatment with Photofrin-PDT than ALA-PDT (33 vs. 9 % and 43 vs. 6 %, respectively, p<0.05). The rate of buried glands with either drug was significantly higher post-PDT (48 % of patients) than pre-PDT (20 %). ALA-PDT has a better risk profile than Photofrin-PDT. In patients with BE length ≤ 6 cm, preliminary results show ALA-PDT is associated with significantly higher CR-HGD. In longer segments of BE, neither PDT drug is sufficiently efficacious to warrant routine use.

Use of an implanted sacral nerve stimulator to restore urine voiding in chronically paraplegic dogs.

BACKGROUND: Loss of urinary control after spinal cord injury increases risk of urinary tract disease and is problematical for owners of affected dogs. OBJECTIVES: To design, implant, and test a sacral nerve stimulating device for controlling urine voiding in paraplegic dogs. ANIMALS: Nine pet dogs with severe thoracolumbar spinal cord injury causing paraplegia, loss of hindquarter sensation, and incontinence for more than 3 months. The procedure was offered prospectively to owners of suitable candidates after the irreversibility of the incontinence had been ascertained. METHODS: Open label clinical study. Surgically implantable electrode "books" were designed for insertion and retention of mixed sacral nerves. Sacral nerves were accessed via laminectomy and stimulated to test their ability to elicit detrusor contraction and then inserted into the electrode book, which was attached to a subcutaneously implanted, externally activated receiver. RESULTS: In 8/9 dogs, S2 nerves elicited the largest increases in intravesicular pressure with minimum stimulation and were placed in electrode books. Voiding efficiency was >90% in 8 of the 9 implanted dogs. No important detrimental effects of the procedure were observed. CONCLUSIONS AND CLINICAL IMPORTANCE: This sacral nerve stimulating implant is a simple and apparently effective neuroprosthetic device that restores urine voiding in paraplegic dogs.

Optical scanning for rapid intraoperative diagnosis of sentinel node metastases in breast cancer.

BACKGROUND: Intraoperative diagnosis of sentinel node metastases enables an immediate decision to proceed to axillary lymph node dissection, avoiding a second operation in node-positive women with breast cancer. METHODS: An optical scanner was developed that interrogated the cut surface of bivalved, but otherwise unprocessed, sentinel lymph nodes with pulses of white light by elastic scattering spectroscopy (ESS). The scattered light underwent spectral analysis, and individual spectra were initially correlated with conventional histology to develop a diagnostic algorithm. This algorithm was used to create false colour-coded maps of scans from an independent set of nodes, and the optimal criteria for discriminating between normal and cancer spectra were defined statistically. RESULTS: The discriminant algorithm was developed from a training set of 2989 spectra obtained from 30 metastatic and 331 normal nodes. Subsequent scans from 129 independent nodes were analysed. The scanner detected macrometastases (larger than 2 mm) with a sensitivity of 76 per cent (69 per cent including micrometastases) and specificity of 96 per cent. CONCLUSION: In this proof-of-principle study, the ESS results were comparable with current intraoperative diagnostic techniques of lymph node assessment.

Image cytometry accurately detects DNA ploidy abnormalities and predicts late relapse to high-grade dysplasia and adenocarcinoma in Barrett's oesophagus following photodynamic therapy.

BACKGROUND AND AIMS: DNA ploidy abnormalities (aneuploidy/tetraploidy) measured by flow cytometry (FC) are strong predictors of future cancer development in untreated Barrett's oesophagus, independent of histology grade. Image cytometric DNA analysis (ICDA) is an optical technique allowing visualisation of abnormal nuclei that may be undertaken on archival tissue. Our aim was to determine the accuracy of ICDA vs FC, and evaluate DNA ploidy as a prognostic biomarker after histologically successful treatment with photodynamic therapy (PDT). METHODS: Nuclei were extracted from 40 mum sections of paraffin-embedded biopsies and processed for ICDA at UCL and FC at UW using standardised protocols. Subsequently, DNA ploidy was evaluated by ICDA on a cohort of 30 patients clear of dysplasia 1 year after aminolaevulinic acid PDT for high-grade dysplasia (HGD). The results were correlated with long-term outcome. RESULTS: In the comparative study, 93% (41 out of 44) of cases were classified identically. Errors occurred in the near-diploid region by ICDA and the tetraploid region by FC. In the cohort study, there were 13 cases of late relapse (7 cancer, 6 HGD) and 17 patients who remained free of dysplasia after a mean follow-up of 44 months. Aneuploidy post-PDT was highly predictive for recurrent HGD or cancer with a hazard ratio of 8.2 (1.8-37.8) (log-rank P=0.001). CONCLUSIONS: ICDA is accurate for the detection of DNA ploidy abnormalities when compared with FC. After histologically successful PDT, patients with residual aneuploidy are significantly more likely to develop HGD or cancer than those who become diploid. DNA ploidy by ICDA is a valuable prognostic biomarker after ablative therapy.

T lymphocyte subset abnormalities in the blood and lung in pulmonary arterial hypertension.

RATIONALE: Mounting data suggest that immune cell abnormalities participate in the pathogenesis of pulmonary arterial hypertension (PAH). OBJECTIVE: To determine whether the T lymphocyte subset composition in the systemic circulation and peripheral lung is altered in PAH. METHODS: Flow cytometric analyses were performed to determine the phenotypic profile of peripheral blood lymphocytes in idiopathic PAH (IPAH) patients (n=18) and healthy controls (n=17). Immunocytochemical analyses of lymphocytes and T cell subsets were used to examine lung tissue from PAH patients (n=11) and controls (n=11). MEASUREMENTS AND MAIN RESULTS: IPAH patients have abnormal CD8+ T lymphocyte subsets, with a significant increase in CD45RA+ CCR7- peripheral cytotoxic effector-memory cells (p=0.02) and reduction of CD45RA+ CCR7+ naive CD8+ cells versus controls (p=0.001). Further, IPAH patients have a higher proportion of circulating regulatory T cells (T(reg)) and 4-fold increases in the number of CD3+ and CD8+ cells in the peripheral lung compared with controls (p<0.01). CONCLUSIONS: Alterations in circulating T cell subsets, particularly CD8+ T lymphocytes and CD4+ T(reg), in patients with PAH suggest that a dysfunctional immune system contributes to disease pathogenesis. A preponderance of CD3+ and CD8+ T lymphocytes in the peripheral lung of PAH patients supports this concept.

A novel use of T-tag sutures for the safe creation and closure of the NOTES gastrotomy using a hybrid technique.

Transgastric Natural Orifice Translumenal Endoscopic Surgery (NOTES) procedures are presently limited by the lack of a reliable method for creating and closing the gastrotomy created during the procedure. Furthermore, due to difficulties with the NOTES technique, the majority of NOTES procedures are presently performed in a "hybrid" fashion in which some degree of laparoscopic assistance is used alongside the NOTES approach. We describe a hybrid approach with a minimal laparoscopic component allowing a very controlled gastrotomy creation and closure. This technique would also allow laparoscopic suturing through a single, small cannula.

Transesophageal endoscopic ultrasound-guided access to the heart.

BACKGROUND AND STUDY AIMS: Endoscopic ultrasound and fine-needle aspiration of paramural lesions are established diagnostic techniques in gastroenterology and are now also used for therapeutic purposes. The proximity of the heart to the esophagus and the utility of the diagnostic technique of transesophageal echography prompted us to explore the possibilities of approaching the heart through the esophagus. METHODS: In acute experiments (n = 2) and survival experiments (n = 6) on anesthetized pigs, the anatomical landmarks were first identified and studied, before introduction of the needle through the posterior cardiac wall into the left atrium, and then beyond, as far as the aortic valve. The smallest structure targeted was the coronary artery. The animals in the survival group were monitored clinically over a 2-week period and also underwent endoscopic and cardiologic re-examinations prior to autopsy. Three patients were also investigated using the technique. RESULTS: No visible damage was observed in the heart in the two animals which were sacrificed immediately or in the six surviving pigs (except for one small hematoma). The needle could be introduced repeatedly into the left atrium, followed by the injection of saline. Reaching the aortic valve was more difficult because of the moving target, but ablation therapy was technically possible. The coronary artery was successfully punctured in three of the animals (all three weighed 40 kg or more); in smaller animals, the needle overshot the lumen of these minute arteries. Of the three patients investigated, pericardial fluid was successfully aspirated in two patients and a left atrial mass was punctured in the third patient (excluding neoplasia, the final diagnosis being thrombus). CONCLUSION: These animal studies and clinical cases suggest that transesophageal intracardiac procedures could become feasible and that further exploration by gastroenterologists and cardiologists may be justified.

Photodynamic therapy using meso tetra hydroxy phenyl chlorin (mTHPC) in early prostate cancer.

BACKGROUND AND OBJECTIVES: Prostate cancer is increasing in incidence, but current treatments including surgery and radiotherapy have significant side effects. This pilot study was designed to assess the potential of photodynamic therapy (PDT) using meso tetra hydroxy phenyl chlorin (mTHPC) for organ confined prostate cancer. STUDY DESIGN/PATIENTS AND METHODS: Six men with organ confined prostate cancer were photosensitised with mTHPC (0.15 mg/kg). Between 2 and 5 days later, red light (652 nm) was delivered to areas of biopsy proven cancer via fibres inserted through transperineal needles (50-100 J per site). RESULTS: After 8 of 10 PDT sessions, the prostate specific antigen (PSA) fell by up to 67%. Early MRI scans showed oedema and patchy necrosis, which resolved over 2 months. Biopsies of treated areas revealed necrosis and fibrosis at 1-2 months. CONCLUSIONS: PDT for primary prostate cancer appears safe and can reduce PSA levels. As this was a phase I study, no attempt was made to treat the whole prostate; this or targeted tumour ablation could be attempted in a phase II study with an increased number of fibres. This technique merits further investigation in early prostate cancer.

A system to monitor for fibre breakage during photodynamic therapy with diffuser fibres.

There is concern that the delicate fibres and cylindrical diffuser tips used for intraluminal PDT of blood vessels might break during the treatment. We have developed and tested a simple system to monitor for fibre breakage during PDT. Light from the laser is passed through a beam expander, then a beam splitter, and then is again contracted into the inlet of a diffuser fibre. Light reflected from the distal diffuser is also partially reflected by the beam splitter into a photodiode, which monitors changes in the intensity of the reflected light. The system was tested by simulating catastrophic failures in four fibres. In each case the output fell very significantly (DV=0.44-1.68 V, SD=0.01 V). Despite the small statistical sample, the average change in the reflected light intensity is still significant (p < 0.025, paired Student's t-test). Our conclusion was that this device can monitor the integrity of diffuser fibres during PDT.

Tyrosinase degradation via two pathways during reverse translocation to the cytosol.

Previous studies established that after inhibition of proteasome activity, tyrosinase could be detected in the cytosol after initial translation in the endoplasmic reticulum (ER), with a molecular weight consistent with that of a full-length, deglycosylated polypeptide. Here we show that most of these molecules are glycosylated, but have been proteolyzed at the carboxyl terminus by a protease that is insensitive to proteasome inhibitors. We also demonstrate the inhibitor-dependent accumulation of a membrane species that appears structurally homologous to the glycosylated and partially proteolyzed cytosolic form. Under some circumstances, cytosolic tyrosinase that had been deglycosylated and not proteolyzed prior to proteasomal degradation could also be detected. The presence of cytosolic tyrosinase was dependent upon glycosylation of the molecule during synthesis in the ER. These results suggest the existence of at least two alternative pathways for degradation of tyrosinase in the cytosol.

Electrical stimulation for propelling endoscopes.

BACKGROUND: Methods are needed for propulsion of endoscopes and wireless video capsules along the small intestine. This work aims to test the hypothesis that electrical stimulation could propel an endoscope by stimulating muscular contraction. METHODS: Prototype acrylic ovoid-shaped devices were constructed with 2 stainless steel electrodes mounted on the tapered section. Five devices 15 to 23 mm diameter with a taper of 28 degrees to 40 degrees (included angle) were tested. When these devices were 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 the small intestine and esophagus of anesthetized pigs. RESULTS: Electrostimulation caused the ovoid to advance rapidly (6 mm/sec) up and down the esophagus by inducing circular esophageal muscle contraction. When stimulated at 15 Hz with 30-ms pulses, the threshold for movement in the small intestine was 12 mA; at 20 mA the device moved reliably in either direction in the small intestine at speeds of up to 4.5 mm/sec and negotiated tight curves. CONCLUSION: Electrostimulation can move endoscopes in the small intestine.

The measurement of forces exerted during colonoscopy.

BACKGROUND: The widely varying forces used at colonoscopy have not been measured. An electronic device was designed to measure the forces exerted by the clinician on the endoscope during colonoscopy. METHODS: The device featured a handle designed in the shape of a hinged split cylinder that could be locked around the endoscope but readily moved up and down the insertion tube as the colonoscopy proceeded. This cylinder contained strain-gauges arranged so that the forces transmitted could be accurately measured. The device recorded the torque forces in addition to the push and pull forces exerted during diagnostic colonoscopy. RESULTS: In a series of 21 colonoscopies in 20 patients: peak pushing force = 4.4 kg, pulling force = -1.8 kg, anti-clockwise torque = 1.0 Newton meters, clockwise torque = 0.8 Newton meters. Percentage time force greater than 1 kg = 5%. Peak anal insertion force = 1.8 kg. CONCLUSIONS: These measurements represent the first accurate measurements of the forces exerted during colonoscopy. Reducing the force during colonoscopy is likely to diminish pain and reduce the risk of perforation. A knowledge of these forces may also help with the design of new instruments and models for teaching or research.

Technical advances and experimental devices for enteroscopy.

Enteroscopy remains the procedure in the gastrointestinal tract that is most inaccessible to endoscopy, and technical limitations severely impair the ability to advance and examine the small bowel reliably or completely. Push-type enteroscopy not only suffers limitations owing to looping in the stomach, but is intrinsically associated with increasing loss of transmission of force to the tip and consequent failure of advancement. Development is this area has been slow, partly owing to the limited clinical need compared with upper gastrointestinal endoscopy, and colonoscopy and consequent financial limitations imposed on further development. Practical and useful technical advances have been made, especially in push-type as well as sonde-type enteroscopy. These are reviewed briefly and are covered in other articles elsewhere in this issue.

Device for measuring the forces exerted on the shaft of an endoscope during colonoscopy.

Colonoscopy involves advancing a flexible endoscope into and along the entire length of the colon. The procedure can be painful and carries the risk of perforating the organ, yet very little is known of the forces involved. A device to measure the forces exerted on the endoscope during colonoscopy is described. The device features a handle designed in the shape of a hinged split cylinder that locks around the endoscope, gripping it tightly. The handle has two parts, an inner part that grips the endoscope, and an outer part that is gripped by the endoscopist. The two parts are joined together by members that transmit the forces through to the endoscope. One of the members incorporates strain gauges that measure the torque applied to the endoscope, as well as the push and pull forces. The handle can easily be unlocked and moved along the endoscope as the colonoscopy proceeds. The device is used to measure the forces applied to the endoscope during 11 routine colonoscopies, and summary results are presented. These are believed to be the first accurate measurements of the forces exerted during colonoscopy.

The class I antigen-processing pathway for the membrane protein tyrosinase involves translation in the endoplasmic reticulum and processing in the cytosol.

Formation of major histocompatibility complex class I-associated peptides from membrane proteins has not been thoroughly investigated. We examined the processing of an HLA-A*0201-associated epitope, YMDGTMSQV, that is derived from the membrane protein tyrosinase by posttranslational conversion of the sequence YMNGTMSQV. Only YMDGTMSQV and not YMNGTMSQV was presented by HLA-A*0201 on cells expressing full-length tyrosinase, although both peptides have similar affinities for HLA-A*0201 and are transported by TAP. In contrast, translation of YMNGTMSQV in the cytosol, as a minigene or a larger fragment of tyrosinase, led to the presentation of the unconverted YMNGTMSQV. This was not due to overexpression leading to saturation of the processing/conversion machinery, since presentation of the converted peptide, YMDGTMSQV, was low or undetectable. Thus, presentation of unconverted peptide was associated with translation in the cytosol, suggesting that processing of the full-length tyrosinase occurs after translation in the endoplasmic reticulum. Nevertheless, presentation of YMDGTMSQV in cells expressing full-length tyrosinase was TAP (transporter associated with antigen processing) and proteasome dependent. After inhibition of proteasome activity, tyrosinase species could be detected in the cytosol. We propose that processing of tyrosinase involves translation in the endoplasmic reticulum, export of full-length tyrosinase to the cytosol, and retransport of converted peptides by TAP for association with HLA-A*0201.

Computer-generated titanium cranioplasty: report of a new technique for repairing skull defects.

A review of 40 cases of titanium cranioplasty fabricated from impressions taken of the defect through the patient's scalp in the conventional way showed that 23% were ill-fitting and 41% of frontal plates had a poor aesthetic result. Attributable factors were difficulty in defining the defect border accurately and limited information of the surrounding tissue architecture which led to strains produced during insertion. Inadequate communication between surgeon and prosthetist compounded these difficulties. A prospective study of six cases fabricated from CT computer-generated models of challenging cranial defects appears to show significant improvements in plate design, resulting in better plate adaptation, stability and aesthetic contour. Plate insertion was rapid (mean time 27 min) thereby minimizing operating time. This paper also discusses the advantages of the enhanced information derived from CT and describes the potential for pre-craniotomy template and matching cranioplasty, thereby permitting a one-stage procedure.