Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. Malinowski, D. Lin, S. Alam, Z. Zhang, M. Ibsen, D. Richardson, J. Young, P. Wright, K. Ozanyan, M. Stringer, and B. Miles, "Fiber MOPA Based Tunable Source for Terahertz Spectroscopy," in CLEO:2011 - Laser Applications to Photonic Applications, OSA Technical Digest (CD) (Optica Publishing Group, 2011), paper JWA120. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

We report on tomographic measurements in the terahertz spectral range and subsequent image reconstruction of a phantom subject. At terahertz wavelengths we abandon the traditional hard-field tomography approach to use attenuation measurements for imaging, because of the strong beam steering at the periphery of objects and the existence of a substantial diffusely scattered component. Under these conditions we focus on imaging from the measurements of the terahertz pulse propagation delay, taken with a system for time-domain terahertz spectroscopy, and reconstruct the subject's optical density instead of e.g. material density as in x-ray tomography. The novelty is our experimental approach to retain, by spatial and temporal filtering, only the photons that propagate along the shortest straight paths allowing hard-field tomography, approach for the image reconstruction. We show that pulse delay measurements result in path integrals of the light's group velocity in the subject and therefore the image reconstruction yields the spatial distribution of the real part of the refractive index. Furthermore, we suggest a procedure whereby the pulse delay time is calculated from the time-domain waveform with a better precision, taking into account the physics of THz generation by ultrashort pulses in a biased-gap antenna.

BACKGROUND:Yorkshire Laser Centre experience of PDT in early oesophageal cancer (EOCa) to determine long survival at 3 and 5 years (absolute) and factors which might influence outcome. MATERIAL/METHOD:The records of patients who had PDT (1997-2009) for oesophageal cancer were reviewed and those with EOCa were studied and analysed. All patients had standard work up and staging. PDT was carried out using Photofrin 2 mg/kw bw, iv followed 24-72 h later by endoscopic illumination with 630 nm laser light. Results were assessed based on pathological response to treatment and survival at 3 and 5 years post-PDT. RESULTS:There were 40 patients with EOCa amongst 144 who had PDT for oesophageal cancer. 30 male and 10 female (mean age 77, range 48-84). 35 had adenocarcinoma and 5 squamous cell carcinoma. 20 of the former had Barrett's mucosa. There was no operative or 30-day mortality and no serious complications. Adverse effects were noted in 10 patients including 2 with skin photosensitivity and 3 with mild stricture requiring one dilatation. The median follow up was 76.1 (range 36-150 months). In this period 24 patients have died between 2 and 150 months (median 41 months). 16 patients are alive in between 36 and 110 months. 3 and >or=5 years or more survival (absolute) were 72.5% and 53.8%, respectively. CONCLUSION:Endoscopic PDT should be considered as the treatment of choice in patients with EOCa who are ineligible for surgical resection. We suggest that a carefully designed study of a cohort of patients with EOCa comparing surgical resection with endoscopic PDT is warranted.

Laser spectroscopy in the visible and NIR is widely used to study flame behaviour in internal combustion engines and turbines, but is inapplicable at high pressures because high soot concentration renders flames opaque; however they remain transparent to THz radiation. We use THz time-domain transmission spectroscopy to characterise gaseous species in flames. A specially designed high-pressure burner vessel has been built which allows spectroscopy to be carried out at pressures above 5 bar.

We present a method to quantify the linearity and dynamic range of terahertz detectors and show that terahertz time-domain-spectrometers exhibit a non-linear amplitude response at frequencies below 1.5 THz.

The link between cigarette smoking and lung cancer is well documented. The introduction of autofluorescence bronchoscopy ( AFB) has allowed visualization of preinvasive neoplastic changes of bronchial mucosa. We evaluate the sensitivity of AFB to show epithelial changes compared with white light bronchoscopy ( WLB) in a group of healthy, asymptomatic smokers. Inclusion criteria demanded heavy smokers (> 20 pack-years) at least 40 years old, asymptomatic with no history of cancer and clear chest x-ray. Candidates completed a questionnaire and were interviewed to record medical history and smoking habit. Bronchoscopy was carried out under topical or general anesthesia with standard flexible fiberoptic bronchoscope for WLB and the Xillix LIFE Lung system for AFB. The study included 93 subjects ( 57 men, 36 women) aged 40 to 75 years. AFB indicated positive images in the bronchial tree of 51 subjects, biopsies showed epithelial abnormalities in 27 ( 15 metaplasia, 12 inflammatory changes). WLB showed abnormality in 1 subject but with no pathologic changes revealed by cytohistology. Therefore, the sensitivity of AFB to metaplasia was 75% compared with zero for WLB. AFB yields positive predictive values for metaplastic and overall mucosal changes of 29.4% and 52.9%, respectively. Over 16% of asymptomatic smokers had metaplastic changes in their bronchial mucosa. AFB proved more sensitive in revealing early preneoplastic changes than WLB. We suggest the follow-up of such individuals to evaluate progress particularly in those who continue to smoke.

Objectives: To review the Yorkshire Laser Centre experience with bronchoscopic photodynamic therapy (PDT) in early central lung cancer in subjects not eligible for surgery and to discuss diagnostic problems and the indications for PDT in such cases.Methods: Of 200 patients undergoing bronchoscopic PDT, 21 had early central lung cancer and were entered into a prospective study. Patients underwent standard investigations including white light bronchoscopy in all and autofluorescence bronchoscopy in 12 of the most recent cases. Indications for bronchoscopic PDT were recurrence/metachronous endobronchial lesions following previous treatment with curative intent in 10 patients (11 lesions), ineligibility for surgery because of poor cardiorespiratory function in 8 patients (9 lesions) and declined consent to operation in 3 patients. PDT consisted of intravenous administration of Photofrin 2 mg/kg followed by bronchoscopic illumination 24-48 h later.Results: 29 treatments were performed in 21 patients (23 lesions). There was no procedure-related or 30 day mortality. One patient developed mild skin photosensitivity. All patients expressed satisfaction with the treatment and had a complete response of variable duration. Six patients died at 3-103 months (mean 39.3), three of which were not as a result of cancer. Fifteen patients were alive at 12-82 months.Conclusion: Bronchoscopic PDT in early central lung cancer can achieve long disease-free survival and should be considered as a treatment option in those ineligible for resection. Autofluorescence bronchoscopy is a valuable complementary investigation for identification of synchronous lesions and accurate illumination in bronchoscopic PDT.

Twenty-three patients, 12 males and 11 females aged 42–86 years (mean age 69.6), with inoperable oesophageal cancer were treated by endoscopic photodynamic therapy. Inoperability in 20 patients was due to extent of tumour and existence of metastases, in two because of poor general condition and in one patient due to recurrence at the site of previous anastomosis. Prior to treatment, patients' degree of dysphagia and their functional status were recorded. Using barium contrast studies and endoscopy, the extent and location of the tumour within the lumen of the oesophagus were mapped out. Treatment protocol consisted of intravenous administration of the photosensitizer, Polyhaematoporphyrin, followed 24–48 h later by illumination of the tumour with 630 nm light produced by a copper vapour pumped-dye laser and delivered via a 400μm internal diameter optical fibre with a cylindrical diffusing end. All treatments were undertaken under general anaesthesia as day case procedures. There was no treatment-related mortality nor was there any complication apart from a mild skin photosensitivity reaction in one case. Every patient's swallowing and functional status was improved at 6 weeks post-treatment. Ten patients needed more than one treatment: five required oesophageal dilatation. Thirteen patients survived a mean period of 6.2 months. Two needed oesophageal intubation 3–4 weeks before their death. Ten patients are alive at 6–14 months. This study suggests photodynamic therapy in inoperable oesophageal cancer to be a useful treatment method and in suitable cases an alternative to other forms of palliation. Its value lies in the fact that it can be used to treat cancer at any level of the oesophagus irrespective of histology.