Computer-aided design and fabrication of nasal prostheses: a semi-automated algorithm using statistical shape modeling.

PURPOSE: This research aimed to develop an innovative method for designing and fabricating nasal prostheses that reduces anaplastologist expertise dependency while maintaining quality and appearance, allowing patients to regain their normal facial appearance. METHODS: The method involved statistical shape modeling using a morphable face model and 3D data acquired through optical scanning or CT. An automated design process generated patient-specific fits and appearances using regular prosthesis materials and 3D printing of molds. Manual input was required for specific case-related details. RESULTS: The developed method met all predefined requirements, replacing analog impression-making and offering compatibility with various data acquisition methods. Prostheses created through this method exhibited equivalent aesthetics to conventionally fabricated ones while reducing the skill dependency typically associated with prosthetic design and fabrication. CONCLUSIONS: This method provides a promising approach for both temporary and definitive nasal prostheses, with the potential for remote prosthesis fabrication in areas lacking anaplastology care. While new skills are required for data acquisition and algorithm control, these technologies are increasingly accessible. Further clinical studies will help validate its effectiveness, and ongoing technological advancements may lead to even more advanced and skill-independent prosthesis fabrication methods in the future.

Clinical validation of the accuracy of an intra-operative assessment tool using 3D ultrasound compared to histopathology in patients with squamous cell carcinoma of the tongue.

BACKGROUND: Histopathological analysis often shows close resection margins after surgical removal of tongue squamous cell carcinoma (TSCC). This study aimed to investigate the agreement between intraoperative 3D ultrasound (US) margin assessment and postoperative histopathology of resected TSCC. METHODS: In this study, ten patients were prospectively included. Three fiducial cannulas were inserted into the specimen. To acquire a motorized 3D US volume, the resected specimen was submerged in saline, after which images were acquired while the probe moved over the specimen. The US volumes were annotated twice: (1) automatically and (2) manually, with the automatic segmentation as initialization. After standardized histopathological processing, all hematoxylin-eosin whole slide images (WSI) were included for analysis. Corresponding US images were found based on the known WSI spacing and fiducials. Blinded observers measured the tumor thickness and the margin in the caudal, deep, and cranial directions on every slide. The anterior and posterior margin was measured per specimen. RESULTS: The mean difference in all measurements between manually segmented US and histopathology was 2.34 (SD: ±3.34) mm, and Spearman's rank correlation coefficient was 0.733 (p < 0.001). The smallest mean difference was in the tumor thickness with 0.80 (SD: ±2.44) mm and a correlation of 0.836 (p < 0.001). Limitations were observed in the caudal region, where no correlation was found. CONCLUSION: This study shows that 3D US and histopathology have a moderate to strong statistically significant correlation (r = 0.733; p < 0.001) and a mean difference between the modalities of 2.3 mm (95%CI: -4.2; 8.9). Future research should focus on patient outcomes regarding resection margins.

Implementing a deep learning model for automatic tongue tumour segmentation in ex-vivo 3-dimensional ultrasound volumes.

Three-dimensional (3D) ultrasound can assess the margins of resected tongue carcinoma during surgery. Manual segmentation (MS) is time-consuming, labour-intensive, and subject to operator variability. This study aims to investigate use of a 3D deep learning model for fast intraoperative segmentation of tongue carcinoma in 3D ultrasound volumes. Additionally, it investigates the clinical effect of automatic segmentation. A 3D No New U-Net (nnUNet) was trained on 113 manually annotated ultrasound volumes of resected tongue carcinoma. The model was implemented on a mobile workstation and clinically validated on 16 prospectively included tongue carcinoma patients. Different prediction settings were investigated. Automatic segmentations with multiple islands were adjusted by selecting the best-representing island. The final margin status (FMS) based on automatic, semi-automatic, and manual segmentation was computed and compared with the histopathological margin. The standard 3D nnUNet resulted in the best-performing automatic segmentation with a mean (SD) Dice volumetric score of 0.65 (0.30), Dice surface score of 0.73 (0.26), average surface distance of 0.44 (0.61) mm, Hausdorff distance of 6.65 (8.84) mm, and prediction time of 8 seconds. FMS based on automatic segmentation had a low correlation with histopathology (r = 0.12, p = 0.67); MS resulted in a moderate but insignificant correlation with histopathology (r = 0.4, p = 0.12, n = 16). Implementing the 3D nnUNet yielded fast, automatic segmentation of tongue carcinoma in 3D ultrasound volumes. Correlation between FMS and histopathology obtained from these segmentations was lower than the moderate correlation between MS and histopathology.

Comparison of image quality of 3D ultrasound: motorized acquisition versus freehand navigated acquisition, a phantom study.

PURPOSE: Intra-operative assessment of resection margins during oncological surgery is a field that needs improvement. Ultrasound (US) shows the potential to fulfill this need, but this imaging technique is highly operator-dependent. A 3D US image of the whole specimen may remedy the operator dependence. This study aims to compare and evaluate the image quality of 3D US between freehand acquisition (FA) and motorized acquisition (MA). METHODS: Multiple 3D US volumes of a commercial phantom were acquired in motorized and freehand fashion. FA images were collected with electromagnetic navigation. An integrated algorithm reconstructed the FA images. MA images were stacked into a 3D volume. The image quality is evaluated following the metrics: contrast resolution, axial and elevation resolution, axial and elevation distance calibration, stability, inter-operator variability, and intra-operator variability. A linear mixed model determined statistical differences between FA and MA for these metrics. RESULTS: The MA results in a statistically significant lower error of axial distance calibration (p < 0.0001) and higher stability (p < 0.0001) than FA. On the other hand, the FA has a better elevation resolution (p < 0.003) than the MA. CONCLUSION: MA results in better image quality of 3D US than the FA method based on axial distance calibration, stability, and variability. This study suggests acquiring 3D US volumes for intra-operative ex vivo margin assessment in a motorized fashion.

A hybrid registration method using the mandibular bone surface for electromagnetic navigation in mandibular surgery.

PURPOSE: To utilize navigated mandibular (reconstructive) surgery, accurate registration of the preoperative CT scan with the actual patient in the operating room (OR) is required. In this phantom study, the feasibility of a noninvasive hybrid registration method is assessed. This method consists of a point registration with anatomic landmarks for initialization and a surface registration using the bare mandibular bone surface for optimization. METHODS: Three mandible phantoms with reference notches on two osteotomy planes were 3D printed. An electromagnetic tracking system in combination with 3D Slicer software was used for navigation. Different configurations, i.e., different surface point areas and number and configuration of surface points, were tested with a dentate phantom (A) in a metal-free environment. To simulate the intraoperative environment and different anatomies, the registration procedure was also performed with an OR bed using the dentate phantom and two (partially) edentulous phantoms with atypical anatomy (B and C). The accuracy of the registration was calculated using the notches on the osteotomy planes and was expressed as the target registration error (TRE). TRE values of less than 2.0 mm were considered as clinically acceptable. RESULTS: In all experiments, the mean TRE was less than 2.0 mm. No differences were found using different surface point areas or number or configurations of surface points. Registration accuracy in the simulated intraoperative setting was-mean (SD)-0.96 (0.22), 0.93 (0.26), and 1.50 (0.28) mm for phantom A, phantom B, and phantom C. CONCLUSION: Hybrid registration is a noninvasive method that requires only a small area of the bare mandibular bone surface to obtain high accuracy in phantom setting. Future studies should test this method in clinical setting during actual surgery.

Registration methods for surgical navigation of the mandible: a systematic review.

Image-to-patient registration in navigated mandibular surgery is complex due to the mobile nature of the mandible compared with other craniofacial bones. As a result, surgical navigation is rarely employed in the mandibular region. This systematic review provides an overview of the different registration methods that are used for surgical navigation of the mandible. A systematic search was performed in the MEDLINE Ovid, Scopus, and Embase databases on March 25, 2021. Search terms included synonyms for mandibular surgery, surgical navigation, and registration methods. Articles about navigated mandibular surgery, where the registration method was explicitly mentioned, were included. The database search yielded a total of 2952 articles, from which 81 articles remained for analysis. Four main registration methods were identified: point registration, surface registration, hybrid registration, and computer vision-based registration. The mobility of the mandible is accounted for by either keeping the mandible in a fixed position during preoperative imaging and surgery, or by tracking the mandibular movements. Although different registration methods are available for navigated mandibular surgery, there is always a trade-off between accuracy, registration time, usability, and invasiveness. Future studies should focus on testing the different methods in larger patient studies and should report the registration accuracy.

Electromagnetic surgical navigation in patients undergoing mandibular surgery.

The purpose of this study was to evaluate the feasibility of electromagnetic (EM) navigation for guidance on osteotomies in patients undergoing oncologic mandibular surgery. Preoperatively, a 3D rendered model of the mandible was constructed from diagnostic computed tomography (CT) images. Cutting guides and patient specific reconstruction plates were designed and printed for intraoperative use. Intraoperative patient registration was performed using a cone beam CT scan (CBCT). The location of the mandible was tracked with an EM sensor fixated to the mandible. The real-time location of both the mandible and a pointer were displayed on the navigation system. Accuracy measurements were performed by pinpointing four anatomical landmarks and four landmarks on the cutting guide using the pointer on the patient and comparing these locations to the corresponding locations on the CBCT. Differences between actual and virtual locations were expressed as target registration error (TRE). The procedure was performed in eleven patients. TREs were 3.2 ± 1.1 mm and 2.6 ± 1.5 mm using anatomical landmarks and landmarks on the cutting guide, respectively. The navigation procedure added on average half an hour to the duration of the surgery. This is the first study that reports on the accuracy of EM navigation in patients undergoing mandibular surgery.

Evaluating the accuracy of resection planes in mandibular surgery using a preoperative, intraoperative, and postoperative approach.

In mandibular surgery, three-dimensionally printed patient-specific cutting guides are used to translate the preoperative virtually planned resection planes to the operating room. This study was performed to determine whether cutting guides are positioned according to the virtual plan and to compare the intraoperative position of the cutting guide with the resection performed. Nine patients were included. The exact positions of the resection planes were planned virtually and a patient-specific cutting guide was designed and printed. After surgical placement of the cutting guide, intraoperative cone beam computed tomography (CBCT) was performed. Postoperative CT was used to obtain the final resection planes. Distances and yaw and pitch angles between the preoperative, intraoperative, and postoperative resection planes were calculated. Cutting guides were positioned on the mandible with millimetre accuracy. Anterior osteotomies were performed more accurately than posterior osteotomies (intraoperatively positioned and final resection planes differed by 1.2±1.0mm, 4.9±6.6°, and 1.8±1.5°, respectively, and by 2.2±0.9mm, 9.3±9°, and 8.3±6.5° respectively). Differences between intraoperatively planned and final resection planes imply a directional freedom of the saw through the saw slots. Since cutting guides are positioned with millimetre accuracy compared to the virtual plan, the design of the saw slots in the cutting guides needs improvement to allow more accurate resections.

Utilization of a 3D printed dental splint for registration during electromagnetically navigated mandibular surgery.

PURPOSE: A dental splint was developed for non-invasive rigid point-based registration in electromagnetically (EM) navigated mandibular surgery. Navigational accuracies of the dental splint were compared with the common approach, that is, using screws as landmarks. METHODS: A dental splint that includes reference registration notches was 3D printed. Different sets of three points were used for rigid point-based registration on a mandibular phantom: notches on the dental splint only, screws on the mandible, contralateral screws (the side of the mandible where the sensor is not fixated) and a combination of screws on the mandible and notches on the dental splint. The accuracy of each registration method was calculated using 45 notches at one side of the mandible and expressed as the target registration error (TRE). RESULTS: Average TREs of 0.83 mm (range 0.7-1.39 mm), 1.28 mm (1.03-1.7 mm), 2.62 mm (1.91-4.0 mm), and 1.34 mm (1.30-1.39 mm) were found, respectively, for point-based registration based on the splint only, screws on the mandible, screws on the contralateral side only, and screws combined with the splint. CONCLUSION: For dentate patients, rigid point-based registration performs best utilizing a dental splint with notches. The dental splint is easy to implement in the surgical, and navigational, workflow, and the notches can be pinpointed and designated on the CT scan with high accuracy. For edentate patients, screws can be used for rigid point-based registration. However, a new design of the screws is recommended to improve the accuracy of designation on the CT scan.

Intra-cavity Photodynamic Therapy for malignant tumors of the paranasal sinuses: An in vivo light dosimetry study.

BACKGROUND: Photodynamic therapy (PDT) is a promising treatment option for recurrent sinonasal malignancies. However, light administration in this area is challenging given the complex geometry, varying tissue optical properties and difficult accessibility. The goal of this study was to estimate the temporal and spatial variation in fluence and fluence rate during sinonasal mTHPC-mediated PDT. It was investigated whether the predetermined aim to illuminate with a fluence of 20 J⋅cm-2 and fluence rate of 100 mW⋅cm-2 was achieved. METHODS: In eleven patients the fluence and fluence rates were measured using in vivo light dosimetry at the target location during real-time sinonasal PDT. There was a variance in sinonasal target location and type of light diffuser used. In four patients two isotropic detectors were used within the same cavity. RESULTS: All measurements showed major fluence rate fluctuations within each single isotropic detector probe over time, as well as between probes within the same cavity. The largest fluence rate range measured was 328 mW⋅cm-2. Only one probe showed a mean fluence rate of ∼100 mW⋅cm-2. Taken all probes together, a fluence rate above 80 mW⋅cm-2 was measured in 31 % of the total light exposure; in 22 % it was less than 20 mW⋅cm-2. Thirty-three percent showed a fluence of at least 20 J⋅cm-2. CONCLUSIONS: The current dosimetry approach for sinonasal intra-cavity PDT shows major temporal and spatial variations in fluence rate and a large variance in light exposure time. The results emphasize the need for improvement of in vivo light dosimetry and dosimetry planning.

Intraoperative verification of resection margins of maxillary malignancies by cone-beam computed tomography.

Resection of maxillary cancer often results in incomplete excision because of the tumour's proximity to important structures such as the orbit. To deal with this problem we prospectively investigated the feasibility of intraoperative imaging during maxillectomy to verify the planned resection margins. In total, six patients diagnosed with maxillary cancer listed for maxillectomy were included, irrespective of the histological type of tumour. Before resection, an accurate intended resection volume was delineated on diagnostic images. At the end of the operation we took a cone-beam computed tomographic (CT) scan of the treated maxilla, after which the accuracy of the resection was quantitatively evaluated by comparing the preoperative resection plan and the images acquired intraoperatively, based on the anatomy. Further resection was then done if necessary and quantitatively evaluated with a second cone-beam CT scan. Postoperatively we compared the results of the scan with those of the histological examination. Of the six, two resections were reported pathologically as less than radical, each of which was detected by intraoperative CT and resulted in extensions of the original resections. The mean (SD) distance between the planned and the actual resection was 1.49 (2.78)mm. This suggests that intraoperative cone-beam CT imaging is a promising way to make an adequate intraoperative assessment of planned surgical margins of maxillary tumours. This allows for intraoperative resection margins to be improved, possibly leading to a better prognosis for the patient.

The use of photodynamic therapy as adjuvant therapy to surgery in recurrent malignant tumors of the paranasal sinuses.

BACKGROUND: Malignant tumors of paranasal sinuses and anterior skull base recur frequently after surgery and adjuvant radiotherapy. The vicinity of essential structures limits additional treatment options, such as salvage surgery and re-radiation. We report the feasibility of photodynamic therapy (PDT) as an adjuvant treatment to surgery. METHODS: Fifteen patients with recurrent tumors of the paranasal sinuses were treated with mtetrahydroxyphenylchlorin (mTHPC) mediated PDT as an adjuvant treatment to salvage surgery. All patients had previously curative radiotherapy. The treated tumors were squamous cell cancer (8), adenocarcinoma (3), undifferentiated carcinoma (2), adenoid cystic carcinoma (1) and radiotherapyinduced sarcoma (1). In five cases there was extension to the skull base. Two approaches of surgery where used, namely in eight cases an open approach, in the other seven endoscopic approach. Complete macroscopic resection with microscopic tumor positive margins was possible in three patients. The remaining twelve patients received debulking surgery followed by PDT. RESULTS: None of the patients had cerebrospinal fluid leak, meningitis, major bleeding or vision loss. Four patients developed temporary diplopia due to edema of the medial rectus muscle, one patient suffered from extensive necrosis leading to oro-nasal fistula. Complete response was observed in five patients. CONCLUSION: Photodynamic therapy can be used with relative safety as adjuvant therapy to surgery in recurrent tumors of the paranasal sinuses and the anterior skull base where complete resection is not achievable.

Temoporfin mediated photodynamic therapy in patients with local persistent and recurrent nasopharyngeal carcinoma after curative radiotherapy: a feasibility study.

BACKGROUND: The treatment of persistent and recurrent nasopharyngeal carcinoma (NPC) remains a challenge, especially in Indonesia. We investigated the safety and efficacy of temoporfin mediated photodynamic therapy (PDT) for patients with local persistent and recurrent NPC. MATERIAL AND METHODS: Twenty-two patients with persistent and recurrent NPC (maximum tumor depth < 10mm) underwent PDT under local anesthesia with use of a nasopharyngeal light applicator. Three different drug doses and light intervals have been administered: treatment arm A: 0.15 mg/kg Foscan; 96 h drug-light interval; B: drug dose of 0.10 mg/, 48 h drug-light interval; C: drug dose of 0.075 mg/kg, 24 h drug-light interval. Toxicity was measured by using the CTCAE 3.1 scale. RESULTS: Arm A consisted of eight patients, arms B and C consisted of seven patients. The treatment procedure was well tolerable under local anesthesia. The most common grade III toxicities for all groups is headache (n = 7; 33%). No grade IV toxicity was seen. One patient died 2 days after treatment due to a misdiagnosed pneumonia. In 17 of the 22 patients a biopsy was performed after 40 weeks and showed no tumor in all biopsies. Arm A seems, in addition to comparable toxicity, clinically more effective than arms B and C. CONCLUSION: The present study demonstrated that temoporfin mediated photodynamic therapy is a relatively simple technique that can be utilized to treat residual or recurrent nasopharyngeal cancer, restricted locally to the nasopharynx.

Performance of a dedicated light delivery and dosimetry device for photodynamic therapy of nasopharyngeal carcinoma: phantom and volunteer experiments.

UNLABELLED: The objective of this study was to develop a light delivery and measurement device for photodynamic therapy (PDT) in the nasopharyngeal cavity, which achieves a homogeneous and reproducible fluence rate distribution to a target area and provides proper shielding of predefined risk areas. MATERIALS AND METHODS: A flexible silicone applicator was developed, incorporating light delivery and dosimetry fibers. The applicator can be inserted through the mouth and fixed in the nasopharyngeal cavity. Tissue optical phantoms were prepared on the basis of optical properties measured in vivo using diffuse reflectance spectroscopy (DRS). The fluence rate over the length of the applicator surface was measured in air, in tissue optical phantoms and in five healthy volunteers. RESULTS: The fluence rate distribution over the applicator surface in air and tissue optical phantom was found to be more homogeneous (SD/mean 3.8% and 18.3%, respectively) than the fluence rate distribution in five volunteers (SD/mean ranging from 19% up to 52%). The maximum observed fluence rate build-up in the nasopharynx varied between subjects and ranged from a factor of 4.1-6.9. Shielding of the risk area such as the soft palate and tongue was effective. CONCLUSIONS: In air and in tissue optical phantoms the fluence rate distribution of the device was highly homogeneous. The observed inter-subject and intra-subject variations in fluence rate in healthy volunteers originated from differences in optical properties and nasopharyngeal geometry. Light delivery based on a single tissue surface measurement will not be adequate. In situ dosimetric measurements are required to determine the light fluence delivered to a geometrically complex site such as the nasopharynx. These observations should be taken in consideration when developing light applicators for PDT of the nasopharynx and other non-uniform surfaces.

In vivo fluence rate measurements during Foscan-mediated photodynamic therapy of persistent and recurrent nasopharyngeal carcinomas using a dedicated light applicator.

The objective of this study was to evaluate the performance of a dedicated light applicator for light delivery and fluence rate monitoring during Foscan-mediated photodynamic therapy of nasopharyngeal carcinoma in a clinical phase I/II study. We have developed a flexible silicone applicator that can be inserted through the mouth and fixed in the nasopharyngeal cavity. Three isotropic fibers, for measuring of the fluence (rate) during therapy, were located within the nasopharyngeal tumor target area and one was manually positioned to monitor structures at risk in the shielded area. A flexible black silicon patch tailored to the patient's anatomy is attached to the applicator to shield the soft palate and oral cavity from the 652-nm laser light. Fourteen patients were included in the study, resulting in 26 fluence rate measurements in the risk volume (two failures). We observed a systematic reduction in fluence rate during therapy in 20 out of 26 illuminations, which may be related to photodynamic therapy-induced increased blood content, decreased oxygenation, or reduced scattering. Our findings demonstrate that the applicator was easily inserted into the nasopharynx. The average light distribution in the target area was reasonably uniform over the length of the applicator, thus giving an acceptably homogeneous illumination throughout the cavity. Shielding of the risk area was adequate. Large interpatient variations in fluence rate stress the need for in vivo dosimetry. This enables corrections to be made for differences in optical properties and geometry resulting in comparable amounts of light available for Foscan absorption.

Determination of visible near-IR absorption coefficients of mammalian fat using time- and spatially resolved diffuse reflectance and transmission spectroscopy.

In-vivo optical spectroscopy and the determination of tissue absorption and scattering properties have a central role in the development of novel optical diagnostic and therapeutic modalities in medicine. A number of techniques are available for the optical characterization of tissue in the visible near-IR region of the spectrum. An important consideration for many of these techniques is the reliability of the absorption spectrum of the various constituents of tissue. The availability of accurate absorption spectra in the range 600 to 1100 nm may allow for the determination of the concentration of key tissue constituents such as oxy- and deoxy-hemoglobin, water, and lipids. The objective of the current study is the determination of a reliable absorption spectrum of lipid(s) that can be used for component analysis of in-vivo spectra. We report the absorption spectrum of a clear purified oil obtained from pig lard. In the liquid phase above 36 degrees C, the oil is transparent and thus suitable for collimated transmission measurements. At room temperature, the oil is a solid grease that is highly scattering. The absorption and scattering properties in this solid phase are measured using time- and spatially resolved diffuse reflectance spectroscopy. Using these three independent measurement techniques, we have determined an accurate estimate for the absorption spectrum of mammalian fat.

Intraoperatively assessed optical properties of malignant and healthy breast tissue used to determine the optimum wavelength of contrast for optical mammography.

We use spatially resolved diffuse remittance spectroscopy (DRS) for the measurement of absorption (mu(a)) and reduced scattering (mu(s)') coefficients of normal and malignant breast tissue in vivo during surgery. Prior to these measurements, the linearity of the measurement technique was evaluated on liquid optical phantoms. In addition, the reproducibility of in-vivo tissue measurements was determined on a healthy volunteer. We present results of the in-vivo measurement of optical properties in the wavelength range from 600 to 1100 nm performed during radical mastectomy. A total of 24 patients were included in the study. Both the absorption and reduced scattering properties show large variations. Significant differences in optical properties between normal (glandular plus lipid rich tissue) and tumor tissues are present in 74% of all patients. However, in some cases the tumor showed lower values than normal tissue, and in other cases this was the other way around. Thus, a general trend in optical properties is not observed. However, the average absorption contrast of all patients as a function of wavelength reveals an optimal contrast peak at 650 nm. We believe that this relates to a difference in vascular saturation between tumor and adjacent normal tissue.

5-aminolevulinic acid photodynamic therapy versus argon plasma coagulation for ablation of Barrett's oesophagus: a randomised trial.

BACKGROUND: Photochemical and thermal methods are used for ablating Barrett's oesophagus (BO). The aim of this study was to compare 5-aminolevulinic acid induced photodynamic therapy (ALA-PDT) with argon plasma coagulation (APC) with respect to complete reversal of BO. METHODS: Patients with BO (32 no dysplasia and eight low grade dysplasia) were randomised to one of three treatments: (a) ALA-PDT as a single dose of 100 J/cm(2) at four hours (PDT100; n = 13); (b) ALA-PDT as a fractionated dose of 20 and 100 J/cm(2) at one and four hours, respectively (PDT20+100; n = 13); or (c) APC at a power setting of 65 W in two sessions (APC; n = 14). If complete elimination of BO was not achieved by the designated treatment, the remaining BO was treated by a maximum of two sessions of APC. RESULTS: Mean endoscopic reduction of BO at six weeks was 51% (range 20-100%) in the PDT100 group, 86% (range 0-100%) in the PDT20+100 group, and 93% (range 40-100%) in the APC group (PDT100 v PDT20+100, p<0.005; PDT100 v APC, p<0.005; and PDT20+100 v APC, NS) with histologically complete ablation in 1/13 (8%) patients in the PDT100 group, 4/12 (33%) in the PDT20+100 group, and 5/14 (36%) in the APC group (NS). Remaining BO was additionally treated with APC in 23/40 (58%) patients. Histological examination at 12 months revealed complete ablation in 9/11 (82%) patients in the PDT100 group, in 9/10 (90%) patients in the PDT20+100 group, and in 8/12 (67%) patients in the APC group (NS). At 12 months, no dysplasia was detected. Side effects (that is, pain (p<0.01), and nausea and vomiting (p<0.05)) and elevated liver transaminases (p<0.01) were more common after PDT than APC therapy. One patient died three days after treatment with PDT, presumably from cardiac arrhythmia. CONCLUSION: APC alone or ALA-PDT in combination with APC can lead to complete reversal of Barrett's epithelium in at least two thirds of patients when administered in multiple treatment sessions. As the goal of treatment should be complete reversal of Barrett's epithelium, we do not recommend these techniques for the prophylactic ablation of BO.

Diffuse-reflectance spectroscopy from 500 to 1060 nm by correction for inhomogeneously distributed absorbers.

Diffuse-reflectance spectroscopy for measurement of the absorption and scattering coefficients of biological tissue produces reliable results for wavelengths from 650 to 1050 nm. Implicitly, this approach assumes homogeneously distributed absorbers. A correction factor is introduced for inhomogeneous distribution of blood concentrated in discrete cylindrical vessels. This factor extends the applicability of diffusion theory to lower wavelengths. We present measurements of in vivo optical properties in the wavelength range 500-1060 nm.