An optical evaluation of the phenomenon of red out in neuroendoscopic surgery: what is the physical background?

BACKGROUND

The loss of visualization in neuroendoscopy due to intraoperative bleeding is called "red out". Although red out is a well-known problem during endoscopy, clear physical descriptions of this phenomenon are lacking.

OBJECTIVE

The aim of this study was to investigate the optical properties of red out. In particular, the attenuation coefficient, comprising scattering, and absorption, of various blood/Ringer solutions was quantified and measured spectrally resolved. Small amounts of blood virtually preclude neuroendoscopic visualization. In blood/Ringer solutions with a dilution of 1:101, it was not possible to distinguish characters (font size 10, Arial) at a distance of 5 mm. We have concluded, from our physical investigations, that the problem of red out is dominated by scattering rather than by absorption. Accordingly, technical developments aimed at increasing information acquisition under red out conditions should be based on optical measurement concepts for scattering media.

Biological intercomparison using gut crypt survivals for proton and carbon-ion beams

Charged particle therapy depends on biological information for the dose prescription. Relative biological effectiveness or RBE for this requirement could basically be provided by experimental data. As RBE values of protons and carbon ions depend on several factors such as cell/tissue type, biological endpoint, dose and fractionation schedule, a single RBE value could not deal with all different radiosensitivities. However, any biological model with accurate reproducibility is useful for comparing biological effectiveness between different facilities. We used mouse gut crypt survivals as endpoint, and compared the cell killing efficiency of proton beams at three Japanese facilities. Three Linac X-ray machines with 4 and 6 MeV were used as reference beams, and there was only a small variation (coefficient of variance < 2%) in biological effectiveness among them. The RBE values of protons relative to Linac X-rays ranged from 1.0 to 1.11 at the middle of a 6-cm SOBP (spread-out Bragg peak) and from 0.96 to 1.01 at the entrance plateau. The coefficient of variance for protons ranged between 4.0 and 5.1%. The biological comparison of carbon ions showed fairly good agreement in that the difference in biological effectiveness between NIRS/HIMAC and GSI/SIS was 1% for three positions within the 6-cm SOBP. The coefficient of variance was < 1.7, < 0.6 and < 1.6% for proximal, middle and distal SOBP, respectively. We conclude that the inter-institutional variation of biological effectiveness is smaller for carbon ions than protons, and that beam-spreading methods of carbon ions do not critically influence gut crypt survival.

Anterior Uncoforaminotomy in the Treatment of Recurrent Radiculopathy after Anterior Cervical Discectomy with Fusion

BACKGROUND

In patients after anterior cervical discectomy (ACD) with fusion newly developed retrospondylophytes or incomplete decompression of the nerve root can cause recurrent radicular pain. Anterior cervical uncoforaminotomy (uncoforaminotomy) is an operative method which removes the causative degenerative pathology at the level of the neural foramen leaving untouched the inserted graft at this level.

METHOD

Between February 2004 and April 2005, 7 patients underwent uncoforaminotomy after ACD with fusion for the treatment of recurrent cervical radiculopathy in our neurosurgical department. Prior to treatment patients received a computed tomography (CT) and a neurological examination. Anterior uncoforaminotomy was performed thereafter (for technical details see publication by Jho, 1996). A postoperative CT scan was done before discharge. Follow-up examination was performed eight weeks after surgery.

FINDINGS

Five patients underwent the operation at C5/6, one patient was operated at C6/7 and one patient had the operation at two levels (C5/6 and C6/7). At discharge six patients had excellent or good results.

CONCLUSION

Uncoforaminotomy is a good method for the treatment of newly acquired spondylotic spurs in the foramen or incomplete osseous decompression after ACD with fusion and recurrent radicular pain.

Is There an Indication for Frozen Section Examination of the Ureteral Margins During Cystectomy for Transitional Cell Carcinoma of the Bladder?

PURPOSE

We evaluated the incidence of pathological findings of the ureter at cystectomy for transitional cell carcinoma of the bladder and assessed the usefulness of intraoperative frozen section examination of the ureter.

MATERIALS AND METHODS

Histopathological findings of ureteral frozen section examination were compared to the corresponding permanent sections and the diagnostic accuracy of frozen section examination was evaluated. These segments were then compared to the more proximal ureteral segments resected at the level where they cross over the common iliac arteries. The histopathological findings of the ureteral segments were then correlated for upper urinary tract recurrence and overall survival.

RESULTS

Transitional cell carcinoma or carcinoma in situ was found on frozen section examination of the distal ureter in 39 of 805 patients (4.8%) and on permanent sections in 29 (3.6%). In 755 patients the false-negative rate of frozen section examination of the ureters was 0.8%. Of the patients with carcinoma in situ diagnosed on the first frozen section examination 80% also had carcinoma in situ in the bladder. Transitional cell carcinoma or carcinoma in situ in the most proximally resected ureteral segments was found in 1.2% of patients. After radical cystectomy there was tumor recurrence in the upper urinary tract in 3% of patients with negative ureteral frozen section examination and in 17% with carcinoma in situ on frozen section examination.

CONCLUSIONS

Routine frozen section examination of the ureters at radical cystectomy is only recommended for patients with carcinoma in situ of the bladder, provided the ureters are resected where they cross the common iliac arteries.

Radiation tolerance of the rat spinal cord after 6 and 18 fractions of photons and carbon ions: Experimental results and clinical implications

PURPOSE

The tolerance of the rat spinal cord to photon and carbon ion irradiations was investigated to determine the relative biologic effectiveness (RBE) of carbon ions ((12)C) in the plateau region and in a 1 cm spread-out Bragg-peak.

METHODS AND MATERIALS

The cranial part of the cervical and thoracic spinal cord of 336 rats was irradiated with 6 or 18 fractions (Fx) of photons or (12)C-ions, respectively. Animals were followed up for 300 days for the onset of paresis grade II and dose-response curves were calculated.

RESULTS

The D(50)-values (dose at 50% complication probability) were 42.9 +/- 0.5 Gy, 62.2 +/- 0.9 Gy (6 and 18 Fx, (12)C-plateau) and 19.2 +/- 0.2 Gy, 17.6 +/- 0.2 Gy (6 and 18 Fx (12)C-peak), respectively. For photons, the D(50)-values were 57.0 +/- 0.7 Gy for 6 and 88.6 +/- 0.7 Gy for 18 Fx. The corresponding RBE-values were 1.33 +/- 0.02, 1.42 +/- 0.02 (6 and 18 Fx, (12)C-plateau) and 2.97 +/- 0.05, 5.04 +/- 0.08 (6 and 18 Fx (12)C-peak), respectively. Including data of a previously performed experiment for 1 and 2 Fx (1) the parameter alpha/beta of the LQ-model was found to be 2.8 +/- 0.4 Gy, 2.1 +/- 0.4 Gy and 37.0 +/- 5.3 Gy for photon-, (12)C-plateau- and (12)C-peak irradiations, respectively.

CONCLUSIONS

Carbon ion irradiations of the spinal cord are significantly more effective in the peak than in the plateau region. The alpha/beta-values indicate a significant fractionation effect only for the plateau irradiations. In the Bragg-peak, the applied RBE-model correctly describes the main features although it generally underestimates the RBE by 25%. In the plateau region, maximum deviations of up to 20% were found. The acquired data contribute significantly to the validation of the applied RBE-model.

Oral bisphosphonates fail to prevent bone loss from androgen deprivation therapy in men with prostate cancer

14643

Background: Androgen deprivation therapy (ADT) is a widely administered treatment for prostate cancer. However, ADT is associated with accelerated bone loss, osteoporosis, and fractures (Shahinian, NEJM 2005; 352:154). According to Smith et al, annual bone loss on ADT approaches 9% (Smith, NEJM 2001;345:948), using QCT densitometry, a highly sensitive test for the detection of osteoporosis in men. Intravenous bisphosphonates (pamidronate, zolendronate) have been shown to prevent ADT-related bone loss in randomized phase III trials. We performed a retrospective analysis to determine if oral bisphosphonates effectively prevent bone loss in men receiving ADT. Methods: Twenty two men, ages 60–80, were placed on alendronate or risendronate at the initiation of ADT. Baseline and follow-up bone mineral densitometry (BMD) studies were performed with QCT densitometry. Repeat BMD was performed 12- 27 months (mean = 17mo) after the baseline BMD. Percentage change in bone density was annualized. Within each treatment group, the hypothesis of no mean change from baseline was analyzed using a paired t test. Results: Mean baseline bone density was 122.6mg/cc. Mean follow-up bone density was 112.7mg/cc. For the whole group, the annualized mean change in BMD was negative 7.77%/yr (p = 0.0003). Of note, 9/22 men maintained or gained bone density (-1.26% to +5.95%). 13/22 men lost at least 6.03% (-6.03% to -23.2%). There was no unexpected toxicity or fractures. Conclusions: In this retrospective study, prophylactic oral bisphosphonates do not protect against accelerated ADT-induced bone loss in men with prostate cancer.

No significant financial relationships to disclose.

Strahlenexposition bei der digitalen Vollfeldmammographie mit einem Selen-Flachdetektor

PURPOSE

Calculation of the average glandular dose for mammography on a full-field digital mammography system using a selenium flat-panel detector.

MATERIALS AND METHODS

Mammographic examinations were carried out using the Selenia digital mammographic system from Lorad/Hologic. 1992 mammographies of 500 patients in cranio-caudal and medio-lateral projections were evaluated. Based on the recorded exposure conditions (tube voltage, tube loading, filtration, compressed breast thickness), the entrance surface air kerma was calculated by multiplying the tube loading by the measured tube output and was corrected according to the inverse square law. The average glandular dose was determined for each exposure by multiplying the entrance surface air kerma value by the relevant conversion factor for a breast composition of 50 % adipose tissue and 50 % glandular tissue by weight.

RESULTS

The mean values for patient age and compressed breast thickness were 61 years and 58 mm, respectively. The average glandular dose was 1.57 mGy for a single view (1.46 mGy for cranio-caudal view images and 1.68 mGy for medio-lateral view images).

CONCLUSION

Full-field digital mammography with a selenium flat-panel detector requires a dose similar to that of units with a flat-panel detector based on amorphous silicon and a dose approximately 20 % lower than that of conventional screen/film mammography.

Choroidal innervation and optic neuropathy in macacque monkeys with laser- or anterior chamber perfusion-induced short-term elevation of intraocular pressure

Long-term intraocular pressure (IOP) elevation leads to a significant reduction of the intrinsic choroidal innervation and axon loss in the optic nerve. In this study we investigated early changes in these tissues in order to clarify the putative sequence of events between choroidal ganglion cell loss and optic nerve axon loss in 19 monkeys with experimentally induced glaucoma. After 1 month of increased IOP, severe optic neuropathy but no reduction of choroidal ganglion cells (CGC) was detectable. Beginning at 2 months after treatment signs of degeneration in CGC morphology were observed. Laser treatment of the trabecular meshwork without IOP elevation caused no changes in choroidal innervation. Our results show that there is no apparent association between reduction of CGC and optic neuropathy in the early stages of IOP elevation.

Deutsch-jozsa algorithm using triggered single photons from a single quantum dot

We demonstrate a two-qubit Deutsch-Jozsa algorithm with single photons from a single InP quantum dot. The qubits are implemented via the spatial mode and the polarization of a single photon. Our photon source is operated both under continuous and pulsed excitation, the latter allowing deterministic quantum logic by generating photons on demand with a strong suppression of two-photon events. The computation reached a success probability of up to 79%. We also exploit the concept of decoherence-free subspaces that helps to make our experimental setup robust against sources of phase noise.

Dynamic Cerebral Autoregulation in Patients with Ruptured and Unruptured Aneurysms after Induction of General Anesthesia

INTRODUCTION

Blood pressure management in patients undergoing surgery for clipping of aneurysms is demanding. More information about the ability of cerebral vessels to normally regulate cerebral blood flow may have a direct influence on the intraoperative management. In patients with subarachnoid hemorrhage (SAH) a disturbance of cerebral autoregulation has been reported and it correlated with the severity of the bleeding in these studies. The impairment of autoregulation was demonstrated using static measurements of cerebral pressure autoregulation. However, the dynamic component of the autoregulatory capacity seems to be of importance in the acute setting after SAH. The aim of this study was to evaluate dynamic pressure autoregulation in patients undergoing surgery for intracranial aneurysms.

PATIENTS/MATERIAL AND METHODS

36 patients with a mean age of 45 years were evaluated, 26 patients with acute SAH, 10 patients with unruptured aneurysms. Cerebral autoregulation in normocapnia was tested using thigh cuffs to alter arterial blood pressure and continuous registration of the blood flow velocities with transcranial Doppler sonography. After the induction of general anesthesia under normocapnia the autoregulatory index (ARI) was calculated (values between 0-9). Patient groups were compared using Wilcoxon- and Spearman's rank test.

RESULTS

The two patient groups were comparable with regard to gender, age, PaCO(2), blood flow velocities and blood pressure. In patients with SAH mean ARI was 3.1/3.3 (right/left side) compared to 4.7/4.6 (right/left side) in patients without SAH. The difference was statistically significant (Wilcoxon p = 0.0399). The degree of impairment of the autoregulatory capacity increased significantly (p = 0.006) with the severity of the SAH (Hunt&Hess and Fisher scale).

CONCLUSION

Dynamic pressure autoregulation is impaired in patients after SAH compared to patients without SAH and correlates with the severity of the SAH. We propose that autoregulation should be measured in all patients with SAH or that an impaired autoregulation should be taken into account in patients with SAH undergoing surgery in the acute phase.

Neurosurgical operations with the patient in sitting position: analysis of risk factors using transcranial Doppler sonography

BACKGROUND

One major risk factor of the sitting position for neurosurgery is air embolism, especially in patients with persistent foramen ovale (PFO). The first aim of this prospective study was to evaluate a bedside method for detecting PFO using transcranial Doppler sonography (TCD) with contrast medium. A second aim was to address intraoperative monitoring, patient positioning and the occurrence and clinical relevance of air embolism.

METHODS

Ninety patients with a mean age of 56.5 yr (range 14-81 yr) undergoing surgery in sitting position were investigated by TCD with contrast agent to detect functional PFO, that is PFO that can be provoked with a Valsalva manoeuvre. In patients in whom TCD was not possible, transcranial duplex sonography, duplex sonography of the carotid artery at the neck or transoesophageal ECG was performed.

RESULTS

In 26 patients PFO was detected. Thirteen of them presented a persistent PFO with high-intensity transient signal in both middle cerebral arteries without Valsalva manoeuvre. The intraoperative positioning in these patients was adapted to the risk for a paradoxical air embolism, although, after surgical recommendations, three patients with a persistent PFO underwent surgery in sitting position. Intraoperative air embolisms were seen in 8 of 80 patients in sitting or semi-sitting position with air aspirable through the central venous catheter.

CONCLUSION

To address the risk of a paradoxical air embolism, especially in patients undergoing surgery in sitting position, preoperative detection of PFO is advisable. If surgery is performed in seated PFO patients, additional monitoring and special care are warranted.

Analysis of Surgical Management of Calvarial Tumours and First Results of a Newly Designed Robotic Trepanation System

This study was performed to evaluate the surgical strategy in patients with calvarial tumours, in order to design and modify a robot-assisted trepanation system. A total of 75 patients underwent craniectomy for the treatment of calvarial tumours during the 10-year period from 1993 to 2002. The patients' complaints, the size, location and histology of the tumour, and the various cranioplasty techniques used were analysed retrospectively. In a second procedure several craniectomies at typical locations according to the study's results were performed in a laboratory setting using a hexapod robotic tool, constructed at the Helmholtz-Institute, RWTH Aachen University, and plastic model heads. The workflow was documented and the reproducibility and the accuracy of the procedure were registered. A total of 83 surgical procedures were performed on 75 patients. The majority (87 %) of lesions treated surgically were located in the frontal, temporal and anterior parts of the parietal region. Histological examination revealed benign lesions in 66 % of the patients and dural involvement in 46 %. According to these results craniectomies were performed using the robotic system. Mean positioning accuracy of the robotic system while milling was 0.24 mm, with a standard deviation of 0.04 mm, and maximum error under 1 mm. Craniectomies leaving a 1-mm layer of the tabula interna intact to ensure a healthy dura were performed in several regions successfully. The majority of calvarial tumours, requiring surgical treatment in our patients, were located in cosmetically relevant areas in which drilling can be carried out with the robotic trepanation system. Consequently, the surgical approach had to be planned carefully in order to achieve a good cosmetic outcome.

Rapid calculation of biological effects in ion radiotherapy

We describe a method for fast calculation of biological effects after ion irradiation. It is an alternative derivative of the established local effect model (LEM) and has been integrated into GSI's TRiP98 treatment planning system. We show that deviations from our classic approach for treatment planning are less than 5% for therapeutical doses, but calculational speed can be improved by one to two orders of magnitude. This will allow sophisticated methods of treatment planning for ion irradiation, taking biological effects fully into account.