Unilateral cochlea sparing in locoregionally advanced head and neck cancer: a planning study.

BACKGROUND: Cochlea sparing can reduce late ototoxicity in head and neck cancer patients treated with cisplatin-based radiochemotherapy. In this situation, a mean cochlear dose (MCD) constraint of 10 Gy has been suggested by others based on the dose-effect relationship of clinical data. We aimed to investigate whether this is feasible for primary and postoperative radiochemotherapy in locoregionally advanced tumors without compromising target coverage. PATIENTS AND METHODS: Ten patients treated with definitive and ten patients treated with adjuvant intensity-modulated radiotherapy (IMRT) and concurrent chemotherapy were investigated. The cochleae and a planning risk volume (PRV) with a 3 mm margin were newly delineated, whereas target volumes and other organs at risk were not changed. The initial plan was recalculated with a constraint of 10 Gy (MCD) on the low-risk side. The quality of the resulting plan was evaluated using the difference in the equivalent uniform dose (EUD). RESULTS: A unilateral MCD of below 10 Gy could be achieved in every patient. The mean MCD was 6.8 Gy in the adjuvant cohort and 7.6 Gy in the definitive cohort, while the non-spared side showed a mean MCD of 18.7 and 30.3 Gy, respectively. The mean PRV doses were 7.8 and 8.4 Gy for the spared side and 18.5 and 29.8 Gy for the non-spared side, respectively. The mean EUD values of the initial and recalculated plans were identical. Target volume was not compromised. CONCLUSION: Unilateral cochlea sparing with an MCD of less than 10 Gy is feasible without compromising the target volume or dose coverage in locoregionally advanced head and neck cancer patients treated with IMRT. A prospective evaluation of the clinical benefit of this approach as well as further investigation of the dose-response relationship for future treatment modification appears promising.

Efficacy of MR angiography in the detection and characterization of occlusive disease in the vertebrobasilar system.

PURPOSE: The purpose of this work was to determine the efficacy of MR angiography (MRA) in the detection and characterization of occlusive disease in the vertebrobasilar system. METHOD: We retrospectively reviewed the posterior circulation registry of our institution to select 42 consecutive patients with posterior circulation ischemic symptoms who underwent both MRA and angiography. The extracranial vertebral arteries (ECVAs) were examined by two-dimensional time-of-flight MRA above the C6 level, and the intracranial vertebral arteries (ICVAs) and basilar arteries (BAs) were examined by three-dimensional time-of-flight MRA. Sixty-two ECVAs, 63 ICVAs, and 39 BAs were examined by the readers. RESULTS: Occlusive disease was seen on angiography in 22 of the 42 patients. The sensitivity and specificity values for detection of lesions in 12 ECVA, 19 ICVA, and 12 BA abnormalities were as follows: ECVA, 92 and 96% for Reader A and 100 and 90% for Reader B; ICVA, 84 and 93% for Reader A and 74 and 82% for Reader B; and BA, 100 and 88% for Reader A and 100 and 78% for Reader B. For ICVA, the sensitivity of MRA was less than that of angiography because of lesions missed by the readers at the junctional area of the extra-and intracranial MRA. MRA accurately characterized 9 of the 12 (75%) ECVA, 10 of the 19 (43%) ICVA, and 11 of the 12 (92%) BA lesions. CONCLUSION: MRA is an effective method for detection of occlusive lesions in the ECVAs and BAs. Clinically important lesions can be missed by MRA in the ICVA. MRA is more accurate in characterization of occlusive lesions in BAs than in ECVAs or ICVAs.

Utility of wiring nitrate reductase by alkylpyrroleviologen-based redox polymers for electrochemical biosensor and bioreactor applications.

The purpose of this work was to see if the alkylpyrroleviologen redox polymer technology previously developed for a reagentless nitrate biosensor based on nitrate reductase (NaR) from Escherichia coli (Cosnier, S.; Innocent, C.; Jouanneau, Y. Anal. Chem. 1994, 66, 3198-3201) could be applied to the isozyme from Aspergillus niger. In particular, the enzyme viability after immobilization was of great interest, as Cosnier et al. reported a residual activity of only 0.33% of the amount initially applied. The present work showed that A. niger NaR lost 99.2% of soluble activity on vacuum-drying in the presence of 2.5 nM N-methyl-N'-(12-[pyrrol-1-yl]dodecyl)-4,4'-bipyridinium ditetrafluoroborate monomer (C12V2+) and that most of this loss was due to monomer inhibition (91%). The loss due to dehydration was only 8%. In the biosensor configuration, the enzyme gave a residual activity of 0.18% of the amount originally applied and a specific response of 1.7 mA M-1 cm-2, but all activity was lost after 4 d storage at 4 degrees C in phosphate buffer. It was concluded that for practical biosensors and bioreactors, modification of the redox polymer format was needed, for example by covalent immobilization, to effect higher loading of viable NaR and improved enzyme stability.

Cerebrospinal fluid flow waveforms: effect of altered cranial venous outflow. A phase-contrast MR flow imaging study.

Our purpose was to assess the effect of alterations in the cranial venous outflow on cerebrospinal fluid (CSF) flow waveforms using phase-contrast MRI. Thirteen healthy subjects were assessed for CSF flow and cerebral vascular flow at the C2-3 level, both before and after jugular venous compression (JVC). The flow waveforms were assessed both as an aggregate, and after dividing subjects in two groups based on percent jugular venous flow (PJVF) i.e. jugular outflow expressed as percent of cerebral arterial inflow. Group 1:7 subjects with PJVF more than and including median (predominantly jugular outflow); Group 2:6 subjects with PJVF less than median (predominantly extra-jugular outflow). CSF waveforms: JVC produced rounding of contours and flattening of dicrotic waves, with the effect being greater in group 1 than group 2. In group 1, systolic upslopes of the waveforms increased. No significant aggregate amplitude changes were noted; amplitudes increased in group 1 (P = 0.001), and decreased in group 2 (P = 0.03). Temporal interval to the maximum CSF systolic flow significantly increased in group 1. Vascular flow: Arterial flow significantly decreased in group 1. Jugular flow significantly decreased in both groups. The results suggest that CSF flow waveforms are sensitive to alterations in the cranial venous outflow. Changes in group 1 are most likely because of an elevation in intracranial pressure. Analysis of CSF flow waveforms appears a promising noninvasive tool for assessment of cranial compartment.

Cerebrospinal fluid pulsation amplitude and its quantitative relationship to cerebral blood flow pulsations: a phase-contrast MR flow imaging study.

Our purpose in this investigation was to explain the heterogeneity in the cerebrospinal fluid (CSF) flow pulsation amplitudes. To this end, we determined the contributions of the cerebral arterial and jugular venous flow pulsations to the amplitude of the CSF pulsation. We examined 21 healthy subjects by cine phase-contrast MRI at the C2-3 disc level to demonstrate the CSF and vascular flows as waveforms. Multiple regression analysis was performed to calculate the contributions of (a) the arterial and venous waveform amplitudes and (b) the delay between the maximum systolic slopes of the arterial and venous waveforms (AV delay), in order to predict the amplitude of the CSF waveform. The contribution of the arterial waveform amplitude was positive (r = 0.61; p = 0.003) to the CSF waveform amplitude and that of the venous waveform amplitude was negative (r = -0.50; p = 0.006). Both in combination accounted for 56% of the variance in predicting the CSF waveform amplitude (p < 0.0006). The contribution of AV delay was not significant. The results show that the variance in the CSF flow pulsation amplitudes can be explained by concurrent evaluation of the CSF and vascular flows. Improvement in the techniques, and controlled experiments, may allow use of CSF flow pulsation amplitudes for clinical applications in the non-invasive assessment of intracranial dynamics by MRI.

Functional analysis of third ventriculostomy patency with phase-contrast MRI velocity measurements.

Our purpose was to explore the utility of cine phase-contrast MRI velocity measurements in determining the functional status of third ventriculostomies, and to correlate the quantitative velocity data with clinical follow-up. We examined six patients with third ventriculostomies and 12 normal subjects by phase-contrast MRI. The maximum craniocaudal to maximum caudocranial velocity range was measured at regions of interest near the third ventricular floor, and in cerebrospinal fluid anterior to the upper pons and spinal cord on midline sagittal images. Ratios of the velocities of both the third ventricle and prepontine space to the space anterior to the spinal cord were obtained. The velocities near the third ventricular floor and in the pontine cistern were significantly higher in patients than in normal subjects, but the velocity anterior to the spinal cord was similar between the groups. The velocity ratios, used to normalize individual differences, were also higher in patients than in controls. Two patients had lower velocity ratios than their fellows at the third ventricular floor and in the pontine cistern; one required a shunt 11 months later, while in the other, who had a third ventricular/thalamic tumor, the lower values probably reflect distortion of the third ventricular floor. We conclude that phase-contrast MR velocity measurements, specifically the velocity ratio between the high pontine cistern and the space anterior to the spinal cord, can help determine the functional status of third ventriculostomies.