1/4. Intensity-modulated stereotactic radiosurgery using dynamic micro-multileaf collimation.PURPOSE: The implementation of dynamic leaf motion on a micro-multileaf collimator system provides the capability for intensity-modulated stereotactic radiosurgery (IMSRS), and the consequent potential for improved dose distributions for irregularly shaped tumor volumes adjacent to critical organs. This study explores the use of IMSRS to provide improved tumor coverage and normal tissue sparing for small cranial tumors relative to plans based on multiple fixed uniform-intensity beams or traditional circular collimator arc-based stereotactic techniques. methods AND MATERIALS: Four patient cases involving small brain lesions are presented and analyzed. The cases were chosen to include a representative selection of target shapes, number of targets, and adjacent critical areas. Patient plans generated for these comparisons include standard arcs with multiple circular collimators, and fixed noncoplanar static fields with uniform-intensity beams and IMSRS. Parameters used for evaluation of the plans include the percentage of irradiated volume to tumor volume (PITV), normal tissue dose-volume histograms, and dose-homogeneity ratios. All IMSRS plans were computed using previously established IMRT techniques adapted for use with the BrainLAB M3 micro-multileaf collimator. The algorithms comprising the IMRT system for optimization of intensity distributions and conversion into leaf trajectories of the BrainLab M3 were developed at our institution. The ADAC Pinnacle(3) radiation treatment-planning system was used for dose calculations and for input of contours for target volumes and normal critical structures. RESULTS: For all cases, the IMSRS plans showed a high degree of conformity of the dose distribution with the target shape. The IMSRS plans provided either (1) a smaller volume of normal tissue irradiated to significant dose levels, generally taken as doses greater than 50% of the prescription, or (2) a lower dose to an important adjacent critical organ. The reduction in volume of normal tissue irradiated in the IMSRS plans ranged from 10% to 50% relative to the other arc and uniform fixed-field plans. CONCLUSION: The case studies presented for IMSRS demonstrate significant dosimetric improvements for small, irregularly shaped lesions of the brain when compared to treatments using multiple static fields or standard SRS arc techniques with circular collimators. For all cases, the IMSRS plan yielded a smaller volume of normal tissue irradiated, and/or a reduction in the volume of an adjacent critical organ (i.e., brainstem) irradiated to significant dose levels.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |
2/4. Objective facial motion analysis in patients with facial nerve dysfunction.OBJECTIVES/HYPOTHESIS: To objectively measure facial motion at various facial landmarks using a video-computer interactive system. STUDY DESIGN: Clinical, prospective, non-randomized. methods: A video-computer interactive system, The Peak Motus motion Measurement System, was used to study linear displacement at preselected facial landmarks in the normal and abnormal face. Subjects with normal facial function (n = 34) and patients with abnormal facial function (n = 26) from various etiologies were studied. The sites studied were marked with reflective beads. Of a larger repertoire of expressions, two expressions (eyes closed and closed-lip smile) were studied in all subjects. The percent asymmetry in facial displacement between the sides of the face was calculated. The sensitivity of this measurement to facial dysfunction was evaluated. The presence of synkinesis was examined by quantifying the displacement at facial sites that were remote to the sites primarily involved in a given facial expression. Test-retest reliability of the percent asymmetry measurement was evaluated with the paired t test. RESULTS: The video-computer interactive approach used accurately detected and quantified gross and subtle changes in facial function. The sensitivity of the percent asymmetry measurement was 95% (both expressions) for patients with apparent facial dysfunction (House-Brackmann rating >I/VI). In patients with facial nerve dysfunction, displacement on the presumably normal side was significantly excessive in 27% to 35%, depending on the expression. With this interactive computer-video system, synkinesis was detected in 58% of the pathologic subjects during the eyes closed or closed-lip smile expressions. The paired t test indicated strong test-retest reliability (r = 0.73-0.99) of the percent asymmetry measurement. CONCLUSIONS: The present report indicates that this approach to the assessment of facial motion is sensitive to facial dysfunction. This computer-video interactive system is able to quantify synkinesis. A grading system for the magnitude of synkinesis, based on the magnitude of the displacement at remote facial sites, is proposed. The common occurrence of excessive facial motion on the presumably normal side of affected individuals indicates that patients with facial paralysis often overcompensate by exaggerating the normal side in an effort to move the affected side. This system is of value in the objective measurement of normal facial function and may prove a useful tool to quantify the outcomes of various medical and surgical treatments for facial nerve dysfunction.- - - - - - - - - - ranking = 7keywords = motion (Clic here for more details about this article) |
3/4. A new lid sign in seventh nerve palsy.This paper describes a new lid sign in two patients with facial nerve paralysis. The facial nerve palsy was secondary to a pontine abscess in the first case and a complication of acoustic neuroma resection in the second patient. Both patients were found to have absence of the normal nasal twist of the lower lid during eyelid closure. The nasal twist is felt to help pump tears into the lacrimal drainage system. This paper will describe the absence of an important eyelid function in a patient with facial nerve paralysis. By way of background, Doane's slow motion movies have shown that during a normal blink, the upper lid moves both down and nasally, while the lower lid moves from 2 to 5 mm nasally. As the upper lid descends, the lower lid normally moves 2 to 5 mm in a horizontal and nasal direction. This motion of the lower lid helps produce a partial vacuum in the lacrimal system and is responsible for moving the fluid and debris in the tear mentiscus across the eye and into the lacrimal drainage system. The two cases of facial nerve paralysis to be presented demonstrate absence of tear drainage on the side of the lesion and a build-up and overflow of the tears on that side.- - - - - - - - - - ranking = 2keywords = motion (Clic here for more details about this article) |
4/4. Patterns of facial nerve synkinesis.facial nerve synkinesis is an extremely distressing sequela of facial paralysis, and its prevention and treatment are less than adequate. Improved therapeutic interventions await better understanding of its pathogenesis. In this study, 11 patients with synkinesis and 11 normal control subjects were quantitatively assessed using a new computer-assisted, motion-sensitive system. Two additional, informative cases presenting at the completion of the study are also briefly reported. The observed synkinetic patterns appear predictable and nonrandom. In addition, these observations tend to raise doubts that the aberrant fiber regeneration hypothesis is the sole explanation of synkinesis. They further implicate facial nuclear hyperexcitability as an explanation in at least some cases of synkinesis. Understanding these patterns enhances clinical detection and evaluation and may lead to a better knowledge of the fundamental pathophysiology of synkinesis and its prevention.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |