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PubMed2005

Assessment of rigid multi-modality image registration consistency using the multiple sub-volume registration (MSR) method.

Registration of different imaging modalities such as CT, MRI, functional MRI (fMRI), positron (PET) and single photon (SPECT) emission tomography is used in many clinical applications. Determining the quality of any automatic registration procedure has been a challenging part because no gold standard is available to evaluate the registration. In this note we present a method, called the 'multiple sub-volume registration' (MSR) method, for assessing the consistency of a rigid registration. This is done by registering sub-images of one data set on the other data set, performing a crude non-rigid registration. By analysing the deviations (local deformations) of the sub-volume registrations from the full registration we get a measure of the consistency of the rigid registration. Registration of 15 data sets which include CT, MR and PET images for brain, head and neck, cervix, prostate and lung was performed utilizing a rigid body registration with normalized mutual information as the similarity measure. The resulting registrations were classified as good or bad by visual inspection. The resulting registrations were also classified using our MSR method. The results of our MSR method agree with the classification obtained from visual inspection for all cases (p < 0.02 based on ANOVA of the good and bad groups). The proposed method is independent of the registration algorithm and similarity measure. It can be used for multi-modality image data sets and different anatomic sites of the patient.

Algorithms↗
PubMed2002

The bending rigidity of mitotic chromosomes.

The bending rigidities of mitotic chromosomes isolated from cultured N. viridescens (newt) and Xenopus epithelial cells were measured by observing their spontaneous thermal bending fluctuations. When combined with simultaneous measurement of stretching elasticity, these measurements constrain models for higher order mitotic chromosome structure. We measured bending rigidities of B approximately 10(-22) N. m(2) for newt and approximately 10(-23) N. m(2) for Xenopus chromosomes extracted from cells. A similar bending rigidity was measured for newt chromosomes in vivo by observing bending fluctuations in metaphase-arrested cells. Following each bending rigidity measurement, a stretching (Young's) modulus of the same chromosome was measured in the range of 10(2) to 10(3) Pa for newt and Xenopus chromosomes. For each chromosome, these values of B and Y are consistent with those expected for a simple elastic rod, B approximately YR(4), where R is the chromosome cross-section radius. Our measurements rule out the possibility that chromosome stretching and bending elasticity are principally due to a stiff central core region and are instead indicative of an internal structure, which is essentially homogeneous in its connectivity across the chromosome cross-section.

Animals↗
PubMed2004

Intubating laryngeal mask airway allows tracheal intubation when the cervical spine is immobilized by a rigid collar.

BACKGROUND: An intubating laryngeal mask airway (ILMA) facilitates tracheal intubation with the neck in neutral position, which is similar to the neck position maintained by a rigid cervical collar. However, a cervical collar virtually obliterates neck movement, even small movements that normally facilitate airway insertion. We therefore tested the hypothesis that the ILMA will allow tracheal intubation even in patients wearing a rigid cervical collar. METHODS: We performed blind tracheal intubation via an ILMA under general anaesthesia in 50 patients with a rigid Philadelphia collar in place undergoing cervical spine surgery and 50 general surgical patients. Time required for intubation, intubation success rate, and numbers and type of adjusting manoeuvres used were recorded. RESULTS: Inter-incisor distance was significantly smaller (4.1 (0.8) vs 4.6 (0.7) cm, mean (sd), P<0.01) and Mallampati scores were significantly greater (P<0.001) in the patients with collars. ILMA insertion took longer (30 (25) vs 22 (6) s), more patients required two insertion attempts (15 vs 3; P<0.005), and ventilation adequacy with ILMA was worse (P<0.05) in collared patients. However, there were no significant differences between the collars and control patients in terms of total time required for intubation (60 (41) vs 50 (30) s), number of intubation attempts, overall intubation success rate (96 vs 98%), or the incidence of intubation complications. CONCLUSIONS: Blind intubation through an ILMA is thus a reasonable strategy for controlling the airway in patients who are immobilized with a rigid cervical collar.

Adolescent↗
PubMed2005

Evolution of flexural rigidity according to the cross-sectional dimension of a superelastic nickel titanium orthodontic wire.

The choice of the most suitable orthodontic wire for each stage of treatment requires estimation of the forces generated. In theory, the selection of wire sequences should initially utilize a lower flexural rigidity; thus clinicians use smaller round cross-sectional dimension wires to generate lighter forces during the preliminary alignment stage. This assessment is true for conventional alloys, but not necessarily for superelastic nickel titanium (NiTi). In this case, the flexural rigidity dependence on cross-sectional dimension differs from the linear elasticity prediction because of the martensitic transformation process. It decreases with increasing deflection and this phenomenon is accentuated in the unloading process. This behaviour should lead us to consider differently the biomechanical approach to orthodontic treatment. The present study compared bending in 10 archwires made from NiTi orthodontics alloy of two cross-sectional dimensions. The results were based on microstructural and mechanical investigations. With conventional alloys, the flexural rigidity was constant for each wire and increased largely with the cross-sectional dimension for the same strain. With NiTi alloys, the flexural rigidity is not constant and the influence of size was not as important as it should be. This result can be explained by the non-constant elastic modulus during the martensite transformation process. Thus, in some cases, treatment can begin with full-size (rectangular) wires that nearly fill the bracket slot with a force application deemed to be physiologically desirable for tooth movement and compatible with patient comfort.

Dental Alloys↗
PubMed2004

Origin of the intrinsic rigidity of DNA.

The intrinsic rigidities of DNA and RNA helices are generally thought to arise from some combination of vertical base-stacking interactions and intra-helix phosphate-phosphate charge repulsion; however, the relative contributions of these two types of interaction to helix rigidity have not been quantified. To address this issue, we have measured the rotational decay times of a 'gapped-duplex' DNA molecule possessing a central, single-stranded region, dT24, before and after addition of the free purine base, N6-methyladenine ((me)A). Upon addition of (me)A, the bases pair with the T residues, forming a continuous stack within the gap region. Formation of the gapped duplex is accompanied by a nearly 2-fold increase in decay time, to values that are indistinguishable from the full duplex control for monovalent salt concentrations up to 90 mM. These results indicate that at least 90% of the rigidity of the dT(n)-dA(n) homopolymer derives from base pair stacking effects, with phosphate-phosphate interactions contributing relatively little to net helix rigidity at moderate salt concentrations.

Adenine↗
PubMed1999

Extrapyramidal type rigidity in rheumatoid arthritis.

OBJECTIVES: We had noted cogwheel rigidity in a number of patients with rheumatoid arthritis (RA). Based on this finding, we aimed to investigate formally the presence of rigidity and cogwheeling in RA patients. Our secondary aim was to survey the co-existence of RA and Parkinson's disease (PD). METHODS: A total of 87 consecutive patients with a diagnosis of RA, 78 patients with PD and 67 otherwise healthy patients attending a dedicated headache clinic participated in the study. RESULTS: Rigidity was observed in 24% of RA, 60% of PD and 2% of headache patients. The frequency among the RA patients was significantly higher compared to that of patients with headache (chi 2 = 15.2; P = 0.00009). The frequency of PD among the RA patients was 2/87 (2.3%), while the frequency of RA among the PD patients was 6/78 (7.7%). CONCLUSION: Rigidity can be observed in approximately a quarter of patients with RA.

Adult↗
PubMed1993

Obtaining rigidity in the neophallus of female-to-male transsexuals: a review of the literature.

In phalloplasty, the use of transplants and implants to obtain sufficient rigidity allowing for sexual penetration is difficult and often has resulted in complications and failure. Resorption, curving, and fracture of autologous cartilage and bone transplants are reported, and rigid implants have a tendency to erode and extrude. Besides, a constantly rigid phallus may serve as a source of embarrassment to the patient. On the other hand, hydraulic prostheses frequently show mechanical failure compared with nonhydraulic implants. For these reasons, some authorities have their patients use external devices for erection. Others fully rely on edema, scar fibrosis, or congestion to give sufficient rigidity. In this review, the literature on baculum implantation--on the use of external devices as well as on the use of no stiffener at all--is discussed.

Female↗
PubMedDate not supplied

Comparison and evaluation of rigid, affine, and nonrigid registration of breast MR images.

PURPOSE: A new nonrigid registration method, designed to reduce the effect of movement artifact in subtraction images from breast MR, is compared with existing rigid and affine registration methods. METHOD: Nonrigid registration was compared with rigid and affine registration methods and unregistered images using 54 gadolinium-enhanced 3D breast MR data sets. Twenty-seven data sets had been previously reported normal, and 27 contained a histologically proven carcinoma. The comparison was based on visual assessment and ranking by two radiologists. RESULTS: When analyzed by two radiologists independently, all three registration methods gave better-quality subtraction images than unregistered images (p < 0.01), but nonrigid registration gave significantly better results than the rigid and affine registration methods (p < 0.01). There was no significant difference between rigid and affine registration methods. CONCLUSION: Nonrigid registration significantly reduces the effects of movement artifact in subtracted contrast-enhanced breast MRI. This may enable better visualization of small tumors and those within a glandular breast.

Adult↗
PubMed1998

Biochemistry and biomechanics of healing tendon: Part I. Effects of rigid plaster casts and functional casts.

PURPOSE: Traditional treatment of surgically repaired Achilles tendons includes complete immobilization of the joint in rigid casts for 6 to 8 wk. We tested the use of functional polyurethane casts as an alternative to rigid plaster casts after experimental tenotomy and repair of the rabbit Achilles tendon. METHODS: After repair the limbs of 15 experimental rabbits were immobilized in a functional polyurethane cast for 15 d, while those of 14 controls were immobilized in traditional rigid plaster casts for the same period. RESULTS: Functional casting resulted in a 60% increase in total collagen in the neotendon compared with that in rigid casting (P < 0.05). Mature collagen cross-links declined 8% in the tendons with functional casts. The biomechanical parameters of the tendons changed with functional casting, showing a 20% increase in maximum load and 21% increase in maximum stress. CONCLUSIONS: These changes were noted without any cases of tendon re-rupture in either type of cast. Thus, functional casting following surgery of Achilles tendons appears to improve healing without significant risks of re-rupture.

Achilles Tendon↗
PubMed1999

Endoscopic resection of colloid cysts: surgical considerations using the rigid endoscope.

OBJECTIVE: Colloid cysts of the third and lateral ventricles have traditionally been treated by transfrontal and transcallosal microsurgical resection or by stereotactic aspiration. Recently, rigid and flexible ventricular endoscopic techniques have been used to treat these lesions. Our study was undertaken to examine the efficacy of rigid endoscopy in the resection of colloid cysts. METHODS: Fifteen patients with a radiological diagnosis of colloid cysts were given the option of undergoing either endoscopic surgery or craniotomy. The average tumor size was 1.43 cm. Fourteen patients underwent planned endoscopic resections, and a craniotomy was performed initially in one patient. RESULTS: Entire tumor resection was achieved with the endoscope in 12 patients (86%). A craniotomy was required for two colloid cysts that could not be resected endoscopically. In total, complete radiographic resections were achieved in 14 patients (93%). There were no permanent complications, although postoperative deficits included short-term memory loss and hemiparesis, each in one patient. CONCLUSION: Rigid endoscopy affords good optical resolution, high magnification, and excellent illumination. Total or near total resection of colloid cysts should be the goal for all patients and can be achieved using the rigid endoscope, with little morbidity, shortened operative time, reduced length of stay, and resolution of symptoms. Although long-term follow-up is needed, we think that endoscopy should be considered as a primary treatment for most patients.

Adult↗
PubMed1985

Closed-form ametropic pressure-volume and ocular rigidity solutions.

Basic closed-form theoretical results are derived relating the stress-strain sigma = sigma(epsilon), pressure-volume p = p(V), and ocular rigidity-pressure K = K(p) functions for a spherically symmetric eye of contant thickness and material properties. The results can be used to predict the pressure-volume and ocular rigidity behavior of both hyperopic and myopic eyes, in addition to the emmetropic case. The theoretical results are compared with eight different experimental studies from the literature. Five experimentally obtained mechanical variables, the pre-exponential stress-strain constant A (Pascals), the dimensionless exponential stiffening constant alpha, the pressure-volume globe stiffness intercept a (mm Hg/mm3), the globe stiffness slope b (mm-3), and the ocular rigidity K(mm-3) are found on average to agree with the theoretical predictions within a factor of 3 or better. Possible clinical applications might include measuring the ocular rigidity function K = K(p, Vo) to infer the mechanical strength of the corneo-scleral shell. The results may also be useful to help understand glaucoma dynamics as a function of refraction, and also with respect to tonometer calibration.

Biomechanical Phenomena↗
PubMed1998

"Pillar and collar" technique for measuring the axial edge lift of multicurve rigid lenses.

BACKGROUND: The method of using an optical spherometer and a lens thickness gauge, in combination with a pillar and collar, has previously been shown to be repeatable and accurate (to 0.01 mm) in measuring the edge lift of rigid monocurve lenses. PURPOSE: This paper goes on to validate the technique for measurements taken on edge-finished multicurve rigid lenses. METHODS: The axial edge lift (AEL) of a series of multicurve rigid lenses having known values of AEL was measured using an optical spherometer, a thickness gauge, and contact lens V gauge in a similar way as was described in the companion paper. RESULTS: The results show that as long as a correction factor of 0.01 mm is applied, as found in the previous paper, the technique will allow satisfactory verification of the edge lift. CONCLUSIONS: The technique is accurate and reproducible, even in multicurve lens designs, provided that a calibrating correction factor of 0.01 mm is applied to account for methodological error. It will also indirectly allow the accuracy of manufacture of the peripheral curves and diameters of any rigid contact lens to be verified.

Contact Lenses↗
PubMed1998

Palatal fractures: classification, patterns, and treatment with rigid internal fixation.

A classification of palatal fracture types is developed from patterns observed on CT scans, and success with open reduction techniques is correlated with fracture pattern. The six palatal fracture types are as follows: I, anterior and posterolateral alveolar; II, sagittal; III, parasagittal; IV, para-alveolar; V, complex; and VI, transverse. Associated fractures were LeFort I (100 percent), LeFort II and III (55 percent), mandible (48 percent), and dental (55 percent). Large segment, sagittally oriented palatal fractures could be stabilized with rigid internal fixation. Complete rigid fixation of the palate consists of (1) roof of mouth, (2) pyriform or alveolar, and (3) four LeFort I buttress stabilization. Comminuted palatal fractures were managed by standard LeFort I and alveolar buttress fixation, palatal splinting, and intermaxillary, fixation. If complete rigid fixation was employed in the palate in type II, III, and IV fractures, a palatal splint was avoided in 60 percent of these cases. Rigid internal fixation is therefore concluded to facilitate the treatment of certain types of palatal fractures by reduced length of intermaxillary fixation and avoidance of palatal splinting.

Alveolar Process↗
PubMed1997

Vertebral column resection for the treatment of rigid coronal decompensation.

STUDY DESIGN: A retrospective study of patients with rigid coronal decompensation. OBJECTIVES: To determine if patients with rigid coronal decompensation can be safely and successfully treated by anterior-posterior vertebral column resection, spinal shortening, posterior instrumentation, and fusion to correct their deformities. SUMMARY OF BACKGROUND DATA: Previous investigators have described reconstructive techniques used to treat patients with sagittal and coronal spine deformities. These techniques include osteotomy and anterior or posterior fusion. Although a number of these studies consider the problems associated with failed back syndrome (flatback, coronal and axial imbalance, pseudarthrosis), they have not satisfactorily addressed the management of rigid coronal decompensation. The patient population of the current study, on average, presented with more severe, fixed deformities than those detailed in the literature, and required more extensive surgery than previously described. METHODS: Twenty-four patients (average age, 27 years) with rigid coronal decompensation underwent anterior-posterior vertebral column resection, spinal shortening, posterior instrumentation, and fusion. Degree of curvature was measured in the coronal and sagittal planes, and decompensation was assessed. Follow-up was from 2 to 10 years. RESULTS: Coronal and sagittal decompensation were corrected an average of 82% and 87%, respectively; T1 tilt and pelvic obliquity were improved by 65% and 53%, respectively; and scoliosis was improved by 52%. Complications occurred in 14 patients, but at follow-up all patients rated their results as either good or excellent. CONCLUSIONS: Patients with fixed, decompensated spinal deformity may be safely corrected by vertebrectomy, decancellation, spinal shortening, instrumentation, and fusion. Complications are transient, and the benefits in this select group of patients outweigh the risks.

Adolescent↗
PubMed1998

Treatment of stable burst fracture of the atlas (Jefferson fracture) with rigid cervical collar.

STUDY DESIGN: A retrospective review of a clinical series. OBJECTIVE: To evaluate the use of a rigid cervical collar alone as the treatment for stable Jefferson fracture, and to devise an algorithm for treatment of Jefferson fracture with or without an associated cervical injury. SUMMARY OF BACKGROUND DATA: The traditional treatment for Jefferson fracture, if there is no indication for surgery, is immobilization by halo vest. Because halo vest placement is associated with intracranial infection and a significant degree of patient discomfort, slightly less rigid forms of external immobilization may be useful for the treatment of stable Jefferson fractures. No standard protocol calling for the use of one form of stabilization device has been reported. MATERIALS: The medical records and radiographs of 16 consecutive patients with Jefferson fracture during a 2-year period were reviewed. Each patient underwent a complete cervical radiograph series and a computed tomographic scan. The mean C1 lateral mass displacement was 1.8 mm. Cervical spine radiographs, including lateral flexion-extension views were obtained 10 to 12 weeks after injury before the removal of an external immobilization device. RESULTS: Of these 16 patients, 1 sustained a complete injury, and 7 sustained an incomplete injury. Eight patients were neurologically intact. Twelve patients sustained a stable Jefferson fracture and were treated with a rigid cervical collar (Miami-J collar [Jerome Medical, Moorestown, NJ]) alone from 10 to 12 weeks. The patient sustaining the complete neurologic injury died of multisystem trauma. All 15 live patients showed no instability on their follow-up plain radiographs before the removal of an external stabilization device. Six patients underwent further plain radiographs approximately 1 year after the fracture and similarly demonstrated no instability. CONCLUSIONS: Isolated stable burst fracture of the atlas can be treated effectively with a rigid cervical collar alone for 10 to 12 weeks with good neurologic recovery and segmental stability. Unstable Jefferson fractures with concurrent unstable fracture of other cervical vertebrae, especially C2, requires surgical stabilization.

Adolescent↗
PubMed2003

Comfort response to rigid and soft hyper-transmissible contact lenses used for continuous wear.

PURPOSE: To assess subjective comfort during the first three months of continuous wear of hyper-transmissible soft and rigid contact lenses. METHODS: One hundred subjects (50 experienced wearers and 50 neophytes) were fitted with either the Focus Night & Day lens (CIBA Vision, Duluth, GA) or the Z alpha lens (Menicon, Nagoya, Japan). Comfort was monitored at regular intervals using a vertical analog comfort scale. RESULTS: Good comfort scores (generally indicating very comfortable lenses) were recorded for the two soft lens groups (experienced and neophytes) and the experienced rigid lens group; these scores remained approximately constant throughout the study. Comfort reported by neophyte rigid lens wearers was initially recorded as being between slightly uncomfortable and comfortable; however, after 1 week of daily wear and 1 night of overnight wear, the mean comfort score of this group reached a level that was similar to that recorded by subjects in the other three study groups. CONCLUSION: The comfort data presented in this study can be used by clinicians to anticipate the subjective response of both new and existing lens wearers to new-generation hyper-transmissible soft and rigid contact lenses.

Adult↗
PubMed2005

Posterior vertebral column resection for severe rigid scoliosis.

STUDY DESIGN: Retrospective study. OBJECTIVE: To report on the technique and results of posterior vertebral column resection (PVCR) for severe rigid scoliosis. SUMMARY OF BACKGROUND DATA: The treatment of severe rigid scoliosis is a demanding surgical challenge. Conventional procedures such as combined anteroposterior instrumentation enable limited correction. In rigid scoliosis, vertebral column resection is a better option for accomplishing translation of spinal column. PVCR is performed through a single posterior approach. METHODS: A total of 16 patients with scoliosis (average age 29 years) subjected to PVCR were retrospectively reviewed after a minimum follow-up of 2 years (range 2-6.8). The indication for PVCR was scoliosis more than 80 degrees , with flexibility less than 25%. The radiographic parameters were evaluated, and clinical records were reviewed. RESULTS: The number of vertebrae removed averaged 1.3, and 21 total (15 thoracic and 6 lumbar). Average fusion extent was 10.6 vertebrae. The mean preoperative scoliosis of 109.0 degrees was corrected to 45.6 degrees (59% correction) at the most recent follow-up, and the minor curve of 59.3 degrees was corrected to 29.2 degrees (51% correction). The mean preoperative coronal imbalance of 4.0 cm was improved to 1.0 cm at the most recent follow-up, and sagittal imbalance of 4.2 cm was improved to 1.6 cm. Complications were encountered in 4 patients, including 1 complete paralysis, 1 hematoma, 1 hemopneumothorax, and 1 proximal junctional kyphosis. CONCLUSIONS: PVCR is an effective alternative for severe rigid scoliosis. It is a highly technical procedure and should only be performed by an experienced surgical team.

Adult↗
PubMed2005

Scoliosis correction in an adolescent with a rigid spine syndrome: case report.

STUDY DESIGN: Details of presentation and approach to the treatment of scoliosis in a case of a Rigid Spine Syndrome (RSS). OBJECTIVE: To report on the results of conservative and operative treatment of scoliosis associated with RSS, and, based on this, to propose an assessment and treatment protocol for this condition. SUMMARY OF BACKGROUND DATA: Congenital muscular dystrophies (CMD) are a group of disorders marked by hypotonia at birth and a generally nonprogressive course of muscle weakness. Spinal rigidity is present in a number of patients with CMD. RSS is classified as a CMD, and is characterized by early rigidity of the spine, limb contractures, and restrictive respiratory dysfunction. An approach to the treatment of scoliosis in RSS has not been established. METHODS: Details of history, diagnostic tests, and treatment of an adolescent with RSS associated with progressive scoliosis and cervical spine extension contracture is presented. The role of brace treatment, Botox (Allergan, Inc., Irvine, CA), and details of operative correction, including histology of back muscles, is defined. RESULTS: In this case of RSS with rigid scoliosis nonresponsive to brace therapy and Botox injections, an anterior thoracolumbar spine fusion with instrumentation was successfully performed for correction of the scoliosis, and the cervical spine was addressed through a posterior approach and an occiput-cervical fusion. We outline the details of surgical procedure and restoration of spinal balance in both sagittal and coronal planes. CONCLUSIONS: The chromosomal bases of CMD and characteristic features of RSS, including diagnostic tests, have been reviewed. Surgical intervention with spinal deformity fusion, correction, and instrumentation is indicated in RSS with progressive spinal imbalance not responding to conservative therapy is safe and can give promising results.

Adolescent↗