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PubMed2004

Non-rigid image registration: theory and practice.

Image registration is an important enabling technology in medical image analysis. The current emphasis is on development and validation of application-specific non-rigid techniques, but there is already a plethora of techniques and terminology in use. In this paper we discuss the current state of the art of non-rigid registration to put on-going research in context and to highlight current and future clinical applications that might benefit from this technology. The philosophy and motivation underlying non-rigid registration is discussed and a guide to common terminology is presented. The core components of registration systems are described and outstanding issues of validity and validation are confronted.

Algorithms↗
PubMed2005

[Anatomical accuracy of lesion localization. Retrospective interactive rigid image registration between 18F-FDG-PET and X-ray CT].

UNLABELLED: The aim of this study was to evaluate the anatomical accuracy and reproducibility of retrospective interactive rigid image registration (RIR) between routinely archived X-ray computer tomography (CT) and positron emission tomography performed with 18F-deoxyglucose (FDG-PET) in oncological patients. METHODS: Two observers registered PET and CT data obtained in 37 patients using a commercially available image fusion tool. RIR was performed separately for the thorax and the abdomen using physiological FDG uptake in several organs as a reference. One observer performed the procedure twice (O1a and O1b), another person once (O2). For 94 malignant lesions, clearly visible in CT and PET, the signed and absolute distances between their representation on PET and CT were measured in X-, Y-, and Z-direction with reference to a coordinate system centered in the CT representation of each lesion (X-, Y-, Z-distances). RESULTS: The mean differences of the signed and absolute distances between O1a, O1b, and O2 did not exceed 3 mm in any dimension. The absolute X-, Y-, and Z-distances ranged between 0.57 +/- 0.58 cm for O1a (X-direction) and 1.12 +/- 1.28 cm for O2 (Z-direction). When averaging the absolute distances measured by O1a, O1b, and O2, the percentage of lesions misregistered by less than 1.5 cm was 91% for the X-, 88% for the Y-, and 77% for the Z-direction. The larger error of fusion determined for the remaining lesions was caused by non-rigid body transformations due to differences in breathing, arm position, or bowel movements between the two examinations. Mixed effects analysis of the signed and absolute X-, Y-, and Z-distances disclosed a significantly greater misalignment in the thorax than in the abdomen as well as axially than transaxially. CONCLUSION: The anatomical inaccuracy of RIR can be expected to be <1.5 cm for the majority of neoplastic foci. Errors of alignment are bigger in the thorax and in Z-direction, due to non-rigid body transformations caused, e.g., by breathing.

Fluorodeoxyglucose F18↗
PubMedDate not supplied

Detachable functional focused rigidity cast for metatarsal fractures.

This article aims to assess whether a detachable functional focused rigidity cast can be used as a one-off definitive treatment for proximal 5th metatarsal fractures. A prospective trial was carried out over a 2-year period. Forty-one patients with proximal 5th metatarsal fractures (tuberosity and Jones) were recruited and treated with a detachable focused rigidity cast after appropriate consent. Of the 39 patients with follow-up, six had a Jones fracture and 33 had tuberosity fractures. All 33 patients with tuberosity fractures achieved clinical union within 4-5 weeks (mean of 4.2 weeks). Four of the six patients with Jones fractures achieved clinical union in 8-12 weeks. One achieved union in 14 weeks and one underwent open reduction and internal fixation for delayed union. There were no complications related to the cast. The results support the use of a detachable focused rigidity cast as a one-off definitive treatment of tuberosity fractures of the 5th metatarsal. However, all the Jones fractures and the diaphyseal fractures should be referred to an orthopaedic team for further management.

Adhesives↗
PubMed2004

Amantadine in the akinetic-rigid variant of Huntington's disease.

OBJECTIVE: To report the effects of amantadine on an akinetic-rigid variant of Huntington's disease (HD). CASE SUMMARY: We describe a 36-year-old woman with HD who was treated with intravenous amantadine for 5 days. The woman was evaluated with the Unified Huntington's Disease Rating Scale before and after treatment. Parkinsonism, bradykinesia, and dystonia improved significantly. DISCUSSION: Amantadine is a noncompetitive N-methyl d-aspartate receptor antagonist. It is mainly used in the treatment of Parkinson's disease, as it increases dopamine levels in the brain. This effect is said to ameliorate akinesia. Although the effect of amantadine on choreatic dystonia in HD has been reported in several studies, to the best of our knowledge, this is the first report of the ameliorative effects of amantadine on the rigid form of HD. Our patient showed improvements of gait, parkinsonism, and dystonia. Fine-motor tasks and eye movement did not change significantly. CONCLUSIONS: We suggest that amantadine treatment might be of value to patients with the akinetic-rigid variant of HD.

Adult↗
PubMed1991

Comparative studies using a rigid thoracoscope and fiberoptic bronchoscope to treat spontaneous pneumothorax.

Prior to 1978, the conventional treatment of pneumothorax generally consisted of conservative therapies such as rest, needle puncture, or thoracic cavity drainage; however, when conservative therapies were ineffective or relapse occurred therapeutic approach, 34 percent (11/32) of our patients required a thoracotomy. Consequently, in 1981, we began to use alternative therapies to reduce the need for thoracotomy. In this report, we describe the results of using a rigid thoracoscope and fiberoptic bronchoscope for the treatment of spontaneous pneumothorax. Initially, we treated 31 of 79 patients with a rigid thoracoscope and electrocoagulation therapy. Therapy was effective in 17 (55 percent) of the patients. Only 13 (16 percent) of the 79 patients required a thoracotomy, which represents a 50 percent reduction in incidence. Of the 14 cases in which therapy was ineffective, the major cause of failure was our inability to view a broad thoracic area and treat all blebs with a rigid thoracoscope. Subsequently, we developed a method using a fiberoptic bronchoscope (FB), which allows an unrestricted view of the thoracic area, in combination with electrocoagulation and fibrinogen or thrombin solution (or both) for the treatment of spontaneous pneumothorax. We treated 19 of 39 patients with the FB method. Treatment was effective in 15 (80 percent) of the patients. Only 4 (10 percent) of the 39 patients required a thoracotomy, which is a reduction of over 60 percent in our original incidence.

Adult↗
PubMed2000

Negative pressure ventilation vs external high-frequency oscillation during rigid bronchoscopy. A controlled randomized trial.

STUDY OBJECTIVES: To compare the effectiveness of two modalities of external ventilation during rigid bronchoscopy: intermittent negative pressure ventilation (INPV) and external high-frequency oscillation (EHFO). DESIGN: Prospective, controlled, randomized, nonblinded study. SETTING: University-affiliated hospital. PATIENTS: Seventy patients undergoing interventional rigid bronchoscopy for tracheobronchial lesions were enrolled into the study. INTERVENTIONS: Mechanical ventilation was performed by INPV or EHFO. When pulse oximetry was < 90%, manually assisted ventilation was delivered. MEASUREMENTS AND RESULTS: Arterial blood gases were sampled preoperatively and intraoperatively. Most patients in both groups had normal intraoperative PaCO(2) (mean, 43. 6 +/- 11.8 mm Hg under EHFO and 37.4 +/- 8.2 mm Hg under INPV; p = 0.012), and acidemia occurred in 9 of 35 patients of EHFO group and in 2 of 35 patients of INPV group (p = 0.049). Hypercapnia (PaCO(2) > 50 mm Hg) was observed in 10 patients under EHFO and in 2 with INPV (p = 0.026). Intraoperative mean PaO(2) was similar (101.4 +/- 52.9 mm Hg with EHFO and 124.2 +/- 50.3 mm Hg with INPV; p = 0.07), but O(2) supply was different (3.5 +/- 2.3 L/min during INPV and 8.5 +/- 6.2 L/min during EHFO; p < 0.001). Intraoperative hypoxemia (PaO(2) < 60 mm Hg) occurred in five patients with EHFO and two with INPV (p = 0.426). Three EHFO patients required manually assisted ventilation (mean, 0.2 +/- 0.9), but no INPV patient did (p = 0.142). CONCLUSIONS: External negative pressure ventilation appears to be a suitable choice during rigid bronchoscopy: both EHFO and INPV ensure effective ventilation and comfortable operating conditions in the majority of patients. Some patients may receive inadequate ventilation with EHFO, developing respiratory acidosis and requiring manually assisted ventilation. In comparison with INPV, EHFO requires a higher fraction of inspired oxygen.

Adult↗
PubMed2004

A bending mode analysis for growing microtubules: evidence for a velocity-dependent rigidity.

Microtubules are dynamic protein polymers that continuously switch between elongation and rapid shrinkage. They have an exceptional bending stiffness that contributes significantly to the mechanical properties of eukaryotic cells. Measurements of the persistence length of microtubules have been published since 10 years but the reported values vary over an order of magnitude without an available explanation. To precisely measure the rigidity of microtubules in their native growing state, we adapted a previously developed bending mode analysis of thermally driven shape fluctuations to the case of an elongating filament that is clamped at one end. Microtubule shapes were quantified using automated image processing, allowing for the characterization of up to five bending modes. When taken together with three other less precise measurements, our rigidity data suggest that fast-growing microtubules are less stiff than slow-growing microtubules. This would imply that care should be taken in interpreting rigidity measurements on stabilized microtubules whose growth history is not known. In addition, time analysis of bending modes showed that higher order modes relax more slowly than expected from simple hydrodynamics, possibly by the effects of internal friction within the microtubule.

Algorithms↗
PubMed2005

Flexural rigidity of individual microtubules measured by a buckling force with optical traps.

We used direct buckling force measurements with optical traps to determine the flexural rigidity of individual microtubules bound to polystyrene beads. To optimize the accuracy of the measurement, we used two optical traps and antibody-coated beads to manipulate each microtubule. We then applied a new analytical model assuming nonaxial buckling. Paclitaxel-stabilized microtubules were polymerized from purified tubulin, and the average microtubule rigidity was calculated as 2.0 x 10(-24) Nm2 using this novel microtubule buckling system. This value was not dependent on microtubule length. We also measured the rigidity of paclitaxel-free microtubules, and obtained the value of 7.9 x 10(-24) Nm2, which is nearly four times that measured for paclitaxel-stabilized microtubules.

Animals↗
PubMed2005

Change in rigidity in the activated form of the glucose/galactose receptor from Escherichia coli: a phenomenon that will be key to the development of biosensors.

Recently a periplasmic glucose/galactose binding protein, GGRQ26C, immobilized on a gold surface has been used as an active part of a glucose biosensor based on quartz microbalance technique. However the nature of the glucose detection was not clear. Here we have found that the receptor protein film immobilized on the gold surface increases its rigidity when glucose is added, which explains the unexpected detection signal. To study the rigidity change, we developed a new fast and simple method based on using atomic force microscopy (AFM) in tapping mode. The method was verified by explicit measurements of the Young's modulus of the protein film by conventional AFM methods. Since there are a host of receptors that undergo structural change when activated by ligand, AFM can play a key role in the development and/or optimization of biosensors based on rigidity changes in biomolecules.

Biophysics↗
PubMed2006

Torsional rigidities of weakly strained DNAs.

Measurements on unstrained linear and weakly strained large (> or =340 bp) circular DNAs yield torsional rigidities in the range C = 170-230 fJ fm. However, larger values, in the range C = 270-420 fJ fm, are typically obtained from measurements on sufficiently small (< or =247 bp) circular DNAs, and values in the range C = 300-450 fJ fm are obtained from experiments on linear DNAs under tension. A new method is proposed to estimate torsional rigidities of weakly supercoiled circular DNAs. Monte Carlo simulations of the supercoiling free energies of solution DNAs, and also of the structures of surface-confined supercoiled plasmids, were performed using different trial values of C. The results are compared with experimental measurements of the twist energy parameter, E(T), that governs the supercoiling free energy, and also with atomic force microscopy images of surface-confined plasmids. The results clearly demonstrate that C-values in the range 170-230 fJ fm are compatible with experimental observations, whereas values in the range C > or = 269 fJ fm, are incompatible with those same measurements. These results strongly suggest that the secondary structure of DNA is altered by either sufficient coherent bending strain or sufficient tension so as to enhance its torsional rigidity.

Biophysics↗
PubMed2005

[Efficacy and low cost in keratoconus treatment with rigid gas-permeable contact lens].

PURPOSE: To study the efficacy of rigid gas-permeable contact lens (RGPCL) fitting in keratoconus patients and to determine treatment costs. METHODS: The records of 126 patients treated at the Hospital das Clínicas de Ribeirão Preto from January 2001 to June 2002 were retrospectively studied. Information about sex, age and treated eyes was collected. Visual acuity (VA) with and without correction was measured and plotted against corneal base curve (K) and toricity. Average price of the lenses was calculated. RESULTS: Fitting rigid gas-permeable contact lens was successful in 86.18% of the patients, resulting in VA=0.8 in 40.00% of them. Visual acuity improvement was observed in patients with steep base curve and in patients with high corneal toricity. Age of most patients ranged from 15 to 45 years; 60.31% of them were female. Corneal transplantation was indicated in 11.24% of the cases. Cost of each lens averaged R$ 40.00 (USD 13.00). CONCLUSION: Rigid gas-permeable contact lens proved to be an efficient, low-cost resource for improving visual acuity in most of the treated patients.

Adolescent↗
PubMed2003

Rigid external distraction osteogenesis for a patient with maxillary hypoplasia and oligodontia.

OBJECTIVE: In this report, the orthodontic treatment combined with rigid external distraction osteogenesis in a 5.5-year-old girl with midfacial hypoplasia and oligodontia is described. PATIENT: The child presented with a reduced maxilla, protruding lower lip, skeletal Class III jaw relationship with a low mandibular plane angle, a short and flattened nose, anterior crossbite, and aplasia of 16 permanent teeth. The patient was treated with rigid external maxillary distraction osteogenesis, maxillary protraction headgear, and Class III elastics. Following treatment, the maxilla was displaced in a forward direction with new bone formation at the tuberosities and the mandible rotated backward in relation to the anterior cranial base. The anterior crossbite was corrected, and the skeletal jaw relationship changed from a Class III to a Class I skeletal pattern. The soft tissue facial profile showed that the nasal projection had been increased, the nasolabial angle increased, and the lower lip protrusion was reduced. Postoperative treatment results were acceptable. CONCLUSION: This report documents that early maxillary advancement with rigid external osteogenesis offers a promising treatment alternative for a very young patient with maxillary hypoplasia and oligodontia.

Anodontia↗
PubMedDate not supplied

Efficacy of shock-absorbing versus rigid pylons for impact reduction in transtibial amputees based on laboratory, field, and outcome metrics.

Prosthetic manufacturers have marketed shock-absorbing pylons (SAPs) for attenuation of injurious loads from foot-ground contact. In this study, we compared a commonly prescribed SAP with a conventional rigid pylon, using a within-subject design (n = 15 unilateral transtibial amputees), to assess effect on gait mechanics, measure transmitted accelerations in situ, and determine functional outcomes using step counts and questionnaires. No differences were found across pylons for self-selected walking speed, prosthetic-side step length, prosthetic-side loading rate and decelerative peak of the vertical ground reaction force, peak pylon acceleration, step count per week, or questionnaire results that examined pylon performance and subjects' pain and fatigue levels. The only statistically significant finding was for the prosthetic-side knee angle at initial contact, where subjects displayed an average of 2.6 degrees more flexion with the rigid pylon than the SAP while walking at a controlled speed (p = 0.004); this result indicates that transtibial amputees are able to modulate the effective stiffness of their residual limb in response to changes in prosthetic component stiffness. The results from the laboratory, field, and subjective outcome measurements suggest that the SAP in this study is as effective as a rigid pylon for unilateral transtibial amputees.

Activities of Daily Living↗
PubMed2005

[3D finite element analysis in consideration of the slide on residual ridge and the rigidity of mandibular complete denture].

PURPOSE: The motions and stress distributions of mandibular complete dentures during use were compared and investigated in terms of denture rigidity using 3D finite element method (FEM) stress analysis. METHODS: Four models for analysis of mandibular complete dentures with different elastic modulus (1. A resin base denture (C), 2. A resin base denture with reinforcement wire (R), 3. A metal base denture (M), 4. A metal plate denture consisting of a double structure (T)) and measured using 3D FEM. Modes were separated into two elastic bodies: the dentures and residual ridge. Analyses were executed under the same conditions total loads of 20 kgf and contact. RESULTS: 1. The total equivalent-potential strain of dentures was high beneath the load point for C and R (2.38 approximately 2.86 x 10(-3)epsilon at buccal-shelf of working side and 0.55 approximately 0.68 x 10(-3)epsilon at posterior residual ridge). The entire dentures barely distorted for M and T (0.98 approximately 1.17 x 10(-3)epsilon at buccal-shelf of working side and 0.21 approximately 0.25 x 10(-3)epsilon at posterior residual ridge). 2. In the main stress distribution of mucosa beneath denture bases, high loads were located beneath the loading point of dentures, at lingual distal areas of the working side in C and R. In M and T, increasing the rigidity of dentures reduced the stress beneath the loading point of dentures. Stress was distributed widely and evenly. CONCLUSIONS: When the rigidity of dentures is high, the strain of dentures decreases, the stress of the residual mucous membrane will evenly become distributed, and the distance of the balancing side from the denture border to the residual mucous membrane at the time of unilateral balanced position will decrease.

Dental Stress Analysis↗
PubMed1981

Decision-making in old age: cautiousness and rigidity.

The purpose of the present study was to test the findings of Botwinick's work on cautiousness and decision-making in old age [1,2], along with an examination of two factors not previously studied: rigidity and certainty of decision outcome. Sixty-four elderly participants of both sexes participated in filling out the Choice Dilemmas Questionnaire (CDQ) after having been classified as high or low on Schaie's Test of Behavioral Rigidity [3]. In general, Botwinick's conclusions were supported: 1. when given the opportunity to avoid making decisions on the CDQ, the elderly did so, even under conditions of no risk at all concerning the outcome of the decision; 2. elderly individuals appeared to become more conservative and cautious in their decisions when the outcome was directed at the lives of young individuals than when older individual's lifestyles were of concern. This latter phenomenon, however was not seen when the elderly participant was required to make a decision and could not elect to abstain. In addition, rigidity was found to be related to risky decisions made by the elderly individual.

Aged↗
PubMed2005

Effects of autoclaving on dimensional qualities and physical properties (flexural rigidity and brittleness) of newly developed root canal filling point made of polypropylene (FLEX POINT NEO).

In this study, we investigated the effects of 10 cycles of conventional autoclaving (121 degrees C, 20 min) on the dimensional integrity and physical properties (flexural rigidity and brittleness) of a newly developed root canal filling point made of polypropylene (FLEX POINT NEO). We measured the diameters of autoclave-sterilized and non-treated polypropylene points (020 through 070) and calculated the incidence of deviation from ISO specifications (6877.4.4.1, 1995). In order to ascertain physical properties, we tested autoclave-sterilized and non-treated polypropylene points (030, 050 and 070) for flexural rigidity. This was done by evaluating deflection value when a load was placed at the free tip-end of the point and brittleness in accordance with ISO specifications (6877.6.5.2). Ten cycles of autoclaving showed no significant effect on the diameters of the polypropylene points. All the polypropylene points in both the non-treated and the autoclave-sterilized groups met ISO specifications in terms of dimensional integrity of diameter. In the autoclave-sterilized group, 030 and 050 polypropylene points showed a slight decrease in flexural rigidity (3.4% in 030, 10.0% in 050). In terms of brittleness, none of polypropylene points showed any sign of fracture.

Hot Temperature↗
PubMed1997

Forward-facing motion biases for rigid and nonrigid biologically likely transformations.

When observers are presented directionally ambiguous motion, they exhibit a bias for experiencing movement in the direction in which shapes appear to face. We examined the influence of rigidity of a shape on the forward-facing bias with stimuli whose directionality is biologically specified. In general, the lack of shape correspondence during a nonrigid transformation should weaken the motion percept and decrease forward-facing bias. In contrast, representational momentum cues associated with a biologically likely nonrigid transformation should enhance the motion percept and increase forward-facing bias. Analysis for both rigid and nonrigid conditions indicated statistically significant forward-facing biases, but strength of bias did not differ significantly. The lack of difference between the two conditions suggests that the transformation was not one which allowed the influence of either consistency of correspondence or representational momentum to dominate and confirms that a comparably sized forward-facing bias can occur with both rigidly and nonrigidly transformed shapes.

Cues↗
PubMed1991

Depression, general anxiety, test anxiety, and rigidity of gifted junior high and high school children.

27 gifted students in junior high and high school from north central Kansas school districts were administered the Children's Depression Inventory, the Beck Depression Scale, Test Anxiety Scale, General Anxiety Scale, and Breskin's Rigidity Scale. Sex, age, and grade were not considered, as the sample was small. The gifted students' mean scores for depression were below the cut-off score while their test anxiety, general anxiety, and rigidity scores were at moderate levels. Pearson correlations were significant for Beck Depression with the Children's Depression (r = .82) and General Anxiety Scales (r = .60). Scores on the General Anxiety Scale correlated significantly with those on the Children's Depression Inventory (r = .69) and the Test Anxiety Scale (r = .55). Rigidity scores were not correlated significantly with any other measure and scores on the depression scales did not correlate significantly with those on the Test Anxiety Scale.

Adolescent↗