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Results for “Anatomic Landmarks”

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At least 235 records · Page 13Linked to original sources

PubMed1999

Surface laser scanning of the cleft palate deformity--validation of the method.

Innovations in laser technology have led to the development of three-dimensional surface laser digitisation techniques capable of registering surface topology accurately. The clinical application of this technology in cleft palate documentation requires validation of the technique. This study determined the reliability of the surface laser scanning technique and assessed the reliability of interactive three-dimensional landmark localization. Original and duplicate plaster models of an infant with a complete unilateral cleft lip and palate were digitised with the Cyberware 3030R-HIREZ surface laser scanner. Seven anatomic landmarks were marked permanently on the palatal surface of the duplicate model only, which acted as visual cues for landmark localisation. Each model was scanned ten times serially, and ten composite three-dimensional images were obtained for each. On-line interactive computer landmark localisation permitted the assessment of variance for the x, y and z coordinates of each landmark. The precision of the laser scanning technique was found to be less than 0.06 mm in all three axes. Anatomic landmarks with the clearest visual cue were the least variable after ten rounds of scanning. Significant differences existed between visually aided and non-aided landmark localisation (P < 0.05). While landmarks could be localised repeatedly without the aid of a visual marker, landmarks well defined by a clearly visible visual cue on the three-dimensional image were more reliable.

Cleft Palate↗

PubMedDate not supplied

A study on the efficacy of digital enhancement of on-line portal images.

A novel method for evaluation of observer performance with portal images has been developed, in which the observer is required to identify and localize predefined anatomical landmarks in digital portal images. The method was employed to compare the spatial accuracy and decision time for landmark localization in unenhanced on-line portal images and images enhanced digitally by selective adaptive histogram modification. The results indicate that anatomical landmarks were more readily identified in the enhanced images, leading to significantly higher accuracy in landmark localization.

Evaluation Studies as Topic↗

PubMed2003

Alignment of CT images of skull dysmorphology using anatomy-based perpendicular axes.

Rigid body registration of 3D CT scans, based on manual identification of homologous landmarks, is useful for the visual analysis of skull dysmorphology. In this paper, a robust and simple alignment method was proposed to allow for the comparison of skull morphologies, within and between individuals with craniofacial anomalies, based on 3D CT scans, and the minimum number of anatomical landmarks, under rigidity and uniqueness constraints. Three perpendicular axes, extracted from anatomical landmarks, define the absolute coordinate system, through a rigid body transformation, to align multiple CT images for different patients and acquisition times. The accuracy of the alignment method depends on the accuracy of the localized landmarks and target points. The numerical simulation generalizes the accuracy requirements of the alignment method. Experiments using a human dried skull specimen, and ten sets of skull CT images (the pre- and post-operative CT scans of four plagiocephaly, and one fibrous dysplasia patients), demonstrated the feasibility of the technique in clinical practice.

Adolescent↗

PubMed2000

Digital selenium radiography: anti-scatter grid for chest radiography in a clinical study.

The purpose of this study was to evaluate the diagnostic performance of an additional stationary anti-scatter grid in digital selenium radiography (DSR) compared with images acquired with only an air gap. Chest radiographs were obtained with DSR in 100 patients with and without an anti-scatter grid. Four observers scored 12 anatomical landmarks, catheters and wire cerclages for their visualization in both subsets of images. Statistical analysis was performed using a paired t-test. Anatomical landmarks, catheters and wire cerclages were statistically better visualized in regions of high attenuation when the images were performed with an anti-scatter grid. No statistically significant difference was noted for peripheral regions, nor for sex and weight of the patient between the two modalities. Therefore, an anti-scatter grid is not recommended for chest radiography as it increases the radiation exposure of patients without having a significant impact on visualization for all regions of the chest.

Adult↗

PubMed1988

A method for analysis of back shape in scoliosis.

The shape of the back is an important factor in the clinical assessment of various spinal disorders, in particular scoliosis. A method of analysis of back surface shape is described which was designed to present most of the numerical parameters needed to assess the progress of the disease as it affects body shape. Measurements of back surface shape and manually marked anatomical landmarks were taken from a television/computer surface measurement system in which a plane of light was scanned over the back and from moiré topographs. The anatomical landmarks were used to define reference planes from which successive analyses were matched. Asymmetry in the transverse plane was illustrated by horizontal cross-sections and skin surface angles. The lateral deformity was shown by an estimate of the line of the vertebral bodies beneath the skin, derived by adding an extra lateral displacement to the palpated positions of the spinous processes, proportional to the rotation of the skin in the transverse plane. This model was used to estimate vertebral end-plate angles and Cobb angles. Lateral sections showed kyphosis and lordosis. Correlations of Lateral Asymmetry from the surface shape analysis with Cobb angle from X-ray measurements in three groups of patients (totalling 119 subjects) were in the range r = 0.77 to r = 0.94, p less than 0.0001. The analysis has reduced follow-up X-ray examinations at the Nuffield Orthopaedic Centre because it indicates quantitatively and with complete safety both lateral asymmetry and deformity in the transverse plane.

Adolescent↗

PubMed1990

Gynecologic radiotherapy fields defined by intraoperative measurements.

Whole-pelvis radiation therapy has been traditionally delivered through fields, the dimensions of which have been determined by convention and based largely on textbook anatomic landmarks. Since July 1986, 100 patients have had intraoperative retroperitoneal measurements carried out at the time of radical surgery in an effort to examine this anatomic basis for field dimensions. Structural measurements of the pelvic and paraaortic arterial branches were made in reference to the lumbosacral prominence to correlate with lymphatic pathways. The mean level of the aortic bifurcation was found to be 6.7 cm above the lumbosacral prominence. The mean level of the bifurcation of the common iliac artery was 1.7 cm above this reference point on the right and 1.4 cm above on the left. Both common iliac bifurcations were cephalad to the level of the lumbosacral prominence in 87% of patients. In only three patients were both bifurcations located below this level. Transverse pelvic dimension measurements demonstrated a width of 12.3 cm at the level of the obturator fossa and of 13.0 cm at the most inferior outside width of the external iliac arteries. To establish a simple external reference which could assist in defining radiotherapy field widths, the maximal separation of the femoral arteries at the level of inguinal ligaments was measured and averaged 14.6 cm. These data suggest that conventional fields frequently fail to correspond to true anatomic landmarks and that to optimally cover the lymphatics in radiotherapy, fields should, ideally, be based on intraoperative measurements. If such surgical guides are not available, we would suggest that standard whole-pelvis radiotherapy for cervical cancers should employ anterior and posterior fields with widths of at least 16 cm which will fully include the bifemoral separation. A superior border at the L4-L5 interspace is required to cover lymphatic pathways to the mid-common iliac nodal level. It may also be convincingly pointed out that the attachments of the uterosacral and cardinal ligaments are clearly posterior to the rectosigmoid, mandating lateral fields that should encompass the entire anterior sacral silhouette.

Female↗

PubMed1994

An investigation of maxillary superimposition techniques using metallic implants.

The purpose of this study was to determine if there are discernable, stable, anatomic landmarks in the maxilla that may reliably be used for maxillary superimposition. It was hypothesized that, through the evaluation of cephalometric radiographs of patients with metallic implants, such anatomic landmarks could be identified. The material for this study consisted of pairs of cephalometric radiographs from 50 subjects, 23 males and 27 females ages 8.7 to 20.3 years. All films were taken at least 3 years apart. The mean age at the time of the first film was 11.9 +/- 1.4 years, and the mean age at the time of the second film was 16.0 +/- 1.7 years. The two serial tracings from each subject were superimposed on the implants and evaluated for best fit of anatomic structures. The maximum distance that the structures varied from perfect superimposition was measured. Rotational changes of the maxilla relative to the cranial base and of the palatal plane relative to the maxilla were evaluated. In the vertical plane, the floor of the orbit raised more than the palatal plane lowered by an average ratio of 1.5 to 1 mm. The maxilla demonstrated varying degrees and directions of rotation relative to the cranial base. The palatal plane demonstrated varying degrees and directions of rotation within the maxilla. Internal structure of the palate was of limited value as a stable area of registration. Infraorbital foramen, PTM, ANS, PNS, A point, and superior and inferior borders of the palate were not found to be stable landmarks for maxillary superimposition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2001

Validation of the non-stereo corresponding points stereoradiographic 3D reconstruction technique.

Several 3D reconstruction techniques deriving from stereoradiographic DLT have been presented during the last 15 years, but these techniques have usually been limited in accuracy because of the small number of corresponding anatomical landmarks identified on both radiographs. A new technique has recently been proposed to perform 3D reconstruction of the spine using not only the stereo-corresponding anatomical landmarks (seen on both frontal and sagittal X-ray films) but also some non-stereo-corresponding ones. This technique (called non-stereo-corresponding points or NSCP) has already been used for cervical dry vertebrae. In the present study, we focus on the validation of this technique for lumbar vertebrae by comparing four techniques: direct measurement, CT scan, 3D reconstruction by stereoradiography using a direct linear transformation (DLT) algorithm and the NSCP technique. The accuracy of the NSCP technique was also evaluated on different vertebral regions. The global results show mean errors of 1.1 mm and maximum of 7.8 mm with regard to direct measurements. These mean errors are close to those obtained using 3D reconstructions from CT scan using 1 mm cuts.

Aged↗

PubMed1999

Use of lingual frenum in determining the original vertical position of mandibular anterior teeth.

STATEMENT OF PROBLEM: There is no accurate method for determining the correct vertical dimension of occlusion in edentulous patients. Preextraction diagnostic casts may facilitate determination of vertical dimension of occlusion. In the maxilla, the incisive papilla is a stable anatomic landmark and can be used as a guide to determine the vertical relation of the edentulous patient. Unfortunately, the mandible is devoid of such a stable anatomic landmark. PURPOSE: This study evaluated the reliability of measurement of the distance between the anterior attachment of the lingual frenum and the incisal edges of the mandibular incisors, on casts, to be used as a preextraction record for determining the vertical position of the mandibular incisors in complete denture patients. MATERIAL AND METHODS: Eighteen dentate subjects (9 men, 9 women; 21-28 years; mean age 23 years) were selected. Four mandibular casts were made from irreversible hydrocolloid impression material in plastic stock trays for each subject. All subjects were instructed to elevate the tongue while the impressions were made. The vertical distance between the anterior attachment of the lingual frenum and incisal edges of mandibular central incisors was measured on the casts. Means and standard deviations of the 4 measurements were calculated and statistically analyzed. RESULTS: The mean standard deviation of the distance between the anterior attachment of the lingual frenum and incisal edges of mandibular central incisors among the subjects was 0.1326 mm (coefficient of variation 1.292%). The distance between the anterior attachment of the lingual frenum and incisal edges of mandibular incisors was relatively stable when the frenum was recorded during function. CONCLUSION: The distance between the anterior attachment of the lingual frenum and incisal edges of the mandibular central incisors can be used on preextraction diagnostic casts as a preextraction record for determining the original vertical position of the mandibular anterior teeth.

Adult↗

PubMed1996

Size and asymmetry of the planum temporale. A new three-dimensional method for analysis of the supratemporal plane using MR imaging and computer-aided graphics.

The planum temporale of the supratemporal plane is important for language function and shows left-right asymmetry in most brains. To estimate the size and allow side comparison of the planum temporale, we developed a new technique for 3-D MR analysis of the supratemporal plane using a personal computer and computer-aided graphics. The temporal lobes of 5 human cadavers were imaged by MR in the sagittal plane, at a slice thickness of 2 mm. The images of the supratemporal plane were entered into a personal computer using the original software to determine the positions of anatomic landmarks and the size of the planum temporale. The data were then transferred to a supercomputer to reconstruct the 3-D surface image of the supratemporal plane. Computer images of the supratemporal plane agreed with macroscopic observations. The positions of anatomic landmarks and the size of the planum temporale also agreed with macroscopic measurements. Thus, the present technique provides valuable anatomic data on the supratemporal plane which should be useful for further clarification of the anatomic basis of language function.

Adult↗

PubMed1982

Extralaryngeal divisions of the recurrent laryngeal nerve. Surgical and clinical significance.

Extralaryngeal branches of the recurrent laryngeal nerve have been noted in the literature, but frequently the researchers fail to indicate with accuracy the site of bifurcation. The current study was undertaken to designate the exact level of bifurcation of the recurrent laryngeal nerve, with more precise localization using a standard anatomic landmark. A prospective study based on 83 surgical patients was performed. The location of all nerves was measured using the inferior border of the cricoid cartilage as the anatomic landmark. A total of 153 recurrent laryngeal nerves were observed. Sixty-three (41.2 percent) bifurcated or trifurcated into extralaryngeal branches. Of these, there were four instances of trifurcations. The remaining 59 nerves bifurcated. Of these, 14 nerves bifurcated into equal-sized branches which went in an anterior or posterior direction. The remaining 45 nerve bifurcations indicated that 39 (86.7 percent) of the small branches went in a posterior direction, whereas only 6 (13.3 percent) of the large branches went in that direction. Surgical and clinical implications of this finding were discussed. Two instances of a "nonrecurrent" laryngeal nerve (that occurred on the right side) were also noted. The results of this study demonstrate conclusively that extralaryngeal branches of the recurrent laryngeal nerve are not an anatomic rarity. Therefore, thyroid surgery must include identification and preservation of the recurrent laryngeal nerve and all of its divisions.

Adolescent↗

PubMed2002

The precision of anatomical normalization in the medial temporal lobe using spatial basis functions.

We investigated the accuracy of spatial basis function normalization using anatomical landmarks to determine how precisely homologous regions are colocalized. We examined precision in terms of: (1) the number of nonlinear basis functions used by the normalization procedure; (2) the degree of (Bayesian) regularization; and (3) the effect of substituting different templates and how this interacted with the number of basis functions. The face validity of spatial normalization was assessed as a function of these parameters, using the colocalization of homologous landmarks in a test sample of 20 normally developing children and 5 children with bilateral hippocampal pathology. Our results suggest that when optimal normalization parameters are used, anatomical landmarks in the medial temporal lobes are colocalized to within a standard deviation of about 1 mm. When suboptimal parameters are used this standard deviation can increase up to 3 mm. Interestingly the optimal parameters are those that provide a rather constrained normalization as opposed to those that optimize intensity matching at the expense of rendering the warps "unlikely." The implications of our results, for users of voxel-based morphometry, are discussed.

Adolescent↗

PubMed2006

Acromial morphology: effects of suboptimal radiographs.

Acromial morphology is one of the important factors related to rotator cuff pathology, especially if there is acromial encroachment onto the supraspinatus tendon. This is the rationale for many surgeons performing an acromioplasty, based on preoperative radiographs, in their treatment of rotator cuff disease. However, geometric measurements of the acromion are dependent on the radiographic view, and suboptimal radiographs of the scapula might bias the acromial morphology on the radiographs. Our objective was to study the effect of suboptimal lateral-view radiographs of the scapula on 6 acromial angles, which have been correlated with rotator cuff pathology, by use of a computational method. Anatomic landmarks were digitized on 12 cadaveric scapulae via a spatial linkage system. A coordinate system based on the scapula was then created that allowed projection of the anatomic landmarks on the sagittal plane and simulated the optimal lateral-view radiograph of the scapula. By rotating the coordinate system in the coronal plane (cranial and caudal projections) and axial plane (anterior and posterior projections) with 5 degrees, 10 degrees, 15 degrees, and 20 degrees increments, 16 suboptimal lateral-view radiographs of the scapula were simulated. Significant differences in the 6 acromial angles (P < .01) between the optimal and suboptimal lateral-view radiographs of the scapula were found in almost every cranial and caudal projection. Rotating the projection in the axial plane did not significantly affect the acromial angles (P > .05) up to 20 degrees of rotation in the anterior and posterior direction. Of the 6 different acromial angles, the acromial slope was least affected when the projection was varied. In contrast, the anterior slope of the acromion was highly affected by errors in the projection.

Acromion↗

PubMed1997

Surface-marker cluster design criteria for 3-D bone movement reconstruction.

When three-dimensional (3-D) human or animal movement is recorded using a photogrammetric system, bone-embedded frame positions and orientations are estimated from reconstructed surface marker trajectories using either nonoptimal or optimal algorithms. The effectiveness of these mathematical procedures in accommodating for both photogrammetric errors and skin movement artifacts depends on the number of markers associated with a given bone as well as on the size and shape characteristics of the relevant cluster. One objective of this paper deals with the identification of marker-cluster design criteria aimed at the minimization of error propagation from marker coordinates to bone-embedded frame position and orientation. Findings allow for the quantitative estimation of these errors for any given cluster configuration and suggest the following main design criteria. A cluster made up of four markers represents a good practical compromise. Planar clusters are acceptable, provided in quasi-isotropic distribution. The root mean square distance of the markers from their centroid should be greater than ten times the standard deviation of the marker position error. The second objective of this paper deals with the identification of the optimal cluster position and orientation on the limb aimed at the minimization of error propagation to anatomical landmark laboratory coordinates. Cluster position should be selected to minimize skin movement artifacts. The longest principal axis of the marker distribution should be oriented toward the relevant anatomical landmark position.

Animals↗

PubMed1999

The tendons of Todaro and the "triangle of Koch": lessons from eponymous hagiolatry.

INTRODUCTION: There is growing use of the Todaro tendon and triangle of Koch as anatomic icons for invasive cardiac electrophysiologists. Reasons exist to doubt this validity. METHODS AND RESULTS: Histologic sections were prepared from 96 anatomically normal human hearts. The study area extended from the crista supraventricularis to the eustachian valve and included the AV node and His bundle. This encompasses any tendon of Todaro. Because the purported triangle of Koch includes the tendon of Todaro, all of Koch's available publications were examined. The tendon of Todaro is absent in only one fourth of infant hearts, but in two thirds of adult hearts. Tendons present were less often single than double or more, rarely exceeded 4 mm in length, and were seldom > 1 mm in diameter. Tendons usually originated from the central fibrous body and ended in the eustachian valve. Their origin most often was over the His bundle or its junction with the AV node, rather than the AV node. Tendons were primarily composed of collagen. Koch never described any triangle or acknowledged existence of tendons of Todaro. CONCLUSION: Todaro tendons are too often absent (or multiple) to warrant use as anatomic landmarks. Without this side of the supposed triangle of Koch, the entire tendon and triangle concept collapses and should be abandoned. There are numerous far more constant anatomic landmarks available to orient one to the human AV node and His bundle; these are briefly reviewed.

Adolescent↗

PubMed2005

The accuracy of computer-aided surgery in neurotologic approaches to the temporal bone: a cadaver study.

OBJECTIVE: To assess the accuracy of computer-aided surgery for common neurotologic approaches to the temporal bone. STUDY DESIGN AND SETTING: Cadaveric heads were dissected by using standard neurotologic approaches to the temporal bone including translabyrinthine, middle fossa, and retrosigmoid. Dissected anatomic landmarks from each approach were compared with CT images that were obtained before dissection on the VectorVision 2 system (BrainLAB Corp, Munich, Germany) and the variability measured from digital images. Each approach was performed 5 times, with each anatomic landmark measured 3 times from each approach. RESULTS: The accuracy of the computer-aided surgery system was less than 1 mm for all anatomic points measured. Forty-two of the 49 measured points were accurate to less than 0.5 mm. CONCLUSIONS: Computer-aided surgery of the temporal bone using common neurotologic approaches can be performed accurately and reliably in cadaver specimens. SIGNIFICANCE: The utility and limitations of computer-aided surgery in the temporal bone are discussed. EBM RATING: B-2.

Cadaver↗

PubMed1998

Anatomically based patellar resection criteria for total knee arthroplasty.

Thirty-six patellae were used to geometrically assess anatomically based patellar resection criteria for total knee arthroplasty. The plane of resection was defined in the coronal plane by three distinct anatomic landmarks on the undersurface of the patella: the medial and lateral edges of the quadriceps tendon insertion and the lateral edge of the patellar ligament insertion. The depth of the resection plane is defined by the anatomic landmark points approximately 1 mm posterior to the posterior aspect of the superior and inferior ligament insertions. Following resection, the resected patellae were geometrically characterized using two dimensional rectangular Cartesian coordinate system. The anatomically based patellar resection yielded a simple, consistent, and reliable method for patellar resection for total knee arthroplasty. The proportionate geometric characteristics of both the remaining anterior piece and the resected posterior piece were remarkably uniform. Following resection, the remaining patellar thickness was 65.6+/-5.3% (mean+/-SD) of the original thickness. The maximum width to height ratio of the resected surface was approximately 1:1. The thickness to diameter ratio of the resected portion of the patella was approximately 1:5. The apex of the patella was slightly off to the medial-distal quadrant from the geometric center of the resected surface. The results of this study indicate that anatomically based patellar resection criteria may help reduce the surgical variations associated with patellar resurfacing in total knee arthroplasties with dome-shaped prostheses.

Anthropometry↗

PubMed2002

The tibial attachment of the anterior cruciate ligament in children and adolescents: analysis of magnetic resonance imaging.

Recent studies have demonstrated that skeletally immature athletes with an ACL injury may require surgical reconstruction if they return to high-demand sports. This study used MRI to compare the anatomy of the ACL in skeletally immature and adult subjects. Measurements were recorded in the sagittal plane for the anterior-posterior dimension of the proximal tibia, and the anterior, center, and posterior limits of the ACL, and the roof inclination angle of the femur. These values were compared to established reference values for adult knee anatomy. In skeletally immature women ( n=7) the ACL anterior limit, center and posterior limit, and roof inclination angle were 28%, 46%, 63%, and 38 degrees, respectively, compared to 28%, 44%, 60%, and 35 degrees in adult women. In skeletally immature men ( n=15) the ACL anterior limit, center, posterior limit, and roof inclination angle were 27%, 43%, 59%, and 40 degrees, respectively, compared to 28%, 44%, 59%, and 37 degrees in adult men. In the younger subjects the overall dimensions of the proximal tibia were smaller than that in adults, but the anatomical landmarks for the ACL were proportional. If ACL reconstruction is performed in skeletally immature subjects, the smaller dimensions of the tibia need to be considered, and the use of anatomical landmarks is an important factor in graft placement

Adolescent↗