Cervical Vertebral Column Research Articles

Iatrogenic Cushing Syndrome and Secondary Adrenal Insufficiency Related to Concomitant Triamcinolone and Ritonavir Administration

Triamcinolone is a long-acting glucocorticoid medication that can be responsible for transient suppression of the hypothalamic–pituitary–adrenal (HPA) axis. This physiologic alteration may persist for weeks after repeated or even single localized injection of this agent. However, when this glucocorticoid agent is given to patients receiving the HIV protease inhibitor (PI) ritonavir (RTV), inhibition of their shared cytochrome P450 3A4 degradation pathway leads to an increased bioavailability of triamcinolone, with subsequent heightening and prolongation of the glucocorticoid serum levels. In those instances, iatrogenic Cushing syndrome may ensue. The authors encountered such an event in an HIV-infected patient on chronic treatment with an antiretroviral regimen containing RTV. The patient’s clinical presentation and laboratory investigations confirmed a diagnosis of Cushing syndrome and secondary adrenal insufficiency. This was believed to have occurred in close association following cervical vertebral column facet joint injections with triamcinolone acetonide for cephalagia deemed related to cervical spine disease. The discontinuation of the RTV-boosted PI therapy alone, promoting the clearance of the elevated triamcinolone serum levels and restoration of HPA homeostasis, proved successful in this patient. For this case, the authors review the published English medical literature relating to this uncommon phenomenon.

Cervical vertebral column morphology in patients with obstructive sleep apnoea assessed using lateral cephalograms and cone beam CT. A comparative study

Few studies have described morphological deviations in obstructive sleep apnoea (OSA) patients on two-dimensional (2D) lateral cephalograms, and the reliability of 2D radiographs has been discussed. The objective is to describe the morphology of the cervical vertebral column on cone beam CT (CBCT) in adult patients with OSA and to compare 2D lateral cephalograms with three-dimensional (3D) CBCT images. For all 57 OSA patients, the cervical vertebral column morphology was evaluated on lateral cephalograms and CBCT images and compared according to fusion anomalies and posterior arch deficiency. The CBCT assessment showed that 21.1% had fusion anomalies of the cervical column, i.e. fusion between two cervical vertebrae (10.5%), block fusions (8.8%) or occipitalization (1.8%). Posterior arch deficiency occurred in 14% as partial cleft of C1 and in 3.5% in combination with block fusions. The agreement between the occurrence of morphological deviations in the cervical vertebral column between lateral cephalograms and CBCT images showed good agreement (κ = 0.64). Prevalence and pattern in the cervical column morphology have now been confirmed on CBCT. The occurrence of morphological deviations in the cervical vertebral column showed good agreement between lateral cephalograms and CBCT images. This indicates that 2D lateral cephalograms (already available after indication in connection with, e.g. treatment planning) are sufficient for identifying morphological deviations in the cervical vertebral column. For a more accurate diagnosis and location of the deviations, CBCT is required. New 3D methods will suggest a need for new detailed characterization and division of deviations in cervical vertebral column morphology.

Possible death mechanisms other than respiratory asphyxia in a suicidal hanging case

Hanging is the most common suicide method that has seen in the routine autopsy practice. Known mechanisms of death include asphyxiation due to airway obstruction, cerebral ischemia due to arterial blockage, vagal inhibition (reflex cardiac arrest) due to carotid sinus compression, congestion due to venous blockage, fractures in cervical vertebral column with the cord injury. A 84 year-old man with totally laryngectomy found hanging from a tree in the garden of his house, and referred to Council of Forensic Medicine to determine cause of death. On the autopsy upper airway found to be ligatured from the level of hypopharynx. Case has been breathing via laryngectomy hole on his neck before suicide attempt. Case has been determined to be an interesting example for mechanism of death other than respiratory asphyxia in hanging cases.

Coupling between the spinal cord and cervical vertebral column under tensile loading

Current neck injury criteria are based on structural failure of the spinal (vertebral) column without consideration of injury to the spinal cord. Since one of the primary functions of the vertebral column is to protect the cord, it stands to reason that a more refined measure of neck injury threshold would be the onset of spinal cord injury (SCI). This study investigated the relationship between axial strains in the cervical vertebral column and the spinal cord using an in vitro primate model (n=10) under continuous tensile loading. Mean failure loads occurred at 1951.5±396N with failure strains in the vertebral column of 16±5% at the level of failure. Average tensile strains in the spinal cord at failure were 11±5% resulting in a mean coupling ratio of 0.54±0.17 between C1 and C7. The level of peak strain measured in the spinal cord did not always occur at the location of vertebral column failure. Spinal cord strains were less than spine strains and coupling ratios were not significantly different along the length of the spine. The largest coupling ratio was measured in the atlanto–occipital joint whereas the smallest coupling ratio occurred at the adjacent C1–C2 joint.

Clavicles, interclavicles, gastralia, and sternal ribs in sauropod dinosaurs: new reports from diplodocidae and their morphological, functional and evolutionary implications.

Ossified gastralia, clavicles and sternal ribs are known in a variety of reptilians, including dinosaurs. In sauropods, however, the identity of these bones is controversial. The peculiar shapes of these bones complicate their identification, which led to various differing interpretations in the past. Here we describe different elements from the chest region of diplodocids, found near Shell, Wyoming, USA. Five morphotypes are easily distinguishable: (A) elongated, relatively stout, curved elements with a spatulate and a bifurcate end resemble much the previously reported sauropod clavicles, but might actually represent interclavicles; (B) short, L-shaped elements, mostly preserved as a symmetrical pair, probably are the real clavicles, as indicated by new findings in diplodocids; (C) slender, rod-like bones with rugose ends are highly similar to elements identified as sauropod sternal ribs; (D) curved bones with wide, probably medial ends constitute the fourth morphotype, herein interpreted as gastralia; and (E) irregularly shaped elements, often with extended rugosities, are included into the fifth morphotype, tentatively identified as sternal ribs and/or intercostal elements. To our knowledge, the bones previously interpreted as sauropod clavicles were always found as single bones, which sheds doubt on the validity of their identification. Various lines of evidence presented herein suggest they might actually be interclavicles - which are single elements. This would be the first definitive evidence of interclavicles in dinosauromorphs. Previously supposed interclavicles in the early sauropodomorph Massospondylus or the theropods Oviraptor and Velociraptor were later reinterpreted as clavicles or furculae. Independent from their identification, the existence of the reported bones has both phylogenetic and functional significance. Their presence in non-neosauropod Eusauropoda and Flagellicaudata and probable absence in rebbachisaurs and Titanosauriformes shows a clear character polarity. This implicates that the ossification of these bones can be considered plesiomorphic for Sauropoda. The proposed presence of interclavicles in sauropods may give further support to a recent study, which finds a homology of the avian furcula with the interclavicle to be equally parsimonious to the traditional theory that furcula were formed by the fusion of the clavicles. Functional implications are the stabilizing of the chest region, which coincides with the development of elongated cervical and caudal vertebral columns or the use of the tail as defensive weapon. The loss of ossified chest bones coincides with more widely spaced limbs, and the evolution of a wide-gauge locomotor style.

Cervical Myelomalacia in a Lamb (Ovis aries) and an Alpaca (Vicugna pacos) after Attempted Intramuscular Injection

Cervical Myelomalacia in a Lamb (<i><scp>O</scp>vis aries</i>) and an Alpaca (<i><scp>V</scp>icugna pacos</i>) after Attempted Intramuscular Injection

Evaluation of intersegmental vertebral motion during performance of dynamic mobilization exercises in cervical lateral bending in horses

To identify differences in intersegmental bending angles in the cervical, thoracic, and lumbar portions of the vertebral column between the end positions during performance of 3 dynamic mobilization exercises in cervical lateral bending in horses. 8 nonlame horses. Skin-fixed markers on the head, cervical transverse processes (C1-C6) and spinous processes (T6, T8, T10, T16, L2, L6, S2, and S4) were tracked with a motion analysis system with the horses standing in a neutral position and in 3 lateral bending positions to the left and right sides during chin-to-girth, chin-to-hip, and chin-to-tarsus mobilization exercises. Intersegmental angles for the end positions in the various exercises performed to the left and right sides were compared. The largest changes in intersegmental angles were at C6, especially for the chin-to-hip and chin-to-tarsus mobilization exercises. These exercises were also associated with greater lateral bending from T6 to S2, compared with the chin-to-girth mobilization or neutral standing position. The angle at C1 revealed considerable bending in the chin-to-girth position but not in the 2 more caudal positions. The amount of bending in different parts of the cervical vertebral column differed among the dynamic mobilization exercises. As the horse's chin moved further caudally, bending in the caudal cervical and thoracolumbar regions increased, suggesting that the more caudal positions may be particularly effective for activating and strengthening the core musculature that is used to bend and stabilize the horse's back.

Cervical Vertebral Column Morphology Associated with Head Posture and Craniofacial Morphology

Significant associations have previously been described between craniofacial morphology, posture of the head and neck, and obstruction of the upper airways as seen in patients with obstructive sleep apnea. Morphological deviations in the cervical vertebral column have also been described in relation to craniofacial syndromes and to cleft lip and/or palate. New findings have been made concerning associations between fusion of the cervical vertebral column and craniofacial morphology, including the cranial base, in patients with severe skeletal malocclusions. Another new finding was the association between fusion of the cervical vertebral column and head posture and between fusion of the cervical vertebral column and obstructive sleep apnea. Accordingly, it is suggested that fusion of the cervical vertebral column is associated with the development and function of the craniofacial morphology in the sagittal, vertical, and transversal planes. Significant associations have previously been described between craniofacial morphology, posture of the head and neck, and obstruction of the upper airways as seen in patients with obstructive sleep apnea. Morphological deviations in the cervical vertebral column have also been described in relation to craniofacial syndromes and to cleft lip and/or palate. New findings have been made concerning associations between fusion of the cervical vertebral column and craniofacial morphology, including the cranial base, in patients with severe skeletal malocclusions. Another new finding was the association between fusion of the cervical vertebral column and head posture and between fusion of the cervical vertebral column and obstructive sleep apnea. Accordingly, it is suggested that fusion of the cervical vertebral column is associated with the development and function of the craniofacial morphology in the sagittal, vertical, and transversal planes.

Different Mechanisms of Decapitation: Three Classic and One Unique Case History

Three classic cases and one exceptional case are reported. The unique case of decapitation took place in a traffic accident, while the others were seen after homicide, vehicle-assisted suicide, and after long-jump hanging. Thorough scene examinations were performed, and photographs from the scene were available in all cases. Through the autopsy of each case, the mechanism for the decapitation in each case was revealed. The severance lines were through the neck and the cervical vertebral column, except for in the motor vehicle accident case, where the base of skull was fractured. This case was also unusual as the mechanism was blunt force. In the homicide case, the mechanism was the use of a knife combined with a saw, while in the two last cases, a ligature made the cut through the neck. The different mechanisms in these decapitations are suggested.

MRI FEATURES OF CERVICAL ARTICULAR PROCESS DEGENERATIVE JOINT DISEASE IN GREAT DANE DOGS WITH CERVICAL SPONDYLOMYELOPATHY

Cervical spondylomyelopathy or Wobbler syndrome commonly affects the cervical vertebral column of Great Dane dogs. Degenerative changes affecting the articular process joints are a frequent finding in these patients; however, the correlation between these changes and other features of cervical spondylomyelopathy are uncertain. We described and graded the degenerative changes evident in the cervical articular process joints from 13 Great Danes dogs with cervical spondylomyelopathy using MR imaging, and evaluated the relationship between individual features of cervical articular process joint degeneration and the presence of spinal cord compression, vertebral foraminal stenosis, intramedullary spinal cord changes, and intervertebral disc degenerative changes. Degenerative changes affecting the articular process joints were common, with only 13 of 94 (14%) having no degenerative changes. The most severe changes were evident between C4-C5 and C7-T1 intervertebral spaces. Reduction or loss of the hyperintense synovial fluid signal on T2-weighted MR images was the most frequent feature associated with articular process joint degenerative changes. Degenerative changes of the articular process joints affecting the synovial fluid or articular surface, or causing lateral hypertrophic tissue, were positively correlated with lateral spinal cord compression and vertebral foraminal stenosis. Dorsal hypertrophic tissue was positively correlated with dorsal spinal cord compression. Disc-associated spinal cord compression was recognized less frequently.

Intervertebral disk width in dogs with and without clinical signs of disk associated cervical spondylomyelopathy

BackgroundDisk-associated cervical spondylomyelopathy (DA-CSM) is a multifactorial neurological disorder in which progressive caudal cervical spinal cord compression is mainly caused by one or more intervertebral disk protrusions. The Doberman pinscher breed seems predisposed for this condition. The underlying cause and pathophysiology of DA-CSM are currently unknown. Recently, wider intervertebral disks have been put forward as a risk factor for development of clinically relevant DA-CSM. However, little is known about other factors affecting intervertebral disk width. Therefore the aim of this study was to assess the association between intervertebral disk width, measured on magnetic resonance imaging (MRI), and clinical status, age, gender and intervertebral disk location in dogs with and without clinical signs of DA-CSM.MethodsDoberman pinschers with clinical signs of DA-CSM (N=17),clinically normal Doberman pinschers (N=20), and clinically normal English Foxhounds (N=17), underwent MRI of the cervical vertebral column. On sagittal T2-weighted images, intervertebral disk width was measured from C2-C3 to C6-C7. Intra –and interobserver agreement were assessed on a subset of 20 of the 54 imaging studies.ResultsIntervertebral disk width was not significantly different between Doberman pinschers with clinical signs of DA-CSM, clinically normal Doberman pinschers or clinically normal English Foxhounds (p=0.43). Intervertebral disk width was positively associated with increasing age (p=0.029). Each monthly increase in age resulted in an increase of disk width by 0.0057mm. Intervertebral disk width was not significantly affected by gender (p=0.056), but was significantly influenced by intervertebral disk location (p <0.0001). The assessed measurements were associated with a good intra –and interobserver agreement.ConclusionsThe present study does not provide evidence that wider intervertebral disks are associated with clinical status in dogs with and without DA-CSM. Instead, it seems that cervical intervertebral disk width in dogs is positively associated with increase in age.

Oculoauriculovertebral spectrum with a full range of severe clinical manifestations – Case report

Oculoauriculovertebral spectrum (OAVS) is a rare congenital malformation consisting of epibulbar dermoids, lid colobomas, auricular deformities, hypoplasia of the soft and bony tissues of the face, associated oral deformities and vertebral anomalies. This report presents a child with a choroid of the right eye, coloboma of the upper eyelid, epibulbar dermoid of the left eye, mandibular hypoplasia, facial asymmetry, bilateral complete cleft lip and palate, hypoplasia of the left alar cartilage, appendage of the left nose, butterfly vertebral defects of Th-1, Th-2 and abnormality of rib XI. Widened sulci of frontal and parietal lobes, bilateral white matter density decrease and calcifications of falx cerebelli were noted. Axial hypotony and delayed psycho-motor development were apparent. This rare case presents a range of severe clinical manifestations of oculoauriculovertebral spectrum. Despite a normal cervical vertebral column, tracheostenosis was present. It caused difficulties in tracheal intubation, creating the need for a tracheostomy, and death after a failed attempt at decannulation. This case indicates that in patients with clinical manifestations including cerebral anomalies, a risk of respiratory insufficiency should be always taken under consideration, when planning surgery.

Magnetic resonance imaging vertebral canal and body ratios in Doberman Pinschers with and without disk-associated cervical spondylomyelopathy and clinically normal English Foxhounds

To determine magnetic resonance imaging (MRI) vertebral ratio values representing vertebral canal height, vertebral canal shape, and vertebral body shape in Doberman Pinschers with and without disk-associated cervical spondylomyelopathy (DACSM) and clinically normal English Foxhounds. Doberman Pinschers with (n = 18) and without (20) DACSM and clinically normal English Foxhounds (18). All dogs underwent low-field MRI of the cervical vertebral column. From 5 specific measurements made at C3 through C7, 4 linear vertebral ratios were calculated and assessed for correlation: vertebral canal height-to-body height ratio (CBHR), vertebral canal height-to-body length ratio (CBLR), caudal canal height-to-cranial canal height ratio (CCHR), and vertebral body length-to-height ratio (BLHR). The CBHR and CBLR described vertebral canal height, CCHR described vertebral canal shape, and BLHR described vertebral body shape. A midvertebral canal-occupying ratio (mVCOR) for the spinal cord was calculated at C5. RESULTS; Compared with both groups of unaffected dogs, CBHR, CBLR, and BLHR for Doberman Pinschers with DACSM were significantly smaller. The C7 CCHR was significantly larger in DACSM-affected Doberman Pinschers, compared with clinically normal English Foxhounds. Ratios did not differ significantly between unaffected Doberman Pinschers and clinically normal English Foxhounds. Correlation coefficients between CBHR, CBLR, and mVCOR were low and not significant. Doberman Pinschers with DACSM had significantly smaller vertebral canal heights and more square-shaped vertebral bodies, compared with unaffected Doberman Pinschers, combined with a funnel-shaped vertebral canal at C7. Breed-specific differences were not evident. Linear MRI vertebral canal-to-body ratios do not appear to predict relative vertebral canal stenosis.

Percutaneous minimally invasive techniques in the treatment of cervical disc herniation

Objective To compare the therapeutic effects of percutaneous cervical discectomy (PCD group),percutaneous cervical disc nucleoplasty(PCN) and the association of them (PCDN) for the treatment of cervical intervertebral disk displacement and instability of cervical vertebral column.Methods From February 2003 to April 2011,171 consecutive patients with cervical disc herniation have presented at the authors' hospital and were retrospectively studied.The average age of patients was 47.8 years (ranged,21-74).Ninety-seven cases were treated with PCD,50 cases with PCN,and the other 24 cases with PCDN.Clinical result and the stability of cervical vertebral column after operation were evaluated and compared among the 3 groups.Results All cases had been followed up for a median of 4.1 years.There was significant difference in the pre- and post-operation the Japanese Orthopaedic Association(JOA) scoring system on within 3groups (PCD:t=21.85,P＜0.05; PCN:t=14.50,P＜0.05; PCDN:t=8.56,P＜0.05).All cases had been successfully operated.There was no significant difference between groups among the 3 groups in terms of the clinical outcomes(The recovery rate of JOA standard evaluation,F=2.19,P=0.12).According to Odom criteria,the excellent and good rate are as follows:81.35％ in PCD,82.44％ in PCN,83.19％ in PCDN,respectively.There was no significant difference between groups among the 3 groups in terms of the clinical success rate (P＞0.05).There was no instability of cervical vertebral column cases in 3 groups after operation (P＞0.05),and no significant difference was found in terms of cervical vertebral column stability in pre- and post-operation in each group.Conclusion All the three operations including PCN,PCD and PCDN are safe,minimally invasive spine surgery for the treatment of cervical intervertebral disk displacement; they achieve good clinical outcomes and there are no difference on the stability of cervical vertebral column between preoperation and postoperation. Key words: Cervical vertebrae; Intervertebral disk displacement; Diskectomy, percutaneous

Cervical arthroplasty in two dogs with disk-associated cervical spondylomyelopathy

A 4-year-old sexually intact male Doberman Pinscher (dog 1) was evaluated for signs of recurrent cervical pain and ataxia, and a 12-year-old neutered male mixed-breed dog (dog 2) was evaluated for a 4-month history of ataxia and tetraparesis. Examination via magnetic resonance imaging (MRI) revealed spinal cord compression due to disk-associated cervical spondylomyelopathy at C6-7 in dog 1 and at C5-6 in dog 2. Both dogs were surgically treated with a ventral slot procedure and spinal cord decompression, followed by insertion of a titanium cervical disk prosthesis at the affected site. Evaluation of radiographs obtained immediately after surgery indicated that each prosthesis was appropriately placed and provided adequate distraction. Radiographic and neurologic evaluations were performed 2 weeks and 3, 6, and 12 months after surgery in both dogs and 18 months after surgery in dog 1. Distraction of the vertebral bodies decreased moderately over time in both dogs. Intervertebral mobility determined via radiographic assessment of the prosthetic disk during neutral positioning, flexion, and traction of the cervical vertebral column was lost over time in dog 1 and was not achieved in dog 2. Eighteen months after surgery, results of MRI in dog 1 indicated adequate spinal cord decompression with no degeneration in other cervical disks. Cervical arthroplasty was well tolerated with no complications, and outcome was excellent in both dogs; prosthesis presence did not affect ability to reassess the area via MRI. Studies of cervical arthroplasty in dogs with disk-associated cervical spondylomyelopathy are warranted.

Movement associated reduction of spatial capacity of the equine cervical vertebral canal

Laterolateral radiographs of equine necks are reported to be inaccurate in determining the site of spinal cord lesions even when a myelogram is carried out. The goal of this study was to assess constrictions present in the cervical vertebral canal at any time point throughout the extremes of movement. Sixteen equine cervical vertebral columns without history of cervical disease were used. After removal of the spinal cord, the dura mater was filled with polyurethane foam and during its plastic phase the cervical vertebral column was passively moved in flexion-extension, lateral bending and 30° rotated flexion and extension. Resulting moulded foam structures were scanned with a 3D laser scanner. Functional narrowing of the vertebral canal was located in the dorsolateral or ventrolateral regions, explaining its under-representation on laterolateral radiographs.

Laryngohyoid and Cervical Vertebra Lesions After a Fall From a Low Height

The aim of this study was to determine the frequency and nature of cervical trauma in the case of low-height falls (up to 2.50 m). A retrospective study was carried out on 114 autopsy cases that died after low-height falls. For each case, age, sex, manner and cause of death, estimated height of fall, ground type, type of primary impact, type of laryngeal and hyoid bone trauma, presence of associated local trauma in the neck and cephalic region, and toxicological data were reported. Fractures of the hyoid bone and/or of the laryngeal cartilages were present in 2.5% of the cases (n = 3). Cervical soft tissue bruising was found in 13% of the cases (n = 15). About 6% of the cases (n = 7) showed blunt cervical vertebral column trauma, including 3 cases with ruptured intervertebral disk. Interpretation and mechanisms of these lesions are discussed.

Cervical vertebral column morphology related to craniofacial morphology and head posture in preorthodontic children with Class II malocclusion and horizontal maxillary overjet

In preorthodontic children with Class II malocclusion and horizontal maxillary overjet, cervical column morphology was examined and related to craniofacial morphology and head posture for the first time. Two hundred thirteen children (aged 7-15 years) with a horizontal maxillary overjet of more than 6 mm were divided into 2 groups of skeletal and dentoalveolar overjets. The skeletal overjet group comprised 99 patients (43 girls, 56 boys). The dentoalveolar overjet group comprised 114 subjects (58 girls, 56 boys). Visual assessments of the cervical column and measurements of craniofacial morphology and head posture were made on profile radiographs. Deviations in the cervical vertebral column morphology occurred significantly more often in the skeletal overjet group (28%) compared with the dentoalveolar overjet group (17%) (P<0.05). Fusion anomalies were associated with a large sagittal jaw relationship, retrognathia of the jaws, large inclination of the jaws, and extended head posture (P<0.05 and 0.01, respectively). Furthermore, a partial cleft was significantly associated with a large cranial base angle (P<0.01). New associations were found between cervical column morphology, craniofacial morphology, and head posture in preorthodontic children with horizontal maxillary overjet. These findings are considered important for diagnostics and thus for a more accurate treatment plan of these patients.

Radiographic vertebral canal and vertebral body ratios in Doberman Pinschers with and without clinical signs of caudal cervical spondylomyelopathy

To determine radiographic vertebral ratio values representing vertebral canal stenosis in Doberman Pinschers with and without clinical signs of caudal cervical spondylomyelopathy (CCSM). Doberman Pinschers with (n = 81) and without (39) signs of CCSM. All dogs underwent lateral survey radiography of the cervical vertebral column. Five specific measurements were made at C3 through C7, and from those data, 3 ratios were calculated and analyzed for use in diagnosis of CSSM: canal height-to-vertebral body height ratio (CBHR), canal height-to-vertebral body length ratio (CBLR), and caudal vertebral canal height-to-cranial vertebral canal height ratio (CCHR). The CBHR and CBLR were considered indicators of vertebral canal stenosis, and CCHR described vertebral canal shape. Compared with Doberman Pinschers without CCSM, mean CBHR and CBLR values were significantly smaller for Doberman Pinschers with CCSM; for CBHR, this difference was evident at each assessed vertebra. The CCHR value for C7 was significantly larger in dogs with CCSM. Receiver operating characteristic statistics did not identify a threshold point that had combined high sensitivity and specificity sufficient to differentiate between Doberman Pinschers with and without CCSM. Doberman Pinschers with CCSM had vertebral canal stenosis combined with a funnel-shaped vertebral canal at C7 significantly more often than did Doberman Pinschers without CCSM. Despite these significant differences, no reliable threshold ratio values were identified to differentiate groups of dogs.

SU-E-J-38: Tracking Changes in Head-and-Neck Rotation and Flexion Using Megavoltage Cone-Beam CT and Deformable Image Registration

Purpose: Megavoltage cone‐beam CT (MVCBCT) images used for patient positioning can also detect complex changes in neck flexion and head rotation. Deformable image registration (DIR) algorithms could automate detection of positional variability and facilitate adaptive therapy strategies. This study investigates the ability of DIR to track changes in neck flexion, jaw position, and head tilt in MVCBCT images of head‐and‐neck radiotherapy patients.Methods: Landmark points at the base of skull, along the cervical vertebral column and on the mandible were identified and annotated on planning kVCT and MVCBCT images of patients. Baseline MVCBCT images were first fused to the kVCT via rigid registration, and distances between corresponding landmark points were computed. The same MVCBCT images were then fused via DIR, and the vector displacement between landmark points and deformed points was calculated. The change in the distance using DIR versus rigid registration was used to quantify how well the deformation algorithm tracked the shift of landmark positions. The same tests were also performed by registering and deforming the baseline MVCBCT to another MVCBCT taken at a different time. Results: Data for 11 reference points and images from five patients were analyzed. Changes in landmark distance of greater than 1 mm were considered. Deforming the MVCBCT to the kVCT, one patient showed an average decrease in landmark distance of 3 mm after DIR. However, the landmark distance increased by an average of 2 mm for another patient. When deforming the baseline MVCBCT to another MVCBCT, all five patients showed an improvement in landmark matching. The average decrease in landmark distance varied from 0.4 mm to 3.4 mm Conclusions: Deforming MVCBCT to kVCT images of the head‐and‐neck region did not consistently improve landmark matching. However, DIR consistently improved landmark matching when applied to two MVCBCT images acquired at different times.