Biomedical subjects

B Harkness

Publications and source records attributed to B Harkness.

9 recordsLinked to original sources

PubMed1998

The role of lateral cephalometric radiography and fluoroscopy in assessing mandibular advancement in sleep-related disorders.

Mandibular advancement splints are successful in managing obstructive sleep apnoea (OSA) in selected subjects. For these to be effective, some improvement in the dimensions of the oropharyngeal airway must occur. Twenty subjects with proven obstructive sleep apnoea were examined using lateral cephalometric radiography and a fluoroscopic technique. Cephalograms were analysed, and assessed for both skeletal and soft tissue abnormalities known to be present in OSA subjects. On the basis of these, a prediction was made as to whether the subject's oropharyngeal airway would increase during mandibular protrusion. From the fluoroscopic sequences, the narrowest antero-posterior dimensions of the post-palatal and post-lingual airways were recorded as the mandible moved from the intercuspal position into maximal protrusion. The changes in airway size were noted and these were compared with the predictions made from the static films. In nine subjects, fluoroscopy indicated that the airway opened well during mandibular protrusion, seven did not improve and in four the changes were minimal. Post-palatally the mean airway increase was 2.6 mm, whilst behind the tongue a mean improvement of 3.1 mm was seen. In all but two instances, the cephalometric prediction agreed exactly with the outcome demonstrated by fluoroscopy. All subjects whose airways clearly increased were correctly identified by the cephalogram alone. Cephalometric features associated with a good airway response to protrusion were a reduced lower facial height, low maxillomandibular planes angle and a high hyoid position, accompanied by a normal anteroposterior relationship of the jaws, relatively normal mandibular body length and soft palate area. The more abnormal the skeletal and soft tissue dimensions, the poorer the prognosis. Thus, whilst a single radiograph could indicate whether a positive mandibular response to protrusion could be expected, where doubt existed, a fluoroscopic analysis could provide a useful adjunct to diagnosis.

Adult↗

PubMed1996

A method of studying adaptive changes of the oropharynx to variation in mandibular position in patients with obstructive sleep apnoea.

The aim of this study was to develop a method of studying the effects of mandibular advancement on oropharyngeal airway dimensions in the sagittal plane in conscious, supine patients. Six white, dentate, male patients with proven obstructive sleep apnoea had sagittal fluoroscopic recordings taken in the resting supine position. Images were recorded at four frames per second as the mandible was advanced with the teeth in contact to maximum protrusion and then opened. Software in the fluoroscopic imaging system permitted measurement of the change in mandibular position together with oropharyngeal airway dimensions expressed as the narrowest dimension observable in the post-palatal and post-lingual sites. Plotting of airway dimensions during mandibular advancement enabled estimation of the degree of protrusion associated with maximal airway benefits. Progressive mandibular advancement produced variable adaptive changes in the post-palatal and post-lingual regions of the oropharynx. The amount of airway opening appeared to be related to the horizontal and vertical relationships of the face and to the dimensions of the soft palate. The changes in post-palatal and post-lingual airway dimensions were not always identical, despite the observation that both tongue and soft palate were seen to move in unison, with close contact being maintained between the two structures. Jaw opening resulted in synchronous posterior movement of both tongue and soft palate, with consequent narrowing of oropharyngeal airspace. Fluoroscopy is a simple method of assessing upper airway changes with mandibular advancement in the conscious patient. The technique should facilitate the selection of subjects for whom mandibular advancement would seem advantageous. The nature of the adaptive response is dependent on individual structural variation. It is suggested that, where artificial mandibular advancement with dental devices is considered beneficial, jaw opening should be kept to a minimum.

Adaptation, Physiological↗

PubMed1996

The importance of a multidisciplinary approach to the assessment of patients with obstructive sleep apnoea.

Obstructive sleep apnoea may present with a wide range of symptoms resulting in a variety of referral pathways. A multidisciplinary approach to examination and diagnosis helps to determine the most appropriate treatment plan for each individual. The subject is seen by each member of the team, appropriate investigations undertaken and a further meeting arranged at which all opinions are discussed. A reasoned treatment regime is produced, taking into consideration the patient's wishes and overall medical condition. This paper describes the team approach currently employed in the Department of Thoracic Medicine at The Prince Charles Hospital, Brisbane, Australia. The thoracic physician and ENT surgeon work in close collaboration with their dental colleagues: an orthodontist, prosthodontist and a maxillofacial surgeon. An outline of the examination and investigations made by each is described and the multidisciplinary approach is illustrated by a description of the management of five subjects with suspected obstructive sleep apnoea.

Adult↗

PubMed1996

Lag phase quantification for solid gastric emptying studies.

UNLABELLED: This study compared the different calculation methods of the solid gastric emptying lag phase and evaluated the effect of the temporal sampling interval on the calculated value using the modified power exponential (MPE) method. METHODS: Twenty normal control subjects and 42 patients had anterior and posterior image acquisition on a multihead gamma camera, one frame per minute x 90. ROIs were selected for the stomach, gastric antrum and small bowel. Time-activity curves (TACs) were generated for anterior, posterior and geometric mean data. The lag phase was calculated using various methods such as transition point, starting index, first appearance of bowel activity (FABA), MPE and antral peak filling time. To determine the importance of the temporal sampling rate on the calculation of the lag phase by the MPE, intervals between 1 and 20 min were analyzed. RESULTS: The transition point, starting index and FABA correlated extremely high (r = > or = 0.92) in normal control subjects and patients. Normal lag phase values were mean 22-24 +/- 10 min for transition point, starting index and FABA compared with 47 +/- 18 min for the MPE method (p < 0.0001). The MPE correlated poorly with the other method (r = 0.74). Antral peak filling time correlated poorly (r = 0.47) with transition point, starting index and FABA, but somewhat better with the MPE (r = 0.70). Comparing 15-min versus 1-min sampling intervals using the MPE, 35% of subjects had values that differed by > or = 7.5 min and 10% had values differing by > or = 15 min. CONCLUSION: The lag phase calculated by the MPE correlated poorly with other methods, and its accuracy was limited by the rate of the temporal sampling. The transition point, starting index and FABA all highly correlated with each other; the latter is a particularly reliable physiological indicator and is easily quantified using a small-bowel TAC.

Adolescent↗

PubMed1995

The importance of a multidisciplinary approach to the assessment of patients with obstructive sleep apnoea.

Adult↗

PubMed1993

The diagnosis of acute pyelonephritis in the piglet using single photon emission computerized tomography dimercaptosuccinic acid scintigraphy: a pathological correlation.

Single photon emission computerized tomography (SPECT) scintigraphy has proved to be an extremely sensitive renal imaging modality in children with genitourinary pathology, including pyelonephritis, particularly when compared to 2-dimensional planar imaging. This study was undertaken to corroborate SPECT dimercaptosuccinic acid (DMSA) scintigraphic findings with specific histopathology in acute pyelonephritis. Unilateral vesicoureteral reflux was produced in 19 Yorkshire piglets 3 to 4 weeks old. The bladders of 12 animals were inoculated with Escherichia coli 2 weeks later, after baseline SPECT DMSA scans had been obtained. The animals were then re-imaged at 3 (4), 7 (4) or 14 (4) days after infection and sacrificed for histological evaluation. Seven purposefully uninfected piglets with unilateral reflux served as controls and were followed for up to 6 weeks before imaging and sacrifice. SPECT proved to be 97% sensitive and 93% specific in providing the diagnosis of acute pyelonephritis. The SPECT findings were manifest by a spectrum of abnormal findings (mottling, striations, inner cortical scalloping and focal cortical defects), which correlated precisely with the extent and severity of cortical involvement in the acute pyelonephritic process. We propose a new classification scheme for SPECT DMSA renal scintigraphic imaging, and believe that this modality is exquisitely sensitive in providing the diagnosis as well as in evaluating the extent of renal parenchymal involvement when acute pyelonephritis is induced in the animal model.

Acute Disease↗

PubMed1991

Improved detection of small cavernous hemangiomas of the liver with high-resolution three-headed SPECT.

The purpose of this study was to review our experience with 99mTc-red blood cell scintigraphy for diagnosis of cavernous hemangiomas of the liver using a new three-headed, high-resolution dedicated SPECT system. Of 19 patients referred with a total of 38 lesions seen on CT, US, or MRI, 14 patients had 24 lesions that were hemangioma-positive with SPECT (all true-positives). Six of these 14 patients also had 9 hemangioma-negative lesions; all were less than or equal to 1.3 cm in size and false-negative. The remaining five patients had hemangioma-negative lesions only (1 false-negative, 4 true-negatives). Two hemangiomas were seen by SPECT that were not detected by CT, US, or MR. The sensitivity for hemangiomas greater than or equal to 1.4 cm. was 100% (20/20). The sensitivity was 33% for lesions 0.9-1.3 cm, and 20% for lesions less than or equal to 0.8 cm. The smallest hemangioma detected was 0.5 cm. These results show a definite improvement in sensitivity with high-resolution triple-headed SPECT over previously reported results using single-headed SPECT. High-resolution SPECT has improved our ability to detect small cavernous hemangiomas of the liver.

Erythrocytes↗

PubMed1990

High resolution single photon emission computerized tomography (SPECT) 99mtechnetium-dimercapto-succinic acid renal imaging: a state of the art technique.

The 99mtechnetium-dimercapto-succinic acid renal scan has become the gold standard for evaluating renal parenchymal pathology. The traditional pinhole technique provides 2-dimensional imaging. Recent application of high resolution single photon emission computerized tomography (SPECT) has provided the means to obtain even greater cortical detail. With 360-degree imaging and computer reconstruction, SPECT provides coronal, sagittal and transaxial imaging. We prospectively compared the SPECT and pinhole techniques in 33 patients (65 renal units) ranging in age from 2.5 months to 18 years. Both scans were obtained in all patients. All scans were reviewed by an independent interpreter. Using SPECT imaging, diagnostic information was enhanced in 46 of the 65 kidneys (71%). Of the 24 kidneys that appeared "normal" by pinhole imaging 15 (63%) had defects on SPECT imaging. High resolution SPECT imaging improves the ability to identify cortical defects and visualize asymmetry of cortical thickness compared to standard pinhole imaging.

Adolescent↗

PubMedDate not supplied

Comparison and evaluation of retrospective intermodality brain image registration techniques.

PURPOSE: The primary objective of this study is to perform a blinded evaluation of a group of retrospective image registration techniques using as a gold standard a prospective, marker-based registration method. To ensure blindedness, all retrospective registrations were performed by participants who had no knowledge of the gold standard results until after their results had been submitted. A secondary goal of the project is to evaluate the importance of correcting geometrical distortion in MR images by comparing the retrospective registration error in the rectified images, i.e., those that have had the distortion correction applied, with that of the same images before rectification. METHOD: Image volumes of three modalities (CT, MR, and PET) were obtained from patients undergoing neurosurgery at Vanderbilt University Medical Center on whom bone-implanted fiducial markers were mounted. These volumes had all traces of the markers removed and were provided via the Internet to project collaborators outside Vanderbilt, who then performed retrospective registrations on the volumes, calculating transformations from CT to MR and/ or from PET to MR. These investigators communicated their transformations again via the Internet to Vanderbilt, where the accuracy of each registration was evaluated. In this evaluation, the accuracy is measured at multiple volumes of interest (VOIs), i.e., areas in the brain that would commonly be areas of neurological interest. A VOI is defined in the MR image and its centroid c is determined. Then, the prospective registration is used to obtain the corresponding point c' in CT or PET. To this point, the retrospective registration is then applied, producing c" in MR. Statistics are gathered on the target registration error (TRE), which is the distance between the original point c and its corresponding point c". RESULTS: This article presents statistics on the TRE calculated for each registration technique in this study and provides a brief description of each technique and an estimate of both preparation and execution time needed to perform the registration. CONCLUSION: Our results indicate that retrospective techniques have the potential to produce satisfactory results much of the time, but that visual inspection is necessary to guard against large errors.

Brain↗