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Biomedical subjects

J M Fitzpatrick

Publications and source records attributed to J M Fitzpatrick.

At least 91 records · Page 5Linked to original sources
PubMed1998

Surface-based registration of CT images to physical space for image-guided surgery of the spine: a sensitivity study.

This paper presents a method designed to register preoperative computed tomography (CT) images to vertebral surface points acquired intraoperatively from ultrasound (US) images or via a tracked probe. It also presents a comparison of the registration accuracy achievable with surface points acquired from the entire posterior surface of the vertebra to the accuracy achievable with points acquired only from the spinous process and central laminar regions. Using a marker-based method as a reference, this work shows that submillimetric registration accuracy can be obtained even when a small portion of the posterior vertebral surface is used for registration. It also shows that when selected surface patches are used, CT slice thickness is not a critical parameter in the registration process. Furthermore, the paper includes qualitative results of registering vertebral surface points in US images to multiple CT slices. The method has been tested with US points and physical points on a plastic spine phantom and with simulated data on a patient CT scan.

Humans↗
PubMed1998

Registration of head CT images to physical space using a weighted combination of points and surfaces.

Most previously reported registration techniques that align three-dimensional image volumes by matching geometrical features such as points or surfaces use a single type of feature. We recently reported a hybrid registration technique that uses a weighted combination of multiple geometrical feature shapes. In this study we use the weighted geometrical feature (WGF) algorithm to register computed tomography (CT) images of the head to physical space using the skin surface only, the bone surface only, and various weighted combinations of these surfaces and one fiducial point (centroid of a bone-implanted marker). We use data acquired from 12 patients that underwent temporal lobe craniotomies for the resection of cerebral lesions. We evaluate and compare the accuracy of the registrations obtained using these various approaches by using as a reference gold standard the registration obtained using three bone-implanted markers. The results demonstrate that a combination of geometrical features can improve the accuracy of CT-to-physical space registration. Point-based registration requires a minimum of three noncolinear points. The position of a bone-implanted marker can be determined much more accurately than that of a skin-affixed marker or an anatomic landmark. A major disadvantage of using bone-implanted markers is that an invasive procedure is required to implant each marker. By combining surface information, the WGF algorithm allows registration to be performed using only one or two such markers. One important finding is that the use of a single very accurate point (a bone-implanted marker) allows very accurate surface-based registration to be achieved using very few surface points. Finally, the WGF algorithm, which not only allows the combination of multiple types of geometrical information but also handles point-based and surface-based registration as degenerate cases, could form the foundation of a "flexible" surgical navigation system that allows the surgeon to use what he considers the method most appropriate for an individual clinical situation.

Algorithms↗
PubMed1998

Sexual dysfunction associated with the management of prostate cancer.

Improvements in the management of prostate cancer have increased the need to consider patients' quality of life, in particular in relation to sexual function. The causes of sexual dysfunction are varied and derive from both the condition and its management. Health professionals must choose their treatment strategies with great care. Patient expectations must be understood, and patients should be offered counselling, as an understanding of what can reasonably be expected contributes to patients' perception of their quality of life. There are few studies on sexual dysfunction in patients with prostate cancer. A first step would be to develop reliable questionnaires for the assessment of the problem. This article describes and discusses the findings of one such recently developed questionnaire. When baseline measures of sexual function have been established and the extent of sexual dysfunction in patients with prostate cancer is reliably quantified, large multicentre trials can be performed to evaluate the impact of different therapies on sexual function and quality of life. Sexual dysfunction is an area which will be of increasing importance to urologists who manage prostate cancer and one that should not be underestimated.

Aged↗
PubMed1997

Measuring clinical nurse performance: development of the King's Nurse Performance Scale.

The development of the King's Nurse Performance Scale to measure clinical nurse performance is described. Instrument construction was informed by the Slater Nursing Competencies Rating Scale [Wandelt, M. A. and Stewart, D. S. (1975) Slater Nursing Competencies Rating Scale. Appleton-Century Crofts, New York] together with key literature and the use of expert opinion. The instrument was utilised to observe the clinical performance of senior student nurses (n = 99) and data which were at the ordinal level were statistically analysed using a variety of non-parametric tests. Key findings of students' observed nursing practice are presented in a separate paper (While et al., unpublished document). Internal consistency testing of the King's Nurse Performance Scale using Cronbach's alpha coefficient revealed a promising alpha for the total instrument (r = 0.93). The subsection alphas indicated that further refinement may enhance the strength of the instrument as a tool for the measurement of performance in different domains of practice. The possible use of the Scale in the professional development of newly qualified nurses is suggested.

Clinical Competence↗
PubMed1997

Transurethral needle ablation of the prostate for the treatment of benign prostatic hyperplasia: a collaborative multicentre study.

OBJECTIVE: To assess the efficacy and safety of transurethral needle ablation of the prostate (TUNA) for patients with symptomatic benign prostatic hyperplasia (BPH) in a multicentre trial. PATIENTS AND METHODS: Seventy-six patients were recruited from five centres; all were treated with the TUNA system consisting of a powered radiofrequency generator and a TUNA catheter. The patients were evaluated prospectively using the international prostate symptom score (IPSS), uroflowmetry, quality-of-life score, and other variables, and followed for a mean of 12 months after treatment. RESULTS: Sixty-eight patients were available for follow-up: TUNA produced significant improvements in the IPSS (median 22 before, to 7.5 after treatment). urinary flow rate (mean 8.7 before, to 11.6 mL/s after treatment) and quality-of-life score (median 5 before, to 2 after treatment) at 12 months. CONCLUSIONS: If these early promising results are maintained. In the medium to long term, TUNA therapy will be a useful low-morbidity alternative for patients with symptomatic BPH.

Aged↗
PubMed1997

High-intensity focused ultrasound in the treatment of benign prostatic hyperplasia.

OBJECTIVE: To assess the role of high-intensity focused ultrasound (HIFU) in the treatment of symptomatic benign prostatic hyperplasia (BPH). PATIENTS AND METHODS: Thirteen patients (mean age 65 years, range 58-74) were treated with HIFU as part of a phase-2 clinical trial and evaluated prospectively using the International Prostate Symptom Score, uroflowmetry, and transrectal and transabdominal ultrasonography to determine prostate size and post-void residual urine volume, respectively. The results and the patients' satisfaction were assessed at regular intervals for 2 years. RESULTS: The new procedure was learned quickly and was easy to perform. Symptom scores decreased from a mean of 23 before treatment to 5 after 12 months and 7 after 2 years. There was an initial improvement in flow rates but they then declined. The size of the prostate and the post-void residual volume were both decreased after treatment. CONCLUSIONS: The treatment is safe, easy to implement and was effective in substantially reducing symptom scores in these few patients. However, we would not encourage its use as an alternative to other well established treatment modalities until it has been assessed fully in a randomized trial.

Aged↗
PubMed1997

Determination of testicular function after torsion by DNA flow cytometry of serial fine-needle aspirates.

OBJECTIVE: To determine the efficacy of DNA flow cytometric analysis of testicular percutaneous fine-needle aspirates in the assessment and follow-up of testicular function after torsion, and to determine the relationship between the duration of torsion and testicular injury. MATERIALS AND METHODS: Three groups of 15 adult rats underwent a 720 degrees torsion, with fixation of the mesorchial ligament, for 1, 3 or 5 h. Bilateral aspirations, performed 7, 21 and 35 days after torsion were examined by flow cytometry. Testes were harvested and evaluated histologically using Johnsen's scoring. RESULTS: Irreversible testicular injury occurred in all three groups of rats, with loss of function after 1 h and loss of viability after 3 and 5 h. The results from flow cytometry suggested significant contralateral testicular injury (P < 0.025) but this was not supported by the histological evaluation. There was a strong correlation between the testicular function assessed by flow cytometry and by Johnsen's scoring of histological specimens (r2 = 0.95). CONCLUSION: The assessment of testicular aspirates by flow cytometry allows testicular function to be followed after torsion in rats, and potentially in humans. Using DNA flow cytometry, the temporal course of the twisted testis in the adult rat was determined; contralateral testicular injury following the reversal of torsion could not be excluded.

Animals↗
PubMed1997

Registration of head volume images using implantable fiducial markers.

In this paper, we describe an extrinsic-point-based, interactive image-guided neurosurgical system designed at Vanderbilt University, Nashville, TN, as part of a collaborative effort among the Departments of Neurological Surgery, Computer Science, and Biomedical Engineering. Multimodal image-to-image (II) and image-to-physical (IP) registration is accomplished using implantable markers. Physical space tracking is accomplished with optical triangulation. We investigate the theoretical accuracy of point-based registration using numerical simulations, the experimental accuracy of our system using data obtained with a phantom, and the clinical accuracy of our system using data acquired in a prospective clinical trial by six neurosurgeons at four medical centers from 158 patients undergoing craniotomies to resect cerebral lesions. We can determine the position of our markers with an error of approximately 0.4 mm in X-ray computed tomography (CT) and magnetic resonance (MR) images and 0.3 mm in physical space. The theoretical registration error using four such markers distributed around the head in a configuration that is clinically practical is approximately 0.5-0.6 mm. The mean CT-physical registration error for the phantom experiments is 0.5 mm and for the clinical data obtained with rigid head fixation during scanning is 0.7 mm. The mean CT-MR registration error for the clinical data obtained without rigid head fixation during scanning is 1.4 mm, which is the highest mean error that we observed. These theoretical and experimental findings indicate that this system is an accurate navigational aid that can provide real-time feedback to the surgeon about anatomical structures encountered in the surgical field.

Brain Diseases↗
PubMed1996

Methods of renal blood flow measurement.

Variations in regional renal blood flow have been implicated in a variety of disease states. Many techniques have been developed in an attempt to accurately assess these changes. The microsphere technique is the most widely used method at the present time. This technique allows focal measurements to be performed, but there is a conflict between the resolution of the method and the number of microspheres necessary in each sample. New imaging techniques such as tomography and autoradiography enable visual assessment of renal blood flow. Though there is no ideal method, these techniques have opened up new possibilities in the quantification of regional renal blood flow.

Autoradiography↗
PubMed1996

Operationalisation of an observation instrument to explore nurse performance.

This paper explores the operationalization of an observation instrument to explore actual situated behaviour in the clinical setting. Challenges encountered during this process and strategies employed to address these difficulties are discussed. This work formed part of a comparative study of outcomes of pre-registration nurse education programmes commissioned by the English National Board for Nursing, Health Visiting and Midwifery.

Clinical Competence↗
PubMed1996

Key influences on the professional socialisation and practice of students undertaking different pre-registration nurse education programmes in the United Kingdom.

A principal aim of pre-registration nurse education programmes is the process of effective socialisation of students into the professional role. Key influences on the professional socialisation and practice of students undertaking such programmes were explored using a semi-structured interview approach (N = 99). This work formed part of a major comparative study of outcomes of pre-registration nurse education programmes in the United Kingdom. Analysis revealed differences between the programmes regarding positive influences of the respective courses; therapeutic influences of the practice environment; modelling performance on exemplars of high quality practice; and the identification of teachers within the educational setting and nurses in practice as key persons. This study has confirmed that the positive influence of the education programmes and the practice environment as well as high quality role models from both education and practice establishments are critical to the professional socialisation of student nurses.

Curriculum↗
PubMed1996

Laparoscopic-assisted rectopexy using a novel hand-access port.

Many surgeons who were ready converts to laparoscopic cholecystectomy did not translate the technique to more advanced procedures. There are several reasons: increased operating times, a steeper learning curve, concern for oncological efficacy, and the loss of manual tactile ability. As shown with this report on laparoscopic assisted rectopexy, many of these difficulties can be overcome using the IntromitTM while still maintaining the benefits of minimally invasive surgery.

Aged↗
PubMed1996

An automatic technique for finding and localizing externally attached markers in CT and MR volume images of the head.

An image processing technique is presented for finding and localizing the centroids of cylindrical markers externally attached to the human head in computed tomography (CT) and magnetic resonance (MR) image volumes. The centroids can be used as control points for image registration. The technique, which is fast, automatic, and knowledge-based, has two major steps. First, it searches the entire image volume to find one voxel inside each marker-like object. We call this voxel a "candidate" voxel, and we call the object a candidate marker. Second, it classifies the voxels in a region surrounding the candidate voxel as marker or nonmarker voxels using knowledge-based rules and calculates an intensity-weighted centroid for each true marker. We call this final centroid the "fiducial" point of the marker. The technique was developed on 42 scans of six patients-one CT and six MR scans per patient. There are four markers attached to each patient for a total of 168 marker images. For the CT images the false marker rate was zero. For MR the false marker rate was 1.4% (Two out of 144 markers). To evaluate the accuracy of the fiducial points, CT-MR registration was performed after correcting the MR images for geometrical distortion. The fiducial registration accuracy averaged 0.4 mm and was better than 0.6 mm for each of the eighteen image pairs.

Algorithms↗
PubMed1996

A universal method for geometric correction of magnetic resonance images for stereotactic neurosurgery.

Accurate stereotactic navigation depends strongly upon the spatial fidelity of the image used for registration. Clinically significant levels of geometric distortion are present in standard MR images, limiting their utility. A technique for correction of all geometric distortions in spine echo MR images was assessed in a prospective clinical trial of 19 stereotactic craniotomies. The Euclidean error in target registration between CT and MR was significantly reduced, from 3.833 +/- 0.992 to 1.986 +/- 0.605 mm. The results of this clinical trial support the incorporation of this MR image rectification protocol into standard clinical practice.

Evaluation Studies as Topic↗