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Biomedical subjects

F Wallis

Publications and source records attributed to F Wallis.

At least 19 recordsLinked to original sources
PubMed2005

3-D numerical simulation of blood flow through models of the human aorta.

A Spiral Computerized Tomography (CT) scan of the aorta were obtained from a single subject and three model variations were examined. Computational fluid dynamics modeling of all three models showed variations in the velocity contours along the aortic arch with differences in the boundary layer growth and recirculation regions. Further down-stream, all three models showed very similar velocity profiles during maximum velocity with differences occurring in the decelerating part of the pulse. Flow patterns obtained from transient 3-D computational fluid dynamics are influenced by different reconstruction methods and the pulsatility of the flow. Caution is required when analyzing models based on CT scans.

Aged↗
PubMed2003

Metastatic pulmonary ameloblastoma. An unusual case.

We present a patient who had a large metastatic pulmonary ameloblastoma resected 25 years after removal of an apparently benign primary ameloblastoma of the jaw. It highlights three areas: problems with the histopathological diagnosis of pulmonary metastases using fine needle aspiration; a noted radiological improvement after a 5-year course of oral cyclophosphamide, in keeping with occasional patients who have responded to chemotherapy; and the technical difficulties of resection of a large pulmonary metastasis, particularly when it is adherent to the mediastinum.

Ameloblastoma↗
PubMed2003

Endovascular exclusion of iliac artery to iliac vein fistula after lumbar disk surgery.

Iliac arteriovenous (AV) fistula is rare after lumbar disk surgery. Traditionally, open repair through the arterial lumen was performed. We report endovascular exclusion of an iliac AV fistula in a 41-year-old woman 8 years after lumbar diskectomy. An angiogram showed an AV fistula connecting the right common iliac artery and vein. This was repaired with placement of two covered wall stents in the right common artery and external iliac artery, and embolization of the right internal iliac artery. Contrast medium-enhanced computed tomography scan at 5 months confirmed elimination of the AV fistula and right iliac artery patency. This technique should be considered in management of iliac AV fistulas.

Adult↗
PubMed2002

Magnetic resonance imaging appearances of the uterus following microwave endometrial ablation.

AIM: Microwave endometrial ablation (MEA) is a treatment for dysfunctional uterine bleeding. It is a second generation ablative technique which is as effective as hysteroscopic methods but quicker and easier to perform. Our aim is to describe the Magnetic Resonance Imaging (MRI) appearances of the uterus following this procedure. METHODS: 15 women underwent MRI immediately before MEA, and again at one day and 4 months after treatment. T1 and T2 sequences were performed at 1.0T using a body coil. Images were assessed by 2 independent observers for quantitative and qualitative changes. Clinical questionnaires were completed before treatment and at 4 months. RESULTS: On images obtained one day post-ablation, 14 patients had a low signal intensity band subjacent to the treated area of the endometrial cavity on T2 images. Imaging at 4 months showed significant amounts of endometrial tissue in 11 patients, including 3 of the 6 patients who were amenorrhoeic. There were no changes in the appearances of myometrium or uterine dimensions and there were no haematometra. CONCLUSIONS: The detection of residual endometrium by MRI means that unopposed oestrogen hormone replacement therapy should be avoided after MEA, even in women who have amenorrhoea. Thepost-operative sub-endometrial low signal intensity zone corresponds to the region of tissue necrosis detected on vital staining of the treated uterus in in vivotesting. Depth of tissue destruction is a surrogate marker for clinical effectiveness. MRI may have a role in early assessment of patients participating in clinical research who are undergoing a modified MEA technique while retaining their uterus.

Cervix Uteri↗
PubMed2001

The measurement of fetal liver T(*)(2) in utero before and after maternal oxygen breathing: progress towards a non-invasive measurement of fetal oxygenation and placental function.

Utero-placental insufficiency is thought to be a major cause of growth retardation in utero and an important risk factor in the perinatal period. The purpose of this study was to investigate whether MRI could detect changes of fetal oxygenation, based on the blood oxygenation level dependence (BOLD) of the MRI tissue signal. Nine third trimester women (34-38 weeks) with normal pregnancies underwent abdominal MRI examinations. Following localization of the fetal liver using T(2)-weighted single-shot HASTE scans, up to 7 breath-held transaxial single-slice gradient-echo image sets were obtained through the fetal liver. The mother then commenced oxygen breathing with the imaging procedure repeated after 20 minutes of O(2) breathing. For each image set, T(*)(2) values are calculated using linear regression of log (signal) versus TE for a region of interest within the fetal liver selected by the attending radiologist. Fetal liver T(*)(2) values were calculated before and after O(2) breathing for each multi-echo image acquisition set. A signed rank test was used to test for a significant change in fetal liver T(*)(2) between the pre-O(2) and post-O(2) image sets. A significant increase in T*(2) (alpha < 0.05) was seen in 5 of the 9 fetal livers, a smaller increase (of borderline statistical significance, alpha = 0.057) in 2 livers, and no significant change (alpha > 0.05) in 2 livers. Our study indicates that T(*)(2) measurement of the fetal liver may detect alteration in fetal oxygen level following maternal oxygenation using the BOLD effect. This technique may potentially be applied to the identification and understanding of placental dysfunction in intra-uterine growth retardation.

Adolescent↗
PubMed2000

Inflammatory abdominal aortic aneurysms: diagnosis with gadolinium enhanced T1-weighted imaging.

AIM: Inflammatory abdominal aortic aneurysms (IAAA) are a variant of abdominal aortic aneurysms, which are associated with an increased morbidity. The diagnosis of IAAA has traditionally been established with a combination of clinical and laboratory findings together with contrast enhanced CT. There is a high incidence of renal impairment in this group, and therefore contrast enhanced CT may be harmful. PATIENTS AND METHODS: Five patients with IAAA underwent T1-weighted spin echo and gradient echo gadolinium enhanced abdominal MRI. A total of eight examinations were performed, including three patients who underwent repeat MRI following steroid therapy. RESULTS: The inflammatory cuff was clearly identified following gadolinium administration in all eight examinations. The cuff enhanced homogeneously in all patients with no alteration in appearance following steroid therapy. The intravenous administration of gadolinium DTPA enabled clearer definition of locally involved structures. CONCLUSION: Gadolinium enhanced MRI readily demonstrates features of IAAA. In view of potential renal impairment in this patient group, we recommend this technique in preference to contrast enhanced CT in the initial investigation of inflammatory abdominal aortic aneurysms.

Aged↗
PubMed2000

Signs and senses: diagnosis and prognosis in early medieval pulse and urine texts.

The character of early medieval medical manuscripts makes it difficult to generalize about the nature of medical knowledge in this period. In order to reconstitute one field of medical science, namely diagnosis and prognosis, while avoiding the pitfalls of unjustified generalization, this essay limits itself to reconstructing the understanding of pulse and urine inspection available in a particular place and time: the Italian monastery of Monte Cassino at the end of the first millennium. The available texts reveal little about the rationale behind these bedside techniques; indeed, pulse and urine seem to be signs without any semiotics, any underlying theory. The clue to this paradox is the fact that these texts see pulse and urine as primarily prognostic rather than diagnostic. Prognosis was understood to be analogous to forms of intuition, judgement, revelation, and prophecy that operated outside the logic of causality. Hence a fully rationalized semiotics was not regarded as necessary for effective medical practice.

Diagnosis↗
PubMed2000

Inventing diagnosis: Theophilus' De urinis in the classroom.

This paper shows how the two earliest Latin expositions of Theophilus' De urinis understood diagnosis in different ways. The "Chartres" commentator sees urine as a sign of physiological process and something which is derived from a disease state. By contrast, the Digby commentator is more concerned with how uroscopy functions at the bedside as a tool that enables us to infer disease states from urine. Though they understand the role of diagnosis differently, both commentaries reflect the new intellectual context of twelfth century medicine, where physical signs cease to be mere prognostic omens, and become tools for attaining knowledge of processes otherwise inaccessible to the senses.

Anatomy↗
PubMed1999

Hickmans in unusual places.

Radiologists now commonly insert long-term indwelling right atrial catheters. The insertion of these catheters in patients with limited venous access is a challenging clinical problem. Our experience in dealing with patients with limited venous access from a series of 500 Hickman catheter insertions is presented, as are the problems encountered during the insertion of catheters in patients with anomalies of the venous system.

Adult↗
PubMed1999

Evaluation of 18F-FDG positron emission tomography in gastric and oesophageal carcinoma.

The aim of this study was to evaluate 18F-fluoro-deoxyglucose (FDG) positron emission tomography (PET) in gastric and oesophageal carcinoma. 16 patients with biopsy proven oesophageal or gastric carcinoma had PET scans. Four patients had advanced disease and received palliative treatment. The remaining 12 patients were randomized to immediate surgery or neoadjuvant chemotherapy. Three patients had repeat PET scans following chemotherapy. PET detected the primary tumour in all cases including stage T1 lesions. Involved locoregional nodes (N1, N2) were not identified separately from the primary tumour. Semiquantitative analysis was performed in the form of tumour to liver activity ratios (TLR). In general, the TLR values were higher in the higher T stages, although there was only one case each of T1 and T2 lesions. PET scanning using 18F-FDG is a sensitive method for detecting primary oesophageal and gastric cancers but is limited in locoregional staging.

Adult↗
PubMed1999

Magnetic resonance imaging in oncology: an overview.

This review discusses a growing area of imaging in oncology. Traditionally, the primary role of magnetic resonance imaging (MRI) has been in the investigation of neurological diseases and in the diagnosis of musculoskeletal abnormalities. With the increasing availability of MRI systems and with the advances in technology, the role of this modality out with these areas is rapidly expanding. This review outlines the areas where MRI has a specific role in the imaging of patients with cancer. In particular, emphasis is placed on areas outside of the central nervous and musculoskeletal systems. This review describes the areas where MRI may be advantageous over other imaging modalities such as computerised tomography (CT). Specific emphasis is placed on the staging of abdominal and pelvic malignancies, the detection of recurrence and the impact of MRI in hepatic imaging. In addition this article reviews the value of dynamic contrast enhanced MRI sequences, as well as the importance of newer organ specific MR contrast agents in hepatic and lymph node imaging.

Abdominal Neoplasms↗
PubMed1998

CT and MRI appearances of a thoracic chordoma.

A case of a chordoma in the thoracic spine is presented. This is a very rare tumour in this location and should be considered in the differential diagnosis of any posterior mediastinal mass. The appearances on CT and MRI were similar to chordomas described in other locations. On T2-weighted images septae of low signal intensity radiated throughout the large high-signal mass. This feature may be of use in differentiating chordomas from other posterior mediastinal masses.

Adult↗
PubMed1998

Self-expanding metal stents in the management of colorectal carcinoma--a preliminary report.

AIMS: The role of diagnostic imaging in colorectal carcinoma is in the initial diagnosis, staging and detection of complications of the disease. Seven cases of colorectal carcinoma are presented where expandable metallic stents were placed for the management of stenosing lesions in patients with advanced metastatic disease or with serious medical complications which prevented immediate surgery. RESULTS: Seven patients (five male, two female) with an age range of 51-76 years had expandable metallic stents placed over a 9-month period. All stents were placed successfully with no immediate complications. The stents remained in situ for a range of 7-210 days. CONCLUSION: Expandable metallic stents can be successfully and safely placed in the colon. These stents may be useful in the management of patients with advanced metastatic disease or in those presenting with large bowel obstruction in which decompression by a stent allows treatment of coexisting medical complications to enable surgery to be carried out at a later date.

Adenocarcinoma↗
PubMed1998

Detection of response to chemotherapy using positron emission tomography in patients with oesophageal and gastric cancer.

BACKGROUND: The aim of the study was to determine whether 2-[18F]-fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) could detect response to chemotherapy in patients with oesophageal and gastric cancer. METHODS: Fourteen patients underwent imaging before and after chemotherapy using FDG-PET. Computed tomography (CT), dysphagia scores and weight changes were used for comparison of evidence of response. Tumour to liver ratios (TLRs) and influx constants for FDG (K) were used for quantification purposes. RESULTS: Thirteen of 14 lesions were successfully imaged before therapy. Changes were seen in all follow-up scans, ranging from a complete response to a 15 per cent increase in tumour FDG uptake. Response was demonstrated by CT in four patients; all four had large reductions in FDG uptake after chemotherapy. Two patients with an increase in FDG uptake reported no improvement in dysphagia and continued to lose weight during therapy. CONCLUSION: Changes in tumour FDG uptake were seen in all tumours after chemotherapy. FDG-PET may have a role to play in the assessment of patients with upper gastrointestinal malignancy receiving chemotherapy.

Adenocarcinoma↗