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Biomedical subjects

W R Lees

Publications and source records attributed to W R Lees.

At least 19 recordsLinked to original sources
PubMed2002

Dynamic three-dimensional color Doppler ultrasound of human fetal intracardiac flow.

OBJECTIVES: To develop dynamic three-dimensional ultrasound techniques for prenatal imaging of the intracardiovascular flow as well as the cardiovascular structure to address difficulties in assessing the spatially complex hemodynamics and morphology of the fetal heart. METHODS: Gray-scale and color (velocity) Doppler echocardiography were performed on 12 fetuses to provide serial anatomical and rheological tomograms which were spatially registered in three dimensions. Using a second ultrasound machine simultaneously, spectral Doppler ultrasound was performed to record umbilical arterial waveforms, thus providing the temporal (fourth) dimension in terms of the cardiac cycle and facilitating removal of motion artifacts. RESULTS: Acquisitions were successful in eight of 15 attempts. Imaging of the flow of blood in four dimensions was achieved in six of the eight datasets. In one case with complex cardiac malformations, three-dimensional reconstructions at systole and diastole offered dynamic diagnostic views not appreciated on the cross-sectional images. CONCLUSIONS: Our novel technique has made possible the prenatal visualization of the spatial distribution and true direction of intracardiac flow of blood in four dimensions in the absence of motion artifacts. The technique suggests that diagnosis of cardiac malformations can be made on the basis of morphological and hemodynamic changes throughout the entire cardiac cycle, offering unique and significant information complementary to conventional techniques. Further work to integrate the several non-purpose-built machines into a single system will improve the rate of acquisition of data, and may provide a new means of imaging and modeling structure and hemodynamics, not only for the fetal heart but for many other moving body parts.

Coronary Circulation↗
PubMed2002

Comparison of B-mode and conventional colour/power Doppler ultrasound, contrast-enhanced Doppler ultrasound and spiral CT in the diagnosis of focal lesions of the liver: Results of a multicentre study.

AIM: In patients with lesions of the liver we compared diagnoses based on different methods of ultrasound as well as spiral CT with the final diagnosis reached at the time of the patient's discharge from hospital. METHOD: From records of a prospective multicentre study including 90 liver lesions investigated with B-mode baseline and conventional colour/power Doppler ultrasound, contrast-enhanced colour/power Doppler ultrasound and spiral-CT, we evaluated only those where diagnoses for all modalities were available, and where the diagnosis at discharge comprising all clinical, laboratory and imaging data as well as histologic proof was at least "highly probable". RESULTS: 60 lesions met the inclusion criteria. 20 lesions were ultimately diagnosed as benign, and 40 as malignant. With respect to the diagnosis of malignancy, sensitivity was 92.5 % (37/40) with B-mode and unenhanced conventional colour/power Doppler US ultrasound, 97.5 % (39/40) with contrast-enhanced colour/ power Doppler ultrasound, and 100 % with CT; the corresponding specificities were 65 % (13/20), 85 % (17/20) and 80 % (16/20). 4 of 7 false positive, and 2 of 3 false negative results in the unenhanced technique were diagnosed correctly with contrast-enhanced Doppler ultrasound. CONCLUSION: Compared to conventional ultrasound, contrast-enhanced Doppler ultrasound improved the diagnostic accuracy in 10 % of the cases. Its accuracy in our study was equal to that of CT.

Contrast Media↗
PubMed2002

Photodynamic therapy for cancer of the pancreas.

BACKGROUND: Few pancreatic cancers are suitable for surgery and few respond to chemoradiation. Photodynamic therapy produces local necrosis of tissue with light after prior administration of a photosensitising agent, and in experimental studies can be tolerated by the pancreas and surrounding normal tissue. AIMS: To undertake a phase I study of photodynamic therapy for cancer of the pancreas. PATIENTS: Sixteen patients with inoperable adenocarcinomas (2.5-6 cm in diameter) localised to the region of the head of the pancreas were studied. All presented with obstructive jaundice which was relieved by biliary stenting prior to further treatment. METHODS: Patients were photosensitised with 0.15 mg/kg meso-tetrahydroxyphenyl chlorin intravenously. Three days later, light was delivered to the cancer percutaneously using fibres positioned under computerised tomographic guidance. Three had subsequent chemotherapy. RESULTS: All patients had substantial tumour necrosis on scans after treatment. Fourteen of 16 left hospital within 10 days. Eleven had a Karnofsky performance status of 100 prior to treatment. In 10 it returned to 100 at one month. Two patients with tumour involving the gastroduodenal artery had significant gastrointestinal bleeds (controlled without surgery). Three patients developed duodenal obstruction during follow up that may have been related to treatment. There was no treatment related mortality. The median survival time after photodynamic therapy was 9.5 months (range 4-30). Seven of 16 patients (44%) were alive one year after photodynamic therapy. CONCLUSIONS: Photodynamic therapy can produce necrosis in pancreatic cancers with an acceptable morbidity although care is required for tumours invading the duodenal wall or involving the gastroduodenal artery. Further studies are indicated to assess its influence on the course of the disease, alone or in combination with chemoradiation.

Adenocarcinoma↗
PubMed2001

Spiral CT pneumocolon: applications, status and limitations.

CT pneumocolon is a promising new technique in the diagnosis and management of colon pathology. CT pneumocolon can detect (sensitivity >95%) and stage (accuracy 79%) colorectal cancer and is very accurate in the differentiation of malignant from benign colonic pathologies. It has excellent detection rates for polyps >10 mm in diameter. Several studies using 3D virtual colonoscopy have already proven its high sensitivity and specificity in polyp detection making this technique robust as a screening tool. The combined results for virtual colonoscopy, from all centres, show a sensitivity of >85% in the detection of polyps 10 mm or greater in size, 70-80% for 5-9 mm polyps and an overall specificity of 90%. CT pneumocolon is a safe, non-invasive and cost-effective method for detecting colonic carcinomas and adenomas and correctly identifying which patients need further colonoscopy. The technique is quick, well tolerated and non-operator dependent. It can also image the proximal colon when distal stenoses prevent endoscopic and barium examination. CT pneumocolon is able to identify the features and complications of inflammatory bowel disease. Further research is warranted to fully assess its impact in terms of a screening tool, acceptability, availability and cost benefit.

Air↗
PubMed2001

Online motion-gated dynamic three-dimensional echocardiography in the fetus--preliminary results.

The aim of this study was to visualise the fetal heart in dynamic three dimensions (4-D) during an ultrasound (US) scan (online), rather than after (offline). With special pairing and sequential setting to minimise interference between two scanners, umbilical arterial Doppler waveforms (UADWs) from one scanner were used as an online motion gating source to trigger simultaneous 3-D cardiac structural data acquisition by another. Of 25 data sets from 10 fetuses, 18 were acquired in 15 to 30 s per set with > or = 50% Doppler waveforms efficiently converted to triggering signals. Of 15 valid 4-D data sets, 10 were reconstructed in 2 to 20 min, compared to over 2 h previously reported (mainly for offline gating). Fine structures (including chordae tendinae and trabecular muscles) were depicted in six sets. The main problems in degrading 4-D images were extensive shadowing (6) from bony structures during rigid mechanical scanning, and random motion artefacts (6) from prolonged setting-up time with a complex combination of several systems. Integration of these systems is, therefore, recommended.

Artifacts↗
PubMed2001

Conversion of umbilical arterial Doppler waveforms to cardiac cycle triggering signals: a preparatory study for online motion-gated three-dimensional fetal echocardiography.

To remove motion artefacts, a device was built to convert "noisy" umbilical arterial Doppler waveforms (UADWs) from an ultrasound (US) system into sharp ECG R-wave-like cardiac cycle triggering signals (CCTSs). These CCTSs were then used to gate a simultaneous (online) 3-D acquisition of sectional fetal echocardiograms from another US system. To test the conversion performance, a study was carried out in sheep fetal twins. Pulmonary arterial flow waveforms (PAFWs) from implanted probes were traced, in the meantime, to determine the reference cardiac cycle. Interference caused by running the two nonsynchronised US systems was controlled to three degrees (not-noticeable, moderate, and severe), together with high (> or = 40 cm/s) and low (< 40) flow velocities on UADWs. The conversion efficiency, assessed by the percentage of UADWs converted into CCTSs, was in the range of 83% to 100% for not-noticeable and moderate interference, and 0% to 71% for severe interference. The triggering accuracy, assessed by [(time lag mean between the onsets of PAFWs and corresponding CCTSs) -- (its 99% confidence level)] / the mean, was 90% to 96% for the not-noticeable interference high- and low-flow groups and for the moderate interference high-flow group; 19% to 93% for the moderate interference low-flow group; and from not obtainable up to 90% for the severe interference groups. The results show that UADWs can be used as a satisfactory online motion-gating source even in the presence of moderate interference. The major problems are from severe interference or moderate interference with low-flow velocity, which can be minimised/eliminated by the integration of the individual systems involved.

Animals↗
PubMed2001

Multi-slice technology in computed tomography.

Multi-slice systems represent a considerable advance in CT and will assure the future of the technique for many years to come. This article describes this new technology, indicating its provenance and its position in the evolution of CT. While it does not seek to be a physics and engineering text, enough detail of these are given to allow an informed discussion of the many advantages and a few potential problems associated with the technology. A discussion of a number of applications and a brief consideration of contrast enhancement regimens and the possible need for their modification are presented.

Equipment Design↗
PubMed2001

Neo-adjuvant therapy improves resectability rates for colorectal liver metastases.

PURPOSE: Liver resection improves survival in selected patients with colorectal liver metastases. However, the majority of patients with colorectal liver metastases have inoperable disease at presentation. Neo-adjuvant therapy (systemic or regional chemotherapy and interstitial laser therapy) used singly or in combination may convert a selected group of patients with irresectable liver metastases into an operable state. PATIENTS AND METHODS: We report a series of patients with initially inoperable multiple colorectal liver metastases who became operable after neo-adjuvant therapy. Operability was defined as unilateral disease limited to the liver. Twelve patients (7 female, 5 male, median age 57 years, range 38-69 years) with multiple inoperable colorectal liver metastases (8 synchronous, 4 metachronous) were initially treated with systemic chemotherapy (n = 7), hepatic arterial chemotherapy (n = 2) and chemotherapy plus interstitial laser therapy (n = 3). RESULTS: In all cases, a significant response was achieved which enabled subsequent liver resection to be undertaken. There was only one postoperative complication (8%) and no peri-operative deaths. 3 patients were operated on within the last 12 months and are still alive. Of the remainder, 1 died within 1 year with recurrent disease. The remaining patients have a median survival of 2.5 years, range 1.39-4 years. CONCLUSIONS: These results are similar to those reported for patients undergoing resection for operable metastases without neo-adjuvant therapy. Aggressive multimodality treatment of colorectal liver metastases in specialised centres may improve the resectability rates and survival in a selected group of patients.

Adult↗
PubMed2000

Novel technique for three-dimensional visualisation and quantification of deformable, moving soft-tissue body parts.

BACKGROUND: Three-dimensional (3D) imaging of delicate, moving soft-tissue body parts is very difficult. Our understanding of the muscles that control lip movements is based largely on histological and cadaveric studies, which provide scant information about dynamic morphology. Our aim was to develop an innovative scanning technique for the imaging and reconstruction of dynamic orofacial morphology by use of 3D and four-dimensional (4D, ie, 3D plus time) ultrasonography. METHODS: Four volunteers (including one patient) underwent ultrasonography with 3D/4D imaging systems. To avoid deformation of the delicate orofacial structures, a water bath with an acoustic window was devised. The orofacial part was immersed in the bath throughout scanning, and a timer was used to synchronize lip movements with the 4D scan. FINDINGS: 4D views showed the functional differences in superficial and deep muscle groups of the lips, and clearly showed the changes occurring with movement of the lips and mouth. In the patient, a pathological layer and its extension corresponding to surface malformation were clearly identified. INTERPRETATION: We have developed a prototype device that has made possible 3D and 4D examination of orofacial anatomy and function. With further refinement of the device and improvement in 4D acquisition timing, this technique may offer a new way of dynamically imaging and quantifying many soft-tissue parts in 3D without deforming structure or disturbing function.

Adult↗
PubMed2000

Survival after percutaneous, image-guided, thermal ablation of hepatic metastases from colorectal cancer.

PURPOSE: One-year, two-year, three-year, and four-year survival rates and median survival time for patients with inoperable liver metastases from colorectal cancer is 32, 10, and 3 percent and 7.4 to 11 months, respectively. Systemic chemotherapy produces a modest improvement to 48, 21, and 3 percent and 12 months, respectively. Regional chemotherapy produces a further improvement to 64, 25, and 5 percent and 15 to 17 months, respectively. For those with operable disease, hepatic resection survival rates are 90, 62, 48, and 40 percent, respectively, and survival time is 33 months. Thermal ablation is effective in producing necrosis in liver metastases. We report the impact on survival in 69 patients treated from 1993 to 1997, with follow-up to 1998. METHODS: Sixty-nine patients, 50 male, mean age 60 (range, 33-87) years were treated. Liver resection was not feasible because of disease extent in the liver, extrahepatic disease or concurrent medical conditions. The average number of liver metastases was 2.9 (range, 1-16), the mean maximal diameter was 3.9 (range, 1-8) cm, and the mean initial total liver tumor volume was 47 (range, 1-371) ml. Eighteen (26 percent) had undergone previous hepatic resection. Sixty-two of 67 (93 percent) received chemotherapy at some stage. Twenty (29 percent) had extrahepatic disease. RESULTS: One-year, two-year, three-year, and four-year survival rates and median survival time from liver metastasis diagnosis was 90, 60, 34, and 22 percent and 27 months, respectively. Forty of 69 (58 percent) developed new liver metastases, and 23 of 69 (33 percent) developed new extrahepatic disease. Of a subgroup of 24 patients with less than four metastases, <5 cm diameter, treated after January 1995, the median survival time was 33 months from first thermal ablation vs. 15 months for the remainder (P = 0.0004). Major morbidity occurred in 3.2 percent, minor morbidity occurred in 12 percent, and there was one periprocedural death. CONCLUSIONS: Thermal ablation therapy improves survival in patients with inoperable but limited liver metastases. This is an improvement on the natural history of the disease and published chemotherapy results. Recent and ongoing technical refinements, not reflected in these results, are expected to further improve survival.

Adult↗
PubMed2000

Simultaneous use of two ultrasound scanners for motion-gated three-dimensional fetal echocardiography.

The aim of this study was to determine whether or not simultaneous use of an additional Doppler transducer could provide sufficient cardiovascular motion information without significantly interfering with three-dimensional (3-D) cardiac structural data acquisition by a primary two-dimensional (2-D) transducer. To determine sources of interference, paired transducers were activated alternatively and simultaneously in and out of a water bath, with and without electrical insulating and electromagnetic shielding. To determine factors affecting interference, pairs were tested on a phantom with different separating distances and angles between paired ultrasound (US) beams and under different 2-D depths and Doppler scales. Results show that the dominant source of interference is acoustic cross talk. The severity was mainly affected by transducer pairing and by separating distances and angles, and the pattern by display settings. With optimised settings, sufficient structural and motion data were obtained simultaneously in 9 of 12 fetal hearts, and detailed 3-D views could be reconstructed free of motion artefacts, confirming the feasibility of using the method for motion-gated 3-D fetal cardiac imaging. New scanner design strategy was then proposed.

Artifacts↗
PubMed2000

Cavernosal arterial insufficiency is a major component of erectile dysfunction in some recipients of high-dose chemotherapy/chemo-radiotherapy for haematological malignancies.

We studied 24 male patients aged 26-62 years (median 41) prospectively presenting over a 5 year period with clinical features of hypogonadism and erectile dysfunction (ED), who had been treated with autologous or allogeneic bone marrow/stem cell transplant for a variety of haematological malignancies and had received either high-dose chemotherapy or high-dose chemotherapy combined with total body irradiation (TBI). Ten healthy adult controls (aged 35-50 years) were also studied. Erectile dysfunction (ED) was assessed clinically and by colour flow Doppler studies of the cavernosal vessels. Testicular function was assessed by testicular volume including orchidometry, FSH, LH and testosterone measurements. Libido and ejaculatory function were also recorded. Patients had severe hypogonadism as evidenced by low mean testicular volume (7.0 +/- 2.4 ml vs 20 +/- 2.0 ml; P < 0.001), elevated gonadotrophins (FSH = 18.54 +/- 7.61 vs 5 IU/l (P < 0.001); LH = 8.02 +/- 2.89 vs 3. 9 IU/l (P < 0.001)) and low normal mean testosterone levels (16.4 nmol/l +/- 9.1 vs 22.4 nmol/l (P < 0.5)). Cavernosal arterial insufficiency was found in 11/14 of TBI-treated and in 3/10 HDC-treated patients, indicative of vasculogenic damage to corpora cavernosal vessels. Patients were given a therapeutic trial with testosterone replacement therapy (TRT). Those who had diminished libido had a marked improvement in their symptoms but the effect of TRT on ED was equivocal. In conclusion, this is the first report to show vasculogenic insufficiency in patients with haematological malignancies treated by BMT. Although hypogonadism can account for diminished libido, arteriogenic insufficiency is likely to be an important factor accounting for ED in these patients, especially those treated by TBI. We recommend a comprehensive assessment including endocrine profile and colour flow Doppler study in formulating the best management plan in recipients of high-dose therapy presenting after transplant with ED.

Adult↗
PubMed2000

Treatment of recurrent colorectal liver metastases by interstitial laser photocoagulation.

BACKGROUND: Hepatic resection improves survival in selected patients with colorectal liver metastases. The treatment of recurrent hepatic metastases after resection is controversial. Interstitial laser photocoagulation, performed under local anaesthesia, offers a minimally invasive option to repeat resection. The first series of patients with recurrent colorectal liver metastases treated with photo- coagulation is reported. METHODS: Nineteen patients (five women and 14 men, median age 57 (range 44-71) years) who developed recurrent colorectal liver metastases after hepatectomy (five with bilateral disease) were treated with photocoagulation between 1993 and 1997. Fifteen patients also received chemotherapy (14 systemic, one hepatic arterial) before photocoagulation. RESULTS: There were no major complications or deaths related to the treatment. Six patients developed minor complications related to the procedure but did not require any form of intervention. Median survival from commencement of photocoagulation was 16 (range 4-36) months. CONCLUSION: Photocoagulation is a safe, minimally invasive therapy that may be used as an adjunct to chemotherapy and repeat resection in the treatment of recurrent colorectal liver metastases, and may lead to improved survival.

Adult↗
PubMed1998

Helical CT pneumocolon to assess colonic tumors: radiologic-pathologic correlation.

OBJECTIVE: The objective of this study was to determine the accuracy of helical CT pneumocolon in the staging of colonic carcinomas. SUBJECTS AND METHODS: Fifty-two patients (27 men, 25 women; age range, 40-88 years old; mean age, 67 years old) with known or strongly suspected colonic disorders underwent CT pneumocolon. After bowel cleansing, administration of smooth muscle relaxant, and rectal air insufflation, CT pneumocolon was performed with 5-mm collimation, 2.5-mm reconstruction interval, and a pitch of 1.5. Two contrast administration protocols were used. Twelve patients received 100 ml of i.v. contrast material that was injected at 3 ml/sec; scan delay was 45 sec. The other 40 patients received 150 ml of contrast material at 5 ml/sec; scan delay was 25 sec. Images were prospectively evaluated. All patients had pathologic confirmation: 46 patients had resections and six patients had endoscopic biopsies. RESULTS: Diagnostic images were obtained in 47 of 52 patients. In the 47 patients, there were 38 colonic carcinomas (one synchronous), nine diverticular strictures, eight polyps, one ischemic stricture, and one normal study. Thirty of 38 carcinomas were correctly staged by CT. Sensitivity and specificity for serosal infiltration were 100% (35/35 carcinomas) and 33% (one of three carcinomas), respectively; sensitivity and specificity for lymph node involvement were 56% (nine of 16 carcinomas) and 95% (21/22 carcinomas), respectively. Four polyps that were smaller than 5 mm in diameter were not revealed by CT. Twelve of 14 benign lesions were correctly diagnosed and two were believed to be malignant. No malignant lesion was misdiagnosed. CONCLUSION: CT pneumocolon gave an overall staging accuracy of 79% in 38 carcinomas.

Adult↗
PubMed1997

High magnetic susceptibility coatings for visualisation of optical fibres on a specialised interventional MRI system.

The aim of this study was to develop methods of visualising optical fibres on MRI scans for monitoring interstitial laser therapy. Scans were performed on a specialised MRI extremity scanner at 0.17 T. Optical fibres of 0.4 mm diameter used for delivering laser energy were coated with iron particles from a superferromagnetic contrast agent. MR images of the fibres were acquired using gradient echo sequences (TR/TE = 300/10, 1 mm in-plane, 3 mm slice) and assessed for fibre visibility. Coated fibres could be resolved as lines 2 +/- 1 mm wide using the gradient echo sequence. Uncoated fibres were invisible on the sequences used for in vivo therapy monitoring due to partial volume averaging. It is concluded that optical fibre visualisation by MRI may be improved by coating with ferromagnetic particles. Biocompatibility requires further assessment, but direct coating appears to be a promising method for fibre visualisation in MR-guided laser therapy.

Contrast Media↗
PubMed1997

Hepatic artery aneurysms: evaluation using three-dimensional spiral CT angiography.

Hepatic artery aneurysms are rare and frequently difficult to diagnose. Computed tomography (CT) and ultrasound rarely make the definitive diagnosis and angiography is usually required. We present three cases of hepatic artery aneurysms in which the definitive diagnosis was made on three-dimensional (3-D) spiral CT angiography-to our knowledge, this has not previously been described. Our experience shows that in many cases of hepatic artery aneurysm, conventional angiography need only be performed as a prelude to embolization.

Adult↗