Imperial College London

Miss Katherine J Williams

Faculty of MedicineDepartment of Surgery & Cancer

Honorary Clinical Research Fellow
 
 
 
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Contact

 

+44 (0)20 3311 7335k.williams Website

 
 
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Location

 

4N13CNorth WingCharing Cross Campus

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Summary

 

Publications

Publication Type
Year
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28 results found

Ravikumar R, Williams KJ, Babber A, Moore HM, Lane T, Shalhoub J, Davies AHet al., 2018, Neuromuscular electrical stimulation (NMES) for the prevention of venous thromboembolism (VTE), Phlebology, Vol: 33, Pages: 367-378, ISSN: 0268-3555

ObjectiveVenous thromboembolism (VTE), encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE), is a significant cause of morbidity and mortality, affecting 1 in 1000 adults per year. Neuromuscular electrical stimulation (NMES) is the transcutaneous application of electrical impulses to elicit muscle contraction, preventing venous stasis. This review aims to investigate the evidence underlying the use of NMES in thromboprophylaxis.MethodsThe Medline and Embase databases were systematically searched, adhering to PRISMA guidelines, for articles relating to electrical stimulation and thromboprophylaxis. Articles were screened according to a priori inclusion and exclusion criteria.ResultsThe search strategy identified 10 randomised controlled trials, which were used in three separate meta-analyses; 5 trials compared NMES to control, favouring NMES (odds ratio (OR) of DVT 0.29, 95%CI 0.13-0.65; P=.003); 3 trials compared NMES to heparin, favouring heparin (OR of DVT 2.00, 95%CI 1.13-3.52; P=.02); 3 trials compared NMES as an adjunct to heparin versus heparin only, demonstrating no significant difference (OR of DVT 0.33, 95%CI 0.10-1.14; P=.08).ConclusionNMES significantly reduces the risk of deep vein thrombosis compared to no prophylaxis. It is inferior to heparin in preventing DVT and there is no evidence for its use as an adjunct to heparin.

Journal article

Harput S, Christensen-Jeffries K, Brown J, Yuanwei L, Williams KJ, Davies AH, Eckersley R, Dunsby CW, Tang Met al., 2018, Two-stage motion correction for super-resolution ultrasound imaging in human lower limb, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 65, Pages: 803-814, ISSN: 0885-3010

The structure of microvasculature cannot be resolved using conventional ultrasound imaging due to the fundamental diffraction limit at clinical ultrasound frequencies. It is possible to overcome this resolution limitation by localizing individual microbubbles through multiple frames and forming a super-resolved image, which usually requires seconds to minutes of acquisition. Over this time interval, motion is inevitable and tissue movement is typically a combination of large and small scale tissue translation and deformation. Therefore, super-resolution imaging is prone to motion artefacts as other imaging modalities based on multiple acquisitions are. This study investigates the feasibility of a two-stage motion estimation method, which is a combination of affine and non-rigid estimation, for super-resolution ultrasound imaging. Firstly, the motion correction accuracy of the proposed method is evaluated using simulations with increasing complexity of motion. A mean absolute error of 12.2 μm was achieved in simulations for the worst case scenario. The motion correction algorithm was then applied to a clinical dataset to demonstrate its potential to enable in vivo super-resolution ultrasound imaging in the presence of patient motion. The size of the identified microvessels from the clinical super-resolution images were measured to assess the feasibility of the two-stage motion correction method, which reduced the width of the motion blurred microvessels approximately 1.5-fold.

Journal article

Cheung WK, Williams KJ, Christensen-Jeffries K, Dharmarajah B, Eckersley RJ, Davies AH, Tang M-Xet al., 2017, A temporal and spatial analysis approach to automated segmentation of microbubble signals in contrast-enhanced ultrasound images: application to quantification of active vascular density in human lower limbs, Ultrasound in Medicine and Biology, Vol: 43, Pages: 2221-2234, ISSN: 0301-5629

Contrast-enhanced ultrasound (CEUS) using microbubble contrast agents has shown great promise in visualising and quantifying active vascular density. Most existing approaches for vascular density quantification using CEUS are calculated based on image intensity and are susceptible to confounding factors and imaging artefact. Poor reproducibility is a key challenge to clinical translation. In this study, a new automated temporal and spatial signal analysis approach is developed for reproducible microbubble segmentation and quantification of contrast enhancement in human lower limbs. The approach is evaluated in vitro on phantoms and in vivo in lower limbs of healthy volunteers before and after physical exercise. In this approach, vascular density is quantified based on the relative areas microbubbles occupy instead of their image intensity. Temporal features of the CEUS image sequences are used to identify pixels that contain microbubble signals. A microbubble track density (MTD) measure, the ratio of the segmented microbubble area to the whole tissue area, is calculated as a surrogate for active capillary density. In vitro results reveal a good correlation (r(2) = 0.89) between the calculated MTD measure and the known bubble concentration. For in vivo results, a significant increase (129% in average) in the MTD measure is found in lower limbs of healthy volunteers after exercise, with excellent repeatability over a series of days (intra-class correlation coefficient = 0.96). This compares to the existing state-of-the-art approach of destruction and replenishment analysis on the same patients (intra-class correlation coefficient ≤0.78). The proposed new approach shows great potential as an accurate and highly reproducible clinical tool for quantification of active vascular density.

Journal article

Williams KJ, Sounderajah V, Dharmarajah B, Thapar A, Davies AHet al., 2017, Simulated wound assessment using digital planimetry versus three-dimensional cameras: implications for clinical assessment., Annals of Vascular Surgery, Vol: 41, Pages: 235-240, ISSN: 1615-5947

BACKGROUND: Clinical management of wounds can benefit from objective measures of response to treatment. Wound surface area and volume are objective measures of wound healing. Using a synthetic wound model, we compare the accuracy and reproducibility of 2 commercially available 3-dimensional (3D) cameras against planimetry and water displacement. METHODS: Twelve ulcers of various sizes and colors were reproduced in modeling clay and cured. Five naive observers used digital planimetry, water displacement, Eykona camera (Fuel 3D, UK), and Silhouette camera (ARANZ, New Zealand) to measure the wounds. RESULTS: When compared with traditional planimetry, wound surface area measurement with Eykona and Silhouette tended to underestimate wounds by 1.7% and 3.7%, respectively. Spearman correlation coefficients were 0.94 (Eykona) and 0.92 (Silhouette). Intraclass correlations for planimetry and the 2 cameras were all 1. Eykona and Silhouette tended to underestimate wound volumes when compared with water displacement by 58% and 23%, respectively. Spearman correlation coefficients were 0.92 (Eykona) and 0.72 (Silhouette). Intraclass correlations for water displacement and the two cameras were all 1. DISCUSSION: Serial accurate objective area measurements are feasible as part of ongoing clinical assessment of wounds. 3D cameras are reliable but have not shown superior accuracy to manual planimetry, and financial concerns and IT integration may limit general clinical usage. Volume measurements of wounds are practicable as part of clinical care.

Journal article

Ravikumar R, Williams KJ, Babber A, Lane TRA, Moore HM, Davies AHet al., 2016, Randomised Controlled Trial: Potential Benefit of a Footplate Neuromuscular Electrical Stimulation Device in Patients with Chronic Venous Disease, EUROPEAN JOURNAL OF VASCULAR AND ENDOVASCULAR SURGERY, Vol: 53, Pages: 114-121, ISSN: 1078-5884

Journal article

Williams KJ, Babber A, Ravikumar R, Davies AHet al., 2016, Non-invasive management of peripheral arterial disease., Advances in Experimental Medicine and Biology, Vol: 906, Pages: 387-406, ISSN: 0065-2598

BACKGROUND: Peripheral arterial disease (PAD) is common and symptoms can be debilitating and lethal. Risk management, exercise, radiological and surgical intervention are all valuable therapies, but morbidity and mortality rates from this disease are increasing. Circulatory enhancement can be achieved using simple medical electronic devices, with claims of minimal adverse side effects. The evidence for these is variable, prompting a review of the available literature. METHODS: Embase and Medline were interrogated for full text articles in humans and written in English. Any external medical devices used in the management of peripheral arterial disease were included if they had objective outcome data. RESULTS: Thirty-one papers met inclusion criteria, but protocols were heterogenous. The medical devices reported were intermittent pneumatic compression (IPC), electronic nerve (NMES) or muscle stimulators (EMS), and galvanic electrical dressings. In patients with intermittent claudication, IPC devices increase popliteal artery velocity (49-70 %) and flow (49-84 %). Gastrocnemius EMS increased superficial femoral artery flow by 140 %. Over 4.5-6 months IPC increased intermittent claudication distance (ICD) (97-150 %) and absolute walking distance (AWD) (84-112 %), with an associated increase in quality of life. NMES of the calf increased ICD and AWD by 82 % and 61-150 % at 4 weeks, and 26 % and 34 % at 8 weeks. In patients with critical limb ischaemia IPC reduced rest pain in 40-100 % and was associated with ulcer healing rates of 26 %. IPC had an early limb salvage rate of 58-83 % at 1-3 months, and 58-94 % at 1.5-3.5 years. No studies have reported the use of EMS or NMES in the management of CLI. CONCLUSION: There is evidence to support the use of IPC in the management of claudication and CLI. There is a building body of literature to support the use of electrical stimulators in PAD, but this is low

Journal article

Williams KJ, Ravikumar R, Gaweesh AS, Moore HM, Lifsitz AD, Lane TR, Shalhoub J, Babber A, Davies AHet al., 2016, A Review of the Evidence to Support Neuromuscular Electrical Stimulation in the Prevention and Management of Venous Disease, Advances in Experimental Medicine and Biology, Vol: 906, Pages: 377-386, ISSN: 0065-2598

INTRODUCTION: The prevention and management of venous disease is a therapeutic challenge. Movement of blood through the venous system is augmented by the action of muscles on the deep veins, and can be achieved through the application of electrical current. The efficacy of currently available clinical devices for this purpose is unknown, and is investigated here. METHODS: A literature search of the EMBASE and Medline databases was performed, and studies were included if they were full text articles, written in english, pertaining to venous disease and neuromuscular electrical stimulation (NMES). RESULTS: NMES devices increase venous haemodynamic parameters such as peak velocity and volume flow. Studies report them to be non-inferior to intermittent pneumatic compression. They are effective in the prevention of venous thromboembolism, though inferior to low molecular weight heparin. NMES can reduce symptoms of chronic venous disease. DISCUSSION: NMES is an important tool in the prevention and management of venous disease, and avoids the significant risks associated with heparin administration. Data explored here is heterogenous in device, protocol, and reported end-points, therefore should be interpreted with care. Long term effects of treatment with NMES have not been explored.

Journal article

Ravikumar R, Williams KJ, Babber A, Lane T, Moore Het al., 2016, Neuromuscular Electrical Stimulation For Venous Thromboprophylaxis, Vascular-Societies Annual Scientific Meeting, Publisher: WILEY-BLACKWELL, Pages: 21-21, ISSN: 0007-1323

Conference paper

Evans DRS, Williams KJ, Stratton PH, Davies AHet al., 2016, The comparative haemodynamic efficacy of lower limb muscles using transcutaneous electrical stimulation, Annual Meeting of the Society-of-Academic-and-Research-Surgery (SARS), Publisher: Wiley, Pages: 12-12, ISSN: 1365-2168

Conference paper

Williams KJ, Babber A, Ravikumar R, Davies AHet al., 2016, Non-Invasive Management of Peripheral Arterial Disease, Advances in Internal Medicine, Publisher: Springer International Publishing

Book chapter

Evans DR, Williams KJ, Strutton PH, Davies AHet al., 2016, The comparative hemodynamic efficacy of lower limb muscles using transcutaneous electrical stimulation., Journal of vascular surgery. Venous and lymphatic disorders, Vol: 4, Pages: 206-214, ISSN: 2213-3348

BACKGROUND: Circulation in the limbs can be augmented using transcutaneous electrical stimulation devices. The optimum muscle stimulation sites for enhancement of vascular hemodynamic parameters have not been identified. METHODS: Seven suitable anatomic sites were identified within the right leg. Twelve healthy participants were recruited (mean age, 23.1 ± 3 years; body mass index, 23.1 ± 3 kg/m(2)). Muscles were stimulated by transcutaneous bipolar electrodes at a current twice their motor threshold, at 1 Hz, for 5 minutes. Hemodynamic ultrasound measurements were taken from the right femoral vein. Laser Doppler measurements from the feet of the stimulated and nonstimulated sides were obtained. Baseline measurements were compared with readings after 5 minutes of stimulation, with device active. Discomfort experienced for stimulation of each muscle was rated out of 100. RESULTS: Hemodynamic changes displayed large intersubject variation, with no muscle statistically superior to the others. All muscles increased peak velocity; contraction of medial gastrocnemius increased time-averaged maximum velocity and volume flow. All muscles increased foot fluximetry (P < .05). Discomfort correlated weakly with current applied. Tibialis anterior and vastus lateralis were most tenable. CONCLUSIONS: Transcutaneous stimulation increases hemodynamic parameters significantly, locally and systemically. No optimum stimulation site has been identified, and it is limited by comfort and variability in the subject's response. Gastrocnemius, tibialis anterior, and vastus lateralis all provoke large changes in hemodynamic parameters, but clinical efficacy in disease prevention and management has not been explored.

Journal article

Varatharajan L, Williams K, Moore H, Davies AHet al., 2015, The effect of footplate neuromuscular electrical stimulation on venous and arterial haemodynamics, PHLEBOLOGY, Vol: 30, Pages: 648-650, ISSN: 0268-3555

Journal article

Wou J, Williams KJ, Davies AH, 2015, Compression Stockings versus Neuromuscular Electrical Stimulation Devices in the Management of Occupational Leg Swelling, International Journal of Angiology, Vol: 25, Pages: 104-109, ISSN: 1615-5939

Background Occupational edema is reported to occur in healthy individuals after working in a sitting or standing position for extensive periods of time. It can be associated with feelings of tiredness, heaviness of the legs, and pain. Three licensed medical devices were compared in their management of occupational edema. Subjects and Methods A total of 10 subjects were recruited from a clinical workspace. Right leg volume and great saphenous vein diameter was measured in the morning, and 6 hours later. On subsequent separate days, grade 2 graduated compression stockings (Active Compression Socks, Mediven, United Kingdom), geko (Firstkind Ltd, United Kingdom), and Revitive (Actegy Ltd, United Kingdom) were used bilaterally according to manufacturer's instructions. Results Leg volumes increased by median 41 mL (p < 0.05) with no intervention. Percentage increase in leg volume was found to be significantly reduced by stockings compared with control (-1.7%, p < 0.01), and were more effective than electrical devices. Changes in vein diameter poorly correlate with leg volume changes. Conclusion Occupational edema can occur over as little as 6 hours. All devices were well tolerated and reduced leg swelling. Stockings were the only device to significantly reduce leg swelling in this small trial.

Journal article

Williams KJ, Moore HM, Davies AH, 2015, Haemodynamic changes with the use of neuromuscular electrical stimulation compared to intermittent pneumatic compression, PHLEBOLOGY, Vol: 30, Pages: 365-372, ISSN: 0268-3555

Journal article

Williams KJ, Ravikumar R, Babber A, Davies AHet al., 2015, Can neuromuscular stimulation relieve symptoms of chronic venous disease, and improve quality of life?, Annual Meeting of the Society-of-Academic-and-Research-Surgery (SARS(, Publisher: WILEY-BLACKWELL, Pages: 9-9, ISSN: 0007-1323

Conference paper

Williams KJ, Davies AH, 2015, Comparative accuracy and reliability of 3D cameras in simulated wound measurement, Annual Meeting of the Society-of-Academic-and-Research-Surgery (SARS(, Publisher: WILEY-BLACKWELL, Pages: 47-47, ISSN: 0007-1323

Conference paper

Wou J, Williams KJ, Davies AH, 2015, A comparative study of the effect of graduated compression stockings and neuromuscular stimulation devices in the management of occupational leg oedema, Annual Meeting of the Society-of-Academic-and-Research-Surgery (SARS(, Publisher: WILEY-BLACKWELL, Pages: 28-28, ISSN: 0007-1323

Conference paper

Ravikumar R, Williams KJ, Babber A, Davies AHet al., 2015, Electrical stimulation of the foot pump: a pilot randomised control trial in patients with chronic venous insufficiency, Annual Meeting of the Society-of-Academic-and-Research-Surgery (SARS(, Publisher: WILEY-BLACKWELL, Pages: 6-6, ISSN: 0007-1323

Conference paper

Ravikumar R, Williams KJ, Davies AH, 2015, Potential clinical applications of electrical muscle stimulation in venous disease, Annual Meeting of the Society-of-Academic-and-Research-Surgery (SARS(, Publisher: WILEY-BLACKWELL, Pages: 45-46, ISSN: 0007-1323

Conference paper

Williams KJ, Davies AH, 2015, Pilot trial of neuromuscular stimulation in the management of chronic venous disease, BRITISH JOURNAL OF SURGERY, Vol: 102, Pages: 20-20, ISSN: 0007-1323

Journal article

Williams KJ, Ayekoloye O, Moore HM, Davies AHet al., 2014, The calf muscle pump revisited, JOURNAL OF VASCULAR SURGERY-VENOUS AND LYMPHATIC DISORDERS, Vol: 2, Pages: 329-334, ISSN: 2213-333X

Journal article

Williams KJ, Moore HM, Davies AH, 2014, Comparison of intermittent pneumatic compression and neuromuscular electrical stimulation using ultrasound and laser doppler fluximetry, Annual Meeting of the Society-of-Academic-and-Research-Surgery, Publisher: WILEY-BLACKWELL, Pages: 50-50, ISSN: 0007-1323

Conference paper

Williams KJ, Hayes AJ, 2014, A guide to oncological management of soft tissue tumours of the abdominal wall, HERNIA, Vol: 18, Pages: 91-97, ISSN: 1265-4906

Journal article

Williams KJ, Al-Sakkal MN, Alsafi A, Davies AHet al., 2014, Massive localized lymphedema - A rare vascular malformation, Vasomed, Vol: 26, Pages: 46-47, ISSN: 0942-1181

Journal article

Moore HM, Williams KJ, Onida S, Davies AHet al., 2014, Chronic deep venous valve management in the future, Italian Journal of Vascular and Endovascular Surgery, Vol: 21, Pages: 11-15, ISSN: 1824-4777

The present work discusses the recent developments in the treatment of deep venous disease and the future perspectives in the therapeutic approach. Chronic venous disease is common and presents a significant cost in healthcare. The new technologies available for its successful management include endothermal ablation, and tumescent free mechanochemical technologies. Conservative treatments for chronic deep venous insufficiency are limited to leg elevation, weight reduction, walking, exercise and physiotherapy, all of which serve to improve venous return and reduce venous hypertension, whereas future management of deep venous reflux lies in the development of a valve stent device that can be implanted into the deep venous system by a minimally-invasive percutaneous method; the focus must be the development of a non-thrombogenic, biocompatible, hemocompatible, flexible, non-fatigueable material with a valve design that minimises zones of stasis, flow turbulence and shear stress.

Journal article

Williams KJ, Al-Sakkal MN, Alsafi A, Davies AHet al., 2013, Massive localised lymphoedema: a rare vascular malformation., BMJ Case Rep, Vol: 2013

Lymphatic malformations are a subset of congenital vascular malformations, and are caused by a defect in lymphatic development during embryogenesis. When lymphatic mesoderm development is prematurely arrested, it retains it proliferative potential. Stimulus in the future can cause the lesion to proliferate locally without coordination or regulation, resulting in the rare condition known as massive localised lymphoedema (MLL). We present a case report of MLL, a rare and ill-defined soft tissue mass reported in the morbidly obese, with reference to the existing literature.

Journal article

Carter JG, Cherry J, Williams K, Turner S, Bates DO, Churchill AJet al., 2011, Splicing factor polymorphisms, the control of VEGF isoforms and association with angiogenic eye disease., Curr Eye Res, Vol: 36, Pages: 328-335

PURPOSE: Alternative splicing of the last exon (exon 8) of vascular endothelial growth factor (VEGF) pre-mRNA is a key element in the balance of pro- and anti-angiogenic VEGF isoforms in exudative age-related macular degeneration (exAMD) and proliferative diabetic retinopathy (PDR). Three splicing factors, SRp40, ASF/SF2, and SRp55 are predicted to control alternative splicing by binding to exonic splice enhancers (ESE) in VEGF exon 8. This pilot study examines whether there is an association between angiogenic eye disease and splicing factor polymorphisms, and whether there are sequence variations in the alternative splice sites of the VEGF gene. MATERIALS AND METHODS: A case:control pilot study comparing 163 individuals with angiogenic eye disease (94 exAMD and 69 PDR patients) with 95 age-matched controls. Splicing factor polymorphisms were genotyped by Restriction Fragment Length Polymorphism (RFLP) and sequencing, and the VEGF alternatively spliced region was assessed by denaturing High Performance Liquid Chromatography (dHPLC) using a transgenomic WAVE heteroduplex analyzer. RESULTS: No variations were observed in the alternatively spliced region of VEGF exon 8. ASF/SF2 polymorphisms showed no association with exAMD or PDR. For PDR, we observed a trend in SRp40 (rs6573908) where the 5136CC genotype was more frequent in controls (p = 0.0517) and a significant association of the SRp55 (rs2235611), where the 2994C allele was more common in the PDR group (p = 0.03). This remained strong, but not significant, after logistic regression for age, sex, disease type, and duration (p = 0.06). CONCLUSIONS: The lack of variation in the VEGF alternatively spliced region suggests the importance of sequence conservation in this area in maintaining the balance of pro- and anti-angiogenic VEGF isoforms. The link between PDR and the SRp55 2994 polymorphism suggests a disease-specific association between factors controlling VEGF splicing

Journal article

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