Robert Ritchie

University of Oxford, Oxford, England, United Kingdom

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Publications (18)41.77 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: High-intensity focused ultrasound (HIFU) is an attractive therapy for kidney cancer, but its efficacy can be limited by heat deposition in the pre-focal tissues, notably in fat around the kidney (peri-nephric fat), the acoustic properties of which have not been well characterized. Measurements of attenuation were made using a modified insertion-loss technique on fresh, unfixed peri-nephric fat obtained from patients undergoing kidney surgery for cancer. The de-focusing effect of changing the position of the fat layers was also investigated using fresh subcutaneous fat from euthanized pigs. The mean attenuation of human peri-nephric fat was found to be 11.9 ± 0.9 Np/m (n = 10) at 0.8 MHz, the frequency typically used for HIFU ablation of kidney tumors, with a frequency dependence of f(1.2). A typical 2- to 4-cm thickness of peri-nephric fat would result in a de-rated intensity of 3%-62% at 0.8 MHz compared with a hypothetical patient with no peri-nephric fat. Through the use of freshly excised porcine subcutaneous fat, the presence of fat 100 mm in front of the focus was found to have a de-focusing effect of approximately 1 mm in both transverse directions, which corresponds to a full HIFU beam width off-target. Peri-nephric fat may significantly affect both the intensity and accuracy of HIFU fields used for the ablation of kidney cancer.
    Ultrasound in medicine & biology 08/2013; · 2.46 Impact Factor
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    ABSTRACT: HIFU is a minimally-invasive therapy suitable for treating selected intra-abdominal tumors. Treatment is safe although skin burns may occur due to pre-focal heating. HIFU treatment of a renal transplant tumor located in the left lower abdomen was undertaken in our centre. Treatment was performed prone, requiring displacement of the abdominal wall away from the treatment field using a water balloon, constructed of natural rubber latex and filled with degassed water. Intra-operatively, ultrasound imaging and physical examination of the skin directly over the focal region was normal. Immediately post-operative, a full-thickness skin burn was evident at the periphery of the balloon location, outside the expected HIFU path. Three possibilities may account for this complication. Firstly, the water balloon may have acted as a lens, focusing the HIFU to a neo-focus off axis. Secondly, air bubbles may have been entrapped between the balloon and the skin, causing heating at the interface. Finally, heating of the isolated water within the balloon may have been sufficient to cause burning. In this case, the placement of a water balloon caused a significant skin burn. Care should be taken in their use as burns, situated off axis, may occur even if the overlying skin appears normal.
    10/2012;
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    ABSTRACT: Objectives To assess the safety and feasibility of high-intensity focused ultrasound (HIFU) ablation of liver tumours and to determine whether post-operative MRI correlates with intra-operative imaging. Methods 31 patients were recruited into two ethically approved clinical trials (median age 64; mean BMI 26 kg m(-2)). Patients with liver tumours (primary or metastatic) underwent a single HIFU treatment monitored using intra-operative B-mode ultrasound. Follow-up consisted of radiology and histology (surgical trial) or radiology alone (radiology trial). Radiological follow-up was digital subtraction contrast-enhanced MRI. Results Treatment according to protocol was possible in 30 of 31 patients. One treatment was abandoned because of equipment failure. Transient pain and superficial skin burns were seen in 81% (25/31) and 39% (12/31) of patients, respectively. One moderate skin burn occurred. One patient died prior to radiological follow-up. Radiological evidence of ablation was seen in 93% (27/29) of patients. Ablation accuracy was good in 89% (24/27) of patients. In three patients the zone of ablation lay ≤2 mm outside the tumour. The median cross-sectional area (CSA) of the zone of ablation was 5.0 and 5.1 cm(2) using intra-operative and post-operative imaging, respectively. The mean MRI:B-mode CSA ratio was 1.57 [95% confidence interval (CI)=0.57-2.71]. There was positive correlation between MRI and B-mode CSA (Spearman's r=0.48; 95% CI 0.11-0.73; p=0.011) and the slope of linear regression was significantly non-zero (1.23; 95% CI=0.68-1.77; p<0.0001). Conclusions HIFU ablation of liver tumours is safe and feasible. HIFU treatment is accurate, and intra-operative assessment of treatment provides an accurate measure of the zone of ablation and correlates well with MRI follow-up.
    The British journal of radiology 06/2012; 85(1018):1363-70. · 2.11 Impact Factor
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    ABSTRACT: To demonstrate feasibility of monitoring high-intensity focused ultrasound (HIFU) treatment with passive acoustic mapping of broadband and harmonic emissions reconstructed from filtered-channel radiofrequency data in ex vivo bovine tissue. Both passive acoustic emissions and B-mode images were recorded with a diagnostic ultrasound machine during 180 HIFU exposures of five freshly excised, degassed bovine livers. Tissue was exposed to peak rarefactional pressures between 3.6 and 8.0 MPa for 2, 5, or 10 seconds. The B-mode images were analyzed for hyperechoic activity, and threshold levels were determined for the harmonic (1.17 mJ) and broadband (0.0137 mJ) components of the passively reconstructed source energy to predict tissue ablation. Both imaging methods were compared with tissue lesions after exposure to determine their spatial accuracy and their capability to help predict presence of ablated tissue. Performance of both methods as detectors was compared (matched-pair test design). Passive mapping successfully aided prediction of the presence of tissue ablation more often than did conventional hyperechoic images (49 of 58 [84%] vs 31 of 58 [53%], P < .001). At 5.4-6.3-MPa exposures, sensitivity, specificity, negative predictive value, and positive predictive value of the two methods, respectively, were 15 of 20 versus five of 21 (P = .006), eight of nine versus eight of nine (P = .72), 15 of 16 versus five of six (P = .53), and eight of 13 versus eight of 24 (P = .011). Across HIFU exposure amplitude ranges, passive acoustic mapping also aided correct prediction of the visually detected location of ablation following tissue sectioning in 42 of 45 exposures for which the harmonic and broadband threshold levels for tissue ablation were exceeded. Early cavitation activity indicated the focal position within the tissue before irreversible tissue damage occurred. Passive acoustic mapping significantly outperformed the conventional hyperecho technique as an ultrasound-based HIFU monitoring method, as both a detector of lesion occurrence and a method of mapping the position of ablated tissue.
    Radiology 01/2012; 262(1):252-61. · 6.34 Impact Factor
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    ABSTRACT: Study Type--Therapy (case series) Level of Evidence What's known on the subject? and What does the study add? Renal cancer is increasingly diagnosed when tumours are small and asymptomatic, during routine abdominal imaging. Whilst surgery is an effective and potentially curative option, it carries a significant risk of complications. Recent work suggests that thermally ablative therapies (RFA, cryotherapy, HIFU) may be suitable minimally invasive treatment options in selected patients. The success of extracorporeal HIFU has been limited by the abdominal wall and rib-cage limiting energy delivery. For this study, a purpose-built laparoscopic HIFU probe was designed to allow direct application of the transducer to the tumour surface, thus facilitating tumour destruction. Successful and accurate tumour destruction was demonstrated, paving the way for further clinical trials, subject to device modifications. • To test and establish clinical proof of concept for a laparoscopic high-intensity focused ultrasound (HIFU) device that facilitates delivery of ultrasound by direct application of a probe to the tumour surface. •   Twelve patients with renal tumours were treated with laparoscopic HIFU using a newly designed probe inserted via an 18-mm laparoscopic port. • HIFU treatment was targeted at a pre-defined proportion of the tumour and immediate laparoscopic partial or radical nephrectomy was then performed. • No tumour ablation was seen in the first five patients which made modifications in the treatment protocol necessary. After this, definite histological evidence of ablation was seen in the remaining seven patients. • The ablated zones were within the targeted area in all patients and no intra-lesional skipping was seen. • Subcapsular skipping was seen at the probe-tumour interface in two patients with viable tumour cells seen at microscopy. • One patient did not undergo surgical extirpation; subsequent biopsy revealed no viable tumour cells. • There were no intraoperative or postoperative complications directly related to HIFU therapy and patients have reached a mean (range) follow-up of 15 (8-24) months with no evidence of metastatic disease or late complications. • Tumour ablation with laparoscopic HIFU is feasible. • Homogenous ablation can be achieved with no vital tissue within the targeted zone. • The technique is associated with low morbidity and may have a role in the definitive management of small tumours.
    BJU International 04/2011; 107(8):1290-6. · 3.05 Impact Factor
  • The Journal of the Acoustical Society of America 01/2011; 129. · 1.65 Impact Factor
  • Robert Ritchie, Mark Sullivan
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    ABSTRACT: Erectile dysfunction (ED) is common and a significant contributor to poor quality of life and psychosocial morbidity in men. Normal erectile function requires effective co-ordination between a number of complex neural pathways. Penile tumescence occurs in response to rapid arterial inflow to the corpora cavernosa with simultaneous venous outflow restriction due to expansion of the lacunar spaces. This process is under both central and local neuromediation. Endothelins are potent vasoconstrictor peptides that cause strong, slowly developing but sustained contraction of trabecular smooth muscles cells of the corpora cavernosa. Multiple mechanisms of action are proposed, including transmembrane calcium flux, mobilisation of inositol triphosphate sensitive intracellular calcium stores and calcium sensitisation through the Rho-Rho kinase pathway. The exact role of endothelins in the pathogenesis of ED currently remains unclear. Elevated endothelin-1 levels are found in patients with diabetes mellitus and this alone may be sufficient to cause ED. However, this is not borne out in clinical studies. The resultant elevated intracellular calcium may, however, modulate gene expression sufficiently to cause smooth muscle proliferation. Alternatively, alterations in endothelin receptor sensitivity in conditions such as diabetes and hypertension may enhance vasoconstrictor processes. Currently there is contradictory evidence for the role of endothelin receptor antagonists in ED. Animals studies suggest they inhibit corporal vasoconstriction, improve erectile function and protect against diabetes-induced smooth muscle apoptosis. However, the results of clinical studies in ED have been less promising. Uncertainty regarding the exact role of endothelin in penile erection hampers progress in this area. It is possible that the endothelin system may only be relevant to ED in certain conditions where global endothelial dysfunction exists (e.g. diabetes mellitus, systemic sclerosis) and the use of endothelin antagonists in these patient groups may yield improved outcomes.
    Pharmacological Research 12/2010; 63(6):496-501. · 4.35 Impact Factor
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    ABSTRACT: Arrays of detectors placed co-axially with a therapeutic transducer make it possible to receive the high-frequency emissions produced by tissue during therapeutic ultrasound excitation with high sensitivity and in real time, whether in the presence or absence of cavitation activity. The signals received by the array of receivers can be decomposed into broadband, harmonic, and ultraharmonic components and combined using recently developed passive mapping techniques to produce real-time maps of inertial cavitation, stable cavitation, boiling, and of regions of tissue where the high-frequency ultrasonic response changes significantly. In the context of high-intensity focused ultrasound ablation, passive mapping of inertial cavitation makes it possible to visualize the focus in real time, whilst mapping of boiling can identify regions of over-treatment. Further analysis of changes in the harmonic component of high-frequency emissions in the presence or absence of cavitation can also provide reliable detection of the change in viscoelastic tissue properties that corresponds to successful ablation. In the context of ultrasound-enhanced drug delivery, cavitation mapping can help identify the tissue regions where successful extravasation of therapeutic agents from blood vessels has occurred. It is concluded that passive mapping could provide a novel, effective, and low-cost method for real-time guidance and monitoring of ultrasound therapy.
    The Journal of the Acoustical Society of America 10/2010; 128(4):2416. · 1.65 Impact Factor
  • European Urology Supplements 04/2010; 183(4). · 3.37 Impact Factor
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    ABSTRACT: To determine whether primary extracorporeal high-intensity focused ultrasound (HIFU) is safe, feasible and effective for managing small renal tumours. Although surgery currently remains the standard treatment for localized renal cell carcinoma (RCC), the increasing incidence of small renal cancers has led to a shift towards nephron-sparing surgery, with associated morbidity in 20-25% of cases, and minimally invasive ablative therapies present an alternative management. HIFU results in 'trackless' homogenous tissue ablation and when administered via an extracorporeal device, is entirely noninvasive. The study comprised 17 patients (mean tumour size 2.5 cm) with radiologically suspicious renal tumours who underwent extracorporeal HIFU using the Model-JC System (Chongqing HAIFU™, China), under general anaesthesia with one overnight hospital stay. Real-time diagnostic ultrasonography was used for targeting and monitoring. Patients were followed with a clinical review and gadolinium-enhanced magnetic resonance imaging at 12 days and every 6 months for a mean of 36 months. The outcomes measures were patient morbidity and oncological efficacy of HIFU treatment. Of the 17 patients, 15 were treated according to protocol; two procedures were abandoned due to intervening bowel. There were no major complications related to HIFU. Radiological evidence of ablation was apparent at 12 days in seven of the 15 patients. Before the 6-month follow-up one patient had surgery due to persisting central enhancement. Fourteen patients were evaluated at the 6-month follow-up; eight tumours had involuted (mean 12% decrease in tumour area). Four patients had irregular enhancement on imaging and had alternative therapies. Ten patients remain on follow-up at a mean (range) of 36 (14-55) months after HIFU (mean 30% decrease in tumour area). There was central loss of enhancement in all. Renal HIFU achieves stable lesions in two-thirds of patients, with minimal morbidity, and might be appropriate in selected cases. Further trials with accurate histological follow-up are essential to fully evaluate this novel technique.
    BJU International 03/2010; 106(7):1004-9. · 3.05 Impact Factor
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    Robert W. Ritchie, Mark E. Sullivan, Adam Jones
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    ABSTRACT: Background Large volume centres from the USA suggest laparoscopic radical nephrectomy (LRN) for T2 (>7 cm) renal cell carcinoma (RCC) is safe and associated with few complications. Similar data for low and intermediate volume centres in Europe is lacking. Objective To determine whether LRN for T2 RCC in two intermediate volume UK hospitals compares favourably with larger volume centres. To determine whether LRN for T2 RCC is associated with favourable outcomes when compared to LRN for T1 RCC. Patients and methods Data from 118 consecutive LRN performed in Oxford, UK (tertiary academic centre, catchment population 2,000,000) and Reading, UK (large district general hospital, catchment population 500,000). All patients undergoing LRN from 2004 to 2008 were included; outcome data were collected prospectively. All patients underwent a standard 4-port trans-peritoneal LRN with intact specimen removal. Patients were divided into two groups—Group 1 (clinical T1 tumours) and Group 2 (clinical T2 tumours). Demographic data and operative outcome data were collected for every patient including age, weight, operative duration, estimated blood loss, transfusion rates, complications, hospital stay and histology. Data were compared using Chi-square test and the Student t-test. Results Mean patient age was 62.5 years; 57% of tumours were right sided. Mean tumour dimension in Group 1 was 4.3 cm and 9.3 cm in Group 2. Demographics were similar between the two groups. Operative duration, estimated blood loss and transfusion rates were significantly greater in Group 2. Despite this, complication rates, conversion rates and hospital stay were similar. 12% of tumours were benign and nearly half of all clinical T2 tumours were ultimately staged T3 on final histology. Conclusions LRN for T2 RCC can be performed safely in intermediate volume centres. The procedure is more challenging but operative outcomes are similar to LRN for smaller tumours. Many >7 cm RCC are T3 on final histology.
    British Journal of Medical and Surgical Urology 05/2009; 2(3):117–123.
  • Robert W Ritchie, John Reynard
    BJU International 04/2009; 104(6):766-8. · 3.05 Impact Factor
  • The Journal of Urology 04/2009; 181(4):468-468. · 3.75 Impact Factor
  • European Urology Supplements - EUR UROL SUPPL. 01/2009; 8(4):324-324.
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    Robert Ritchie, John Reynard, Tom Lewis
    Journal of the Royal Society of Medicine 09/2008; 101(8):395-9. · 1.72 Impact Factor
  • BJU International 07/2008; 101(11):1336-8. · 3.05 Impact Factor
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    ABSTRACT: Cysts of the kidney usually originate from the renal parenchyma after tubule obstruction; rarely pyelocalyceal cysts occur, originating from transitional urothelium. Neoplasia is a rare but possible complication. A 45-year-old man was found to have a cyst related to the right kidney. Computed tomography demonstrated minimal calcification in the wall (Bosniak II). Symptom-relieving percutaneous drainage yielded clear fluid; resultant cytology was negative. After rapid reaccumulation, laparoscopic deroofing was performed. No communication within the renal pelvis was detected however histology revealed transitional cell carcinoma. An open radical nephroureterectomy was performed; adjuvant chemotherapy was given. Three previous cases of malignancy in a pyelocalyceal cyst have been reported. This is the first reported after laparoscopic deroofing of a cyst. Despite widespread use of the Bosniak renal cyst classification, the management of category II cysts remains contentious. This case should serve as a warning to clinicians that seemingly benign cysts of the kidney may harbor underlying neoplasia. Intraoperative frozen section should be considered in all cases where preoperative imaging suggests Bosniak II classification.
    Surgical laparoscopy, endoscopy & percutaneous techniques 09/2007; 17(4):358-60. · 0.88 Impact Factor
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    R W Ritchie, N Thiruchelvam, A Adamson
    Annals of The Royal College of Surgeons of England 05/2007; 89(3):313. · 1.33 Impact Factor