PubMed Health⌕ Search

Biomedical subjects

Peter Alken

Publications and source records attributed to Peter Alken.

At least 19 recordsLinked to original sources
PubMed2007

Correlation between motor function and lower urinary tract dysfunction in patients with infantile cerebral palsy.

AIMS: The aim of this study was to evaluate urodynamic findings in patients with infantile cerebral palsy (CP) and to correlate the findings with impaired motor function. METHODS: We conducted a videourodynamic investigation on a highly select group of 29 patients (3-53 years). Motor function was assessed in each patient by the Gross Motor Function Classification System for CP (GMFCS). With this system, motor function is divided into five levels: patients in Level I have the most independent motor function and patients in Level V the least. The patients were divided into Group 1 (23 symptomatic patients with recurrent urinary tract infection or urinary incontinence) and Group 2 (6 asymptomatic patients). RESULTS: In Group 1, 21 patients (91%) had reduced compliance (0.6-16.4 ml/cmH(2)O) and 16 patients (70%) had increased DLPP (>40 cmH(2)O). Detrusor overactivity and pelvic floor overactivity were found in all 23 patients. In Group 2, two patients (33%) had reduced compliance (0.7 and 5.8 ml/cmH(2)O) and four (67%) had increased DLPP (>40 cm H(2)O). Detrusor overactivity and pelvic floor overactivity were observed in five patients (83%). Symptomatic patients showed higher GMFCS levels than asymptomatic patients. In the group of asymptomatic patients, there was no one classified as Levels IV or V, while there were no symptomatic patients classified as Level I. CONCLUSIONS: We conclude that urinary symptoms and pathological urodynamic findings increase along with the degree of motor function impairment shown by the GMFCS. Pathologic urodynamic findings can be found in both symptomatic and in asymptomatic patients.

Adolescent↗
PubMed2006

Impact of hypoxia and hypercapnia on calcium oxalate toxicity in renal epithelial and interstitial cells.

Although there is an ongoing controversy about the primary site of calcium oxalate stone (CaOx) formation, there is some evidence for extratubular crystallization. However, the mechanisms leading to such interstitial calcifications are not clear. Anatomical studies have demonstrated a close association between the renal vasculature and renal tubules. It has been hypothesized that disorders of the vasculature may contribute to renal stone formation. The exceptional papillary environment with low oxygen and high carbon dioxide is of interest in this context and its impact on CaOx toxicity to renal cells has to be evaluated. LLC-PK1, Madin-Darby canine kidney (MDCK), human umbilical vein endothelial (HUVEC) and fibroblast cell lines were exposed to hypoxia (3% O2) alone, hypercapnia combined with hypoxia (3% O2, 18% CO2) or standard culture conditions (20% O2) for 72 h. Cell survival rates were determined microscopically after 4 h of incubation with CaOx at final concentrations of 1, 2 and 4 mM. DAPI staining and western blot were used to evaluate the induction of apoptosis. We confirmed that CaOx leads to concentration-dependent effects on the viability of the cell lines. HUVECs were most vulnerable to CaOx among the four cell lines. Incubation under hypoxia alone had no impact on CaOx toxicity to any of the cell lines in terms of survival. However, under combined hypoxic and hypercapnic conditions, all cell lines displayed a significant reduction of cell survival compared to room air incubation. Again, this effect was most pronounced for HUVECs. The induction of apoptosis could not be demonstrated in any experimental setting. Combined hypoxia and hypercapnia clearly aggravate CaOx toxicity to renal cell lines. As we could not demonstrate the induction of apoptosis, this effect may be a result of toxic necrosis. Especially the CaOx effect on interstitial cell lines might be of interest in the chronic ischemic papillary environment. An increased toxicity may lead to recurrent stone formation, and vice versa, diseases of the vasculature, like arteriosclerosis, may further promote stone formation by induction of local ischemia. This issue has to be clarified by further studies.

Animals↗
PubMed2006

Magnetic resonance imaging for assessment of radiofrequency lesions in kidney tissue immediately after ablation: an experimental study.

BACKGROUND AND PURPOSE: Radiofrequency ablation (RFA) is an attractive minimally invasive treatment option for small renal masses. The purpose of this study was to investigate the morphologic imaging appearance of RF lesions immediately after the ablation of kidney tissue using standard clinical MR sequences, as well as to investigate the correlation between MR and gross lesion size. MATERIALS AND METHODS: Ablations were performed 17 times in a standardized model of ex-vivo perfused porcine kidneys using a resistance-controlled RF device (250 W, 470 kHz) and a nonexpandable bipolar applicator inserted into the center of healthy renal parenchyma. The RF current was applied for 9 minutes at 20 W. Imaging was performed after ablation using standard clinical MR sequences: morphologic T(1)/T(2)- weighted images and an isotropic post-contrast T(1) high-resolution measurement (VIBE). Maximum lesion diameters were measured in three directions and were compared with the measurements of the gross lesions. Histologic (hematoxylin + eosin and nicotinamide adenine dinucleotide staining) and statistical analyses were performed. RESULTS: The gross pathologic examination showed a firm, white-yellow ablation zone sharply demarcated from the untreated tissue. The histologic examination confirmed cellular viability outside but not in the treatment zone. The RF lesions were hyperintense on T(1)-weighted images and hypointense on T(2)-weighted images. The lesion size measured in the VIBE images correlated best with the macroscopic lesion size (N = 16). CONCLUSIONS: Morphologic MR T(1) and T(2) sequences of RF lesions immediately after ablation produce reliable and consistent imaging characteristics. The post-contrast, high-resolution sequence (VIBE) enables the extent of the lesion to be determined accurately. The potential uses of this imaging strategy in clinical practise warrant further investigation on human renal-cell carcinoma.

Animals↗
PubMed2006

Low-power holmium:YAG laser urethrotomy for treatment of urethral strictures: functional outcome and quality of life.

PURPOSE: To evaluate the efficacy of endourethrotomy with the holmium:YAG laser as a minimally invasive treatment for urethral stricture. PATIENTS AND METHODS: Between January 2002 and January 2004, 32 male patients with symptomatic urethral strictures (8 bulbar, 9 penile, 9 combined) were treated with Ho:YAG-laser urethrotomy in our department. The stricture was iatrogenic in 60% (N = 18), inflammatory in 16.6% (N = 5), traumatic in 13.3% (N = 4), and idiopathic in 7% (N = 3). The stricture was incised under vision at the 12 o'clock location or the site of maximum scar tissue or narrowing in asymmetric strictures. Laser energy was set on 1200 to 1400 mJ with a frequency of 10 to 13 Hz. Postoperatively, drainage of the bladder was performed for 4 days using a 18F silicone catheter. Triamcinolone was instilled intraurethrally after removal of the catheter in all patients. Patients were followed up by mailed questionnaire, including International Prostate Symptom Score and quality of life. RESULTS: Retrograde endoscopic Ho:YAG laser urethrotomy could be performed in all 32 patients. Most patients (22; 68.7%) did not need any reintervention. Ten patients developed recurrent strictures that were treated by another laser urethrotomy in 4 patients (12.5%), while 6 patients (18.7%) needed open urethroplasty with buccal mucosa. Including 2 patients treated with repeat laser urethrotomy, 24 patients (75%) were considered successful after a mean follow-up of 27 months (range 13-38 months). No intraoperative complications were encountered, although in 5% of patients, a urinary-tract infection was diagnosed postoperatively. No gross hematuria occurred. CONCLUSIONS: The Ho:YAG laser urethrotomy is a safe and effective minimally invasive therapeutic modality for urethral stricture with results comparable to those of conventional urethrotomy. Further data from long-time follow-up are necessary to compare the success rate with that of conventional urethrotomy and urethroplasty. Nevertheless, the Ho:YAG laser urethrotomy might at least be an alternative to urethroplasty in patients with high comorbidity who are not suitable for open reconstruction.

Adult↗
PubMed2006

Risk of collateral damage to endourologic tools by holmium:YAG laser energy.

BACKGROUND AND PURPOSE: Today, the holmium:YAG laser is the gold standard in endourologic stone treatment because of its high efficacy. However, guidewires and stone-extraction tools often are close to the fiber and may be damaged accidentally by the laser. The aim of our study was to evaluate the duration of laser application required to disrupt wires at different energy settings. MATERIALS AND METHODS: Two standard wires (0.035-inch guidewire and 0.025-inch hydrophilic Terumo wire) and two baskets (1.9F Nitinol tipless and 3F stone extraction) were investigated. We used a holmium:YAG laser (Auriga; Wavelight Laser Technologie AG, Erlangen, Germany) and two fibers (230 and 365 microm) at 800 and 2000 mJ and a 5-Hz pulse rate. The laser was brought into direct contact with the wires. RESULTS: The average time required for transection was 55 to 103 seconds for a safety wire. The Terumo wire broke after 20 to 40 seconds of direct laser application; 15 to 34 seconds was required for a Dormia basket. Thin Nitinol basket wires were disrupted after only 1 to 4 seconds. One- and two-factorial variance analysis showed a high degree of significance (P < 0.0001) of the energy level and type of wire. CONCLUSION: The disruption of stone-extraction tools occurs in a remarkably short time with laser exposure, especially in case of Nitinol baskets, whereas guidewires are more resistant. Attention should be paid to avoiding contact of laser energy with wires and baskets during stone fragmentation.

Aluminum↗
PubMed2006

Hans Christian Jacobaeus: Inventor of human laparoscopy and thoracoscopy.

Hans Christian Jacobaeus performed the first clinical laparoscopic surgery in Stockholm. This pioneering procedure was based on the animal experiments of Georg Kelling (1866-1945), a German physician from Dresden, who performed the first laparoscopic intervention in 1901 using a Nitz cystoscope in a dog. In 1910, Jacobaeus published his initial experiences with laparoscopic surgery in the Münchner Medizinischen Wochenschrift under the title "The Possibilities for Performing Cystoscopy in Examinations of Serous Cavities." He used this technique for diagnostic purposes in undefined abdominal complaints and functional impairment. Jacobaeus was the first who pointed out the possibility of injuring organs, especially the intestines, by inserting the trocar. In 1910, Jacobaeus recognized the immense diagnostic and therapeutic possibilities of laparoscopic surgery, as well as its difficulties and limits. He also was the first to realize the need for initial endoscopic training in animals and corpses. He promoted the development of special laparoscopic instruments to optimize and simplify the procedure.

Animals↗
PubMed2006

Ablation of clinically relevant kidney tissue volumes by high-intensity focused ultrasound: Preliminary results of standardized ex-vivo investigations.

PURPOSE: To investigate strategies to achieve confluent kidney-tissue ablation by high-intensity focused ultrasound (HIFU). MATERIALS AND METHODS: Our model of the perfused ex-vivo porcine kidney was used. Tissue ablation was performed with an experimental HIFU device (Storz Medical, Kreuzlingen, Switzerland). Lesion-to-lesion interaction was investigated by varying the lesion distance (5 to 2.5 mm), generator power (300, 280, and 260 W), cooling time (10, 20, and 30 seconds), and exposure time (4, 3, and 2 seconds). The lesion rows were analyzed grossly and by histologic examination (hematoxylin-eosin and nicotinamide adenine dinucleotide staining). RESULTS: It was possible to achieve complete homogeneous ablation of a clinically relevant tissue volume but only by meticulous adjustment of the exposure parameters. Minimal changes in these parameters caused changes in lesion formation with holes within the lesions and lesion-to-lesion interaction. CONCLUSIONS: Our preliminary results show that when using this new device, HIFU can ablate a large tissue volume homogeneously in perfused ex-vivo porcine tissue under standardized conditions with meticulous adjustment of exposure parameters. Further investigations in vivo are necessary to test whether large tissue volumes can be ablated completely and reliably despite the influence of physiologic tissue and organ movement.

Animals↗
PubMed2006

Extracorporeally induced ablation of renal tissue by high-intensity focused ultrasound.

OBJECTIVE: To investigate the safety and the effects on healthy renal tissue of high-intensity focused ultrasound (HIFU) applied extracorporeally. PATIENTS, MATERIALS AND METHODS: Ultrasound waves (1.04 MHz) created by a cylindrical piezo-ceramic element were focused by a parabolic reflector to a physical focus size of 32 x 4 mm (-6 dB). For an in vivo study, HIFU was applied to the healthy tissue of 24 kidneys, monitored by ultrasonography, with a maximum power of 400 W and a spatially averaged intensity (ISAL) in the focus of 1192 W/cm(2). Fourteen kidneys were removed immediately after ablation to evaluate the side-effects and the effects in the focal zone, and 10 kidneys were removed delayed after 1, 7 and 10 days. The clinical study consisted of 19 patients requiring radical nephrectomy for a renal tumour. HIFU was applied to the healthy tissue of 19 kidneys (up to 1600 W, I(SAL) = 4768 W/cm(2)) before proceeding with the radical nephrectomy. RESULTS: There were no major complications after applying HIFU to the 43 kidneys. Side-effects included skin burns (grade 3) in two patients. During the follow-up there were no further HIFU-specific side-effects. In one case (in vivo study) there was a thermal lesion of the small intestine, which was due to mis-focusing. HIFU effects in the focal zone immediately after application were: interstitial haemorrhages, fibre rupture, shrinking of the collagen fibres, and coagulation necrosis. These effects occurred sporadically, and their number and size did not correspond to the number of HIFU pulses applied. After 7 and 10 days, there was a well-demarcated coagulation necrosis in vivo. CONCLUSION: Using this device, extracorporeally applied HIFU can ablate healthy kidney tissue in vivo in combination with diagnostic online ultrasonography. The technique is safe and resulted only in minor complications (skin burns). Refinements in the technology are essential to establish HIFU as a noninvasive treatment option that allows complete and reliable tissue ablation.

Animals↗
PubMed2006

Technical characterization of a new bipolar and multipolar radiofrequency device for minimally invasive treatment of renal tumours.

OBJECTIVE: To investigate the technical characteristics of a newly developed device for bipolar and multipolar radiofrequency ablation (RFA) of kidney tissue with a resistance-controlled power output. MATERIALS AND METHODS: The standardized model of the isolated perfused ex vivo porcine kidney was used. Two different applicators (20 and 30 mm active length) were selected for bipolar RFA, and one pair of applicators (2 x 30 mm active length) for multipolar RFA. RF energy was applied at different power levels (20, 30, 60 W) depending on the total active length of the electrodes. Treatment times were 1, 3, 5 and 9 min. The ablation cycles were recorded in continuous digital real-time and displayed on a monitor showing pre-set power, actual applied power, applied energy, tissue resistance, and impedance. Lesion sizes were measured macroscopically. A coagulation coefficient (coagulated tissue volume per applied energy unit) was calculated. RESULTS: There was a dosage-effect relationship between the generator power/treatment time and the sizes of the lesions. With increasing treatment time, less tissue volume was coagulated per unit of applied energy. The actual applied energy was lower than that calculated theoretically. The resistance and impedance values for the 30-W applicator were lower than those of the 20-W applicator. CONCLUSIONS: The technical features of this RFA device, with internally cooled bipolar and multipolar applicators and a resistance-controlled power output, represents an innovative improvement in RF technology. In vivo studies are needed to confirm the expected advantages and the suitability of this device for complete and reliable ablation of renal tumours.

Animals↗
PubMed2006

The role of the lymphatic system and its specific growth factor, vascular endothelial growth factor C, for lymphogenic metastasis in prostate cancer.

OBJECTIVE: To compare prostate carcinoma, with and with no lymph node metastasis, to benign prostatic hyperplasia (BPH) tissue for lymphatic vessel density (LVD) and the expression of the lymph-endothelial specific growth factor, vascular endothelial growth factor C (VEGF-C), to determine their role in lymphogenic metastasis. PATIENTS, MATERIALS AND METHODS: Lymphatic vessels were stained using lymphatic vessel endothelial hyaluronan receptor 1 and assessed in standard areas. The expression of VEGF-C was assessed by the number of positive epithelial cells. The data were compared with the clinical staging. RESULTS: The lowest LVD was found in tumorous areas as opposed to periphery and nontumorous tissue (P = 0.007; P < 0.001). The highest LVD was in BPH tissue (P < 0.001). There was no correlation with clinical staging. There was more VEGF-C staining in pN1 than in pN0 and in BPH specimens (P = 0.002). CONCLUSION: LVD is not a prognostic variable for the process of lymphogenic metastasis in prostate cancer. VEGF-C is up-regulated in prostate cancer and its correlation with lymph node status suggests a role for the development of lymph node metastasis, e.g. via an increased permeability of lymphatic vessels.

Aged↗
PubMed2006

Intravenous contrast media in uroradiology: evaluation of safety and tolerability in almost 50,000 patients.

OBJECTIVE: To evaluate the frequency of adverse events and possible risk factors after the administration of an intravenous contrast medium (CM), iobitridol, in a large multicentre postmarketing surveillance study. SUBJECTS AND METHODS: A total of 49,975 patients undergoing intravenous urography were included in this study. A water-soluble, non-ionic CM (iobitridol, 1 ml/kg body weight) was administered. Age, sex, indication for the actual examination and adverse events were documented. Also, high-risk patients were identified. RESULTS: Of the 49,975 patients, 28,336 (56.7%) were males and 21,639 (43.3%) females. Indications for urography were mainly urolithiasis (39.1%), inflammatory diseases (25.6%) and tumours (13.9%). Additionally, 7.4% were risk patients: 1.9% with creatinine >1.5 mg/dl (0.1% were on haemodialysis); 0.8% had a history of previous allergic reactions to CM, 3.7% pre-existing asthma or allergies and 2% other risk factors against CM examination. Only 0.9% of the patients experienced acute adverse events that were non-serious and transient. Less than 0.1% of the patients experienced vomiting, dizziness or cardiovascular problems. Only 1 patient developed an anaphylactic shock but recovered fully under treatment. A chi(2) analysis revealed that adverse reactions occurred in patients with pre-existing renal insufficiency or allergies. Significantly more females had contrast-agent-related symptoms compared to men. Patients undergoing urography for urolithiasis had significantly fewer symptoms compared to patients with other indications. CONCLUSION: Iobitridol is clinically safe and well tolerated in urography as demonstrated in this study of a large patient population, producing mainly minor symptoms as adverse events. However, caution is advised when administering iobitridol to high-risk patients.

Acute Disease↗
PubMed2006

Intravesical mitomycin C for superficial transitional cell carcinoma.

Intravesical instillation of mitomycin C after a transurethral resection of a bladder tumor constitutes a standard treatment modality in the management of superficial transitional cell carcinoma in the urinary bladder. An immediate instillation of mitomycin C after transurethral resection has been shown to reduce the recurrence rate of superficial transitional cell carcinoma. Intravesical mitomycin C is generally considered to be a safe treatment option, but the past few years have seen the publication of a number of case reports on severe complications following mitomycin C instillation. This article reports on the mode of action, as well as the intravesical effects and current indications for mitomycin C instillation. This review will summarize the oncological benefits of mitomycin C in comparison with other intravesical treatments, such as bacillus Calmette-Guérin, and elucidate the incidence and types of possible complications associated with intravesical mitomycin C chemotherapy.

Administration, Intravesical↗
PubMed2005

IGF-II serum levels increase discrimination between benign prostatic hyperplasia and prostate cancer and improve the predictive value of PSA in clinical staging.

PURPOSE: IGF-I serum levels have been demonstrated as being associated with prostate cancer (PCa) and can serve as a predictive factor for the risk of PCa development. However, the role of IGF-II in PCa and its importance as a predictive marker is still unclear. Our aim was to determine PSA and IGF-II serum levels in patients with PCa and benign prostatic hyperplasia (BPH) and to analyse the value of IGF-II as an additional predictive factor in the diagnostics of PCa. METHODS: 112 patients who underwent surgery for BPH or PCa (no hormonal treatment, no further malignancies) were included in this study ((I) 38 PCa, PSA < or = 15 ng/ml; (II) 34 PCa, PSA > 15 ng/ml; (III) 40 BPH). Preoperative serum levels of total PSA and total IGF-II were determined by ELFA and ELISA, respectively. RESULTS: PSA levels were (I) 5.7+/-1.9 ng/ml; (II) 25.0+/-11.5 ng/ml and (III) 4.0+/-2.8 ng/ml. (II) was statistically associated with a high grading (2b/3; p = 0.0182), a high Gleason sum score (7-10; p = 0.0049) and a non-organ confined tumor (T3/4; p = 0.0009) compared to (I), all Chi2 test. IGF-II levels were significantly higher in PCa (I+II) compared to BPH (833.8+/-238.9 ng/ml vs. 633.3+/-141.4 ng/ml, p < 0.0001, t-test). Both PSA and IGF-II were associated with tumor staging (p = 0.0097, p = 0.0308; t-test). No significant correlation was observed between PSA and IGF-II levels. Logistic regression analysis revealed that the combination of PSA and IGF-II improves the prediction of tumor staging in PCa (p = 0.0175 and p = 0.0459, Wald test). Additionally, the combination of PSA and IGF-II can significantly increase discrimination between BPH and PCa; each p < 0.0001, Wald test. CONCLUSIONS: This study provides evidence that IGF-II serum levels may serve as an additional parameter for (a) improved determination of tumor staging and (b) better discrimination between BPH and PCa.

Aged↗
PubMed2005

5-year-follow-up of patients with clinically insignificant residual fragments after extracorporeal shockwave lithotripsy.

OBJECTIVES: After SWL treatment, many patients have residual fragments in the kidney or ureter. Fragments </=4mm have high probability to pass spontaneously and are normally not further treated. The term clinically insignificant residual fragment (CIRF) has been established for these stones. However, this term is still controversial, as persisting fragments might be important risk factors for stone growth and recurrence. Aim of this study was to evaluate the impact of CIRF on stone recurrence. METHODS: We evaluated 173 patients (age 3-89 years) who have been treated by SWL and released with CIRF. Mean follow up was 4.9 years (4.5-5.3). 78% of the patients were recurrent stone formers with >2 stones episodes. These patients and their referring urologist received follow-up questionnaires which contained questions about stone clearance, late complications, auxillary measures and dietary or drug metaphylaxis. RESULTS: Most residual stone fragments were located within the lower calyx (17%) and the renal pyelon (14%). Stone analysis was available in 142 patients with CIRF and revealed calciumoxalate calculi in 93.6% of the cases. In 78.6%, CIRF cleared spontaneously within few weeks and did not recur within 5 years. However, residual stones led to stone recurrence and need of re-treatment in 21.4%. Renal pyelon (23%) and calices showed comparable growth of former CIRF (lower calices 26.5%, middle calices 27%, upper calices 26%). Only 48% of the patients with recurrent stone formation followed dietary metaphylaxis. However, a significant correlation between a general or specific metaphylaxis and stone growth of CIRF could not be demonstrated. CONCLUSIONS: Most of the CIRF after SWL pass spontaneously without any complications. But considering that one fifth of the patients developed new stones at the side of residual fragments, it is obvious that close follow-up is required. Although we could not demonstrate a relation between metaphylaxis and stone re-growth, it is conceivable that adequate metaphylaxis can reduce stone recurrences.

Adolescent↗
PubMed2005

Minimally invasive treatment of renal cell carcinoma: comparison of 4 different monopolar radiofrequency devices.

OBJECTIVES: Radiofrequency Ablation is an investigational treatment option for RCC. The aim of our study was to test the ablation algorithms of four different RF systems in a standardized ex vivo perfused porcine kidney model. MATERIALS AND METHODS: A multiline monopolar dry electrode (impedance-based system), a multiline monopolar dry electrode (temperature-based system), a single monopolar wet electrode (impedance-based system) and a single monopolar dry, internally-cooled electrode (impedance-based system) were selected. RF energy was applied at different treatment parameters (power with and without control, tissue temperature, saline enhancement) for 1, 3, 5 and 9 minutes in healthy perfused ex vivo porcine tissue. Each treatment parameter was repeated 5 times. Maximum vertical, long-axis and short-axis diameters of the macroscopic lesion were measured and lesion volumes/ shapes were calculated. RESULTS: Lesion volumes increased significantly with the pre-selected tissue temperature and saline enhancement. Saline enhancement created larger, but irregular shaped lesions. The impedance-based system created lesion volumes that were predictable by treatment time and generator power. Lesions were unpredictable when uncontrolled generator power was applied. The created lesion shape was dependent on the selected electrode configuration. CONCLUSIONS: The currently available monopolar RFA systems offer different specific technical features to control tissue ablation. Detailed knowledge of the specific characteristics of each RF system is necessary to provide a higher chance of successful clinical outcome by complete and reliable ablation.

Animals↗
PubMed2005

Multiple high-intensity focused ultrasound probes for kidney-tissue ablation.

BACKGROUND AND PURPOSE: To investigate kidney-tissue ablation by high-intensity focused ultrasound (HIFU) using multiple and single probes. MATERIALS AND METHODS: Ultrasound beams (1.75 MHz) produced by a piezoceramic element (focal distance 80 mm) were focused at the center of renal parenchyma. One of the three probes (mounted on a jig) could also be used for comparison with a single probe at comparable power ratings. Lesion dimensions were examined in perfused and unperfused ex vivo porcine kidneys at different power levels (40, 60, and 80 W) and treatment times (4, 6, and 8 seconds). RESULTS: At identical power levels, the lesions induced by multiple probes were larger than those induced by a single probe. Lesion size increased with increasing pulse duration and generator power. The sizes and shapes of the lesions were predictably repeatable in all samples. Lesions in perfused kidneys were smaller than those in unperfused kidneys. CONCLUSIONS: Ex vivo, kidney-tissue ablation by means of multiple HIFU probes offers significant advantages over single HIFU probes in respect of lesion size and formation. These advantages need to be confirmed by tests in vivo at higher energy levels.

Animals↗