Long-term clinical outcome of transurethral microwave thermotherapy (TUMT) 1991-1999 at Karolinska Hospital, Sweden.

OBJECTIVE: Minimal invasive methods, such as transurethral microwave thermotherapy (TUMT), are economical and have modest side effects compared with transurethral electro-resection of the prostate (TUR-P). The treatment results from different TUMT-systems vary. Follow-up studies on each system type are therefore necessary. The objectives of this study are to summon the long-term clinical results of our TUMT-system and search for a pre-treatment parameter that can measure responding patients. MATERIAL AND METHODS: Three hundred and seventy-one patients with benign prostate hyperplasia (BPH) were treated with TUMT at Karolinska Hospital, Sweden with the ECP-system (Comair AB, Stockholm), for 30 or 60 min. They were followed up 12 to 72 months after TUMT. RESULTS: At follow up approximately 76% subjectively judged that they had benefited from the treatment and 22% judged that they were fully cured. The over-all IPSS and Quality of Life score decreased approximately 40% and 30% respectively. Forty-one per cent of the patients with CAD (cathéter à demeure) before the treatment became permanently or temporarily catheter-free after the treatment. Q(max) increased 21% and 11% after 1 and 6 months respectively. Q(max) ranging from over 10 ml/s seem to be a selection parameter that increases the number of responding patients. CONCLUSION: These long-term clinical data show that TUMT treatment with ECP (electro-coagulation, prostate), gives a good success-rate, with reduction of symptoms. Furthermore there is a good chance of becoming catheter-free after TUMT.

Miniaturised ultrasonic aspiration handpiece for increased applicability.

OBJECTIVE: At present, ultrasonic aspiration is routinely used in several fields of surgery, especially in brain and spinal micro-surgery for tumour removal. In order to broaden the access to difficult surgical sites, it is important to design highly miniaturised but still efficient handpieces. The internal resonant system, always made of high-grade materials, must be optimally dimensioned. Normally this is done semi-empirically, by successively improving the design during many iterative test steps. This method however involves several additional difficulties when the degree of miniaturisation increases. For example, small transducer weights exacerbate heat-dissipation problems and make design optimisation important. METHODS: To resolve these problems we have produced modelling software that makes it possible to simulate and automatically tune each individual interacting section of the design before it is actually manufactured, thereby assuring optimal efficiency. RESULTS: Using a new mini-handpiece, designed via the software, two cases of dissection of acoustic neurinomas were successfully performed. CONCLUSION: Using conventional physical steps for improving ultrasonic aspiration handpieces, several problems arise when the grade of miniaturisation increases, due to increasing demands. We have designed computer software for handpiece simulation. Using this model it has been possible to manufacture a highly efficient miniaturised handpiece.

The impact of the geometry of the lithotriptor aperture on fragmentation effect at extracorporeal shock wave lithotripsy treatment.

The aim of this study was to determine the impact of the aperture size of an electro-hydraulic lithotriptor on the fragmentation effect. We also wanted to investigate whether a potential change in the capacitance of the pulse forming network (PFN), at a certain energy level, might have an impact on fragmentation rate. Two different apertures with a diameter of 23 and 17 cm respectively were compared using two different values of total PFN capacitance: 50 nF and 80 nF. Model stones of similar size and weight were fragmented. The number of shots for complete fragmentation or the grade of fragmentation after a certain number of shots was measured. This study shows that for the shock wave system used, the 23-cm aperture seems to provide more effective fragmentation as function of the number of shots compared with the 17-cm aperture at the same energy level. Furthermore, a minor change in the PFN capacitance between reasonable limits does not affect the fragmentation efficiency. This article also highlights the fact that it is not relevant simply to compare the voltage level given in the shots in extracorporeal shock wave lithotripsy treatment between different lithotriptors.

Effect of externally applied focused acoustic energy on clot disruption in vitro.

Application of low-frequency ultrasound for clot disruption has been suggested as a potential therapy to enhance thrombus dissolution, but the optimal mode for delivery of ultrasound with clot-disruptive properties has not yet been extensively explored. Target-specific effects are desirable and may be accomplished by focusing the ultrasound. Adequate focusing, however, requires a short wavelength. The aim of this study was to compare the clot-disruptive effects of different modalities of focused acoustic energy. An in vitro model (10 blood clots for each modality) was used to test the clot-disruptive capacity of (i) shock waves generated in an electrohydraulic lithotriptor; (ii) focused continuous ultrasound of frequency 1.1 MHz, delivered from a specially constructed piezoelectric transducer; and (iii) focused pulse-modulated ultrasound of frequency 1.1 MHz delivered from the same transducer. Exposure to 30 s of focused pulse-modulated ultrasound caused a marked reduction (99+/-2%) in clot weight compared with 30 shock waves (11+/-5%) or 30 s exposure to focused continuous wave ultrasound (11+/-6%) (P<0.0001). The observed marked and rapid disruptive effect on blood clots of focused high-frequency ultrasound indicates an alternative approach for external ultrasound-mediated thrombus destruction in vivo. The focused pulse-modulated technique has potential to exhibit the desired effect in a well-defined target volume and provides the means for control of the average power.