[Control parameters for high-intensity focused ultrasound (HIFU) for tissue ablation in the ex-vivo kidney]. / Steuerparameter des hochenergetischen fokussierten Ultraschalls (HIFU) zur Gewebeablation an der Ex-vivo-Niere.

PURPOSE: Therapeutic application of contactless thermoablation by high-intensity focused ultrasound (HIFU) demands precise physical definition of focal size and determination of control parameters. Our objective was to define the focal expansion of a new ultrasound generator and to evaluate the extent of tissue ablation under variable generator parameters in an ex vivo model. MATERIALS AND METHODS: Axial and transversal distribution of ultrasound intensity in the area of the focal point was calculated by needle hydrophone. The extent of tissue necrosis after focused ultrasound was assessed in an ex vivo porcine kidney model applying generator power up to 400 Watt and pulse duration up to 8 s. RESULTS: The measurement of field distribution revealed a physical focal size of 32 x 4 mm. Sharp demarcation between coagulation necrosis and intact tissue was observed in our tissue model. Lesion size was kept under control by variation of both generator power and impulse duration. At a constant impulse duration of 2 s, generator power of 100 W remained below the threshold doses for induction of a reproducible lesion. An increase in power up to 200 W and 400 W, respectively, induced lesions with diameters up to 11.2 x 3 mm. Constant total energy (generator power x impulse duration) led to a larger lesion size under higher generator power. CONCLUSION: It is possible to induce sharply demarcated, reproducible thermonecrosis, which can be regulated by generator power and impulse duration, by means of a cylindrical piezo element with a paraboloid reflector at a focal distance of 10 cm. The variation of generator power was an especially suitable control parameter for the inducement of a defined lesion size.

[Extracorporeal shockwave lithotripsy in cholecystolithiasis using a new type of minilithotripter]. / Extrakorporale Stosswellenlithotripsie bei Cholezystolithiasis mittels eines neuartigen Mini-Lithotripters.

BACKGROUND AND OBJECTIVE: Extracorporeal shock wave lithotripsy (ESWL) of gallstones has until now required fixed, nearly room-sized and expensive equipment. It has become even less cost-effective with an increase in the number of laparoscopic cholecystectomies. The authors have technically modified a mini-lithotripter, used for dissolving salivary stones, for application against gallstones (by changing the energy spectrum and depth of focus). PATIENTS AND METHODS: 125 consecutive patients with solitary gallstone underwent lithotripsy according to a standard protocol (including oral litholysis), 64 of them (average age 42.5 +/- 9.3 years; 44 women, 20 men) by conventional ESWL (with the Modulith), 62 (average age 41.6 +/- 10.1 years; 43 women, 13 men) with a modified mini-lithotripter (Minilith). Clinical and sonographic follow-up took place at 1, 3, 6 and 12 months. Quality of life was documented according to a point score (GIQL), developed specially for patients with gastrointestinal conditions. RESULTS: The mini-lithotripter applied significantly lower voltage and more shock-wave impulses per treatment than the conventional ESWL (p < 0.01), while patient tolerance, measured with a visual analogue scale, was the same. Application of the mini-lithotripter was easier and quicker than with conventional ESWL, namely 31 +/- 8 min vs 41 +/- 12 min (p < 0.01). Frequency of adequate stone fragmentation per patient was the same for both methods, 2.2 +/- 0.5 applications with the mini-lithotripter vs 1.6 +/- 0.3 with conventional ESWL (p < 0.01). There was no significant difference between the methods with regard to improved quality of life (increase of GIQL scale of 16% with the conventional ESWL, 14% with the mini-lithotripter) or freedom from stone at 1 year after lithotripsy (conventional ESWL: 80%, mini-lithotripter: 82%). Colics recurred in 15 of 64 patients receiving conventional ESWL, and in 13 of 61 in the mini-lithotripter group (difference not significant). There were no other complications. CONCLUSION: The cheaper mini-lithotripter, costing only a third of the conventional ESWL, is equally effective in the dissolution of gallstones.

Shock waves (SW) noninvasive extracorporeal thrombolysis treatment (NISWT).

A group of 24 patients were considered for noninvasive shock waves thrombolysis (NISWT). Of these, 15 patients gave their informed consent. NISWT was attempted in eight patients (while seven patients were randomized for follow-up only). NISWT was possible in six of seven patients. In one patient randomized for NISWT, local inguinal scarring, due to previous surgery, made impossible the visualization of the femoral vein, and therefore focusing of shock waves (SWs). No side effects were reported in the days after SWs administration during the 4-month follow-up. In patients treated with NISWT it was possible to observe just after the SWs session the presence of echolucent "acoustic holes" and flow (by color and power Doppler) within the "holes." All "echolucent holes" produced at the first session were still present at 4 months, and color flow imaging also detected new flow channels in echogenic areas of thrombi previously not visible. In one patient thrombolysis was achieved after the first treatment, but at 3 and 4 months the thrombus was completely avascular. In conclusion, thrombolysis using SWs was obtained in selected cases and it was still persisting at 4 months in six of the seven treated patients. NISWT appears feasible and promising. These results should be confirmed by larger, prospective trials.

Shock waves in vascular diseases: an in-vitro study.

UNLABELLED: Three human aortic specimens were used for this in-vitro study on the effects of shock waves on the arterial wall. Specimen one was from a normal (for age) healthy aorta. The full abdominal length was used (including mesenteric and renal arteries and the aortoiliac bifurcation), divided into six pieces (3 cm). The pieces were placed and fixed into degassed water. Shock waves (SW) were focused onto the aortic wall by means of a B-mode ultrasound imager. An SW generator (Minilith SL1, Storz Medical AG, Kreuzlingen, Switzerland) was used for setting of energy flux density between 0.03 and 0.5 mJ/mm2. The six aortic pieces (excluding piece 1, placed in water and left untreated as control) were treated with SW at increasing energy levels. A second aortic specimen of a man with arteriosclerotic plaques was also used and the experiment repeated at energy levels 1, 5, and 8. Another specimen of normal thoracic aorta was exposed at energy levels 1 and 8 only. Energy levels delivered onto the aortic walls were selected from theoretically destructive levels to minimal levels known not to alter vascular tissues. High-resolution ultrasounds of the aortic segments were performed with a 10 MHz high-resolution, broad-band (ATL 3000, USA) probe in water before and after SW application to detect structural changes in the wall after SW. Histology was performed with a standard hematoxylin-eosin staining. RESULTS: The aortic pieces did not show macroscopic damages at visual examination, and at the ultrasound examination no visible changes were observed even at higher levels of SW energy. Also no effects were seen by histology. In conclusion, no damaging effects were observed, visually, by ultrasound, or by histology. At these energy levels SW appear to be safe and do not produce any damage to the aortic wall. Therefore, SW could be considered a safe, nondamaging procedure for potential treatment (ie, thrombolysis) in which vessel walls could be involved. Theoretically it is possible that functional changes could be observed in vivo including cell permeability modifications and other alterations (including changes in the potential of the cells in SW fields to modify themselves and to divide). At the energy levels described in this study SW could, theoretically be, safely used for vascular applications (ie, treating venous and arterial thrombi or in arterial plaques modification) without altering major, structural, arterial wall characteristics. Lesions or alterations that have a different density from the normal wall (thrombi or plaques) could be differently sensitive to the same dosage of SW. These differences in acoustic impedance characteristics could be used for potential treatments with SW without damaging the arterial wall.

Shock wave treatment of salivary duct stones: substantial progress with a minilithotripter.

Extracorporeal shock wave lithotripsy has recently been introduced as the first non-operative treatment alternative for patients with sialolithiasis. Using conventional multipurpose lithotripters, however, successful treatment was achieved in only 36%-53% of patients. Therefore we developed an miniaturized lithotripter meeting the special requirements for extracorporeal shock wave treatment in the head and neck region. During a 1-year prospective trial clinical efficacy and safety were compared in 40 patients treated with a conventional electromagnetic lithotripter (group A) to 33 patients treated with the newly developed, miniaturized device (group B). The groups did not differ statistically regarding stone size or number or the proportion of stones located in the submandibular or parotid gland. Successful stone targeting, a prerequisite for shock wave treatment, was achieved by means of in-line ultrasonography in 30 of the 40 patients in group A and in 29 of 33 patients of group B. The number of shock wave impulses administered per session and the maximum shock wave intensities did not differ in the two groups. Significantly more frequent treatments with a longer mean duration of each session were required in group A (2.4 +/- 1.0 treatments, 47 +/- 11 min) than in group B (1.9 +/- 0.7 treatments, 28 +/- 9 min; P < 0.05). After a 3 month follow-up significantly more patients were free of stones in group B (22/33) than in group A (16/40; P < 0.05). Correspondingly, the number of patients free of complaints was significantly higher in group B (27/33) than in group A (22/40; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A new pressure wave generator for extracorporeal lithotripsy.

A new pressure wave generator has been designed for the Storz Modulith extracorporeal lithotripter. It consists of an electromagnetic cylindrical pressure wave source and a focusing parabolic reflector. Focus size has been designed using electro-acoustic puls forming network (EA-PFN) techniques. Schlieren photographs of the pressure wave are shown. Pressure in the focus is given as a function of PFN charging voltage.