Jens Fehre

A comparison of light spot hydrophone and fiber optic probe hydrophone for lithotripter field characterization

The performance of a newly developed light spot hydrophone (LSHD) in lithotripter field characterization was compared to that of the fiber optic probe hydrophone (FOPH). Pressure waveforms produced by a stable electromagnetic shock wave source were measured by the LSHD and FOPH under identical experimental conditions. In the low energy regime, focus and field acoustic parameters matched well between the two hydrophones. At clinically relevant high energy settings for shock wave lithotripsy, the measured leading compressive pressure waveforms matched closely with each other. However, the LSHD recorded slightly larger |P_| (p < 0.05) and secondary peak compressive pressures (p < 0.01) than the FOPH, leading to about 20% increase in total acoustic pulse energy calculated in a 6 mm radius around the focus (p = 0.06). Tensile pulse durations deviated ~5% (p < 0.01) due to tensile wave shortening from cavitation activity using the LSHD. Intermittent compression spikes and laser light reflection artifacts have been correlated to bubble activity based on simultaneous high-speed imaging analysis. Altogether, both hydrophones are adequate for lithotripter field characterization as specified by the international standard IEC 61846.

Comparison of Light Spot Hydrophone (LSHD) and Fiber Optic Probe Hydrophone (FOPH) for Lithotripter Field Characterization

Characterization of the acoustic field of a shock wave lithotripter is important for determining the performance of the device. In this study, we compare the performance of a newly developed Light Spot Hydrophone (LSHD) with the current standard, i.e., the Fiber Optic Probe Hydrophone (FOPH). An electromagnetic (EM) shock wave lithotripter was selected and each hydrophone was used to map the acoustic field of the lithotripter. The peak positive pressure P+, peak negative pressure P−, pulse duration, and effective acoustic energy were calculated using the collected data. Both the LSHD and the FOPH have similar measurement characteristics. They both provide excellent P+ measurement accuracy and response. Although the LSHD was found to provide more repeatable P− pressure measurements, both devices provide excellent pressure measurement of lithotripter shock fields.

Detection of cancer cells in prostate tissue with time-resolved fluorescence spectroscopy

Goals: Improving cancer diagnosis is one of the important challenges at this time. The precise differentiation between benign and malignant tissue is in the oncology and oncologic surgery of the utmost significance. A new diagnostic system, that facilitates the decision which tissue has to be removed, would be appreciated. In previous studies many attempts were made to use tissue fluorescence for cancer recognition. However, no clear correlation was found between tissue type and fluorescence parameters like time and wavelength dependent fluorescence intensity I(t, λ). The present study is focused on cooperative behaviour of cells in benign or malignant prostates tissue reflecting differences in their metabolism. Material and Methods: 50 prostate specimens were obtained directly after radical prostatectomy and from each specimen 6 punch biopsies were taken. Time-resolved fluorescence spectra were recorded for 4 different measurement points for each biopsy. The pathologist evaluated each measurement point separately. An algorithm was developed to determine a relevant parameter of the time dependent fluorescence data (fractal dimension DF ). The results of the finding and the DF -value were correlated for each point and then analysed with statistical methods. Results: A total of 1200 measurements points were analysed. The optimal algorithm and conditions for discrimination between malignant and non-malignant tissue areas were found. The correct classification could be stated in 93.4% of analysed points. The ROC-curve (AUC = 0.94) confirms the chosen statistical method as well as it informs about the specificity (0.94) and sensitivity (0.90). Conclusion: The new method seems to offer a very helpful diagnostic tool for pathologists as well as for surgery.

In Vitro Comparison between HM‐3 and MODULARIS Lithotripters

Shockwave lithotripsy (SWL) is currently the preferred method of treatment for renal calculi < 10 mm in size. Dornier introduced the electrohydraulic HM‐3 in 1983, which has become the “gold standard” for SWL. Since then other types of lithotripters (electromagnetic and piezoelectric) have been developed. We compared the third‐generation electromagnetic shockwave lithotripter Siemens MODULARIS to the HM‐3 in vitro assessing acoustic measurement and stone comminution in a holder. Similar results were encountered.