Dr. Markus J. Bader Profile

Dr. Markus J. Bader

at Ludwig-Maximilians-Univ München

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Publications (5)

Proceedings Article | 9 March 2015 Paper

In-vivo laser induced urethral stricture animal model for investigating the potential of LDR-brachytherapy

Ronald Sroka, Katja Lellig, Markus Bader, Christian Stief, Patrick Weidlich, G. Wechsel, Walter Assmann, R. Becker, O. Fedorova, Wael Khoder

Proceedings Volume 9303, 93030X (2015) https://doi.org/10.1117/12.2077675

KEYWORDS: Animal model studies, Tissues, In vivo imaging, Inflammation, Modulation, X-rays, Laser energy, Tolerancing, Endoscopy, Collagen

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Purpose: Treatment of urethral strictures is a major challenge in urology. For investigation of different treatment methods an animal model was developed by reproducible induction of urethral strictures in rabbits to mimic the human clinical situation. By means of this model the potential of endoluminal LDR brachytherapy using β-irradiation as prophylaxis of recurrent urethral strictures investigated. Material and Methods: A circumferential urethral stricture was induced by energy deposition using laser light application (wavelength λ=1470 nm, 10 W, 10 s, applied energy 100 J) in the posterior urethra of anaesthetized New Zealand White male rabbits. The radial light emitting fiber was introduced by means of a children resectoscope (14F). The grade of urethral stricture was evaluated in 18 rabbits using videourethroscopy and urethrography at day 28 after stricture induction. An innovative catheter was developed based on a β-irradiation emitting foil containing 32P, which was wrapped around the application system. Two main groups (each n=18) were separated. The "internal urethrotomy group" received after 28days of stricture induction immediately after surgical urethrotomy of the stricture the radioactive catheter for one week in a randomized, controlled and blinded manner. There were 3 subgroups with 6 animals each receiving 0 Gy, 15 Gy and 30 Gy. In contrast animals from the “De Nuovo group” received directly after the stricture induction (day 0) the radioactive catheter also for the duration of one week divided into the same dose subgroups. In order to determine the radiation tolerance of the urethral mucosa, additional animals without any stricture induction received a radioactive catheter applying a total dose of 30 Gy (n=2) and 15 Gy (n=1). Cystourethrography and endoscopic examination of urethra were performed on all operation days for monitoring treatment progress. Based on these investigation a classification of the stricture size was performed and documented for correlation. At further 28 days after catheter removal the animals were euthanasized and the urethra tissue was harvested. Histological examination of tissue with assessment of radiation damage, fibrotic and inflammatory changes were performed. After deblinding histological finding were correlated with the applied dose. Results: All animals developed a stricture, while 15/18 (83,3%) showed a significant, high grade stricture with more than 90% lumen narrowing. Histopathological examination including evaluation of urethral inflammation, fibrosis and collagen content were investigated in additional 6 rabbits confirming the former findings. No rabbits died prematurely during the study. The experiments showed that the procedure of the application of radioactive catheter was safe without any problems in contamination and protection handling. The combination of internal urethrotomy and LDR-brachytherapy results in a stricture free rate of 66.7% in the 15-Gy group, compared with only 33.3% among animals from the 0- and 30-Gy groups. Furthermore histological classification of inflammation and fibrosis of 0 Gy and 15 Gy showed similar extent. Conclusion: This new method of laser induced urethral stricture was very efficient and showed a high reproducibility, thus being useful for studying stenosis treatments. The experiments showed that application of local β-irradiation by means of radioactive catheters modulated the stenosis development. This kind of LDR-brachytherapy shows potential for prophylaxis of urethral stricture. As this was an animal pilot experiment a clinical dose response study is needed.

Proceedings Article | 24 June 2013 Paper

OCT assisted identification of the grade of encrustation of urologic catheters

Ronald Sroka, Michaela Püls, Herbert Stepp, Katja Zilinberg, Markus Bader, Patrick Weidlich

Proceedings Volume 8803, 88030Q (2013) https://doi.org/10.1117/12.2032031

KEYWORDS: Optical coherence tomography, Crystals, Bacteria, Imaging systems, Urinary system, Polyurethane, Statistical analysis, Tumors, Endoscopy, Biomedical optics

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Introduction: Ureteric stenting is a commonly used endourologic procedure for temporary and long-term drainage of an obstructed upper urinary tract. The indication for ureteric stenting is obstruction due to intrinsic (intraureteral stones, strictures, or tumors) or extrinsic (for example compressing pelvic or retroperitoneal mass) causes. Despite the fact that stents do certainly have proven benefits in all fields of urology, there are potential morbidities. The most common problem of indwelling ureteral stents is infection. As foreign body in the urinary system, stents act as a nidus for bacteria colonization, crystallization and encrustation. Bacteria induced biofilm formation predisposes for the crystallization of lithogenic salts, such as calcium-phosphate, calcium-oxalate, magnesium-phosphate on the surface initiating stent encrustation. It was the objective of this study to evaluate whether optical coherence tomography (OCT) using both the surface and the endoluminal technique is feasible to investigate the locations and degree of encrustation process in clinically used ureteral stents. Patients and methods: After removal from patients, fourteen polyurethane JJ stents were investigated. A fresh JJ served as a control. The external surfaces were examined using an endoscopic surface OCT whereas the intraluminal surfaces were investigated by an endoluminal radial OCT device. The focus was on detection of encrustation or crystalline sedimentation. Results: In 12 female and 2 male patients, the median indwelling time of the ureteral catheter was 100 days (range 19- 217). Using the endoluminal OCT, the size and grade of intraluminal encrustation could be expressed as a percentage relating to the open lumen of the reference stent. The maximum encrustation observed resulted in a remaining unrestricted lumen of 15-35% compared to the reference. The luminal reduction caused by encrustation was significantly higher at the proximal end of the ureteral stent as compared to its distal part. The extraluminal OCT-investigations facilitated the characterization of extraluminal encrustation. Conclusion: OCT techniques were feasible and facilitated the detection of encrustation of double pigtail catheters on both the extra and intra luminal surface. Quantitative expression of the degree of intraluminal encrustation could be achieved, with the most dense and thickened occurrence of intraluminal incrustation in the upper curl of the JJ stent.

Proceedings Article | 8 March 2013 Paper

In vitro assessment of fragmentation and repulsion of handheld lithotripsie devices

Ronald Sroka, Thomas Pongratz, Giovanni Crameri, Nicolas Haseke, Markus Bader, Wael Khoder

Proceedings Volume 8565, 85651C (2013) https://doi.org/10.1117/12.2007494

KEYWORDS: In vitro testing, Instrument modeling, High speed photography, Francium, Lead, Mechanics, Carbon dioxide, Silicon, Distance measurement, Metals

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Introduction: Different laser-systems are currently used for stone fragmentation in the upper urinary tract. The aim of our study was to evaluate probe velocity and displacement, retropulsion and fragmentation characteristics two novel devices the electromechanically driven EMS LithoBreaker® (EMS Medical), and of the CO2 cartridge driven LMA StoneBreaker® (Cook Urological) in vitro test models.Testing of the LithoBreaker® included additionally two different cushion guides (harder, softer) to assess the effect of the damper properties on the impulse characteristics. Patients and methods: Maximum probe velocities and displacements were measured using high-speed photography at a resolution of 100.000 frames per second. Repulsion testing was conducted through a 7.5 Fr ureteroscope in an underwater set-up. The probes were projected against a non-frangible led mass placed in a 15 Fr horizontally mounted silicone tube as an in-vitro model of the ureter. Repulsion was determined by measuring the distance the lead mass (0.98g) was displaced. Fragmentation efficiency was assessed by measuring the number of single shots required to break Bego Stone phantoms hard (15:3) and soft (15:6) with an average size of 7.5 mm x 5.5 mm placed on a metal mesh (edge length 3.15mm) into < 3 mm fragments. Mean and standard deviation were computed for all groups and statistical analysis was performed (student’s t-test). Results: The StoneBreaker® yielded the highest velocity of 22.0 ± 1.9 m/sec. followed by the LithoBreaker® assembled with the hard cushion guide of 14.2 ± 0.5 m/sec and the soft probe guide of 11.5 ±0.5 m/sec. accordingly. The maximum probe displacement for the StoneBreaker® was 1.04 mm and for the LithoBreaker® 0.9 mm and 1.1 mm (hard versus soft cushion guide). Repulsion produced using the 1mm probes showed no statistical differences between the devices. Using the 2mm probes, the hardness of the damper used significantly changed the repulsion behaviour of the LithoBreaker®. Using the 1mm probe, the amount of single shots for fragmentation of soft Bego Stones was significantly higher for the LithoBreaker® with soft cushion guide: mean 31.5 ± 11.31 and hard cushion guide: mean 21.5 ± 5.29 compared to the StoneBreaker®: mean 11.2 ± 2.65. Fragmentation efficiency for the hard Bego Stones showed similar statistically significant results. Conclusion: The electromechanic LithoBreaker® and the pneumatic Stonebreaker® were shown to be effective in cracking stone phantoms with relatively low number of pulses. Fragmentation characteristics improved substantially with the higher hardness of the cushion support higher velocity equals higher fragmentation performance of the LithoBreaker®. Repulsion produced were at comparable levels. More testing is required to more detailed information on impulse frequency and capacity for stone clearance time to be used in clinical practice.

Proceedings Article | 13 July 2009 Paper

Photodynamic management of bladder cancer

A. Johansson, H. Stepp, W. Beyer, T. Pongratz, R. Sroka, M. Bader, M. Kriegmair, D. Zaak, R. Waidelich, A. Karl, A. Hofstetter, C. Stief, R. Baumgartner

Proceedings Volume 7380, 73801S (2009) https://doi.org/10.1117/12.828315

KEYWORDS: Bladder, Photodynamic therapy, Luminescence, Cystoscopy, Bladder cancer, Tissue optics, Light sources, Backscatter, Absorption, Light

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Proceedings Article | 23 February 2009 Paper

In vitro comparison of laser induced lithotripsy on artificial stones by means of different laser systems

R. Sroka, V. Hecht, O. Reich, M. Seitz, C. Stief, M. Bader

Proceedings Volume 7161, 71611T (2009) https://doi.org/10.1117/12.812216

KEYWORDS: Pulsed laser operation, Laser systems engineering, Laser ablation, Laser therapeutics, Fiber lasers, Dye lasers, Holmium, Laser damage threshold, Sputter deposition, Calculi

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