[Navigation in urological surgery: Possibilities and limits of current techniques]. / Navigierte urologische Chirurgie : Möglichkeiten und Grenzen aktueller Technik.

Surgical navigation describes the concept of real-time processing and presentation of preoperative and intraoperative data from different sources to intraoperatively provide surgeons with additional cognitive support. Imaging methods such as 3D ultrasound, magnetic resonance imaging (MRI) and computed tomography (CT) and data from optical, electromagnetic or mechanical tracking methods are used. The resulting information of the navigation system will be presented by the means of visual methods. Mostly virtual reality or augmented reality visualization is used. There are different guidance systems for various disciplines introduced. Mostly it operates on rigid structures (bone, brain). For soft tissue navigation motion compensation and deformation detection are necessary. Therefore, marker-based tracking methods are used in several urological application examples; however, the systems are often still under development and have not yet arrived in the clinical routine.

Accuracy in detecting and measuring residual fragments with the Uro Dyna-CT.

BACKGROUND AND PURPOSE: Residual calculi after stone therapy need to be treated if they are clinically significant, mainly depending on the size of the calculi. There are different ways to detect and measure the size of residual calculi as for example KUB or computed tomography. The Uro Dyna-CT (Siemens Healthcare solutions, Erlangen, Germany) allows cross-sectional imaging and 3D reconstructions during endourological interventions. In this ex vivo study, we investigate the accuracy of imaging residual calculi with the Uro Dyna-CT. MATERIALS AND METHODS: Twenty-seven artificial stones (plaster of Paris) were scanned with the Uro Dyna-CT by a special urolithiasis protocol and post-image processing with 3D-reconstruction and cross-sectional imaging was performed. The major diameter of each stone was measured at the dedicated workstation by one investigator. The same stones were measured randomized with a digital caliper (real size). Finally, the two measurements were compared. The paired t test, Pearson's correlation coefficient, the F Test, a reference area for differences, the intraclass correlation coefficient, the Maloney-Rastogi test and the Bland-Altman analysis were used for statistical analyses. RESULTS: The range of stone sizes was 3-5 mm. We did not find significant differences in the size of the stones measured with the Uro Dyna-CT and the digital caliper (paired t test p = 0.3597) and we showed a good correlation between the two measuring methods (intraclass correlation coefficient 0.4465; p = 0.0088). CONCLUSION: Renal calculi can be measured highly accurately with the Uro Dyna-CT. Whether this technique will lead to less residual fragments after stone treatment needs to be shown in further studies.

[Complications in percutaneous lithotomy]. / Komplikationen bei der perkutanen Steinbehandlung.

BACKGROUND: Percutaneous lithotomy is the gold standard in the treatment of large kidney stones. Several steps of the operation might cause severe complications. Safe procedures depend on careful planning, accurate performance, recognition of problems and knowledge of how to handle them. OBJECTIVES: Relevant steps of percutaneous stone treatment with possible complications and their management are presented. MATERIALS AND METHODS: Current topics in percutaneous stone treatment taking into consideration the relevant literature are discussed. Furthermore, rare complications and strategies for safe management are presented. RESULTS: Careful planning and adequate preoperative diagnostic workup are essential for safe procedures. Puncture of the renal calyceal system and tract dilation might lead to severe complications. Bleeding and infectious complications are the most common problems. Availability of interventional radiology provides ideal emergency treatment in case of severe bleeding and helps to avoid surgical revision with high risk of organ loss. CONCLUSIONS: Percutaneous stone treatment is a safe and effective therapy in an experienced physician's hands. Careful planning and accurate performance help to avoid severe complications.

New developed urological protocols for the Uro Dyna-CT reduce radiation exposure of endourological patients below the levels of the low dose standard CT scans.

PURPOSE: Cross-sectional imaging by computed tomography (CT) is associated with higher radiation dose compared to plain X-ray. The Uro Dyna-CT provides CT-like images in the endourological operating room. Our aim was to reduce the radiation exposure of endourological patients with the Uro Dyna-CT and optimize the cross-sectional image quality. MATERIALS AND METHODS: For the hard contrast protocol, two artificial stones were placed in a Rando-Alderson phantom's left kidney region. Relevant parameters of the standard abdomen protocol were changed. After each modification, two urologists subjectively evaluated the image quality. We developed two customized protocols (standard, low-dose) for hard contrast imaging. To optimize the examination protocol for soft tissue imaging a standardized cone beam phantom was used. Parameters of the preset high-resolution protocol were changed to develop a protocol with similar objective image quality but lower radiation dose. To evaluate the effective radiation dose we embedded 129 thermoluminescence dosimeters in the kidney and ureter region of the Rando-Alderson phantom and performed each protocol five times (stone, soft tissue) and ten times (low-dose protocol). Mean effective dose values per 3D-examination were calculated. RESULTS: We detected a dose area product (DAP) 776.2 (standard) and 163.5 µGym(2) (low-dose) for the stone protocols with an effective dose of 1.96 and 0.33 mSv, respectively. The soft tissue protocol produced a DAP of 5,070 µGym(2) and an effective dose of 7.76 mSv. CONCLUSION: Our newly developed examination protocols for the Uro Dyna-CT provide CT-like image quality during urological interventions with low radiation dose.

Laser-guided percutaneous kidney access with the Uro Dyna-CT: first experience of three-dimensional puncture planning with an ex vivo model.

BACKGROUND AND PURPOSE: Safe and successful puncture of the kidney's collecting system is essential for acute therapy of hydronephrosis or as part of percutaneous nephrolithotomy. The procedure is technically challenging and might lead to major complications. We describe the feasibility of a laser guidance system and three-dimensional puncture planning in the endourological operation room. MATERIALS AND METHODS: An Uro Dyna-CT of the biological model was performed with the Artis Zee(®) Ceiling (Siemens Medical Solutions, Erlangen, Germany) to gain multiplanar reconstructions. 10 punctures were performed with the syngo iGuide(®) laser guidance system. Puncture success was depicted with antegrade contrast filling of the collecting system and fluoroscopic control. Puncture time, tract length, and fluoroscopy time was documented. RESULTS: Data acquisition (8 s) and 3D rendering (48 s) was possible in approximately 1 min. Median time for planning the punctures was 7 [5-15] min. Median puncture time was 4.6 [2-10.2] min. Median tract length was 4.96 [4.33-6.5] cm. Median fluoroscopy time was 0.4 [0.2-1] min. 9 of 10 punctures were successful. A second puncture was needed to gain access to the collecting system in one case, and one puncture was broken up. CONCLUSION: The tested laser guidance system was feasible to perform successful percutaneous punctures of the kidney in this ex vivo study. Handling was intuitive and time within acceptable limits. Due to the requirement of multiplanar reconstructions with higher radiation exposure to the patient than with standard fluoroscopy, this technique should be limited to complex cases.

Influence of endourological devices on 3D reconstruction image quality using the Uro Dyna-CT.

PURPOSE: The urological Dyna-CT (Uro Dyna-CT) was established in clinical use for classical imaging as well as for interventional surgery. To evaluate whether irradiation artefacts may occur during interventional surgery, we analysed the impact of different instruments on 3D reconstruction in the Uro Dyna-CT. MATERIALS AND METHODS: Ten different endourological instruments [ureterorenoscope (URS)-fibrescope, percutaneous nephrolithotomy (PCNL) working sheath] and accessory equipments such as ureteral catheter, guide wires and stents (DJ, MJ) were introduced in a porcine renal pelvis either retrograde via the ureter or transparenchymally. Subsequently, digital fluoroscopy, standard X-ray and an Uro Dyna-CT were performed. Three colleagues evaluated the image quality independent from each other. RESULTS: There were basically no limitations regarding image quality in digital fluoroscopy and standard X-ray. In the Uro Dyna-CT, only with the URS fiberscope and the PCNL working sheath, small artefacts and irradiations were detected, whereas ureteric catheter with and without wire, as well as the hydrophilic guide wire, showed no artefacts at all. The remaining material demonstrated minimal artefacts, which did not affect the image quality. CONCLUSIONS: The Uro Dyna-CT can be used for all interventional endourological procedures using the common armamentarium and instruments without significant limitation of image quality. There are only minor limitations according a PCNL working sheath and the rigid URS. These instruments should be removed out of the examination field before performing the computed tomography and be replaced afterwards by using a safety wire.

Optimizing imaging quality in endourology with the Uro Dyna-CT: contrast agent dilution matters.

BACKGROUND AND PURPOSE: The implementation of the Uro Dyna-CT (Siemens Healthcare Solutions, Erlangen, Germany) with interventional 3D- and cross-sectional imaging necessitates the development of new standards for endourologic procedures such as the customized use of diluted contrast agent. Our aim was to find the ideal contrast agent dilution (CAD) for the interventional use of the Uro Dyna-CT in a standardized setting and prove the experimental findings in a clinical case. MATERIALS AND METHODS: Retrograde pyelographies were performed with 10 different CADs of Imeron 300 (Bracco, Konstanz, Germany) in 10 different pig's urinary tracts. Fluoroscopy, X-ray, 3D- and slice-image reconstruction was performed with the Uro Dyna-CT. Image quality was evaluated, blinded and randomized by 5 observers. Small plastic jars were filled with the CADs and 2 artificial stones (Plaster of paris). Images were evaluated by two observers. The ex vivo findings were transferred to a clinical setting in a complex percutaneous lithotomy procedure. Unweighted and weighted kappa coefficients were calculated to indicate the degree of observers' agreement. RESULTS: Twenty percent diluted contrast agent provides the best image quality and stone detection when interventional cross-sectional imaging is considered without limitations in fluoroscopy or X-ray quality. This was proved in a percutaneous lithotomy of an obese patient. CONCLUSIONS: Image quality of the Uro Dyna-CT can be optimized by the use of 20 % diluted contrast agent. This knowledge helps to provide high-quality 3D imaging in the endourological operation room.

[New puncture techniques in urology using 3D-assisted imaging]. / Neue Punktionstechniken in der Urologie mittels 3D-gestützter Bildgebung.

The selective use of various puncture techniques for diagnostic or therapeutic purposes is a component of the daily routine of urologists. The aim of these interventions is always a safe and rapid puncture at the appropriate target point. Nowadays, imaging systems are increasingly being used in urology with the aim to achieve a more precise and safer planning and execution of punctures through an increased accuracy by the use of 3D representation. An approach to the solution to achieve this aim is the fusion of 3D reconstruction by magnetic resonance imaging (MRI) or computed tomography< (CT) with real-time imaging procedures, such as sonography or fluoroscopy.