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At least 667 records · Page 37Linked to original sources
PubMed1998

Catheter-tracking FOV MR fluoroscopy.

Recent improvements in intravascular magnetic resonance imaging techniques mandate an accurate method of monitoring the introduction of MR catheter probes into the vessel of interest. For this purpose, a novel imaging protocol and a display method have been designed. First, a roadmap 3D image data set with standard pulse sequences is obtained using an external imaging coil. Subsequently, using very narrow rectangular-FOV fast-spoiled gradient recalled (SPGR), a movie of the percutaneous placement procedure of an MR catheter probe is acquired at a rate of 7.3 frames/second. In this protocol, the probe is used to transmit RF pulses and receive MR signal. A computer program was written for image unwrapping and for displaying the unwrapped movie frames on the roadmap image. In an alternative protocol, the movie frames in two projection angles were acquired in an interleaved fashion. Frames were unwrapped and combined with a 3D roadmap and displayed on a Silicon Graphics workstation equipped with stereovision goggles. Using these methods, percutaneous catheter placement in a phantom and a dog was examined. In conclusion, a new visualization technique for MR catheter placement is proposed. Combining this technique with high resolution intravascular MRI techniques may result in a very useful diagnostic tool for the evaluation of atherosclerosis and other vessel diseases.

Algorithms↗
PubMed2005

Registration and integration for fluoroscopy device enhancement.

We investigated a method, motion compensated integration (MCI), for enhancing stent Contrast-to-Noise Ratio (CNR) such that stent deployment may be more easily assessed. MCI registers fluoroscopic frames on the basis of stent motion and performs pixel-wise integration to reduce noise. Registration is based on marker balls, high contrast interventional devices which guide the clinician in stent placement. It is assumed that stent motion is identical to that of the marker balls. Detecting marker balls and identifying their centroids with a high degree of accuracy is a non-trivial task. To address the required registration accuracy, in this work we examine MCI's visualization benefit as a function of registration error. We employ adaptive forced choice experiments to quantify human discrimination fidelity. Perception results are contrasted with CNR measurements. For each level of registration inaccuracy investigated, MCI conferred a benefit (p < 0.05) on stent deployment assessment suggesting the technique is tolerant of modest registration error. We also consider the blurring effect of cardiac motion during the x-ray pulse and select frames for integration as a function of cardiac phase imaged.

Artifacts↗
PubMed1998

Creating a digital video-based teaching file for interventional procedures using CT fluoroscopy.

A computerized radiology education teaching file application, MRW (Multimedia Radiology Workstation), was produced in our department as a collaboration of faculty, fellows and a doctoral student. This inexpensive and flexible system is novice-programmable and is capable of capturing images from multiple modalities (including still and cine image) and organizing them into individual electronic teaching cases. Help and tutorial functions support the main case display functions.

Computer-Assisted Instruction↗
PubMed2005

Comparative evaluation of an II based and a flat panel based cardiovascular fluoroscopy system within a clinical environment.

The image quality and dose parameters from a 2004 Siemens Axiom Artis dBC cardiac biplane with flat panel detector were evaluated and compared to similar parameters evaluated for a 1977 Toshiba DPF 2000A biplane cardiac unit with a conventional image intensifier. Image quality assessment was performed with the Westmead test object; using solid water as a patient equivalent absorber. The patient dose comparison of the two systems is based on dose area product meter readings for 1512 patient cases recorded over 6 months following installation of the Siemens flat panel digital unit. The image quality results indicate that: (a) high contrast resolution was better with the digital flat panel unit, (b) low contrast resolution is similar between systems, and (c) the threshold contrast of the flat panel system is the same or inferior to that of the image intensifier system. Input dose to the surface of the flat panel detector showed a strong dependence on field size, similar to the behaviour of image intensifier system. For the most common clinical procedure--Left Heart Study via Judkins--the average total dose area product reading was 64.0 Gy-cm2 against 67.7 Gy-cm2 for the digital and conventional units respectively (p = 0.27) indicating no significant difference in dose performance between the two x-ray machines.

Equipment Failure Analysis↗
PubMed2005

[Fluoroscopy-based 3D navigation of complex correction osteotomies at the proximal femur].

BACKGROUND: Despite great advances in hip alloarthroplasty there are still numerous indications for joint-saving procedures such as correction osteotomies. Often these procedures include complex 3D rearrangements of the proximal femur, which are for the surgeon technically very demanding. The project aim was to develop a precise intraoperative virtual 3D planning tool including a detailed biomechanical analysis and enable the surgeon to realize exactly this plan by using computer-assisted techniques. METHODS: Using only two different angled fluoro frames a simplified femoral model was inversely constructed. For navigation a passive optical system was used with a C-arm calibration kit and PC-based software. For in vitro evaluation complex osteotomies were performed on ten femora under simulated OR conditions. RESULTS: The mean difference between the planning and real surgical outcome for the wedge size was less then 2 degrees and for the femur head center position less then 4 mm. No implant penetrated the femur neck isthmus. CONCLUSION: Without changing the standard operative procedure the method can be of high clinical importance to improve planning accuracy and consecutive operative realization for precise fragment positioning and plate location without penetrating the isthmus of the femoral neck. And -- besides precision -- it can potentially help to reduce intraoperative complications such as implant penetration and minimize X-ray use.

Computer Simulation↗
PubMed2001

Visualization of swallowing using real-time TrueFISP MR fluoroscopy.

The aim of this study was to evaluate the ability of different real-time true fast imaging with steady precession (TrueFISP) sequences regarding their ability to depict the swallowing process and delineate oropharyngeal pathologies in patients with dysphagia. Real-time TrueFISP visualization of swallowing was performed in 8 volunteers and 6 patients with dysphagia using a 1.5 T scanner (Magnetom Sonata, Siemens, Erlangen Germany) equipped with high-performance gradients (amplitude 40 mT/m). Image quality of four different real-time TrueFISP sequences (TR 2.2-3.0 ms, TE 1.1-1.5 ms, matrix 63 x 128-135 x 256, field of view 250 mm(2), acquisition time per image 139-405 ms) was evaluated. Water, yoghurt, and semolina pudding were assessed as oral contrast agents. Functional exploration of the oropharyngeal apparatus was best possible using the fastest real-time TrueFISP sequence (TR 2.2 ms, TE 1.1 ms, matrix 63 x 128). Increased acquisition time resulted in blurring of anatomical structures. As the image contrast of TrueFISP sequences depends on T2/T1 properties, all tested foodstuff were well suited as oral contrast agents, but image quality was best using semolina pudding. Real-time visualization of swallowing is possible using real-time TrueFISP sequences in conjunction with oral contrast agents. For the functional exploration of swallowing high temporal resolution is more crucial than spatial resolution.

Adult↗
PubMed2006

Accuracy and complications in computed tomography fluoroscopy-guided needle biopsies of lung masses.

The aim of this study was to determine the diagnostic accuracy and frequency of complications of lung biopsy procedures with or without CTF guidance of needle insertion. Records and images of 99 consecutive percutaneous coaxial cutting needle lung biopsy procedures performed on 85 patients were reviewed retrospectively. Fifty-seven and 42 procedures had been done with and without CTF guidance, respectively. Histological results were compared to diagnosis after surgery or after a follow-up period of 12 months. Diagnostic accuracy and the occurrence of pneumothorax and/or bleeding related to the procedures were registered. The level of accuracy of the diagnosis was comparable. The diagnostic accuracy was 96% (50/52) and 95% (34/36) sensitivity 95% (35/37) and 93% (26/28), specificity 100% (15/15) and 100% (8/8) with CTF and conventional CT techniques, respectively. There were fewer post procedure pneumothoraces using the CTF than conventional technique [26% (15/57) vs. 38% (16/42)], but the difference was not statistically significant (P = 0.274). The insertion of a chest tube was required in only one (2%) procedure using the CTF technique, while this was needed in four (10%) using the conventional technique. Small or large hemorrhages occurred in 23% of the procedures, with no apparent difference between the two groups. In conclusion, CTF-guided biopsy of lung lesions provides high diagnostic accuracy, comparable to that of conventional CT-guided procedures, with a low rate of complications, even for small tumors.

Adolescent↗
PubMed2006

Peroperative difficulties in fluoroscopy of the femoral head in massive obese patient: enhanced visualization by intra-articular contrast agent.

Peroperative fluoroscopic visualization of the femoral head in massive obese patient can be enhanced by the administration of intra-articular contrast agent into the hip joint. It provides safe alternative for compromised resolution during the introduction of femoral head screws. We report our experiences with one patient as a technical report and believe that in certain cases this method may be quite helpful.

Contrast Media↗
PubMed2007

Microcatheter tip enhancement in fluoroscopy: a comparison of techniques.

We compared three techniques for enhancement of microcatheter tips in fluoroscopic images: conventional subtraction technique (CST); averaged image subtraction technique (AIST), which we have developed; and double average filtering (DAF) technique, which uses nonlinear background estimates. A pulsed fluoroscopic image sequence was obtained as a microcatheter was passed through a carotid phantom that was on top of a head phantom. The carotid phantom was a silicone cylinder containing a simulated vessel with the shape and curvatures of the internal carotid artery. The three techniques were applied to the images of the sequence, then the catheter tip was manually identified in each image, and 100 x 100 pixel images, centered at the indicated microcatheter tip positions, were extracted for the evaluations. The signal-to-noise ratio (SNR) was calculated in each of the extracted images from which the mean value of the SNR and its standard deviation (SD) were calculated for each technique. The mean values and the standard deviations were 4.36 (SD 3.40) for CST, 6.34 (SD 3.62) for AIST, and 3.55 (SD 1.27) for DAF. AIST had a higher SNR compared to CST in almost all frames. Although DAF yielded the smallest mean SNR value, it yielded the best SNR in those frames in which the microcatheter tip did not move between frames. We conclude that AIST provides the best SNR for a moving microcatheter tip and that DAF is optimal for a temporarily stationary microcatheter tip.

Carotid Artery, Internal↗
PubMed1980

Björk-Shiley mitral valvular dehiscence. Documented by radiography, echocardiography, fluoroscopy, and cineangiography.

This case report presents combined radiographic, echocardiographic, fluoroscopic, and cineangiographic findings of the dehiscence of a Bjork-Shiley mitral prosthetic valve. The valvular dehiscence was confirmed at surgery. A distinct rounding of the opening phase of the valve was recorded on the echocardiogram. Other clinical evidence, documenting the severe valvular dehiscence, is reported in detail. Non-invasive procedures are therefore invaluable in recording prosthetic valvular dysfunction.

Adult↗