Correction of patient positioning errors based on in-line cone beam CTs: clinical implementation and first experiences.
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BACKGROUND: The purpose of the study was the clinical implementation of a kV cone beam CT (CBCT) for setup correction in radiotherapy. PATIENTS AND METHODS: For evaluation of the setup correction workflow, six tumor patients (lung cancer, sacral chordoma, head-and-neck and paraspinal tumor, and two prostate cancer patients) were selected. All patients were treated with fractionated stereotactic radiotherapy, five of them with intensity modulated radiotherapy (IMRT). For patient fixation, a scotch cast body frame or a vacuum pillow, each in combination with a scotch cast head mask, were used. The imaging equipment, consisting of an x-ray tube and a flat panel imager (FPI), was attached to a Siemens linear accelerator according to the in-line approach, i.e. with the imaging beam mounted opposite to the treatment beam sharing the same isocenter. For dose delivery, the treatment beam has to traverse the FPI which is mounted in the accessory tray below the multi-leaf collimator. For each patient, a predefined number of imaging projections over a range of at least 200 degrees were acquired. The fast reconstruction of the 3D-CBCT dataset was done with an implementation of the Feldkamp-David-Kress (FDK) algorithm. For the registration of the treatment planning CT with the acquired CBCT, an automatic mutual information matcher and manual matching was used. RESULTS AND DISCUSSION: Bony landmarks were easily detected and the table shifts for correction of setup deviations could be automatically calculated in all cases. The image quality was sufficient for a visual comparison of the desired target point with the isocenter visible on the CBCT. Soft tissue contrast was problematic for the prostate of an obese patient, but good in the lung tumor case. The detected maximum setup deviation was 3 mm for patients fixated with the body frame, and 6 mm for patients positioned in the vacuum pillow. Using an action level of 2 mm translational error, a target point correction was carried out in 4 cases. The additional workload of the described workflow compared to a normal treatment fraction led to an extra time of about 10-12 minutes, which can be further reduced by streamlining the different steps. CONCLUSION: The cone beam CT attached to a LINAC allows the acquisition of a CT scan of the patient in treatment position directly before treatment. Its image quality is sufficient for determining target point correction vectors. With the presented workflow, a target point correction within a clinically reasonable time frame is possible. This increases the treatment precision, and potentially the complex patient fixation techniques will become dispensable. (+info)
Incidence of thromboembolic complications in lumbar spinal surgery in 1,111 patients.
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Hemodynamic response to thoracoscopy and thoracotomy.
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Operations in the pleural cavity are connected with circulatory changes in pulmonary circulation and general changes of hemodynamics. These changes are influenced by the position of patient's body on the operation table and by the introduction of artificial pneumothorax. Thoracoscopy is an advanced surgical approach in thoracic surgery, but its hemodynamic effect is still not known. The aim of the present study was to compare the hemodynamic response to surgeries carried out by open (thoracotomy - TT) and closed (thoracoscopy - TS) surgical approach. Thirty-eight patients have been monitored throughout the operation--from the introduction of anesthesia to completing the surgery. Monitored parameters were systolic blood pressure (BPs), diastolic blood pressure (BPd), O2 saturation (SaO2), systolic blood pressure in pulmonary artery (BPPAs), diastolic blood pressure in pulmonary artery (BPPAd), wedge pressure (P(W)), central venous pressure in right atrium (CVP), cardiac output (CO) and total peripheral resistance (TPR). No significant difference has been found in hemodynamic response between TT and TS groups. Significant changes of hemodynamic parameters occurring during the whole surgical procedure were detected in both technical approaches. The most prominent changes were found after the position of patients was changed to the hip position (significantly decreased BPs, BPd, MAP, SaO2 and BPPAs) and 5 min after the pneumothorax was established (restoration of the cardiac output to the initial value and significant decrease of the TPR). It can be concluded that the thoracoscopy causes almost identical hemodynamic changes like the thoracotomy. (+info)
Head orientation in CBCT-generated cephalograms.
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Patient position and semi-rigid ureteroscopy outcomes.
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INTRODUCTION: Two positions have been reported for ureteroscopy (URS): dorsal lithotomy (DL) position and dorsal lithotomy position with same side leg slightly extended (DLEL). The aim of the present study was to compare the outcomes associated with URS performed with patients in DL vs. DLEL position. MATERIALS AND METHODS: A total of 98 patients treated for ureteral calculi were randomized to either DL or DLEL position during URS, and were prospectively followed. Patients, stone characteristics and operative outcomes were evaluated. RESULTS: Of the 98 patients included in the study, 56.1% were men and 43.9% women with a mean age of 42.6 +/- 16.8 years. Forty-eight patients underwent URS in DL position and 50 in DLEL position. Patients' age, mean stone size and location were similar between both groups. Operative time was longer for the DL vs. DLEL group (81.0 vs. 62.0 minutes, p = 0.045), mainly for men (95.2 vs. 63.9 minutes, p = 0.023). Mean fluoroscopy use, complications and success rates were similar between both groups. CONCLUSIONS: Most factors associated with operative outcomes during URS are inherent to patient's condition or devices available at each center, and therefore cannot be changed. However, leg position is a simple factor that can easily be changed, and directly affects operative time during URS. Even though success and complication rates are not related to position, placing the patient in dorsal lithotomy position with an extended leg seems to make the surgery easier and faster. (+info)
One year's results from a server-based system for performing reject analysis and exposure analysis in computed radiography.
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