Quantifying the Interfractional motion of Esophagus Using Daily Cone Beam Computed Tomography with Oral Contrast During Radiation Therapy for Locally Advanced Non-Small Cell Lung Cancer.

PURPOSE: To quantify the interfractional motion of the esophagus during fractionated radiation therapy for locally advanced non-small cell lung cancer. METHODS AND MATERIALS: We registered simulation 4-dimensional computed tomography (CT) and daily cone beam CT (CBCT) and documented the motion of the esophagus centroid at 5-mm interval slices in right-left (RL) and anterior-posterior (AP) directions. Oral barium sulfate was administrated during CBCT to help localize the esophagus. Thirty-five patients were enrolled. Thirty-five 4-dimensional CT scans, 595 CBCT scans, and 25,970 slices were analyzed. The slice-derived motion values for all patients were presented as 2.5 to 97.5 percentiles and ranges stratified by segments. The magnitude of motion for each individual patient was defined as the standard deviation (SD) of daily motion values stratified by segments. Correlations between the magnitude of motion and clinical variables were explored. RESULTS: The 2.5 to 97.5 percentiles of RL and AP motion were -4.2 to 7.1 and -4.4 to 5.1; -10.3 to 6.0 and -4.3 to 3.8; -8.7 to 5.5 and -6.4 to 2.8; and -9.1 to 4.7 and -5.8 to 3.3 mm for cervical, proximal, middle, and distal thoracic esophagus, respectively. The interfractional motion was direction- and location-dependent. The magnitude of RL motion was greater than that of AP motion for the 4 segments (P < .05). In the RL direction, the magnitude of motion was greater for the middle thoracic esophagus than for the cervical (median SD 2.7 vs 2.0 mm, P = .001) and proximal thoracic esophagus (median SD 2.7 vs 2.1 mm, P = .002). Patients with right lung tumor and bulky lymph nodes tended to display greater RL esophageal motion. CONCLUSIONS: The interfractional motion of the esophagus can be considerable during radiation therapy in locally advanced non-small cell lung cancer, especially for middle thoracic esophagus in RL direction. Strategies to minimize the effect of interfractional esophageal motion on dosimetry should be considered.

Analysis of measurement electrode location in bladder urine monitoring using electrical impedance.

PURPOSE: The aim of this study was to document more appropriate electrode location of a four-electrode-based electrical impedance technology in the monitoring of bladder filling, and to characterize the relationship between bladder filling duration and the measured electrical impedances. METHODS: A simulation study, based on a 2-dimension computational model, was conducted to determine the preferable locations of excitation and measurement electrodes in a conventional four-electrode setup. A human observation study was subsequently performed on eight healthy volunteers during natural bladder urine accumulation to validate the result of the simulation study. The correlation between the bladder filling time and the measured electrical impedance values was evaluated. RESULTS: The preferable location of measurement electrodes was successively validated by the model simulation study and human observation study. Result obtained via the selected electrodes location revealed a significant negative correlation (R = 0.916 ± 0.059, P < 0.001) between the measured electrical impedance and the urine accumulation time, which was consistent with the result of simulation study. CONCLUSIONS: The findings in this study not only documented the desirable electrodes location to monitor the process of bladder urine accumulation using four-electrode measurement, but also validated the feasibility of utilizing electrical impedance technique to monitor and estimate the bladder urine volume for those with urological disorders.

Analyses of the factors influencing the accuracy of three-dimensional ultrasound in comparison with cone-beam CT in image-guided radiotherapy for prostate cancer with or without pelvic lymph node irradiation.

BACKGROUND: Three-dimensional ultrasound (3DUS) is an attractive option in image-guided radiotherapy (IGRT) for prostate cancer (PCa) patients. However, the potential factors influencing the accuracy of 3DUS in comparison with cone-beam CT (CBCT) in IGRT for PCa patients haven't been clearly identified. METHODS: The differences between US/US and CBCT/CT registrations were analyzed over 586 and 580 sessions for 24 and 25 PCa patients treated with or without pelvic lymph node irradiation, respectively. The clinical factors that may influence registration differences were also evaluated. RESULTS: The average discrepancies between US/US and CBCT/CT registrations were - 0.28 ± 5.28 mm, - 0.16 ± 3.48 mm, and - 0.47 ± 4.31 mm in the superior-inferior (SI), left-right (LR), and anterior-posterior (AP) directions, respectively. The discrepancies were respectively less than 5 mm longitudinally, laterally, and vertically in 64.4 and 70.1%, 84.9 and 89.2%, and 75.9 and 79.1% of the patients treated with or without pelvic lymph node irradiation, respectively. The registration differences were significantly smaller at least in one direction in patients younger than 70 years, without pelvic lymph node irradiation, guided by transperineal ultrasonography and had a bladder volume smaller than 300 mL. CONCLUSIONS: Age, irradiated regions, 3DUS modality, and bladder volume are important factors that may influence the differences between US/US and CBCT/CT registrations. 3DUS guidance is more feasible for younger PCa patients with a better control of bladder volume during the treatment and those who did not undergo pelvic lymph node irradiation.