Purpose: The GammaPodTM stereotactic radiotherapy device incorporates a novel stereotactic immobilization system and a fiducial based localization frame for the breast. We present the localization accuracy achieved with this stereotactic system through an IRB approved prospective protocol. Methods: GammaPodTM target localization is achieved using a dual layered immobilization breast cup under a negative pressure which has a built‐in stereotactic frame. Patient CT scans were attained using a pivoted patient loader which automatically lowers the patient from a vertical position to a horizontal prone‐lying position. We then performed two CT scans 30 minutes apart, simulating the pre‐treatment imaging and treatment sessions. The patient is disconnected from the patient loader after the first scan, but the immobilization cup remains on the breast under 150 mmHg of negative pressure until the end of the second scan. Evaluation of target localization was carried out via previously implanted surgical clips (two to five) and superficially positioned markers (three to seven). Scans were performed with 1 mm CT slice thickness. Results: The first 9 patients' results are presented with a total of 25 patients expected. Two patients were excluded due to improper fitting of the breast cup and patient comfort; one patient was excluded due to loss of breast cup pressure between the two scans. In the remaining six patients, the spatial reproducibility of internal markers was found to be 1.2 ± 1.0 mm (range 0.3−3.7) in between the two scans while the external marker positions differed by 0.9 ± 0.9 mm (range 0.1−3.9). The intrinsic accuracy of the stereotactic localization system found to be 0.1 ± 0.1 mm. Conclusion: The GammaPodTM target localization system is a unique approach to breast immobilization employing stereotactic principles. Preliminary results of this study suggest that the overall localization uncertainty of this system is 2.8 mm (95% CL). C. Yu and W. Regine have financial interests in Xcision Medical Systems.
Foram estudadas as artérias da língua de Sus scrofa domestica (Linnaeus, 1758) de 20 animais cujos órgãos foram coletados a fresco e resfriados (4ºC) para transporte. Os vasos, em 15 espécimes, foram perfundidos com água (37ºC), injetados com látex, fixados em formaldeído (7%) e dissecados sob lupa. Injetaram-se 5 peças com ar e acetona PA, depois ar novamente, por fim, solução de acetato de vinil corado. O material foi colocado em água por 24h e, após, mergulhado em solução de ácido sulfúrico a 30% por duas semanas para obtenção de moldes do sistema arterial. As artérias forneceram ramos dorsais, ventrais e colaterais como se segue: ramos dorsais na raiz da língua, três ramos (50%), quatro ramos (46,6%), cinco ramos (3,4%); arranjos de ramos dorsais e ventrais no corpo da língua, um ventral e dois dorsais (46,6%), um ventral e três dorsais (23,3%), um ventral e um dorsal (23,3%), um ventral e quatro dorsais (3,4%) e um ventral (3,4%). No ápice lingual a artéria seguiu paralela, entre os antímeros, encurvou-se medialmente, e se uniu à artéria contralateral estabelecendo uma anastomose por inosculação, formando ilhas arteriais, das quais partiram ramos radiais para o ápice da língua.
Purpose: Recently, template matching has been proposed to track tumor motion using cine‐MRI images. However, the technique has been tested primarily on blood vessels in healthy subjects. In this work, we demonstrate the utility of automated template matching in patients with thoracic tumors. We also compare the variability in predicting tumor position using template matching and 3 human operators. Methods: Five patients with non‐small cell lung cancer (NSCLC) were recruited in a prospective study. Cine‐MRI imaging was performed while the patients were instructed to breathe normally. True FISP (fast imaging in steady state) cine‐images were obtained in the sagittal plane. The centroids of the tumors were determined manually by 3 operators and also by the automatic template matching technique. The differences both in the AP and SI directions between the automatic and manual methods and the inter‐operator variability were calculated respectively and compared. Results: For all patients the variability between automatic and human operators in the SI direction was less than the inter‐operator variability. For 4 out of 5 patients the variability between automatic and human operators in the AP direction was less than the inter‐operator variability. However, the variability in 1 patient was higher by 14%. This is attributed to out‐of‐plane motion that currently is not captured using the cine‐MRI imaging. Conclusion: The effectiveness of template matching to estimate tumor position during respiratory motion was tested in patients with lung cancer. Results show that, the difference between the automatic and manual methods was comparable to the inter‐operator variability. Future efforts to integrate on‐board MRI imaging with linear accelerators can benefit from automated tumor tracking with template matching. Furthermore, the technique can also be utilized to replace the laborious manual tracking process necessary to establish the ground‐truth when evaluating external surrogates of tumor motion. NIH/NCICA 122403
Purpose: To quantitatively evaluate the inter‐fractional variation in tumor volumes with repeated 4D‐CTs and repeated CBCTs for lung patients. To evaluate the uncertainties in patient set‐up that uses internal target volume (ITV) of 4D‐CT to match the soft tissue on CBCTs. Methods: We retrospectively selected 5 lung cancer patients: each with three 4D‐CTs (4D1, 4D2, and 4D3) and three CBCTs (C1, C2, and C3), and each CBCT was scanned within one week of a corresponding 4D‐CT. All CT images are registered to 4D1, together with contours on each image: ITV for 4D‐CT and gross tumor volumes (GTV) for CBCT. Then, these volumes are compared to ITV in 4D1 in terms of tumor volume, centroid distance, and volume overlap coefficient. Results: In each CBCT/4D‐CT pair, GTV in CBCT underestimate the ITV in 4D‐CT by 41.22±1.39 %. When normalized to the ITV volume in the 4D1, other ITVs of 4D‐CTs have an average volume of 1.07±0.13, and GTV in CBCTs have an average volume of 0.58±0.01. The centroid distance between ITV of 4D1 and a GTV of CBCT (5.6±11.9 mm) is larger than that between ITVs of 4D1and 4D2/4D3 (4.6±8.1 mm), while the CBCT GTV volumes are more included in the ITV of 4D1 (BinA: 0.863±0.018) than those of 4D2/4D3 (BinA: 0.735±0.033). From visual observation, the tumors presented in CBCTs are more similar to those in average projections compared to the ITVs of 4D‐CTs. Conclusions: The soft tissue alignment using 4D ITV on CBCT image has room for improvement. Although CBCT tumor seems more included, the centroid distance between CBCT‐GTV and 4D1‐ITV is larger than that between 4D2/4D3‐ITV and 4D1‐ITV. This, together with the underestimation of tumor volume from CBCT, makes current soft tissue alignment not as reliable as it seems. This work is supported in part by Philips Healthcare, Inc.
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