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The study was aimed to introduce a design of a DICOM-RT-based tool box to facilitate 4D dose calculation based on deformable voxel-dose registration. The computational structure and the calculation algorithm of the tool box were explicitly discussed in the study. The tool box was written in MATLAB in conjunction with CERR. It consists of five main functions which allow a) importation of DICOM-RT-based 3D dose plan, b) deformable image registration, c) tracking voxel doses along breathing cycle, d) presentation of temporal dose distribution at different time phase, and e) derivation of 4D dose. The efficacy of using the tool box for clinical application had been verified with nine clinical cases on retrospective-study basis. The logistic and the robustness of the tool box were tested with 27 applications and the results were shown successful with no computational errors encountered. In the study, the accumulated dose coverage as a function of planning CT taken at end-inhale, end-exhale, and mean tumor position were assessed. The results indicated that the majority of the cases (67%) achieved maximum target coverage, while the planning CT was taken at the temporal mean tumor position and 56% at the end-exhale position. The comparable results to the literature imply that the studied tool box can be reliable for 4D dose calculation. The authors suggest that, with proper application, 4D dose calculation using deformable registration can provide better dose evaluation for treatment with moving target.

Purpose: In this article, the breath-hold and gating concepts were combined for application of lung cancer radiation treatment. The tumor movement was immobilized based on deep inspiration breath hold (DIBH), in which the breath-hold consistency and stability were monitored by infrared (IR) tracking and controlled by gating with a predefined threshold. The authors' goal is to derive the benefits from both techniques, namely, the minimized treatment margin and the known advantages of deep inspiration. The efficacy of the technique in terms of tumor immobility and treatment setup accuracy was evaluated in the study., Methods: Fourteen patients who were diagnosed with non small cell lung cancer were included in this study. The control of tumor immobility was investigated interfractionally and intrafractionally. The intrabreath-hold tumor motion was devised based on the external marker movement, in which the tumor-marker correlation was studied. The margin of the planning target volume (PTV) was evaluated based on two factors: (1) The treatment setup error accounts for the patient setup and interbreath-hold variations and (2) the intrabreath-hold tumor motion in which the residual tumor motion during irradiation was studied., Results: As the result of the study, the group systematic error and group random error of treatment setup measured at the isocenter were 0.2(R) +/- 1.6, 1.0(A) +/- 2.0, and 0.3(S) +/- 1.5 mm in the left-right (LR), anterior-posterior (AP), and caudal-cranial (CC) directions, respectively. The Pearson correlation coefficient were 0.81 (LR), 0.76 (AP), and 0.85 (CC) mm and suggest tendency in linear correlation of tumor and marker movement. The intrabreath-hold tumor was small in all directions. The group PTV margins of 3.8 (LR), 4.6 (AP), and 4.8 (CC) mm were evaluated to account for both setup errors and residual tumor motion during irradiation., Conclusions: The study applies the DIBH technique in conjunction with IR positional tracking for tumor immobilization and treatment setup localization. The technique not only proved to be reliable in terms of good tumor immobility and accurate treatment positioning but also to be potentially useful for dose escalation treatment as regarding of the substantially reduced PTV margin and minimizing radiation toxicity from the fully expanded lung volume.

We report 20 cases using hypofractionation stereotactic radiotherapy in medically inoperable stage I non-small cell lung cancer with dose escalation of 45-54 Gy prescribed at 85 or 90% isodose level in 3-4 fractions. Two-year local control and cancer-specific survival were 94.7 and 77.6%, respectively, with minimal toxicity. Though, large fraction size can be safely given to peripheral lung tumors, normal tissue tolerance to hypofractionated radiotherapy to esophagus, trachea, main bronchi, aorta and heart remains unknown. Therefore we also reported the maximum point doses to these critical organs to contribute information to extend this technique to more centrally located lung tumors in future.