The 2D-ARRAY seven29 A new way of dosimetric verification of - PTW

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Fig. 16 finally shows the printout of the IMRT field, as it is provided by VeriSoft and as we use it for documentation. 5.8 Time requirement Figure 16: Documentation of the result The verification process with the 2D-ARRAY seven29 is highly standardized. Therefore, the entire procedure can be performed within an acceptable time. In Tab. 1, the time requirements for the different verification steps for a five-field IMRT plan are collected. Future versions of VeriSoft will allow an even more automated data analysis, so that a further time reduction can be expected. Procedure Section Average time [min] Transfer of the patient treatment fields and dose calculation 5.3 10 Export of the verification dose plane 5.4 5 Verification measurements including setup 5.5 25 Analysis of the measurements with VeriSoft 5.6 20 Total 60 Table 1: Time requirement for the different steps of the verification procedure. The time requirement listed above is for the verification process with the 2D-ARRAY of one patient plan. However, if plans of more than one patient have to be verified, the same hardware setup for the measurements is used, resulting in time savings. The verification process itself is also more efficient if all fields of all patients are checked against the plans in one session. 12 / 16
6. Some clinical examples In Berlin, we use IMRT as a routine treatment option mainly for treatments of the prostate, head and neck tumors and for irradiations of the breast if the internal mammary lymph node chain has to be included into the target volume. In the next sections, some examples of real patient IMRT plans and their verifications are shown. 6.1 Prostate For prostate IMRT treatments we use a simultaneous integrated boost (SIB) technique, where two different doses are simultaneously delivered to different parts of the target volume. The SIB technique provides two advantages: Firstly, it allows an increased dose within a specific target region (e.g., prostate) and a reduced dose to the peripheral region (e.g., periprostatic area). Secondly, it keeps the overall treatment time constant while increasing the target dose. For our patients, the CTV is irradiated with a single dose of 2.0 Gy per fraction whereas the PTV is treated simultaneously with 1.8 Gy. In Fig. 17, a five-field IMRT SIB treatment plan for a prostate patient is shown. With the SIB technique, we are able to increase the therapeutic dose safely up to 82.0 Gy without increasing the doses to the organs at risk, especially the rectum [5]. In Fig. 18 the isodose overlays and gamma distributions for all five prostate IMRT fields of the treatment plan of Fig. 17 are put together. Typically, prostate IMRT fields are not modulated very much. Therefore, no critical areas are normally found during the verifications. 13 / 16 Figure 17: Dose distribution of an IMRT SIB prostate treatment plan with five fields. Field 1 Field 2 Field 3 Field 4 Field 5 Figure 18: Isodose overlays and gamma distributions of all five IMRT fields of a prostate treatment plan (measured isodose lines are dotted). Nearly all gamma values are < 1 in all fields.
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The 2D-ARRAY seven29 A new way of dosimetric verification of - PTW

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