Electron Multileaf Collimator
No block absorber
The EMLC was designed as a substitute for all electron applicators and field shaping block absorbers. Additionally, the EMLC enables remote-controlled beam collimation and isocentric dose delivery through multi-directional sequenced fields without patient realignment.
In photon radiotherapy individually shaped irradiation fields are accurately and economically created using the parallel arranged metal leaves of a multileaf collimator (MLC). In contrast, electron beam therapy still requires manufacturing complex patientspecific absorbers. In spite of the therapeutic benefits, electron radiotherapy has been gradually replaced by advanced photon irradiation due to high labour and material costs. Euromechanics has developed a computer-controlled Electron Multileaf Collimator (EMLC) in cooperation with the University Medical Center Hamburg-Eppendorf, Germany (UKE). Since the beginning of 2012, the EMLC is in clinical use at the UKE.
The EMLC – a prizewinning development
A further milestone: In addition to the economical advantages, the EMLC opens up a new vista for the application of IMRT with electrons. “Better adjustment of the dose distribution on near-surface target volumes can be achieved by means of controlled segmentation using different electron energies”, the German Society of Medical Physics (DGMP) states in the awarding of the Elekta Research Prize for the development of the EMLC. Also the German Society of Radiation Oncology (DEGRO) and the European Society for Therapeutic Radiology and Oncology (ESTRO) awarded this development for its purpose to enable IMRT applications in electron radiotherapy.
Optimal therapy of superficial cancers
Intensity-modulated radiation therapy (IMRT) with photons achieves higher conformity between treated volume and tumour volume and better sparing of the surrounding healthy tissue. In the treatment of superficial tumours such as mamma carcinoma or skin melanoma, however, photon IMRT often results in large volume of normal tissue exposed to a low dose. In contrast, electron radiation penetrates the tissue as deep as defined by the electron energy. Therefore, IMRT with electrons limits the irradiated volume and, as a consequence, protects adjacent and underlying healthy tissue and radiosensitive organs of heart and lung.
IMRT with electrons feasible
The EMLC combines the advantages of electron dose delivery and the technological potential of IMRT. The EMLC allows near-surface tumours to be irradiated and treated in a clinically optimal, effective and economical way. Performing IMRT with electrons using the EMLC is subject of further research and development in collaboration with the University Medical Center Hamburg-Eppendorf.
Close to patient
The EMLC can be used with all widely-used linear accelerators. In comparison to add-on photon MLCs, the EMLC is characterized by a compact design and lower total weight and is – all in all – easier to handle. As a result, the EMLC can be positioned as close to the patient as clinically necessary, without colliding with the patient. The EMLC is light in weight and enables dose delivery from all orientations without relevant tolerances due to gravitation.
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The EMLC consists of 30 brass leaf pairs with bottom edge located 16 cm above the isocenter. The resulting maximum field size at 100 cm isocenter is 21.4 cm x 21.4 cm. All leaves can be moved up to a fourth of the maximum field size beyond the central field axis (leaf overtravel).
In comparison with the standard applicator from 6 to 14 MeV, the only differences in dose distribution are the greater beam penumbra of 0.7 to 0.3 cm and the larger build-up effect in the depth-dose curves quantified by the lower surface dose of 3 to 4%. Radiation leakage of the EMLC at 14 MeV amounts to 1.5 to 2.5% relative dose, which could be effectively reduced up to the dose contribution from photon contamination of the electron beam due to our tongue-and-groove leaf design. The total weight of the EMLC is 23 kg.
Compact and user-optimized control unit
- Dual independent position measuring system for increased safety
- System design enables an independent function of the real controller
- Flexible user interface individually adaptable to the user’s needs
- Space saving single unit directly attached to the EMLC
- Thin cable loom with connectors provides ease of installation and operation