Dosimetric analysis of 0.5 cm versus 1cm multileaf collimator (mlc) for intensity modulated radiation therapy (IMRT) of carcinoma of cervix.

ehab a hegazy


Purpose: To evaluate the effect of multileaf collimator (MLC) different widths 0.5 cm and 1 cm mounted on the gantry of linear accelerator on planning treatment radiotherapy for cervical cancer patients.

Materials and methods: Two commercially linear accelerator type Siemens Artiste with 1 cm and 0.5 cm leaf widths were used. Twelve planes were selected with cervical cancer at Ayadi Al-Mostakbal Oncology Center, Alexandria, Egypt. The comparative analysis between two multileaf thickness 1 cm and 0.5 cm techniques were performed by comparing the basic planning optimization radiotherapy physical parameters. Number of monitor units MUs, number of segments, homogeneity index (HI), conformity index (CI), minimum dose (Dmin), Maximum dose (Dmax) and Mean dose (Dmean) were evaluated and compared.

Results and Discussion.

The average MUs required by using 1 cm mlc was (860.66±48.17) and the average MUs required by using 0.5 cm mlc was (743.75±39.12) the average difference (116.91±27.40). Measurements of number of segments showed no significant difference in number of segments. Homogeneity index absolute average difference was (0.02±0.009). Conformity index showed no significant difference between two multileaf collimators. The optimal algorithmic parameters of 0.5 cm mlc were smaller than 1 cm mlc which increase the accuracy of planning by using 0.5 cm than 1 cm mlc. The difference of Dmean,Dmin and Dmax  were   (27.96±3.04), (23.75±2.86) and (54.84± 7.59) respectively.

Conclusion: The results confirmed that 0.5 multileaf collimator gives better dose distribution, more homogenous field, and reduce Dmax, Dmin, and Dmean which optimizes radiotherapy planning and quality of treatments but failed to enhance conformity index or number of segments.


Multileaf, Radiotherapy, Cervical cancer, Planning, homogeneity, conformity

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