Technical considerations

A linear accelerator with a beam energy of 6 mV is desirable because of its penetration, well-defined edge, and homogeneity throughout an irregular treatment field.

Three-dimensional conformal radiation therapy (3-D CRT) or intensity-modulated radiation therapy (IMRT) are standard techniques in the treatment of lymphoma. Appropriate CT-based, image-guided treatment planning and delivery are standard, preferably with fusion of staging CT and PET imaging with radiation therapy planning CT datasets to delineate the target volumes.[45]

Data are accumulating regarding the efficacy of IMRT and the decrease in median dose to normal surrounding tissues. Some uncertainty exists about the potential for increased late effects from IMRT, particularly subsequent neoplasms, because a larger area of the body receives a low dose compared with conventional techniques (although the mean dose to a volume may be decreased).

Proton therapy is being investigated and may further decrease the mean dose to the surrounding normal tissue compared with IMRT or 3-D CRT, without increasing the volume of normal tissue receiving lower-dose radiation.[56]

Individualized immobilization devices are preferable for young children to ensure accuracy and reproducibility.

Attempts should be made to exclude or position breast tissue under the lung/axillary shielding.

When the decision is made to include some or all of a critical organ (such as liver, kidney, or heart) in the radiation field, then normal tissue constraints are critical, depending on the chemotherapy used and patient age.

Whole-lung irradiation (~10 Gy), with partial transmission blocks or intensity modulation, was historically a consideration in the setting of overt pulmonary nodules that had not achieved a CR.[20,21,55] However, it may be used in exceptional situations.