Biomedical Engineering Reference
In-Depth Information
2.4.1 Changes of Respiratory Patterns
The respiratory patterns identified in the treatment preparation may be changed
before or during the treatment delivery. A real-time tracking method may com-
pensate for changes of respiratory pattern during treatment delivery, but this
method can be interrupted by other parameters, e.g., cardiac and gastrointestinal
motion, baseline shifts, tumor deformation, highly fluctuating amplitudes of
respiratory motion, and so on [ 26 ]. Therefore, it requires clinical solutions to
adjust or construct changes of respiratory patterns.
2.4.2 Tumor Deformation and Target Dosimetry
Lung deformation derived from respiration may change tumor shapes, or a tumor
may change its own shape by itself [ 103 ]. Some studies investigated that irregular
breathing patterns required more extended clinical target volume compared with
regular breathing patterns [ 94 ]. Sophisticated target dosimetry based on tumor
deformation also should be considered for the optimized treatment delivery.
2.4.3 Irregular Pattern Detection
A real-time tumor-tracking method, where the prediction of irregularities really
becomes relevant [ 79 ], has yet to be clinically established. In the thoracic radio-
therapy, other parameters including cardiac and gastrointestinal motion can affect
the prediction of respiratory patterns. Respiratory patterns of some patients may
have dramatically irregular motions of peaks and valleys position, compared with
others [ 104 ]. It requires a new strategy or standard for irregular breathing classi-
fication depending on a degree of breathing irregularity for each patient. Irregular
pattern detection may be used to adjust a margin value, e.g., the patients assigned
with regular patterns would be dealt with tight margins to prevent health tissues
from irradiating by high-dose treatment. For the patients assigned with irregular
patterns, safety margins should be determined by patient-specific irregularity to
compensate for the baseline shifts or highly fluctuating amplitudes that are not
covered by standard safety margins [ 94 , 105 ].
2.5 Summary
In this chapter, we have showed current radiotherapy technologies including tools
for measuring target position during radiotherapy and tracking-based delivery
systems including Linacs, MLC, and robotic couch. We have also explained three
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