Four-Dimensional Computed Tomography Based Respiratory-Gated Radiotherapy with Respiratory Guidance System: Analysis of Respiratory Signals and Dosimetric Comparison

Abstract

Purpose. To investigate the effectiveness of respiratory guidance system in 4-dimensional computed tomography (4DCT) based respiratory-gated radiation therapy (RGRT) by comparing respiratory signals and dosimetric analysis of treatment plans. Methods. The respiratory amplitude and period of the free, the audio device-guided, and the complex system-guided breathing were evaluated in eleven patients with lung or liver cancers. The dosimetric parameters were assessed by comparing free breathing CT plan and 4DCT-based 30–70% maximal intensity projection (MIP) plan. Results. The use of complex system-guided breathing showed significantly less variation in respiratory amplitude and period compared to the free or audio-guided breathing regarding the root mean square errors (RMSE) of full inspiration (P = 0.031), full expiration (P = 0.007), and period (P = 0.007). The dosimetric parameters including V 5 Gy, V 10 Gy, V 20 Gy, V 30 Gy, V 40 Gy, and V 50 Gy of normal liver or lung in 4DCT MIP plan were superior over free breathing CT plan. Conclusions. The reproducibility and regularity of respiratory amplitude and period were significantly improved with the complex system-guided breathing compared to the free or the audio-guided breathing. In addition, the treatment plan based on the 4D CT-based MIP images acquired with the complex system guided breathing showed better normal tissue sparing than that on the free breathing CT.

The Dosimetric and Temporal Effects of Respiratory-Gated, High-Dose-Rate Radiation Therapy in Patients With Lung Cancer

“…As has been demonstrated in previous RGRT studies, 8,9,11,12 the PTV for all patients could be reduced, indicating a smaller total volume received the target dose. The PTV coverage and MTD were able to be maintained, suggesting that the target was just as effectively able to be treated.…”

“…Several recent studies using 4-dimensional computed tomography (4DCT) have shown that the use of patient-specific treatment margins and respiratory gating, rather than standard population-based treatment margins, can reduce normal tissue toxicity. [8][9][10][11][12] However, some have pointed out that the additional dosimetric benefits from respiratory gating may be modest and not justify the challenges of RGRT, including the increased time for treatment delivery and, consequently, the increased potential for uncertainty introduced from patient movement. 11,13 While increased treatment delivery time may not be of great concern for cases which only require a few minutes to complete, as may be true for some treatment plans using volumetric modulated arc therapy (VMAT), cases requiring longer treatment times, such as those using step-and-shoot intensity-modulated radiotherapy (IMRT), may benefit from the ability to estimate treatment time when assessing potential gating windows.…”

The dosimetric impacts of gated radiation therapy and 4D dose calculation in lung cancer patients

“…As has been demonstrated in previous respiratory gated radiation therapy studies [25,26,36,37], the planning target volume for all patients could be reduced, indicating a smaller total volume received the target dose. The PTV coverage and mean tumor dose were able to be maintained, suggesting that the target was just as effectively able to be treated.…”

Clinical Implementation and Initial Validation of Respiratory-Gated Stereotactic Body Radiotherapy for Thoracoabdominal Tumors Under Abdominal Compression Using an Anzai Laser-Based Gating Device With Visual Guidance on an Elekta Linear Accelerator

“…A normal tissue complication probability (NTCP) model estimated that respiratory gating reduced pneumonitis risk from 43% to 32% for the highest-risk lung cancer patients [6]. Previous gating techniques have included free breathing gating with patient body surface measurements, or with fluoroscopic imaging of metal markers embedded near the tumor as a surrogate [1,[7][8][9][10]. Respiratory gating with audio guidance and visual feedback was also reported to improve the reproducibility and regularity of respiratory amplitude and period [8].…”

“…Previous gating techniques have included free breathing gating with patient body surface measurements, or with fluoroscopic imaging of metal markers embedded near the tumor as a surrogate [1,[7][8][9][10]. Respiratory gating with audio guidance and visual feedback was also reported to improve the reproducibility and regularity of respiratory amplitude and period [8]. To the authors' knowledge, no studies have reported respiratory gating under abdominal compression on a standard linear accelerator (linac).…”