Journal of Thai Association of Radiation Oncology

Accuracy of target volume and artifact reduction by optimal sorting methods of 4DCT image reconstruction on lung cancer radiotherapy in patients with mismatched pitch in irregular respiration

Fri, 15 Mar 2024 00:00:00 +0700

Backgrounds: In four-dimensional computed tomography (4DCT), pitch estimates are initially selected before data acquisition. However, during data acquisition, it is observed that pitch values mismatch with the breathing period due to respiratory changes, leading to image artifacts. Addressing this issue requires the selection of an appropriate sorting method, especially for a group of patients in such cases who lack a standardized sorting protocol.

Objective: The study aims to determine the optimal 4DCT scan sorting method for patients with a set-up pitch not aligned with breathing period.

Materials and methods: The respiratory waveforms of 40 lung cancer patients were programmed into the CIRS dynamic thorax phantom, and data were acquired using a CT scanner. Subsequently, 4DCT scans were performed, and the appropriateness of the pitch values, which were set according to standard protocols, was assessed. Three sorting methods, namely phase-based, amplitude-based, and percent Pi-based, were evaluated for their impact on volume accuracy, shape, and the presence of artifacts on 4DCT image in terms of absolute volume difference (AVD), sphericity, and artifact score, respectively, specifically in six subjects with inappropriate parameter settings for acquisition data.

Results: Among the 40 patients studied, six respiratory waveforms had improper parameter settings. The volume of a spherical object for the respiratory phases of 0% and 50% showed similarities to the static volume in all three sorting methods, resulting in an AVD range of 0.18-0.29 cm³. The sphericity values of the three sorting methods with phases of 0% and 50% exhibited variations ranging from 0.001 to 0.003, and the artifacts exhibited a severity level close to 2. Therefore, the study recommended using the images at the 0% and 50% respiratory phase with all sorting methods for target contouring images in clinical practice, as they closely matched the static volume. The findings emphasize the importance of aligning pitch values with the breathing period during data acquisition to maintain image quality.

Conclusion: In patients with irregular breathing amplitude and a mismatch in respiratory rate and breathing period, phase-based or percent Pi-based sorting methods were preferably used for 4DCT reconstructions.

Benefit of radiation therapy in stage III-IV Hodgkin lymphoma after chemotherapy

Thu, 04 Apr 2024 00:00:00 +0700

Background: The benefit of radiation therapy as a consolidation therapy after chemotherapy in advanced-stage Hodgkin lymphoma remains controversial, especially after the widespread use of positron emission tomography (PET)/computed tomography (CT) or Ga-67 scintigraphy.

Objective: We conducted a retrospective review in our institute to evaluate the benefit of consolidative radiotherapy in patients who received a modern chemotherapy regimen.

Materials and methods: Between January 2010 and December 2019, 33 patients with newly diagnosed stage III or IV Hodgkin lymphoma were identified from the Chulabhorn Hospital database. After excluding 15 patients who did not meet our inclusion criteria (1 HIV infection, 5 early-stage after reviewed, 5 did not used PET-CT or Ga-67 scintigraphy and 4 with incomplete medical history), the remaining 18 patients were enrolled.

Results: After a median follow-up of 48 months, the 3-year disease-free survival rate was 66.7% in patients who received radiation therapy, versus 55.6% in patients who did not receive radiation therapy (p = 0.391). The 3-year overall survival rate was 100% in both groups. In total, 11 patients (61%) had complete metabolic response (CMR) after first-line chemotherapy, whereas three (16.7%), one (5.6%), and three (16.7%) had a partial response, stable disease, and disease progression, respectively. Seven patients (38.9%) experienced relapse after treatment, and 71.4% of relapses occurred at the original disease site. Of 7 patients who had residual after first-line chemotherapy, three received further radiotherapy whereas four did not. Relapse occurred in all four patients who did not received radiotherapy after residual disease. No patients who achieved CMR in both the interim and post-treatment evaluations experienced relapse. Four of nine patients with bulky masses more than 7 cm in size had CMR after first-line chemotherapy. Interestingly, in this group, no relapse occurred in patients who did not receive radiation therapy, whereas one of three patients (33.3%) who received radiation therapy exhibited relapse. No grade 3–4 acute radiation toxicities occurred in this study, but two of nine patients (22.2%) had grade 3 late pneumonitis that required hospitalization. No secondary malignancy was observed.

Conclusion: Using functional imaging as an evaluation method, consolidation radiation therapy may not be necessary in advanced Hodgkin lymphoma.