Journal of Thai Association of Radiation Oncology

The Feasibility of Synthetic Computed Tomography (sCT) Generated from Magnetic Resonance for Calculating ATenuation (MRCAT) in Prostate Cancer for External Beam Radiotherapy Dose Calculation

pronpawee pudsena — 2024-04-05

Background: Magnetic resonance (MR) image has recently become a trendy use for external beam radiotherapy (EBRT) dose calculation according to the dominance of high soft tissue contrast. However, the main challenge of applying an MR image for dose calculation is the lack of a correlation between the material's density and the computed tomography (CT) number in the MR image, which is mandatory for dose calculation in a commercial treatment planning system. Thus, synthetic CT (sCT) is introduced for EBRT dose calculation.

Objectives: This study aims to examine the feasibility of using MR image for Calculating ATtenuation (MRCAT)-sCT imaging in prostate cancer patients to calculate the external beam dose.

Materials and methods: Ten prospective prostate cancer patients were enrolled in this study. The pCT and MR images were acquired using the pre-imaging protocol. Tumors and organs at risk (OARs) were delineated on planning CT (pCT) and sCT. The Hounsfield unit (HU) of each organ was compared between pCT and sCT. The volumetric modulated arc therapy (VMAT) plan was generated on pCT and calculated based on the Acuros XB (AXB) algorithm using Eclipse, then recalculated on sCT. The similarity between pCT- and sCT-based dose was evaluated using dosimetric data extracted from the dose-volume histogram and 3D gamma analysis.

Results: This study demonstrated a minor difference in HU between sCT and pCT in soft tissue (13.02 15.58 HU) while the discrimination of HU was larger in femur bone (51.59 49.08 HU). The mean HU of soft tissue in sCT was greater than in pCT; contrastingly, the mean HU of bone from sCT was lower than in pCT. The dose distributions calculated from sCT and pCT were similar (>95% gamma passing rate at all criteria (varies from 3%3mm to 1%1mm). Each dosimetric determination showed insignificant differences across all relevant contours.

Conclusion: MRCAT-generated sCT can calculate prostate cancer EBRT doses with a negligible dose difference from pCT. This study promotes prostate EBRT using MR-only workflow.

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

Kamonchanok Nobphuek — 2024-03-15

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

Ruja Vichitvejpaisal — 2024-04-04

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.

Identifying clinical and treatment factors on survival outcomes of cervical cancer: Sawanpracharak Hospital

Natcha Senawin — 2024-06-14

Backgrounds Cervical cancer is the fourth most common cancer in women globally, including Thailand. The main treatments for locally advanced cervical cancer are concurrent chemoradiation and brachytherapy. Several risk factors are associated with survival outcomes.

Objectives To identify clinical, pathology, and treatment factors that impact on overall survival (OS) and progression-free survival (PFS) in locally advanced cervical cancer.

Materials and Methods A retrospective study of an explorative prognostic factor research was conducted in locally advanced cervical cancer patients treated in Sawanpracharak Hospital from 2017 to 2019. Kaplan-Meier and Log-rank test were used for survival analysis. Cox regression was used for univariate and multivariate analysis to identify the prognostic factors. P-value <0.05 was considered statistically significant.

Result There were 179 patients. The mean age was 53 years old. The 3-year overall survival (OS) was 75%, 72.2%, 44.4-66.7% and 46.2% and the 3-year progression-free survival (PFS) was 93%, 74%, 33.3-80% and 38.5% for stage I, II, III and IVA respectively. Multivariable analysis identified risk factors for poor OS included initial hemoglobin level < 10 g/dl (HR 2.63; 95% CI, 1.41-4.89, p=0.002) non-squamous cell histology (HR 2.07; 95% CI, 1.09-3.93, p=0.026) and tumor size ≥4 cm (HR 2.4; 95% CI, 1.05-5.58, p=0.038). Factors associated with worse PFS included non-squamous cell histology (HR 2.40; 95% CI, 1.31-4.39, p=0.004) and tumor size ≥4 cm (HR 3.59; 95% CI, 1.34-9.63, p=0.011). There was no statistically significant difference in the PFS or OS between those who received 5 cycles or less chemotherapy and total treatment time 56 or more days.

Conclusion Initial hemoglobin level < 10 g/dl was a factor associated with worse overall survival, whereas histological cell type and tumor size were prognostic factors associated with overall survival and progression-free survival outcomes in cervical cancer.

Factors influencing real-time 3D surface image-guided for patient setup in radiotherapy

Metinee Wisetrintong — 2024-06-18

Background: The real-time 3D surface image-guide system (AlignRT) is applied to verify the patient position before treatment and can monitor the patient movement during treatment.

Objective: To study the characteristics and contributing factors of AlignRT.

Materials and Methods: The AlignRT system was installed at Varian TrueBeam linac room. The position errors of phantom were used to study in various parameters such as the effect of gantry angle, room light, skin tone protocol, region of interest, couch angle and time.

Results: From the study, it was found that the gantry angle effect was within 0.3 mm for the range of 100-260 degree. The uncertainty increased in case of dim light in the room with maximum of 0.9 mm. For skin tone protocol, the uncertainty reduced if the matching skin tone was selected. A smaller ROI than 10 x10 cm², small at center, displayed less errors compared with large ROI such as total body, half left or half right. For couch angle effect, the uncertainties were high in the range -40 to 60 degrees and 40 to 60 degrees with the uncertainty range from -1.3 to 1.1 mm. The time of using machine did not affect the accuracy of the system.

Conclusions: The characteristics of AlignRT system were in good condition with small uncertainty. The highest uncertainty was found at couch angle effect, while the gantry angle and time of used had the smallest effect. The other parameters showed small effect. In conclusion, the
AlignRT was a good system because the uncertainties were within 1.5 mm from all factors. It was possible to increase the accuracy of patient positioning.