Page 37 - ARNM-1-2

Advances in Radiotherapy
& Nuclear Medicine Single-channel applicators for cervical cancer

help of an intravaginal obturator and posterior catheters. a computerized randomization procedure. Patients ready
The bladder reference point (B) was identified as the most for treatment were randomized after routine external-
posterior point of the Foley balloon. The rectal reference beam radiotherapy using the above-mentioned dosimetric
point (R) was located on the appropriate axial slice on an procedure, except for the testing dose, which was 7 Gy.
anteroposterior line drawn through the lowest intrauterine
source dwell position, 5 mm behind the posterior vaginal 2.7. Statistical methods
wall. Matched, sheeted LiF was fixed at the homologous Data on physical dosimetry are presented only as raw
sites mentioned above for dose calculation using a TLD data, and we used one-way ANOVA for direct assessment.
(the dose to point A was 2 Gy). CFAP and related devices Dosimetric measurements were analyzed using the t-test,
are shown in Figure 2. while disease characteristics were assessed using the F-test
method. We used SPSS 19.0 software (IBM, Chicago, USA)
2.5. Three-dimensional dosimetry of the SCA and FAS
to analyze the different groups. P < 0.05 was considered
The three-dimensional dose of the FAS (Elekta, Veenendaal, statistically significant.
the Netherlands) was generated using the Oncentra 4.3
TPS (Elekta, Veenendaal, the Netherlands), and the three- 3. Results
dimensional dose of the SCA was generated using the TPS 3.1. Isodose distribution between the SCA and
prepared by our team. tandem on film dosimetry
2.6. Dosimetric points With a testing dose of 2 Gy, the isodose curves of the SCA
Before applicator placement, laxatives were administered to presented a flat buninoid dose distribution, while the
facilitate the elimination of rectal content. A Foley catheter tandem presented a buninoid dose distribution, especially
was inserted to keep the bladder empty, and the catheter’s in cross-section images (Figure 3). Compared to the
balloon was routinely filled with radiopaque solution tandem, the SCA demonstrated an asymmetrical dose
(7 cm ). A clubbed LiF dosimeter was fixed at the forepart distribution due to the asymmetrical shielding of the SCA
3
of the urinary Foley catheter’s balloon, which was placed channel. This asymmetry resulted in a reduction in the
at the point B and point R sites, according to the ICRU high-dose area on distinct axes, making SCA suitable for
38 definitions. Dosimetry measurements between the SCA protecting adjacent organs, such as the rectum and bladder.
and tandem were undertaken in six patients between 2009 The reduction ratios of the SCA were 1.86%, 10.32%, and
and 2010. At the time of administering the last fraction of 19.59% on the coronal, sagittal, and cross-sectional axes,
intracavitary brachytherapy, an extra dose of 20 cGy was respectively (Table 1).
administered to compare the dose contribution to the B
and R points. For a randomized dosimetry comparison 3.2. Isodose distribution between the SCA and
between the SCA and FAS, 41 patients were selected tandem on the CFAP using a TLD
beginning in 2012 based on the findings of our clinical trial With a testing dose of 2 Gy, the absorbed irradiation
of the SCA (ChiCTR-TRC-12002321, Chinese Clinical doses at points A, B, and R with the SCA were 2.18 Gy,
Trail Registry). The total sample size of our randomized 1.47 Gy, and 1.91 Gy, respectively, while those with the
and controlled trial was n = 300 and patients were tandem were 2.26 Gy, 1.95 Gy, and 2.59 Gy, respectively.
randomly assigned to either the SCA or FAS group using Compared to the tandem, the reduction ratios of the SCA

A B C D

Figure 2. CFAP applied for dosimetric detection of TLD relative elements, sheeted LiF applied for CFAH TLD detection and clubbed LiF applied for
patient detection. (A) CFAP; (B) sheeted LiF; (C) clubbed LiF; and (D) measuring instrument for TLD.
Abbreviations: TLD: Thermoluminescent dosimeter; CFAD: Chinese female anthropomorphic phantom.

Volume 1 Issue 2 (2023) 3 https://doi.org/10.36922/arnm.0322