Page 39 - ARNM-1-2

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

Table 2. Chinese female anthropomorphic phantom’s TLD dosimetry between SCA and tandem
Point A (cGy) Point B (cGy) Point R (cGy) B/A R/A
Tandem 226.01±25.71 195.62±13.14 259.88±19.9 6.91±5.24 116.65±21.97
SCA 218.64±22.54 147.10±13.09 191.04±20.04 7.38±2.72 88.67±18.78
Difference 7.37±3.33 48.53±0.36 68.84±5.93 7.55±3.32 10.65±4.35
Difference % 3.18±1.11 24.88±1.62 26.58±2.76 8.57±3.30 8.87±2.24
Notes: SCA was almost the same as tandem at point A; SCA was smaller than tandem at points B and R; B/A: Dose at point B divided by dose at point
A; R/A: Dose at point R divided by dose at point A.
Abbreviations: TLD: Thermoluminescent dosimeter; SCA: Single-channel applicator.

Table 3. Dosimetric TLD dosimetry between SCA and tandem
Tandem SCA (cGy) Difference Difference
(cGy) (cGy) (%)
Point B 6.43±0.79 5.06±0.84 1.37±0.06 21.54±3.35
Point R 8.23±0.35 6.79±0.46 1.45±0.18 17.62±2.61
Abbreviations: TLD: Thermoluminescent dosimeter;
SCA: Single-channel applicator.

node involvement is observed in 60% of patients with stage
IB2 cervical cancer, and patients with IIB or worse disease
should be treated with concomitant chemoradiotherapy [9-11] .
In fact, radiotherapy plays an important role in the
treatment of each stage of cervical cancer, even early-stage
cancer, as it is as effective as surgery.
Brachytherapy is a vital element of radiotherapy, and the
American Brachytherapy Society has affirmed its essential Figure 4. Statistical comparison of dosimetric at points B and R between
curative role in the management of locally advanced SCA and FAS. Detection between SCA and FAS of absorbed irradiation r
showed no significant difference with P values of 0.381 of at point R and
cervical cancer through tandem-based treatment [7,12] . 0.903 at point B.
Bladder and rectal toxicities associated with cervical Abbreviations: SCA: Single-channel applicator; FAS: Fletcher applicator set.
cancer are due to the effects of brachytherapy . The
[13]
importance of the applicator in brachytherapy cannot be thick in the coronal axis (the structure of the SCA is shown
overstated, as it is necessary for delivering the radioactive in Figure 1). First, we observed whether this modified
source. Current applicator sets typically consist of one tube could achieve deformation of the dose distribution
intrauterine applicator combined with vaginal applicators, curve in certain axes. As expected, after the shielding
generating an oblate, and pear-shaped dose curve, which modification, the isodose curve of the SCA definitively
not only covers the tumor mass but also reduces irradiation formed a flat, pear-shaped isodose curve. The reduction
to the bladder and rectum [14,15] . However, during low- ratios of the SCA in the sagittal and cross-sectional planes
dose-rate or high-dose-rate brachytherapy, the position were 10.32% and 19.59%, respectively, compared to those
differences have been observed to be more than 1 cm in observed for the tandem (Figure 3 and Table 1). Thus, the
60% of applications, partly due to insufficient fixation SCA, as a novel applicator for cervical cancer, possessed
of the applicators both to each other and to the table, the most important features to effectively reduce the high-
changes in the two ovoids, or ovoids being higher than dose area along the bladder-rectum axis.
the tandem in non-fixed applications [16-19] . Another issue Next, we compared the results of six patients treated
is the compliance of patients during applicator placement with an additional small dose of 20 cGy, and the findings
without using analgesia [20-23] . were consistent with those obtained with physical
Accordingly, in the present study, we focused on altering dosimetry. The reduction ratios at points B and R with the
the placement pattern of currently used applicators to SCA were 21% and 17%, respectively, compared to those
simplify the procedure of brachytherapy. We modified the obtained with the tandem (Table 2). These dosimetric data
channel of the tandem with an overlay of lead shielding encouraged us to proceed with the subsequent comparison
that was 1.41 mm thick in the sagittal axis and 0.65 mm with the FAS and lay the foundations for future clinical

Volume 1 Issue 2 (2023) 5 https://doi.org/10.36922/arnm.0322