Major geometric variations between intracavitary applications in carcinoma of the cervix: High dose rate vs. low dose rate

Interfraction dose variations in organs at risk during CT-based high-dose-rate brachytherapy in locally advanced carcinoma cervix: An early experience of a tertiary care Center

“…This could lead to interfraction variations in the applicator geometry and its spatial position in relation to the pelvic organs, pelvic bony anatomy, and the OARs. [ 17 18 19 ] These variations have been reported regarding changes in the uterine axis, uterine length, slippage of tandem, and colpostat separation resulting in fluctuations in spatial location of the applicator in craniocaudal axis, lateral, and anteroposterior rotation as well as variation in coronal, transverse, and sagittal planes. [ 20 ] This has been attributed to mainly patient movement, vaginal packings, and tumor regression during the interval between multiple fractions of HDR ICBT.…”

In vivodosimetry: trends and prospects for brachytherapy

“…Interand intrafraction deformations of prostate, bladder and rectum have been studied, [42][43][44][45][46] and the dosimetric impact owing to more general anatomical variations has been evaluated in a multicentre comparison of cervix BT. 41 Organ-applicator movements occurring between patient imaging and treatment delivery stages have been identified as a major source of uncertainty 33,[47][48][49][50][51][52][53] and their impact further analysed. [54][55][56][57] In cervical cancer BT, inter-and intrafraction uncertainties owing to organ movements and deformations account for 20-25% of the D 2cm3 parameter (minimum dose to the most irradiated 2 cm 3 ) per fraction and is the most essential component in the uncertainty budget for OARs.…”

“…Independent dosemeter shifts with respect to the organ within which it was initially positioned may be avoided with proper implementation tools that stabilize the dosemeter position and assure that it remains unchanged with respect to the closest tissue in spite of patient transfers between locations, 108,109 vaginal packing and/or source applicator clamping devices, [47][48][49]52 potential patient posture changes 108 and OAR deformations. 42,43,49 If the tools assure a stable dosemeter position, further patient images and dosemeter reconstructions are not required, hence a less resourcedemanding implementation of IVD can be provided.…”

“…However, the dosimetric accuracy of IVD systems at non-equilibrium conditions should be further studied for BT. Alternatively for rectal wall dosimetry, the inflatable balloons discussed in this section could be filled with water, rather than air, in order to avoid non-equilibrium conditions, as was done for the endorectal balloon by Wootton et al 111 It is important to note that the positions of IVD probes inserted into BT source applicators, or embedded in the surface of inflatable balloons attached to intracavitary applicators, are correlated with the applicator positions, hence most dosemeters (with the exception of RADPOS) would not be able to reveal inter-or intrafraction organ-applicator movements, for example, caused by perineal oedema, 51 vaginal packing and/or source applicator clamping effects [47][48][49]52 or varying filling status of the rectum and/or bladder. 42,43,49 On the other hand, dosemeters inserted into catheters positioned in OARs are minimally correlated with source applicator movements, hence they could allow for the detection of organ-applicator movements.…”

Brachytherapy in cancer cervix: Time to move ahead from point A?

“…However, depending on the institutional protocols HDR ICBT requires multiple applications. This could lead to a variation in the applicator geometry and its spatial position in relation to the pelvic organs, pelvic bony anatomy and the organs at risk [13][14][15][16][17] . These have been reported in terms of changes in the uterine axis, uterine length, slippage of tandem, colpostat separation and vaginal packing, resulting in fluctuations in spatial location of the applicator in craniocaudal axis, lateral and antero-posterior rotation as well as variation in coronal, transverse and saggital planes ( Figure 1) [18] .…”