Lim Seonghee, Truong Van Gia, Kang Hyun Wook
Department of Biomedical Engineering, Pukyong National University, Busan, Republic of Korea.
Industry 4.0 Convergence Bionics Engineering, Pukyong National University, Busan, Republic of Korea.
Lasers Surg Med. 2022 Jul;54(5):767-778. doi: 10.1002/lsm.23527. Epub 2022 Feb 19.
Tubular tissue, such as the bile duct and esophagus, often suffers from stenosis due to chronic inflammation or excessive contraction of smooth muscle. Laser treatment using a balloon catheter has been used to treat tubular tissue stenosis by mechanically expanding the tissue and irradiating laser light circumferentially on the tissue lumen. As the balloon is inflated with saline, the residual air in a delivery channel is often accumulated in the inflated balloon. Thus, the air trap may cause physical discontinuities at air-saline interface, leading to unpredictable and nonuniform photothermal interactions. The aim of the current study was to evaluate the optical-thermal effects of the air trap in the balloon on laser treatment of the tubular tissue by means of numerical simulations and experimental validations.
A balloon-assisted diffusing applicator (BDA) was developed to inflate a balloon and deliver uniform and circumferential laser light. Before the balloon inflation, various numbers of deflations (0, 1, 2, 3, and 4) were applied to estimate the average amount of the air removed from the balloon. Ex vivo experiments using porcine liver duct were conducted with two deflation conditions (D0: no deflation for air trap and D3: three deflations for no air trap). The balloon was horizontally situated during laser irradiation to maintain the air trap at the same position in the balloon by minimizing gravity effect. Upon balloon inflation, 532 nm laser light was delivered through the BDA to the tissue (irradiance = 4 W/cm ) at 10 W for 45 seconds to assess the optical-thermal effects of the air trap on the ductal tissue.
The size of the air trap was noticeably reduced with the number of deflations. The air trap volume in the balloon decreased to 0.5% of the total balloon volume after D3. Ex vivo results demonstrated that thicker coagulative necrosis (CN) for D0 near the air trap region in the tissue than bottom region that contact with saline, representing an asymmetric profile of CN in the tissue. D0 generated 17% thicker and nonuniform CN (overall CN thickness = 1.4 ± 0.7 mm), compared with D3 with no air trap (overall CN thickness = 1.2 ± 0.2 mm; p < 0.05). A threefold larger eccentricity (E) was found in D0 (49 ± 31%) than D3 (15 ± 13%; p < 0.001).
Both numerical simulations and experiments validated the effect of the air trap in a balloon on the distribution of CN in a tubular tissue during BDA-assisted laser treatment. Further in vivo studies will assess the current findings on the air trap for clinical translations of BDA-assisted laser treatment of tubular tissue stenosis.
管状组织，如胆管和食管，常因慢性炎症或平滑肌过度收缩而出现狭窄。使用球囊导管的激光治疗已被用于通过机械扩张组织并在组织腔内周向照射激光来治疗管状组织狭窄。当球囊用盐水充气时，输送通道中的残留空气常积聚在充气的球囊中。因此，空气陷阱可能会在空气 - 盐水界面处导致物理不连续性，从而导致不可预测和不均匀的光热相互作用。本研究的目的是通过数值模拟和实验验证来评估球囊中空气陷阱对管状组织激光治疗的光热效应。
开发了一种球囊辅助扩散器（BDA），用于给球囊充气并提供均匀的周向激光。在球囊充气前，进行不同次数的排气（0、1、2、3和4次），以估计从球囊中排出的空气平均量。使用猪肝管进行离体实验，设置两种排气条件（D0：不排气以形成空气陷阱；D3：排气三次以消除空气陷阱）。在激光照射期间，球囊水平放置，以通过最小化重力效应将空气陷阱保持在球囊中的相同位置。球囊充气后，通过BDA将532 nm激光以10 W的功率照射到组织上（辐照度 = 4 W/cm²），持续45秒，以评估空气陷阱对导管组织的光热效应。
随着排气次数的增加，空气陷阱的尺寸明显减小。D3后，球囊中空气陷阱的体积降至球囊总体积的0.5%。离体实验结果表明，在组织中靠近空气陷阱区域的D0处的凝固性坏死（CN）比与盐水接触的底部区域更厚，表明组织中CN的分布不对称。与无空气陷阱的D3相比，D0产生的CN更厚且不均匀（总体CN厚度 = 1.4 ± 0.7 mm），而D3的总体CN厚度 = 1.2 ± 0.2 mm；p < 0.05）。发现D0的偏心率（E）比D3大三倍（49 ± 31% 对 15 ± 13%；p < 0.001）。
数值模拟和实验均验证了球囊中空气陷阱在BDA辅助激光治疗期间对管状组织中CN分布的影响。进一步的体内研究将评估当前关于空气陷阱的研究结果，以用于BDA辅助激光治疗管状组织狭窄的临床转化。
