**5. Experiences of TAUS-guided brachytherapy in the division of radiation oncology, Department of Radiology, Faculty of Medicine, Chiang Mai University**

In the Faculty of Medicine, Chiang Mai University, TAUS-guided was implemented 10 years ago to support the conventional brachytherapy during the transformation process from 2D to 3D brachytherapy since 2011. The concepts of TAUS-guided brachytherapy were adapted from Van Dyk et al. [34, 40]. From our process, we performed brachytherapy as an outpatient basis. The workflow of our procedure is shown in **Figure 4**.

After walk-in, patients were adjusted to lithotomy position and skin preparation was performed. Then, Foley's application was performed and at least 200 ml of NSS were filled into the bladder to improve the image quality of TAUS. TAUS was performed during uterine sound and intrauterine tandem applications to prevent uterine perforation. After the application finished, TAUS was performed to measure the dimension of the cervix. Eight measurements (L1-L4 and A1-A4) of cervix dimensions (from intrauterine tandem to the uterine wall) were performed (sagittal

**Figure 4.** *Workflow of TAUS-based brachytherapy.*

#### **Figure 5.**

*Measurements in sagittal and axial views by TAUS from The Division of Radiation Oncology, Department of Radiology, Faculty of Medicine, Chiang Mai University.*

and transverse approaches) at the level of the cervical OS, and 2 cm cranially to the cervical OS, adapted from previous work by Van Dyk et al. [40]. **Figure 5** shows the measurement of the cervix by TAUS.

The planning processes of TAUS-guided brachytherapy in our institute were defined as the two methods for delivering TAUS measurements into treatment planning software. When we started TAUS-guided brachytherapy in 2011, conventional brachytherapy by orthogonal X-rays was utilized by the PLATO workstation. At that time, an indirect process (to transfer the measurements from TAUS to the orthogonal X-ray) was performed. After we installed the new Oncentra workstation in 2014, a direct process (to import the DICOM images of TAUS in sagittal view to the workstation) adapted from Peter MacCallum Cancer center [34, 42] was developed to use in our patients. After applicator reconstruction by manual process or applicator library, the eight dimensions were generated to be eight cervix reference points correlated to intrauterine tandem in lateral and anteroposterior view. **Figure 6** shows the cervix reference points in the sagittal view of ultrasound sound.

After generation of eight cervix reference points, dwell weight or time was optimized to achieve a sufficiently minimal dose to the cervix reference points of at least prescribed dose (6–7 Gy per fraction). **Figure 7** shows dose distribution by TAUS.

From our experiences, TAUS-guided brachytherapy improved the dose to the normal tissues. It reduced the cumulative overdose to the bladder (>80 Gy) and rectum (>75 Gy) in comparison to standard point A treatment and our intermediate-term results showed the 2-year local control of 88% [45]. From 2012 to 2018, more than 100 patients were treated with this technique. Nowadays, after CT was installed in our brachytherapy unit in 2019, we totally transformed to 3D (volumebased) brachytherapy. We still use TAUS to evaluate proper placement and support our CT contouring.

*Ultrasound-Guided Brachytherapy for Cervical Cancer - A Tool for Quality Improvement… DOI: http://dx.doi.org/10.5772/intechopen.101853*

#### **Figure 6.**

*TAUS images showed cervix reference points (black star) in sagittal view from The Division of Radiation Oncology, Department of Radiology, Faculty of Medicine, Chiang Mai University.*

#### **Figure 7.**

*Isodose distribution for TAUS-guided brachytherapy for cervical cancer (red line is 100% of prescribed dose that focus on the first 2 centimeter of uterus) from The Division of Radiation Oncology, Department of Radiology, Faculty of Medicine, Chiang Mai University.*

However, TAUS still has some limitations in patients who cannot have a full bladder (cystostomy or vesicovaginal fistula), and the concept of TAUS in adaptive treatment is still on point-based planning (e.g., cervix reference points). The concept of volume-based approaches via 3D ultrasound is pending [31]. However, TAUS is inexpensive, portable, non-ionizing, and real-time equipment. TAUS supports application safely, CT contouring, and planning itself. TAUS encourages treatment quality in low-resource and high-workload centers to propose improvement in conventional brachytherapy (point A) to adaptive point-based planning (adaptive plan to cervix reference points; 2.5D). Further studies in ultrasound in CT-based contouring and planning should be performed to support the alternatives for brachytherapy in place in which MRI or CT are inaccessible.

### **6. Conclusion**

Although trends of brachytherapy turned from point-based to volume-based plans via MRI or CT, not all cancer centers can access this equipment. To improve the quality of the point-based plan, ultrasound supports the whole process of

brachytherapy, for example, applicator insertion, CT-based contouring, and planning process. TAUS-guided brachytherapy shows promising results by international publications and the cost of TAUS is cheap, and portable. Ultrasound can be applied to all levels of the cancer center to improve the quality of brachytherapy.
