Image fusion techniques in permanent seed implantation

Application of three-dimensional multi-imaging combination in brachytherapy of cervical cancer

BACKGROUND

Three-dimensional (3D) imaging has an important role in brachytherapy and the treatment of cervical cancer. The main imaging methods used in the cervical cancer brachytherapy include magnetic resonance imaging (MRI), computer tomography (CT), ultrasound (US), and positron emission tomography (PET). However, single-imaging methods have certain limitations compared to multi-imaging. The application of multi-imaging can make up for the shortcomings and provide a more suitable imaging selection for brachytherapy.

PURPOSE

This review details the situation and scope of existing multi-imaging combination methods in cervical cancer brachytherapy and provides a reference for medical institutions.

MATERIALS AND METHODS

Searched the literature related to application of three-dimensional multi-imaging combination in brachytherapy of cervical cancer in PubMed/Medline and Web of Science electronic databases. Summarized the existing combined imaging methods and the application of each method in cervical cancer brachytherapy.

CONCLUSION

The current imaging combination methods mainly include MRI/CT, US/CT, MRI/US, and MRI/PET. The combination of two imaging tools can be used for applicator implantation guidance, applicator reconstruction, target and organs at risk (OAR) contouring, dose optimization, prognosis evaluation, etc., which provides a more suitable imaging choice for brachytherapy.

Comparison between postoperative TRUS-CT fusion with MRI-CT fusion for postimplant quality assurance in prostate LDR permanent seed brachytherapy

PURPOSE/OBJECTIVE Permanent seed Low-Dose-Rate brachytherapy is planned and delivered using transrectal ultrasound (TRUS). Post-implant evaluation for quality assurance is usually performed using Computed Tomography (CT). Registration of the CT images with MRI reduces subjectivity in contouring by improving prostate edge detection. We hypothesized that a set of TRUS images post procedure may provide the same benefit. MATERIAL/METHODS Consecutive patients undergoing Low-Dose-Rate prostate brachytherapy were recruited. TRUS images were recorded under anesthesia at completion of their implant. In addition, all patients underwent standard post-implant quality assurance including prostate CT and MRI at day 30. These were co-registered, contoured and seeds were identified. Three independent observers contoured and registered the post implant TRUS images to the Day 30 CT using seed matching. Prostate volumes and dosimetric parameters were compared through Intraclass Correlation Coefficient (ICC) to evaluate the concordance between MRI and ultrasound (US). RESULTS 26 patients were recruited from 10/17 to 01/18. Mean prostate volume was 34.5 (SD 10.8) cm³ at baseline on planning TRUS images, 37.4 (SD 11.3) cm³ on Day 0 post implant TRUS and 36.7 (SD 11.7) cm³ on Day 30 MRI. D90 was 112.6% (SD 9.3) on CT-MRI and 112.9% (SD 11.1) on CT-US. V100 was 94.6% (SD 3.8) for CT-MRI, 95.1% (SD 4.3) for CT-US. Student t-tests were used to compare groups. No significant differences were noted. CONCLUSION Post implant TRUS may be useful for quality assurance for post-implant dosimetry particularly if access to an MRI is limited.

MRI and dual-energy CT fusion anatomic imaging in Ru-106 ophthalmic brachytherapy

PURPOSE

Brachytherapy with Ru-106 is widely used for the treatment of intraocular tumors, and its efficacy depends on the accuracy of radioactive plaque placement. Ru-106 plaques are MRI incompatible and create severe metal artifacts on conventional CT scans. Dual-energy CT scans (DECT) may be used to suppress such artifacts. This study examines the possibility of creating fusion images from MRI scans (preoperatively) and DECT scans (with the plaque in place) as a tool for confirming the anatomic accuracy of plaque placement.

METHODS AND MATERIALS

Six patients with intraocular lesions (5 with choroidal melanoma and 1 with a retinal vasoproliferative lesion) were included. Fusion images of preoperative MRI scans and DECT scans with the plaque in place were created with the Demo version of the ImFusion suite (ImFusion GmbH, Munchen Germany). Clearance margins between the tumor and plaque edge in axial, transverse, and coronal planes as well as the elevation of the posterior plaque edge from the sclera were recorded and associated with the location of the lesion.

RESULTS

Plaque-tumor clearance margins for transverse, sagittal, and coronal planes were higher for anteriorly located lesions (5.13 mm ± 0.11 [5.0-5.2], 5.10 mm ± 0.26 [4.9-5.4], and 5.33 mm ± 0.45 [4.9-5.8] respectively) than for posteriorly located lesions (4.16 mm ± 1.44 [2.5-5.1], 4.13 mm ± 1.42 [2.5-5.1], and 4.2 mm ± 1.21 [2.8-5.0], respectively). The elevation of the posterior plaque edge from the sclera was 0.33 mm ± 0.28 [0-0.5] and 0.63 mm ± 0.60 [0.7-1.2] for posterior and anterior lesions, respectively.

CONCLUSIONS

Fusion images between DECT and MRI scans may be used as a tool to confirm the accuracy of Ru-106 plaque placement in relation with the intraocular tumors in ophthalmic brachytherapy.

BrachyView: Reconstruction of seed positions and volume of an LDR prostate brachytherapy patient plan using a baseline subtraction algorithm

PURPOSE

BrachyView is a novel in-body imaging system developed with the objective to provide real-time intraoperative dosimetry for low dose rate (LDR) prostate brachytherapy treatments. The BrachyView coordinates combined with conventional transrectal ultrasound (TRUS) imaging, provides the possibility to localise the effective position of the implanted seeds inside the prostate volume, providing a unique tool for intra-operative verification of the quality of the implantation. This research presents the first complete LDR brachytherapy plan reconstructed by the BrachyView system and is used to evaluate the effectiveness of an imaging algorithm with baseline subtraction.

METHODS

A plan featuring 98 I-125 brachytherapy seeds, with an average activity of 0.248 mCi, were implanted into a prostate gel phantom under TRUS guidance. Images of implanted seeds were obtained by the BrachyView after the implantation of seeds. The baseline subtraction algorithm is applied as a pixel-to-pixel counts subtraction and is applied to every second projection obtained after the implantation of each needle. Seed positions and effectiveness of the baseline reconstruction in the identification of seeds were verified by a high-resolution post-implant CT scan.

RESULTS

A complete brachytherapy plan has been reconstructed with a 100% detection rate. This is possible due to the effectiveness of the baseline subtraction, with its application an overall increase of 11.3% in position accuracy and 8.2% increase in detection rate was noted.

CONCLUSION

It has been demonstrated that the BrachyView system shows the potential to be a solution to providing clinics with the means for intraoperative dosimetry for LDR prostate brachytherapy treatments.

Brachytherapy in the therapy of prostate cancer - an interesting choice

Brachytherapy is a curative alternative to radical prostatectomy or external beam radiation [i.e. 3D conformal external beam radiation therapy (CRT), intensity-modulated radiation therapy (IMRT)] with comparable long-term survival and biochemical control and the most favorable toxicity. HDR brachytherapy (HDR-BT) in treatment of prostate cancer is most frequently used together with external beam radiation therapy (EBRT) as a boost (increasing the treatment dose precisely to the tumor). In the early stages of the disease (low, sometimes intermediate risk group), HDR-BT is more often used as monotherapy. There are no significant differences in treatment results (overall survival rate – OS, local recurrence rate – LC) between radical prostatectomy, EBRT and HDR-BT. Low-dose-rate brachytherapy (LDR-BT) is a radiation method that has been known for several years in treatment of localized prostate cancer. The LDR-BT is applied as a monotherapy and also used along with EBRT as a boost. It is used as a sole radical treatment modality, but not as a palliative treatment. The use of brachytherapy as monotherapy in treatment of prostate cancer enables many patients to keep their sexual functions in order and causes a lower rate of urinary incontinence. Due to progress in medical and technical knowledge in brachytherapy (“real-time” computer planning systems, new radioisotopes and remote afterloading systems), it has been possible to make treatment time significantly shorter in comparison with other methods. This also enables better protection of healthy organs in the pelvis. The aim of this publication is to describe both brachytherapy methods.

Prostate cancer brachytherapy: guidelines overview

Prostate cancer, due to wide availability of PSA tests, is very often diagnosed in early stage, nowadays. This makes management of this disease even harder in every day oncology care. There is a wide range of treatment options including surgery, radiotherapy and active surveillance, but essential question is which treatment patient and oncologist should decide for. Due to recent publication of Prostate Cancer Results Study Group, in which brachytherapy is one of supreme curative options for prostate cancer, we decided to overview most present european and north american recommendations. National Comprehensive Cancer Network, American Society for Radiation Oncology, American Brachytherapy Society, European Association of Urology and Groupe Européen de Curiethérapie of European Society for Therapeutic Radiation Oncology guidelines are overviewed, particularly focusing on HDR and LDR brachytherapy.