Journal of Contemporary Brachytherapy最新文献

Purpose: Oral cavity squamous cell carcinoma (SCC) is conventionally treated with surgery followed by adjuvant radiation therapy. Multiple studies have demonstrated clinical utility of interstitial brachytherapy (BT) alone or external beam radiotherapy (EBRT) with BT boost for T1-T2N0 cancers of lip and buccal mucosa. In case of combined EBRT and BT, dose summation and optimizing doses received by planning target volume (PTV) and organs at risk (OARs) remains challenging.The aim of this study was to generate and evaluate dosimetric parameters of PTV and OARs as a sum of high-dose-rate (HDR)-BT boost and EBRT in early T1-T2N0 cancers of lip and buccal mucosa, using deformable image registration (DIR) software (Velocity^®). 2 Gy equivalent dose (EQD₂) calculated manually (EQD₂-D₉₀ BT + EQD₂-D₉₈ EBRT) was compared with that estimated using DIR.

Material and methods: An analysis was performed in patients with histopathologically proven T1-T2N0 SCC of lip and buccal mucosa, who underwent interstitial BT boost followed by EBRT. Planning computed tomography (CT) images and respective treatment plans of both BT and EBRT were imported into Velocity^® software, and DIR was employed to fuse these images for all patients. A synthetic plan incorporating both plans was generated. Dosimetric parameters of both PTV and OAR (mandible) were analyzed.

Results: This study included a total of 10 patients (cT1N0: n = 6, and cT2N0: n = 4), with median age of 57 years (range, 30-69 years) and male : female ratio of 7 : 3. The median dose to PTV using HDR-BT was 21 Gy (range, 20-21 Gy), delivered in 5-6 fractions, 3.5-4 Gy per fraction. The median dose to PTV using EBRT was 44 Gy (range, 40-46 Gy), delivered in 20-23 fractions, 1.8-2 Gy per fraction.

Conclusions: DIR software-based dose summation provides accurate dose delivery to target and OARs. If performed prospectively, it can potentially enable optimization of limiting the doses to critical OARs, thus, reducing post-RT morbidity.

Purpose: Brachytherapy requires precise applicator placement, especially in complex cases, where standard imaging may not provide sufficient guidance. Virtual reality (VR) technology has emerged as a valuable tool for pre-simulation, enabling improved anatomical understanding and procedural planning. We reported two cases, in which VR pre-simulation was used to enhance brachytherapy planning in challenging anatomical regions.

Cases description: Case 1: A 51-year-old woman with carcinoma of unknown primary and poorly differentiated adenocarcinoma had previously undergone chemotherapy and radiation therapy for a large tumor in the right common iliac region. The tumor recurred and invaded the sacrum, requiring interstitial brachytherapy due to prior radiation dose constraints. Applicator placement was challenging, necessitating collaboration with an interventional radiology (IR) physician. VR pre-simulation facilitated multi-disciplinary communication and optimized puncture, leading to a safer and more accurate procedure. Case 2: A 46-year-old man with floor of the mouth cancer was initially scheduled for total glossectomy and laryngectomy, but opted for radiotherapy after significant tumor shrinkage. To minimize radiation dose to the mandible, interstitial brachytherapy was added. Due to safety concerns regarding prolonged applicator placement, a strategy of daily insertion and removal was adopted. A custom-made mouthpiece with a single guiding applicator was prepared by a dentist, and multiple needle-type applicators were employed. VR pre-simulation enabled precise needle insertion and facilitated procedural consistency, even among radiation oncologists unfamiliar with head and neck brachytherapy.

Conclusions: VR technology enhances pre-procedural planning, improve multi-disciplinary coordination, and optimize needle placement in brachytherapy for complex anatomical sites. By integrating VR into brachytherapy workflows, treatment precision and safety can be improved across various anatomical regions.

Purpose: In this study, a novel auxetic applicator equipped with four-channel catheters for esophageal brachytherapy was presented.

Material and methods: The applicator, made of a new biocompatible material, has an auxetic helical structure with four channels. Details of applicator modeling, construction, commissioning, and insertion were provided. Initial ex vivo trial conducted on a porcine model was outlined.

Results: Simulations and dose calculations closely matched experimental measurements, validating the modeling approach. This applicator achieved highly asymmetric dose distributions. Its unique auxetic helical design allowed smooth insertion, while mitigating sequential inter-fraction hot spot formation.

Conclusions: Ex vivo implementation of the applicator demonstrated feasibility, resulting in consistent and reproducible dose distributions. Initial outcomes showed promise for the applicator's efficacy and versatility in intra-luminal or intra-cavitary applications.

Purpose: In cervical cancer, brachytherapy is a key component of multi-disciplinary treatment. Wide scale studies, such as EMBRACE, demonstrate benefits of volume-oriented and image-guided brachytherapy. However, MRI and CT are too expensive for health systems with scarce resources. The aim of the study was to assess whether ultrasound- and CT-based volumes of high-risk clinical target volume (HR-CTV) in organs at risk (OARs) as well as dose values in a given plan are comparable.

Material and methods: Eighteen applications were evaluated. After CT scans, axial ultrasound images were acquired in 5 mm steps, serving as a secondary set. Post-prescription, HR-CTV, bladder, and rectum were contoured on ultrasound images. Image sets were compared using CT-based volumes as primary reference. Dice coefficient and Jaccard index were calculated. CT-based dosimetric plan was then compared with ultrasound-based volumes to determine D₉₀ HR-CTV, D_2cc bladder, and D_2cc rectum, and these were compared with CT-based values.

Results: The mean dose differences between CT and ultrasound volumes for HR-CTV and D_2cc rectum were less than 5%, with the bladder slightly above 5%. Wilcoxon test showed no significant difference between the mean doses for CT and ultrasound. Dice coefficients indicated good to very good correlation for these volumes.

Conclusions: Ultrasound-based volume acquisition appears comparable with CT volumetric acquisition in both dosimetric and volumetric terms. Further studies are needed to validate this technique, potentially offering a more affordable and feasible volume-based brachytherapy option for low-income health systems.

Purpose: The aim of this study was to retrospectively analyze and report on dose-volume and clinical toxicity of liver high-dose-rate interstitial brachytherapy (HDR-IBT) used in diaphragm and lung tissue.

Material and methods: Computed tomography (CT)-based liver HDR-IBT using Oncentra Brachy treatment planning system (TPS) plans of patients with malignant liver tumor (MLT) from September 2018 to June 2023 were reviewed to identify patients, whose diaphragm and lung tissue were within 100% prescription isodose. These organs at risk (OARs) were contoured in axial CT slices. Maximum point dose (D_max), dose to 0.2 cc, 0.5 cc, 1 cc (D_0.2cc, D_0.5cc, D_1cc), and volume receiving 30 Gy and 50 Gy (V_30Gy and V_50Gy) were analyzed. Toxicity data of these patients were retrieved from hospital electronic records.

Results: The analysis included 27 patients with 43 and 36 MLTs, whose 100% prescription isodose of liver HDR-IBT plan was within diaphragm and lung tissue. Median prescription dose was 25 Gy (range, 15-25 Gy) in single-fraction. Median D_max, D_0.2cc, D_0.5cc, and D_1cc of the diaphragm were 302 Gy (range, 54-396 Gy), 68 Gy (range, 38-234 Gy), 48 Gy (range, 32-128 Gy), and 35 Gy (range, 27-88 Gy), while for the lung, 90 Gy (range, 39-295 Gy), 55 Gy (range, 32-207 Gy), 44 Gy (range, 29-117 Gy), and 34 Gy (range, 25-79 Gy), respectively. Median V_30Gy and V_50Gy for the diaphragm were 1.1 cc (range, 0-5.8 cc) and 0.2 cc (range, 0-2.5 cc), while for the lung, 0.8 cc (range, 0-10.1 cc) and 0.1 cc (range, 0-2.3 cc), receptively. Two patients with repeated HDR-IBT sessions received cumulative D_max diaphragm of 698 Gy and 792 Gy. At median follow-up of 23 months, no patient reported any suspicious symptom of radiation-induced diaphragm or lung injury.

Conclusions: This is the first publication reporting diaphragm and lung tissue dose-volume and clinical toxicity in liver HDR-IBT. Small volume of diaphragm and lung tissue tolerated extreme high radiation doses [5 times of stereotactic body radiotherapy (SBRT) range in single fraction] without clinically significant toxicity. A standardized reporting for diaphragm and lung dose volume is needed for future liver HDR-IBT studies. The results of the current study can be employed in future for expanded indication of brachytherapy, such as CT-guided trans-thoracic lung brachytherapy.

Purpose: High-dose-rate (HDR) interstitial brachytherapy (ISBT) is a curative treatment option for head and neck cancer patients. However, its overall utilization has been declining, particularly in newer cancer setups. This study investigated challenges in ISBT implementation, and reported initial outcomes of early-stage oral cancer patients in a newly established tertiary cancer center.

Material and methods: After reviewing guidelines and addressing administrative requirements, ISBT program was launched. Key steps in the process included establishing brachytherapy suite, staff training, and optimizing workflows. Alongside standard protocols, additional procedures, such as clinical drawing templates, intra-oral ultrasound, and intra-oral spacers were implemented. From August 2020 to July 2022, 18 patients with early-stage (cT1-2N0M0) oral cancer (tongue = 13, lip = 3, buccal mucosa = 2) received treatment with either ISBT alone (n = 3) or external beam radiotherapy (EBRT), followed by ISBT with HDR cobalt-60 source (n = 15). Treatment characteristics, oncological outcomes, and morbidity profiles were analyzed.

Results: The median age of the cohort was 55 years (range, 29-75 years), with two-thirds of males. The majority had T1 stage (72.2%), with infiltrative growth pattern (72.2%). All patients with oral tongue cancer, 1 lip and 1 buccal mucosa cancer, received elective nodal irradiation with EBRT, followed by ISBT, achieving a total median EQD₂ of 74 Gy. The remaining 3 patients (2 with lip and 1 with buccal mucosa primary) received ISBT alone. Post-treatment complete response was observed in 17 patients (94.4%), with no cases of acute toxicity > grade 2. At a median follow-up of 32 months, an overall 3-year local-regional control and overall survival rates were 67.9% and 72.7%, respectively. One patient developed grade 3 myelopathy, and one grade 3 osteoradionecrosis.

Conclusions: Implementing ISBT in a newly established cancer center is feasible and effective for early-stage oral cancer, providing moderate oncological outcomes with manageable toxicity profile.

Purpose: This study showed long-term clinical results and quantitative dose-volume evaluation of image-guided high-dose-rate interstitial brachytherapy (IG HDR-BT) with custom-made surface applicators for lower lip cancer as monotherapy.

Material and methods: Patients with localized lower lip cancer, who received IG HDR-BT with custom-made surface applicators as monotherapy at the NHO Osaka National Hospital between February 2012 and January 2015 were enrolled in this study. One to three applicators were implanted interstitially, and two to six were placed on tumor surface. Planning-aimed dose (PAD) was 54 Gy, 48 Gy for a recurrent case, and irradiation was delivered at 6 Gy/fraction, twice a day. Dosimetric goal was to achieve D₉₀: clinical target volume (CTV) > PAD without excessive dose to the mandible. A lead shield was placed between the gingiva and lower lip during irradiation to reduce the dose to the mandible in all but one edentulous patient. A gauze with 2% lidocaine was inserted intra-orally to reduce the dose to the upper lip and maxilla.

Results: Six patients (T1 : T2 : T3 = 3 : 2 : 1), including one recurrent case, were enrolled in this study. The CTV was contoured on computed tomography and in two cases, magnetic resonance imaging was used as a reference for contouring. The median follow-up was 69.5 months. The primary tumor was controlled in all cases. No serious late adverse reactions were observed. The median D₉₀ (CTV) and V₁₀₀ (PAD) were 108.9% PAD and 99.3% CTV, respectively. The median D_0.1cm3 (mandible) was 3.2 Gy per fraction.

Conclusions: IG HDR-BT with custom-made surface applicators for lower lip cancer as monotherapy showed an excellent CTV dose and acceptable doses to the mandible, with good long-term clinical results.

Purpose: Recent advances in surface high-dose-rate (HDR) brachytherapy imaging indicate that flap applicators, human skin, and fibromatosis can be visualized using MRI. Complete MR-only surface brachytherapy workflows would require skin marker identification to define clinical target edges. However, CT markers are not detected on MR images, and common MR markers are unsuitable for continuous surface target tracing. In this paper, we proposed an alternative skin marker that was evaluated for MRI and CT detectability and contourability using a brachytherapy treatment planning system (TPS).

Material and methods: Commercially obtained silicone rubber tubes of 2 or 3 mm diameter were taped on the hand of an anthropomorphic phantom, a healthy volunteer, and three palmar fascial fibromatosis patients. Subjects were imaged with an optimized 3D pointwise encoding time reduction with radial acquisition (PETRA) sequence, and a volumetric interpolated breath-hold examination (VIBE) sequence with Dixon reconstruction. Additionally, patients underwent standard CT imaging. Obtained images were reviewed for tube conspicuity, and tubes were tracked on axial views using Oncentra Brachy TPS. Independent tube and muscle reference contours were drawn in MIM for quantitative analysis, considering the three orthogonal imaging planes.

Results and conclusions: Silicone rubber tubes were detected with positive signal on PETRA, VIBE, and CT images. Among the MR series, Dixon VIBE fat-only showed the highest contrast against muscle tissue and the best separation from human skin, followed by DIXON opposed-phase. 3 mm diameter tubes were tracked better by TPS than 2 mm diameter ones. Considering MR images in the three orthogonal planes in MIM was more helpful for localizing the entire tube than using axial images only in TPS. All obtained contour shapes generally agreed with the known tube positions. Overall, solid silicone rubber tubes of 3 mm diameter represent a suitable skin marker alternative to CT markers for MR-only surface HDR brachytherapy.

Purpose: This study examined whether sonomicrometry can measure displacements of active ultrasound-tracked needle prototype for prostate brachytherapy application with high linearity, accuracy, and precision as well as triangulate the needle's motion relative to intra-rectal ultrasound probe.

Material and methods: Sonomicrometry detects time-of-flight (ToF) of ultrasound signal transmitted from an active ultrasound-tracked needle (customized with a piezo-electric tracking sensor) to independent sensor. The transmission was tested in water for displacements parallel and perpendicular to the needle axis using distances of up to 35 mm. Three-dimensional (3D) tracking of the active ultrasound-tracked needle utilized a simulated intra-rectal ultrasound probe fitted with 5 piezo-electric sensors, and a sonomicrometry triangulation algorithm was used to measure the distances of the needle from the probe.

Results: Incremental displacements of the active ultrasound-tracked needle were measured by sonomicrometry with strong linearity (R ≥ 0.999), high accuracy (mean difference ≤ 0.55 mm), and precision (1.96 × standard deviation of the mean difference ≤ 0.22 mm) compared with a reference. Sporadic false triggering of ToF detection was eliminated by signal inversion. Acoustic spatial tracking by the off-line triangulation algorithm produced virtual 3D wire meshes, which closely spatially overlapped with the corresponding (ground-truth) video clips of active ultrasound-tracked needle movement at several testing time points.

Conclusions: We introduced an experimental active ultrasound-tracked needle and employed sonomicrometry to measure the needle's displacements and triangulate its spatial position. The measurements and 3D spatial tracking yielded promising results for potential prostate brachytherapy applications. Clinical implementation will necessitate developments of automated triggering, real-time tracking, and a commercially viable acoustic needle design.

Purpose: In cervical interstitial brachytherapy, sub-optimal tandem insertion can lead to inadequate dose coverage of clinical target volume (CTV). This study aimed to evaluate the effectiveness of medial interstitial needles in optimizing dose to CTV, while minimizing toxicity to organs at risk (OARs), such as bladder, rectum, and sigmoid colon.

Material and methods: The study included 25 brachytherapy plans in seven subjects with locally advanced cervical cancer, who had sub-optimal tandem insertions during cervical interstitial brachytherapy, for which 1 or more medial needle was inserted via Utrecht applicator. For each plan, a test plan was created after inactivating medial needles. Doses to 90% of high-risk (HR) CTV (D₉₀) and OARs (D_2cc bladder, rectum, and sigmoid) were evaluated and compared using Wilcoxon signed rank test in SPSS v. 21.0.

Results: Compared with plans without medial needles (x̄ = 5.22 ±1.60 Gy, median = 5.68 Gy), the plans with medial needles activated (x̄ = 6.59 ±1.55 Gy, median = 7.08 Gy) achieved 26.2% and 24.6% improvement (p = 0.001) in CTV D₉₀ mean and median, respectively. The mean total dose per patient in the medial needle activated group (x̄ = 82.84 ±6.32 Gy) was significantly greater (p = 0.018), with a mean difference of 8.48 Gy from the medial needle inactivated group. No significant dose difference was observed across OARs. Fifty-two needles were inserted in total, out of which, 39 had more than 2 cm depth. Complete response was seen in all subjects.

Conclusions: In patients with sub-optimal tandem insertion, the placement of medial needles can compensate dose deficit, while keeping OARs doses within acceptable constraints. Further studies among larger cohorts are warranted to optimize treatment protocol.