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In vivo dosimetry (IVD) is an important tool in external beam radiotherapy (EBRT) to detect major errors by assessing differences between expected and delivered dose and to record the received dose by individual patients. Also, in intraoperative radiation therapy (IORT), IVD is highly relevant to register the delivered dose. This is especially relevant in low-risk breast cancer patients since a high dose of IORT is delivered in a single fraction. In contrast to EBRT, online treatment planning based on intraoperative imaging is only under development for IORT. Up to date, two commercial treatment planning systems proposed intraoperative ultrasound or in-room cone-beam CT for real-time IORT planning. This makes IVD even more important because of the possibility for real-time treatment adaptation. Here, we summarize recent developments and applications of IVD methods for IORT in clinical practice, highlighting important contributions and identifying specific challenges such as a treatment planning system for IORT. HDR brachytherapy as a delivery technique was not considered. We add IVD for ultrahigh dose rate (FLASH) radiotherapy that promises to improve the treatment efficacy, when compared to conventional radiotherapy by limiting the rate of toxicity while maintaining similar tumour control probabilities. To date, FLASH IORT is not yet in clinical use. [ABSTRACT FROM AUTHOR]

Purpose: Intraoperative radiotherapy (IORT) can be used as a boost in combination with external whole breast irradiation. This study reports the clinical and dosimetric factors associated with IORT-related adverse events (AE). Methods and materials: Between 2014 and 2021, 654 patients underwent IORT. A single fraction of 20 Gy was prescribed to the surface of the tumour cavity using the mobile 50-kV X-ray source. For skin dose measurement, at least four optically stimulated luminescent dosimeter (OSLD) chips were annealed and attached to the skin edge in the superior, inferior, medial, and lateral locations during IORT. Logistic regression analyses were conducted to identify factors associated with IORT-related AE. Results: With a median follow-up period of 42 months, 7 patients experienced local recurrence, resulting in a 4-year local failure-free survival rate of 97.9%. The median skin dose measured by OSLD was 3.85 Gy (range, 0.67-10.89 Gy), and a skin dose of > 6 Gy was observed in 38 patients (2%). The most common AE was seroma (90 patients, 13.8%). We also found that 25 patients (3.9%) experienced fat necrosis during follow-up, and among them, 8 patients underwent biopsy or excision to exclude local recurrence. IORT-related late skin injury occurred in 14 patients, and a skin dose > 6 Gy was significantly associated with IORT-induced skin injury (odds ratio 4.942, 95% confidence interval 1.294-18.871, p = 0.019). Conclusions: IORT was safely administered as a boost to various populations of patients with breast cancer. However, several patients may experience severe skin injuries, and for older patients with diabetes, IORT should be performed with caution. [ABSTRACT FROM AUTHOR]

The purpose of the study was to analyze long-term outcomes of intraoperative radiation therapy (IORT) in patients with stage III non-small cell lung cancer (NS CLC).Material and Methods. The study included 103 patients with stage III NS CLC treated at the Cancer Research Institute (Tomsk, Russia). All patients were divided into two groups. Group I consisted of 51 patients, who underwent radical surgery and IORT at a single dose of 15 Gy. Group II (control group) comprised 52 patients, who underwent radical surgery alone. There were 34 (33 %) pneumonectomies, 39 (37.9 %) lob-, bilobectomies, 9 (8.7 %) reconstructive surgeries and 21 (20.4 %) combined surgeries. A compact pulsed betatron MIB-6E with the average electron energy of 6 MeV, located directly in the operating unit, was used for performing IORT. The Kaplan-Meier method was used for survival analysis. The significance of differences in survival between groups was assessed using the log rank test.Results. Excluding the cases lost to follow-up and deaths from concomitant non-malignant diseases, treatment outcomes were followed up in 97 of 103 patients with NS CLC for 3, 5, and 10 years. The 3-year and disease-free survival rates were significantly higher in the IORT group than in the control group (p

This study aims to confirm the usefulness of patient-specific quality assurance (PSQA) using three-dimensional (3D)-printed phantoms in ensuring the stability of IORT and the precision of the treatment administered. In this study, five patient-specific chest phantoms were fabricated using a 3D printer such that they were dosimetrically equivalent to the chests of actual patients in terms of organ density and shape around the given target, where a spherical applicator was inserted for breast IORT treatment via the INTRABEAM™ system. Models of lungs and soft tissue were fabricated by applying infill ratios corresponding to the mean Hounsfield unit (HU) values calculated from CT scans of the patients. The two models were then assembled into one. A 3D-printed water-equivalent phantom was also fabricated to verify the vendor-provided depth dose curve. Pieces of an EBT3 film were inserted into the 3D-printed customized phantoms to measure the doses. A 10 Gy prescription dose based on the surface of the spherical applicator was delivered and measured through EBT3 films parallel and perpendicular to the axis of the beam. The shapes of the phantoms, CT values, and absorbed doses were compared between the expected and printed ones. The morphological agreement among the five patient-specific 3D chest phantoms was assessed. The mean differences in terms of HU between the patients and the phantoms was 2.2 HU for soft tissue and −26.2 HU for the lungs. The dose irradiated on the surface of the spherical applicator yielded a percent error of −2.16% ± 3.91% between the measured and prescribed doses. In a depth dose comparison using a 3D-printed water phantom, the uncertainty in the measurements based on the EBT3 film decreased as the depth increased beyond 5 mm, and a good agreement in terms of the absolute dose was noted between the EBT3 film and the vendor data. These results demonstrate the applicability of the 3D-printed chest phantom for PSQA in breast IORT. This enhanced precision offers new opportunities for advancements in IORT.

This study aims to confirm the usefulness of patient-specific quality assurance (PSQA) using three-dimensional (3D)-printed phantoms in ensuring the stability of IORT and the precision of the treatment administered. In this study, five patient-specific chest phantoms were fabricated using a 3D printer such that they were dosimetrically equivalent to the chests of actual patients in terms of organ density and shape around the given target, where a spherical applicator was inserted for breast IORT treatment via the INTRABEAM™ system. Models of lungs and soft tissue were fabricated by applying infill ratios corresponding to the mean Hounsfield unit (HU) values calculated from CT scans of the patients. The two models were then assembled into one. A 3D-printed water-equivalent phantom was also fabricated to verify the vendor-provided depth dose curve. Pieces of an EBT3 film were inserted into the 3D-printed customized phantoms to measure the doses. A 10 Gy prescription dose based on the surface of the spherical applicator was delivered and measured through EBT3 films parallel and perpendicular to the axis of the beam. The shapes of the phantoms, CT values, and absorbed doses were compared between the expected and printed ones. The morphological agreement among the five patient-specific 3D chest phantoms was assessed. The mean differences in terms of HU between the patients and the phantoms was 2.2 HU for soft tissue and −26.2 HU for the lungs. The dose irradiated on the surface of the spherical applicator yielded a percent error of −2.16% ± 3.91% between the measured and prescribed doses. In a depth dose comparison using a 3D-printed water phantom, the uncertainty in the measurements based on the EBT3 film decreased as the depth increased beyond 5 mm, and a good agreement in terms of the absolute dose was noted between the EBT3 film and the vendor data. These results demonstrate the applicability of the 3D-printed chest phantom for PSQA in breast IORT. This enhanced precision offers new opportunities for advancements in IORT. [ABSTRACT FROM AUTHOR]

Margin negative resection in pancreatic cancer remains the only curative option but is challenging, especially with the retroperitoneal margin. Intraoperative radiation therapy (IORT) can improve rates of local control but requires specially designed facilities and equipment. This retrospective review describes initial results of a novel implantable mesh of uni-directional low dose rate (LDR) Pd-103 sources (sheet) used to deliver a focal margin-directed high-dose boost in patients with concern for close or positive margins. Eleven consecutive patients from a single institution with resectable or borderline resectable pancreatic cancer with concern for positive margins were selected for sheet placement and retrospectively reviewed. Procedural outcomes, including the time to implant the device and complications, and clinical outcomes, including survival and patterns of failure, are reported. A dosimetric comparison of the LDR sheet with hypothetical stereotactic body radiotherapy (SBRT) boost is reported. One patient had a resectable disease, and 10 patients had a borderline resectable disease and underwent neoadjuvant treatment. Sheet placement added 15 min to procedural time with no procedural or sheet-related complications. At a median follow up of 13 months, 64% (n = 7) of patients are alive and 55% (n = 6) are disease-free. Compared to a hypothetical SBRT boost, the LDR sheet delivered a negligible dose to kidneys, liver, and spinal cord with a 50% reduction in max dose to the small bowel. This is the first report of the use of an implantable uni-directional LDR brachytherapy sheet in patients with resected pancreatic cancer with concern for margin clearance, with no associated toxicity and favorable clinical outcomes. [ABSTRACT FROM AUTHOR]

Aggressive hemangiomas invade the spinal canal and/or paravertebral space and may cause cord compression and neurological symptoms. Radiation therapy was recognized as an effective strategy for the treatment of aggressive hemangiomas. Here, it is reported the first case of aggressive vertebral hemangioma treated by a combination of intraoperative radiation therapy and kyphoplasty (Kypho-IORT).

Purpose To investigate Axxent (iCAD, Inc., San Jose, CA) electronic brachytherapy balloon deformation and its dosimetric impact because of an external flexible shield (FlexiShield [FS]; iCAD, Inc.). Methods and Materials Prostheses breast tissue phantom overlaid three spherical balloon applicators to simulate three clinical scenarios depending on minimum skin-to-balloon surface spacing (SS): balloon with SS of 2 cm, 1 cm, and balloon with 1 cm SS and touching the chest wall. Two sets of megavoltage CT (MVCT) scans were obtained with or without FS for 15 different sizes of balloons. For 45 pairs of MVCT scans, balloon deformation was measured in superior–inferior (d SI ) dimension on coronal and sagittal planes and anterior–posterior (d AP ) and lateral (d LAT ) dimensions on the equatorial plane of balloon. SS was also compared. A treatment plan was made on each MVCT scan. Doses at four balloon surface points and skin were compared. Conformity index value was also compared to evaluate three-dimensional dose distribution. Clinically, 20 Gy was prescribed to the surface of balloon. Results Balloon deformation was observed with compression in SI and AP dimensions and expansion in lateral dimension. Average SI compression was 0.5 mm. Average d Lat - d AP was 2.4 mm, which resulted in elevated point doses at AP dimension by 10.8% of prescribed dose and reduced point doses at lateral dimension by 4.6%. FS decreased SS by 1.8 mm, increasing skin dose by 1.2 Gy, on average. Conformity index value was decreased from 0.922 to 0.908, on average. Conclusions This phantom study demonstrates that use of skin shielding during breast intraoperative radiation therapy can cause balloon deformation and SS reduction, resulting in dosimetric changes that are disregarded in current practice. [ABSTRACT FROM AUTHOR]

Objective: The objective of this retrospective study was to analyze the experience with intraoperative radiation therapy (IORT) at the present institution and to evaluate its contribution to the management of patients with recurrent gynecological cancer. Materials and Methods: Retrospectively this study reviewed data of patients with a gynecological malignancy considered for treatment with IORT at Freiburg University Medical Center between 2005 and 2012. For this purpose, an analysis of medical records, radiation oncology records, operation reports, and follow-up data was conducted. Results: During the period of this study, 31 women with gynecological cancer underwent tumor resection in combination with IORT. The median age of the patients at the time of IORT was 62 years (range 38-85). Most patients had undergone surgery at the time of initial diagnosis (87%). More than one-third of the patients received prior radiation therapy. In addition to that, 52% of the patients had already received chemotherapy. The majority of patients suffered from the first relapse of their disease. The local recurrence was predominantly located at the pelvic side wall (32%) or in intra-abdominal lymph nodes (32%). In 12 patients the authors did not apply the planned IORT. Intraoperative complications were rare and IORT was tolerated without severe side-effects. Follow-up was 14 months (range 1-65), progression free survival (PFS) was five months (range 3-31). Conclusions: In carefully selected patients, IORT and cytoreductive surgery contributed to local control and disease palliation. The authors therefore consider IORT an important aspect of modern cancer treatment. [ABSTRACT FROM AUTHOR]

Every year almost 95,000 women are diagnosed with a gynecologic malignancy and over 28,000 women will succumb to their disease. For patients with an isolated locoregional recurrence after primary therapy, surgical resection may sometimes provide a chance of cure. To optimize the chance of local control intraoperative radiation therapy (IORT) has been used. The combination of salvage surgery and IORT has resulted in reasonable control in the IORT field. The addition of external beam radiation to limited volumes seems to result in improved disease control over surgery and IORT alone. Side effects are closely related to radical surgery, although neuropathy is seen more frequently after IORT; especially if doses of > 20 Gy are prescribed. Margin status remains critical, even with IORT. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate disease outcomes and complications in patients with recurrent ovarian cancer treated with cytoreductive surgery and intraoperative radiation therapy (IORT). Methods and Materials: A retrospective study of 24 consecutive patients with ovarian carcinoma who underwent secondary cytoreduction and intraoperative radiation therapy at our institution between 1994 and 2002 was conducted. After optimal cytoreductive surgery, IORT was delivered with orthovoltage X-rays (200 kVp) using individually sized and beveled cone applications. Outcomes measures were local control of disease, progression-free interval, overall survival, and treatment-related complications. Results: Of these 24 patients, 22 were available for follow-up analysis. Additional treatment at the time of and after IORT included whole abdominopelvic radiation, 9; pelvic or locoregional radiation, 5; chemotherapy, 6; and no adjuvant treatment, 2. IORT doses ranged from 9–14 Gy (median, 12 Gy). The anatomic sites treated were pelvis (sidewalls, vaginal cuff, presacral area, anterior pubis), para-aortic and paracaval lymph node beds, inguinal region, or porta hepatitis. At a median follow-up of 24 months, 5 patients remain free of disease, whereas 17 patients have recurred, of whom 4 are alive with disease and 13 died from disease. Five patients recurred within the radiation fields for a locoregional relapse rate of 32% and 12 patients recurred at distant sites with a median time to recurrence of 13.7 months. Five-year overall survival was 22% with a median survival of 26 months from time of IORT. Nine patients (41%) experienced Grade 3 toxicities from their treatments. Conclusion: In carefully selected patients with locally recurrent ovarian cancer, combined IORT and tumor reductive surgery is reasonably tolerated and may contribute to achieving local control and disease palliation. [Copyright &y& Elsevier]

Purpose: Most brachytherapy planning systems are based on a dose calculation algorithm that assumes an infinite scatter environment surrounding the target volume and applicator. Dosimetric errors from this assumption are negligible. However, in intraoperative high-dose-rate brachytherapy (IOHDR) where treatment catheters are typically laid either directly on a tumor bed or within applicators that may have little or no scatter material above them, the lack of scatter from one side of the applicator can result in underdosage during treatment. This study was carried out to investigate the magnitude of this underdosage. Methods: IOHDR treatment geometries were simulated using a solid water phantom beneath an applicator with varying amounts of bolus material on the top and sides of the applicator to account for missing tissue. Treatment plans were developed for 3 different treatment surface areas (4 × 4, 7 × 7, 12 × 12 cm2), each with prescription points located at 3 distances (0.5 cm, 1.0 cm, and 1.5 cm) from the source dwell positions. Ionization measurements were made with a liquid-filled ionization chamber linear array with a dedicated electrometer and data acquisition system. Results: Measurements showed that the magnitude of the underdosage varies from about 8% to 13% of the prescription dose as the prescription depth is increased from 0.5 cm to 1.5 cm. This treatment error was found to be independent of the irradiated area and strongly dependent on the prescription distance. Furthermore, for a given prescription depth, measurements in planes parallel to an applicator at distances up to 4.0 cm from the applicator plane showed that the dose delivery error is equal in magnitude throughout the target volume. Conclusion: This study demonstrates the magnitude of underdosage in IOHDR treatments delivered in a geometry that may not result in a full scatter environment around the applicator. This implies that the target volume and, specifically, the prescription depth (tumor bed) may get a dose significantly less than prescribed. It might be clinically relevant to correct for this inaccuracy. [Copyright &y& Elsevier]

Background. Intraoperative radiation therapy (IORT) has been performed to prevent local recurrence of rectal cancer only when positive margins are suspected. To further reduce local recurrence, we attempted to develop a new IORT irradiation method in which electron beam irradiation is administered as uniformly as possible to the intrapelvic dissection surfaces. Methods. Low anterior resection and abdominoperineal resection were performed in one male and one female cadaver. Electron beam irradiation was administered by four different methods, and absorbed doses were measured at 15 sites within the pelvis. We also attempted to measure absorbed doses at nine sites within the pelvis in 14 patients treated with IORT. Results. The cadaver study revealed low absorbed doses in the lateral walls of the pelvis when a single irradiation was delivered from the anterior. When the lateral walls of the pelvis were irradiated twice, once each time on the right and left, the absorbed doses were low in the central pelvis and presacrum. Relatively high absorbed doses were achieved in all of these areas by a technique that combined these two methods. Adequate absorbed doses were not achieved by a single irradiation administered from the perineum. Conclusion. This study suggests that electron beam irradiation administered three times to the dissected surfaces in the pelvis after resection of rectal cancer (i.e., to the central pelvis and presacrum from the anterior, and to the left and right lateral walls of the pelvis) is the most suitable method for achieving adequate absorbed doses. [ABSTRACT FROM AUTHOR]