Fetal dose assessment in a pregnant patient with brain tumor: A comparative study of proton PBS and 3DCRT/VMAT radiation therapy techniques.

PURPOSE: The treatment of brain tumors in pregnant patients poses challenges, as the out-of-field dose exposure to the fetus can potentially be harmful. A pregnant patient with prior radiation treatment was presented with a brain tumor at our clinic. This work reports on our pre-treatment study that compared fetal dose exposure between intensity-modulated proton therapy (IMPT) using pencil beam scanning (PBS) and conventional photon 3D conformal radiation therapy (3DCRT) and volumetric-modulated arc therapy (VMAT), and the subsequent pregnant patient's radiation treatment. MATERIALS AND METHODS: Pre-treatment measurements of clinical plans, 3DCRT, VMAT, and IMPT, were conducted on a phantom. Measurements were performed using a device capable of neutron detections, closely following AAPM guidelines, TG158. For photon measurements, fetus shielding was utilized. On patient treatment days, which was determined to be proton treatment, shielding was used only during daily imaging for patient setup. Additionally, an in vivo measurement was conducted on the patient. RESULTS: Measurements showed that IMPT delivered the lowest fetal dose, considering both photon and neutron out-of-field doses to the fetus, even when shielding was implemented for photon measurements. Additionally, the proton plans demonstrated superior treatment for the mother, a reirradiation case. CONCLUSION: The patient was treated with proton therapy, and the baby was subsequently delivered at full term with no complications. This case study supports previous clinical findings and advocates for the expanded use of proton therapy in this patient population.

Effect of Cangrelor on Infarct Size in ST-Segment-Elevation Myocardial Infarction Treated by Primary Percutaneous Coronary Intervention: A Randomized Controlled Trial (The PITRI Trial).

BACKGROUND: The administration of intravenous cangrelor at reperfusion achieves faster onset of platelet P2Y12 inhibition than oral ticagrelor and has been shown to reduce myocardial infarction (MI) size in the preclinical setting. We hypothesized that the administration of cangrelor at reperfusion will reduce MI size and prevent microvascular obstruction in patients with ST-segment-elevation MI undergoing primary percutaneous coronary intervention. METHODS: This was a phase 2, multicenter, randomized, double-blind, placebo-controlled clinical trial conducted between November 2017 to November 2021 in 6 cardiac centers in Singapore. Patients were randomized to receive either cangrelor or placebo initiated before the primary percutaneous coronary intervention procedure on top of oral ticagrelor. The key exclusion criteria included presenting <6 hours of symptom onset; previous MI and stroke or transient ischemic attack; on concomitant oral anticoagulants; and a contraindication for cardiovascular magnetic resonance. The primary efficacy end point was acute MI size by cardiovascular magnetic resonance within the first week expressed as percentage of the left ventricle mass (%LVmass). Microvascular obstruction was identified as areas of dark core of hypoenhancement within areas of late gadolinium enhancement. The primary safety end point was Bleeding Academic Research Consortium-defined major bleeding in the first 48 hours. Continuous variables were compared by Mann-Whitney U test (reported as median [first quartile-third quartile]), and categorical variables were compared by Fisher exact test. A 2-sided P<0.05 was considered statistically significant. RESULTS: Of 209 recruited patients, 164 patients (78%) completed the acute cardiovascular magnetic resonance scan. There were no significant differences in acute MI size (placebo, 14.9% [7.3-22.6] %LVmass versus cangrelor, 16.3 [9.9-24.4] %LVmass; P=0.40) or the incidence (placebo, 48% versus cangrelor, 47%; P=0.99) and extent of microvascular obstruction (placebo, 1.63 [0.60-4.65] %LVmass versus cangrelor, 1.18 [0.53-3.37] %LVmass; P=0.46) between placebo and cangrelor despite a 2-fold decrease in platelet reactivity with cangrelor. There were no Bleeding Academic Research Consortium-defined major bleeding events in either group in the first 48 hours. CONCLUSIONS: Cangrelor administered at the time of primary percutaneous coronary intervention did not reduce acute MI size or prevent microvascular obstruction in patients with ST-segment-elevation MI given oral ticagrelor despite a significant reduction of platelet reactivity during the percutaneous coronary intervention procedure. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03102723.

Feasibility of patient-specific quality assurance (PSQA) for real-time robotic stereotactic body radiotherapy (SBRT) based on tumor motion traces.

PURPOSE: To design a patient specific quality assurance (PSQA) process for the CyberKnife Synchrony system and quantify its dosimetric accuracy using a motion platform driven by patient tumor traces with rotation. METHODS: The CyberKnife Synchrony system was evaluated using a motion platform (MODUSQA) and a SRS MapCHECK phantom. The platform was programed to move in the superior-inferior (SI) direction based on tumor traces. The detector array housed by the StereoPhan was placed on the platform. Extra rotational angles in pitch (head down, 4.0° ± 0.15° or 1.2° ± 0.1°) were added to the moving phantom to examine robot capability of angle correction during delivery. A total of 15 Synchrony patients were performed SBRT PSQA on the moving phantom. All the results were benchmarked by the PSQA results based on static phantom. RESULTS: For smaller pitch angles, the mean gamma passing rates were 99.75% ± 0.87%, 98.63% ± 2.05%, and 93.11% ± 5.52%, for 3%/1 mm, 2%/1 mm, and 1%/1 mm, respectively. Large discrepancy in the passing rates was observed for different pitch angles due to limited angle correction by the robot. For larger pitch angles, the corresponding mean passing rates were dropped to 93.00% ± 10.91%, 88.05% ± 14.93%, and 80.38% ± 17.40%. When comparing with the static phantom, no significant statistic difference was observed for smaller pitch angles (p = 0.1 for 3%/1 mm), whereas a larger statistic difference was observed for larger pitch angles (p < 0.02 for all criteria). All the gamma passing rates were improved, if applying shift and rotation correction. CONCLUSIONS: The significance of this work is that it is the first study to benchmark PSQA for the CyberKnife Synchrony system using realistically moving phantoms with rotation. With reasonable delivery time, we found it may be feasible to perform PSQA for Synchrony patients with a realistic breathing pattern.

Evaluation of a novel patient-specific quality assurance phantom for robotic single-isocentre, multiple-target stereotactic radiosurgery, and stereotactic radiotherapy.

OBJECTIVES: To evaluate patient-specific quality assurance (PSQA) of 3 targets in a single delivery using a novel film-based phantom. METHODS: The phantom was designed to rotate freely as a sphere and could measure 3 targets with film in a single delivery. After identifying the coordinates of 3 targets in the skull, the rotation angles about the equator and meridian were computed for optimal phantom setup, ensuring the film plane intersected the 3 targets. The plans were delivered on the CyberKnife system using fiducial tracking. The irradiated films were scanned and processed. All films were analysed using 3 gamma criteria. RESULTS: Fifteen CyberKnife test plans with 3 different modalities were delivered on the phantom. Both automatic and marker-based registration methods were applied when registering the irradiated film and dose plane. Gamma analysis was performed using a 3%/1 mm, 2%/1 mm, and 1%/1 mm criteria with a 10% threshold. For the automatic registration method, the passing rates were 98.2% ± 1.9%, 94.2% ± 3.7%, and 80.9% ± 6.3%, respectively. For the marker-based registration approach, the passing rates were 96.4% ± 2.7%, 91.7% ± 4.3%, and 78.4% ± 6.2%, respectively. CONCLUSIONS: A novel spherical phantom was evaluated for the CyberKnife system and achieved acceptable PSQA passing rates using TG218 recommendations. The phantom can measure true-composite dose and offers high-resolution results for PSQA, making it a valuable device for robotic radiosurgery. ADVANCES IN KNOWLEDGE: This is the first study on PSQA of 3 targets concurrently on the CyberKnife system.

The use of a mini-ridge filter with cyclotron-based pencil beam scanning proton therapy.

BACKGROUND: Pencil beam scanning (PBS) proton therapy allows for far superior dose conformality compared with passive scattering techniques. However, one drawback of PBS is that the beam delivery time can be long, particularly when treating superficial disease. Minimizing beam delivery time is important for patient comfort and precision of treatment delivery. Mini-ridge filters (MRF) have been shown to reduce beam delivery time for synchrotron-based PBS. Given that cyclotron systems are widely used in proton therapy it is necessary to investigate the potential clinical benefit of mini-ridge filters in such systems. PURPOSE: To demonstrate the clinical benefit of using a MRF to reduce beam delivery time for patients with large target volumes and superficial disease in cyclotron-based PBS proton therapy. METHODS: A MRF beam model was generated by simulating the effect of a MRF on our clinical beam data assuming a fixed snout position relative to the isocenter. The beam model was validated with a series of measurements. The model was used to optimize treatment plans in a water phantom and on six patient DICOM datasets to further study the effect of the MRF and for comparison with physician-approved clinical treatment plans. Beam delivery time was measured for six plans with and without the MRF to demonstrate the reduction achievable. Plans with and without MRF were reviewed to confirm clinical acceptability by a radiation oncologist. Patient-specific QA measurements were carried out with a two-dimensional ionization chamber array detector for one representative patient's plan optimized with the MRF beam model. RESULTS: Results show good agreement between the simulated beam model and measurements with mean and maximum deviations of 0.06 mm (0.45%) and 0.61 mm (4.9%). The increase in Bragg peak width (FWHM) ranged from 2.7 mm at 226 MeV to 6.1 mm at 70 MeV. The mean and maximum reduction in beam delivery time observed per field was 29.1 s (32.2%) and 79.7 s (55.3%). CONCLUSION: MRFs can be used to reduce treatment time in cyclotron-based PBS proton therapy without sacrificing plan quality. This is particularly beneficial for patients with large targets and superficial disease such as in breast cancer where treatment times are generally long, as well as patients treated with deep inspiration breath hold (DIBH).

Implementing and evaluating a high-resolution diode array for patient-specific quality assurance of robotic brain stereotactic radiosurgery/radiotherapy.

The purpose of the study was to introduce and evaluate a high-resolution diode array for patient-specific quality assurance (PSQA) of CyberKnife brain stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). Thirty-three intracranial plans were retrospectively delivered on the SRS MapCHECK using fixed cone, Iris, and multileaf collimator (MLC). The plans were selected to cover a range of sites from large tumor bed, single/multiple small brain metastases (METs) to trigeminal neuralgia. Fiducial tracking using the four fiducials embedded around the detector plane was used as image guidance. Results were analyzed before and after registration based on absolute dose gamma criterion of 1 mm distance-to-agreement and 0.5%-3% dose-difference. Overall, the gamma passing rates (1 mm and 3% criterion) before registration for all the patients were above 90% for all three treatment modalities (96.8 ± 3.5%, the lowest passing rate of 90.4%), and were improved after registration (99.3 ± 1.5%). When tighter criteria (1 mm and 2%) were applied, the gamma passing rates after registration for all the cases dropped to 97.3 ± 3.2%. For trigeminal neuralgia cases, we applied 1 mm and 0.5% criterion and the passing rates dropped from 100 ± 0.0% to 98.5 ± 2.0%. The mean delivery time was 33.4 ± 11.7 min, 24.0 ± 4.9 min, and 17.1 ± 2.6 min for the fixed cone, Iris, and MLC, respectively. With superior gamma passing rates and reasonable quality assurance (QA) time, we believe the SRS MapCHECK could be a good option for routine PSQA for CyberKnife SRS/SRT.

Cholangiocarcinoma - Part 2, Tumoral and Nontumoral Mimics and Imaging Features Helpful in Differentiation.

Each of the 3 morphological subtypes of cholangiocarcinoma has a different set of imaging differentials. Emulators of mass-forming cholangiocarcinoma include other primary and secondary hepatic malignancies, benign tumors and tumor-like mimics such as abscess, hemangioma and confluent hepatic fibrosis. Benign inflammatory biliary strictures constitute the major differential of periductal-infiltrative type and intraductal calculi are the main consideration for intraductal-growth type. CT and MRI are the standard imaging tools for characterization of cholangiocarcinoma and differentiating it from close mimics. Here we will describe the various tumoral and non-tumoral mimics of cholangiocarcinoma and discuss specific imaging features useful in differentiation.

Cholangiocarcinoma: Part 1, Pathological and Morphological Subtypes, Spectrum of Imaging Appearances, Prognostic Factors and Staging.

Cholangiocarcinoma (CC) is the most frequent malignant tumor of the biliary tract. The vast majority of cholangiocarcinomas are adenocarcinomas with a high proportion of fibrous stroma. Based on the macroscopic growth pattern, CC is classified as mass-forming, periductal infiltrating, or intraductal, with each type having its own characteristic imaging findings and prognostic outcome. The recently proposed pathological classification of cholangiocarcinoma into two types: perihilar large duct type and peripheral small duct and/or ductular type helps in better understanding of the morphology and the imaging appearances. Computed tomography (CT) and magnetic resonance imaging (MRI) remain the main tools of imaging. We aim to provide a comprehensive outline of the different subtypes and the rationale behind various imaging features of these subtypes. Cholangiocarcinoma is one of the more difficult tumors to treat and till date, surgery remains the only definitive curative treatment.

Impact of sequence type and field strength (1.5, 3, and 7T) on 4D flow MRI hemodynamic aortic parameters in healthy volunteers.

PURPOSE: 4D flow magnetic resonance imaging (4D-MRI) allows time-resolved visualization of blood flow patterns, quantification of volumes, velocities, and advanced parameters, such as wall shear stress (WSS). As 4D-MRI enters the clinical arena, standardization and awareness of confounders are important. Our aim was to evaluate the equivalence of 4D flow-derived aortic hemodynamics in healthy volunteers using different sequences and field strengths. METHODS: 4D-MRI was acquired in 10 healthy volunteers at 1.5T using three different prototype sequences, at 3T and at 7T (Siemens Healthineers). After evaluation of diagnostic quality in three segments (ascending-, descending aorta, aortic arch), peak velocity, flow volumes, and WSS were investigated. Equivalence limits for comparison of field strengths/sequences were based on the limits of Bland-Altman analyses of the intraobserver variability. RESULTS: Non-diagnostic quality was found in 10/144 segments, 9/10 were obtained at 7T. Apart for the comparison of forward flow between sequence 1 and 3, the differences in measurements between field strengths/sequences exceeded the range of agreement. Significant differences were found between field strengths/sequences for forward flow (1.5T vs. 3T, 3T vs. 7T, sequence 1 vs. 3, 2 vs. 3 [P < .001]), WSS (1.5T vs. 3T [P < .05], sequence 1 vs. 2, 1 vs. 3, 2 vs. 3 [P < .001]), and peak velocity (1.5T vs. 7T, sequence 1 vs. 3 [P > .001]). All parameters at all field strengths/with all sequences correlated moderately to strongly (r ≥ 0.5). CONCLUSION: Data from all sequences could be acquired and resulting images showed sufficient quality for further analysis. However, the variability of the measurements of peak velocity, flow volumes, and WSS was higher when comparing field strengths/sequences as the equivalence limits defined by the intraobserver assessments.

Adaptability and responsiveness: keys to operational measures in a regional hospital radiology department during the current COVID-19 pandemic.

The rapid and mostly uncontrolled spread of the coronavirus disease 2019 pandemic over the past 4 months has overwhelmed many healthcare systems worldwide. In Singapore, while our public healthcare institutions were considered well prepared due to our prior experience with the SARS outbreak, there was an unexpected surge of infected patients over the recent 2 months to deal with. We describe our radiology department's experience in modifying operational practices and implementing strict infection control measures aimed at minimizing disease transmission and mitigating the potential impact of possible staff infection. From the perspective of serving a medium-sized regional hospital and limited by physical and manpower constraints, our radiology department had to adapt quickly and modify our initial responses and practices as the disease scenario changed. We have also enumerated some guidelines for planning future radiology departments.

Tract sealing with normal saline after percutaneous transthoracic lung biopsies.

INTRODUCTION: In the present study, we aimed to assess whether normal saline injection for sealing the biopsy track is useful in reducing the incidence of pneumothorax after computed tomography (CT)-guided percutaneous transthoracic lung biopsy (PTLB). METHODS: We retrospectively compared the incidence of pneumothorax in 100 consecutive biopsies (n = 100, group A) that had injection of saline along the track, with historical cohort of same number of consecutive patients who underwent PTLB without injection of saline along the needle track (n = 100, group B). CT-guided biopsies were performed by coaxial technique and 1-3 ml of saline was injected along the tract. Patient chjmirocteristics, lesion size, location and other baseline pjmirometers were compared. Incidence of pneumothorax and number of patients who underwent catheter drainage of pneumothorax was compared in both groups. RESULTS: Baseline chjmirocteristics were compjmiroble in both groups. Track sealing with saline was successful in all patients. Pneumothorax rate was 46% for patients in group B and 32% in group A (P < 0.05). Seven patients (7%) had insertion of chest drain for pneumothorax in the group B and only 1% in the group A (P < 0.05). No mortality was observed in both groups. No complications were observed in any of the patients due to saline injection. CONCLUSION: Track sealing with saline is a simple and safe technique which significantly reduces the incidence of pneumothorax and chest tube insertion after PTLB.

Dual-Source Dual-Energy CT in Submandibular Sialolithiasis: Reliability and Radiation Burden.

OBJECTIVE. This study aims to compare the diagnostic accuracy of virtual unenhanced CT images derived from dual-source dual-energy contrast-enhanced CT with that of standard unenhanced CT images for evaluation of sialolithiasis. MATERIALS AND METHODS. All dual-energy CT studies of the neck performed during the preceding 5 years were reviewed for submandibular gland calculi. Only patients who had unenhanced CT and contrast-enhanced CT performed as part of the same evaluation were included in this study. This review yielded 30 patients. Virtual unenhanced CT images were derived from the dual-energy dataset and compared with the true unenhanced CT images by two separate radiologists who assessed the total number of calculi encountered, their location, the largest dimension, and the attenuation of the calculi. The radiation burden incurred for true unenhanced CT and virtual unenhanced CT and the total radiation burden were calculated. RESULTS. Our analysis revealed that measurements of stone size showed good interobserver agreement. The mean stone size was 7.9 ± 5.9 (SD) mm on virtual unenhanced CT and 8.4 ± 5.9 mm on true unenhanced CT (range, 2.0-31.8 mm); the difference was statistically insignificant. The mean stone attenuation differed considerably (p < 0.01) between the virtual and true unenhanced CT images (494.8 ± 187.5 HU and 924.4 ± 374.9 HU, respectively), but correlated well. The mean radiation dose for a dual-phase IV contrast-enhanced CT study was 23.13 mGy (volume CT dose index). The mean dose was 10.93 mGy for the true unenhanced CT phase, thereby suggesting a 47.25% reduction in administered radiation dose when a single-phase contrast-enhanced CT study with virtual unenhanced image reconstructions is performed. CONCLUSION. Virtual unenhanced CT images derived from dual-source dual-energy CT scans of the neck provide accurate assessment of sialolithiasis akin to that provided by conventional CT protocols but at only a fraction of the radiation dosage.

Sonographic assessment of musculoskeletal causes of calf pain and swelling.

Calf pain or swelling is a common presentation to the emergency department. The differential diagnoses are wide. Deep vein thrombosis (DVT) is often the first diagnosis to be excluded given its potentially fatal complications. Musculoskeletal causes of calf pain or swelling such as Baker's cyst, muscle or tendon tear, soft tissue infection, and inflammation are not uncommon and can often be confidently diagnosed with ultrasonography (US). Familiarity with these conditions and the sonographic findings would be useful in making timely and correct diagnosis.