Design of a filtration system to improve the dose distribution of an accelerator-based neutron capture therapy system

PURPOSE

The aim of this study is to design and evaluate a neutron filtration system to improve the dose distribution of an accelerator-based neutron capture therapy system.

METHODS

An LiF-sintered plate composed of 99%-enriched ⁶ Li was utilized to filter out low-energy neutrons to increase the average neutron energy at the beam exit. A 5-mm thick filter to fit inside a 12-cm diameter circular collimator was manufactured, and experimental measurements were performed to measure the thermal neutron flux and gamma-ray dose rate inside a water phantom. The experimental measurements were compared with the Monte Carlo simulation, particle, and heavy ion transport code system. Following the experimental verification, three filter designs were modeled, and the thermal neutron flux and the biologically weighted dose distribution inside a phantom were simulated. Following the phantom simulation, a dummy patient CT dataset was used to simulate a boron neutron capture therapy (BNCT) irradiation of the brain. A mock tumor located at 4, 6, 8 cm along the central axis and 4-cm off-axis was set, and the dose distribution was simulated for a maximum total biologically weighted brain dose of 12.5 Gy with a beam entering from the vertex.

RESULTS

All three filters improved the beam penetration of the accelerator-based neutron source. Filter design C was found to be the most suitable filter, increasing the advantage depth from 9.1 to 9.9 cm. Compared with the unfiltered beam, the mean weighted dose in the tumor located at a depth of 8 cm along the beam axis was increased by ∼25%, and 34% for the tumor located at a depth of 8 cm and off-axis by 4 cm.

CONCLUSION

A neutron filtration system for an accelerator-based BNCT system was investigated using Monte Carlo simulation. The proposed filter design significantly improved the dose distribution for the treatment of deep targets in the brain.

Improvement in the neutron beam collimation for application in boron neutron capture therapy of the head and neck region

In June 2020, the Japanese government approved boron neutron capture therapy for the treatment of head and neck cancer. The treatment is usually performed in a single fraction, with the neutron irradiation time being approximately 30–60 min. As neutrons scatter in air and loses its intensity, it is preferable to bring the patient as close to the beam port as possible to shorten the irradiation time. However, this can be a challenge, especially for patients with head and neck cancer, as the shoulders are an obstacle to a clean positioning. In this study, a novel neutron collimation system for an accelerator based neutron source was designed to allow for a more comfortable treatment, without compromising the irradiation time. Experimental measurements confirmed the simulation results and showed the new collimator can reduce the irradiation time by approximately 60% (under the same condition where the distance between the source and the patient surface was kept the same). The dose delivered to the surrounding healthy tissue was reduced with the new collimator, showing a 25% decrease in the D₅₀ of the mucosal membrane. Overall, the use of the newly designed collimator will allow for a more comfortable treatment of the head and neck region, reduce the treatment time, and reduce the dose delivered to the surrounding healthy tissue.

[The changes of blood-labyrinth barrier in idiopathic sudden sensorineural hearing loss and the relationship with clinical features and prognosis]

Objective: To investigate the clinical features and prognosis in patients with idiopathic sudden sensorineural hearing loss (ISSNHL) with blood-labyrinth barrier breakdown (BLB-B). Methods: Clinical data of patients with unilateral ISSNHL hospitalized from December 2017 to December 2018 were retrospectively analyzed. According to the results of 3D-FLAIR MRI and enhanced MRI scanning, these patients were divided into two groups, i.e., normal and abnormal inner ear groups. The patients in abnormal inner ear group were further divided into two subgroups: BLB-B and BLB-B with exudation. The differences and correlations among the groups in clinical characteristics, in terms of gender, age, deafness side, basic diseases, dizziness/vertigo, vestibular function, hearing loss degree, as well as classification of hearing curve, and prognosis were analyzed by statistical software SPSS 23.0. Results: Data were collected from 150 cases, in which 68 were male and 82 were female, aged (46.2±14.6) years, including 67 cases with normal inner ears and 83 cases with abnormal inner ears (13 cases with BLB-B; 70 cases with BLB-B and exudation). The dizziness/vertigo incidence, side ratio, hearing loss degree, classification of hearing curve, vestibular dysfunction (vestibular double temperature test, HIT and VAT) and therapeutic effect were different between normal and abnormal inner ear groups (P<0.05). The dizziness/vertigo incidence, side ratio, hearing loss degree, classification of hearing curve, vestibular dysfunction (vestibular double temperature test, o/cVEMP, HIT and VAT) and therapeutic effect were different among normal inner ear, BLB-B and BLB-B with exudation groups (P<0.05). Pairwise comparison between groups revealed that vestibular dysfunction (vestibular double temperature test, o/cVEMP, HIT and VAT) and therapeutic effect were different between normal inner ear and BLB-B groups (P<0.05); The dizziness/vertigo incidence, side ratio, hearing loss degree, classification of hearing curve, vestibular dysfunction (vestibular double temperature test, o/cVEMP, HIT and VAT) and therapeutic effect were different between normal inner ear and BLB-B with exudation groups (P<0.05). There was no significant different between BLB-B and BLB-B with exudation groups. Conclusion: BLB-B displayed by 3D-FLAIR MRI manifestation in ISSNHL patients indicates more serious cochlear and vestibular dysfunction, and worse therapeutic effect.

Comprehensive evaluation of dosimetric impact against position errors in accelerator-based BNCT under different treatment parameter settings

Background

Patients who undergo accelerator‐based (AB) boron neutron capture therapy (BNCT) for head and neck cancer in the sitting position are generally uncomfortably immobilized, and patient motion during this treatment may be greater than that in other radiotherapy techniques. Furthermore, the treatment time of BNCT is relatively long (up to approximately 1 h), which increases the possibility of patient movement during treatment. As most BNCT irradiations are performed in a single fraction, the dosimetric error due to patient motion is of greater consequence and needs to be evaluated and accounted for. Several treatment parameters are required for BNCT dose calculation.

Purpose

To investigate the dosimetric impacts (DIs) against position errors using a simple cylindrical phantom for an AB‐BNCT system under different treatment parameter settings.

Methods

The treatment plans were created in RayStation and the dose calculation was performed using the NeuCure® dose engine. A cylindrical phantom (16 cm diameter × 20 cm height) made of soft tissue was modeled. Dummy tumors in the form of a 3‐cm‐diameter sphere were arranged at depths of 2.5 and 6.5 cm (denoted by T_2.5 and T_6.5, respectively). Reference plans were created by setting the following parameters: collimator size = 10, 12, or 15 cm in diameter, collimator‐to‐surface distance (CSD) = 4.0 or 8.0 cm, tumor‐to‐blood ratio (T/B ratio) using ¹⁸F‐fluoro‐borono‐phenylalanine = 2.5 or 5.0, and ¹⁰B concentration in blood = 20, 25, or 30 ppm. The prescribed dose was D_95% ≥ 20 Gy‐eq for both T_2.5 and T_6.5. Based on the reference plans, phantom‐shifted plans were created in 26 directions [all combinations of left–right (LR), anterior–posterior (AP), and superior–inferior (SI) directions) and three distances (1.0, 2.0, and 3.0 cm). The DIs were evaluated at D_80% of the tumors. The shift direction dependency of the DI in the LR, AP, and SI directions was evaluated by conducting a multiple regression analysis (MRA) and other analyses where required.

Results

The coefficients of the MRA of the DIs for LR, AP, and SI shifts were −0.08, 2.16, and −0.04 (p‐values = 0.084, <0.01, and 0.334) for T_2.5 and −0.05, 2.08, and 0.15 (p‐values = 0.526, <0.01, and 0.065) for T_6.5, respectively. The analysis of variance showed that DIs due to the AP shift were significantly greater for smaller collimator sizes on T_2.5 and smaller CSD on T_6.5. Dose reduction due to SI or LR (lateral) shifts was significantly greater for smaller collimator sizes on both T_2.5 and T_6.5 and smaller CSD on T_2.5, according to the Student's t‐test. There were no significant differences in the DIs against both the AP shift and the lateral shift between the different T/B ratios and ¹⁰B concentrations.

Conclusion

The DIs were largely affected by the shift in the AP direction and were influenced by the different treatment parameters.

[Correlation analysis of 3D-FLAIR MRI characteristics of the inner ear and vestibular function in the patients with vestibular neuritis]

Objective: The characteristics of 3D-FLAIR MRI images of the inner ear of patients with vestibular neuritis were preliminarily studied to explore the possible pathogenesis of vestibular neuritis, and the correlation analysis was conducted in combination with vestibular function to provide a basis for accurate diagnosis of vestibular neuritis. Methods: A total of 36 patients with vestibular neuritis (VN) from December 2019 to October 2020 were collected from the Vertigo Department of Shandong Provincial ENT Hospital, Cheeloo College of Medicine, Shandong University. There were 36 cases (18 females, 18 males) with unilateral acute vestibular neuritis, 17 cases of left ear and 19 cases of right ear. According to the results of 3D-FLAIR MRI in the inner ears, the patients were divided into the enhanced group and the non-enhanced group (the health side served as the normal control group). The results of vestibular function examination in the two groups were compared. SPSS19.0 software was used for statistical processing to analyze the relationship between the vestibular function and the characteristics of 3D-FLAIR imaging in the inner ears. Results: Abnormal enhancement of 3D-FLAIR was found in 31 cases (86.1%) of the 36 cases, including 14 cases of both vestibular nerve and vestibular terminal organ enhancement, eight cases of superior vestibular nerve enhancement alone, seven cases of vestibular terminal organ enhancement alone, and two cases of cochlear enhancement alone. Observation of abnormal reinforcement of vestibular nerve showed: twenty-one cases of superior vestibular nerve reinforcement, one case of superior and inferior vestibular nerve reinforcement. No abnormalities were found in 3D-FLAIR of inner ear in 5 cases. According to the analysis of vestibular function results, there were 19 cases (52.8%) with total vestibular involvement, sixteen cases (44.4%) with superior vestibular involvement alone, and one case (2.8%) with inferior vestibular involvement alone. Comparison of vestibular function between the five cases (non-enhancement group) and the 31 cases (enhanced group) in the 3D-FLAIR group of the inner ears showed that the CP values of caloric tests in the enhanced group were higher (60.81±3.49 vs 34.12±7.37), with statistically significant difference (t=-2.898, P<0.01). Conclusion: In patients with vestibular neuritis, 3D-FLAIR MRI scan of the inner ear provides visual imaging evidence for clinical practice, considering that the lesion site of vestibular neuritis is not only in the vestibular nerve, but also in the vestibular end organ. Patients with 3D-FLAIR enhanced in the inner ear may have more significant vestibular function damage.

[Comparison of hip offset and rotation center reconstruction between robot-assisted and manual total hip arthroplasty]

Objective: To compare the differences of hip offset and rotation center reconstruction between robot-assisted and manual total hip arthroplasty (THA). Methods: Patients underwent robot-assisted and manual THA from May to September of 2020 in the First Affiliated Hospital of Chongqing Medical University were enrolled in this study. The patients included 27 patients (28 hips) in robot-assisted THA (rTHA) group and 29 patients (31 hips) in manual THA (mTHA) group. In rTHA group, there were 16 males and 11 females, with a mean age of (59±13) years. In mTHA group, there were 18 males and 11 females, with a mean age of (63±14) years. Basic information, including gender, age, body mass index (BMI), diagnosis and functional scoring etc, were recorded. In rTHA group, Mako robot system was used for preoperative planning, intraoperative real-time location and navigation. In mTHA group, traditional preoperative template design and surgical procedure were carried out. Operation time and functional scoring were compared postoperatively. Femoral offset, acetabular offset, global offset, rotation center changes in vertical and horizontal directions were measured on pelvis X-ray and analyzed. The correlation between intraoperative feedback of global offset change in robot system and postoperative measured global offset were analyzed. Results: Operation time in rTHA group was (80±10) min, which was statistically longer than that in mTHA group ((58±18) min, P<0.001). With 6 months' follow-up, the Harris scoring in rTHA group was 94.9±2.8, which was statistically higher than that in mTHA group (93.1±2.8, P=0.017), however there was no statistic difference in WOMAC scoring between rTHA and mTHA group (7.0±3.8 vs 7.1±2.4, P=0.840). Absolute global offset change within 5 mm, 5-10 mm and lager than 10 mm were 71.4%(20/28), 28.6%(8/28) and 0 in rTHA group, which were 45.2%(14/31), 29.0%(9/31) and 25.8%(8/31) in mTHA group (all P<0.05). A positive relation was found between intraoperative feedback of global offset change in robot system and postoperative measured global offset in rTHA group (r=0.77, P<0.001). It was found that rotation center changes concentrated in outer upper quadrant in both groups, and rotation center change in rTHA group concentrated mainly in the area less than 10 mm, however, rotation center change in mTHA group was more dispersive compared with rTHA group. Conclusion: rTHA may accurately reconstruct hip offset and rotation center, intraoperation feedback of global offset change may be an effective reference.

The Use of Episodic Memory Tests for Screening in Clinical Trials for Early Alzheimer's Disease: A Comparison of the Free and Cued Selective Reminding Test (FCSRT) and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)

BACKGROUND

Screening procedures for early Alzheimer's disease (AD) trials seek to efficiently identify participants who fulfill clinical and biomarker criteria for AD and enrich for those most likely to experience significant clinical progression during the study. Episodic memory performance is often assessed in screening, but the utility of different memory tests for optimizing screening efficiency and/or rates of clinical progression remains uncertain.

OBJECTIVES

Cross-study comparisons of the effects of inclusion criteria based on performance on the Free and Cued Selective Reminding Test (FCSRT) or the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) on screen-failure rates for episodic memory and β-amyloid (Aβ) positivity (by CSF or PET) and on subsequent rates of clinical disease progression in randomized participants across three clinical trials in early (prodromal-to-mild) AD.

DESIGN

Secondary analyses of cross-sectional and longitudinal clinical trial data.

SETTING

Multi-center international clinical trials.

PARTICIPANTS

Individuals with prodromal-to-mild AD screened and/or randomized in clinical trials for crenezumab (CREAD, CREAD2) or semorinemab (Tauriel). Cross-sectional analyses of screening data for episodic memory impairment included participants from CREAD2 (n=2897) and Tauriel (n=887) and for Aβ positivity included participants from CREAD (n=1138), CREAD2 (n=1119), and Tauriel (n=483). Longitudinal analyses of rates of clinical progression included participants from CREAD (n=779), CREAD2 (n=773), and Tauriel (n=331).

MEASUREMENTS

Cross-sectional analyses examined eligibility rates per cutoffs defined for the FCSRT (CREAD, CREAD2) or RBANS (Tauriel) and per Aβ positivity using CSF and/or PET biomarkers. Longitudinal analyses examined rates of clinical progression on the Clinical Dementia Rating-Sum of Boxes (CDR-SB), the 13-item version of the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog13), and Alzheimer's Disease Cooperative Study-Activities of Daily Living Scale (ADCS-ADL).

RESULTS

Lower rates of study eligibility per episodic memory criteria were seen with the FCSRT (CREAD2) relative to the RBANS (Tauriel), but similar rates of eligibility per Aβ positivity criteria were seen amongst participants with episodic memory impairment per the cutoffs used on either assessment. Similar rates of clinical decline over 18 months on the CDR-SB, ADAS-Cog13, and ADCS-ADL were observed in study populations enriched using the FCSRT (CREAD, CREAD2) or the RBANS (Tauriel).

CONCLUSIONS

Cutoffs for episodic memory impairment on the FCSRT used in the CREAD and CREAD2 studies are more stringent than those on the RBANS used in the Tauriel study, resulting in lower rates of eligibility. However, given that study enrichment with either test yields similar rates of Aβ positivity and clinical progression, considerations beyond these factors may drive the decision of which assessment to use for screening in early AD clinical trials.

Optical imaging of lithium-containing zinc sulfate plate in water during irradiation of neutrons from boron neutron capture therapy (BNCT) system

PURPOSE

Optical imaging of ionizing radiation is a possible method for dose distribution measurements. However, it is not clear whether the imaging method is also applicable to neutrons. To clarify this, we performed the imaging of neutrons in water from boron neutron capture therapy (BNCT) systems. Such systems require efficient distribution measurements of neutrons for quality assessment (QA) of the beams.

METHOD

A water-filled phantom was irradiated from the side with an epithermal neutron beam, in which a lithium-containing zinc sulfate (Li-ZnS(Ag)) plate was set in the beam direction, and during this irradiation the scintillation of the plate was imaged using a cooled CCD camera. In the imaging, Li-6 in the Li-ZnS(Ag) plate captures neutrons and converts them to alpha particles (He-4) and tritium (H-3), while ZnS(Ag) in the Li-ZnS(Ag) plate produces scintillation light in the plate. We also conducted Monte Carlo simulation and compared its results with the experimental results.

RESULTS

The image of the emitted light from the Li-ZnS(Ag) plate was clearly obtained with an imaging time of 0.5 s. The depth and lateral profiles of the measured image using the Li-ZnS(Ag) plate showed the same shapes as the neutron distributions measured with gold foil, within a difference of 8%. The destructive effect of neutrons on the CCD camera increased ∼3 times, but the unit was still working after the measurement.

CONCLUSION

The optical imaging of neutrons in water is possible, and it has the potential to be a new method for efficient QA as well as for research on neutrons. This article is protected by copyright. All rights reserved.

Evaluation of a treatment planning system developed for clinical boron neutron capture therapy and validation against an independent Monte Carlo dose calculation system

Boron neutron capture therapy (BNCT) for the treatment of unresectable, locally advanced, and recurrent carcinoma of the head and neck cancer has been approved by the Japanese government for reimbursement under the national health insurance as of June 2020. A new treatment planning system for clinical BNCT has been developed by Sumitomo Heavy Industries, Ltd. (Sumitomo), NeuCure® Dose Engine_. To safely implement this system for clinical use, the simulated neutron flux and gamma ray dose rate inside a water phantom was compared against experimental measurements. Furthermore, to validate and verify the new planning system, the dose distribution inside an anthropomorphic head phantom was compared against a BNCT treatment planning system SERA and an in-house developed Monte Carlo dose calculation program. The simulated results closely matched the experimental results, within 5% for the thermal neutron flux and 10% for the gamma ray dose rate. The dose distribution inside the head phantom closely matched with SERA and the in-house developed dose calculation program, within 3% for the tumour and a difference of 0.3 Gy_w for the brain.

Development of an irradiation method for superficial tumours using a hydrogel bolus in an accelerator-based BNCT

The aim of this study is the development of an irradiation method for the treatment of superficial tumours using a hydrogel bolus to produce thermal neutrons in accelerator-based Boron Neutron Capture Therapy (BNCT).To evaluate the neutron moderating ability of a hydrogel bolus, a water phantom with a hydrogel bolus was irradiated with an epithermal neutron beam from a cyclotron-based epithermal neutron source. Phantom simulating irradiation to the plantar position was manufactured using three-dimensional printing technology to perform an irradiation test of a hydrogel bolus. Thermal neutron fluxes on the surface of a phantom were evaluated and the results were compared with the Monte Carlo-based Simulation Environment for Radiotherapy Applications (SERA) treatment planning software. It was confirmed that a hydrogel bolus had the same neutron moderating ability as water, and the calculation results from SERA aligned with the measured values within approximately 5%. Furthermore, it was confirmed that the thermal neutron flux decreased at the edge of the irradiation field. It was possible to uniformly irradiate thermal neutrons by increasing the bolus thickness at the edge of the irradiation field, thereby successfully determining uniform dose distribution. An irradiation method for superficial tumours using a hydrogel bolus in the accelerator-based BNCT was established.

TB-6 Experimental evaluation of the therapeutic potential of boron neutron capture therapy in primary central nervous system lymphoma

Background: High-dose methotrexate and whole brain radiation therapy (WBRT) is the recommended treatment for primary central nervous system lymphoma (PCNSL). Although the initial treatment is successful, the recurrence rate is high and the prognosis is poor. Boron neutron capture therapy (BNCT) is a nuclear reaction-based tumor cell-selective particle irradiation that occurs when non-radioactive boron-10 is irradiated with neutrons to produce α particles (10B [n, α] 7Li). In this study, we conducted a basic research to explore the possibility of BNCT as a treatment option for PCNSL. Methods: Cellular uptake of boron using human lymphoma cell-lines after exposure to boronophenylalanine (BPA) were evaluated. The cytotoxicity of lymphoma cells by photon irradiation or neutron irradiation with BPA were also evaluated. The lymphoma cells were implanted into the mouse brain and the bio-distribution of boron after administration of BPA were measured. In neutron irradiation studies, the therapeutic effect of BNCT on mouse CNSL models were evaluated in terms of survival time. Results: The boron concentration in lymphoma cells after BPA exposure was sufficiently high, and lymphoma cells showed cytotoxicity by photon irradiation, and also by BNCT. In in vivo bio-distribution study, lymphoma cells showed enough uptake of BPA with well contrasted to the brain. In the neutron irradiation experiment, the BNCT group showed a significant prolongation in their survival time compared to the control group. Conclusions: In our study, BNCT showed its effectiveness for PCNSL in a mouse brain tumor model. PCNSL is a radio-sensitive tumor with a extremely good response rate, but it also has a high recurrence rate / a high rate of adverse events, so there is no effective treatment for recurrence after treatment. Our translational study showed that BNCT is possibly have an important role against PCNSL during the therapy lines as a new treatment option for PCNSL patients.

Efficacy of Boron Neutron Capture Therapy in Primary Central Nervous System Lymphoma: In Vitro and In Vivo Evaluation

Background: Boron neutron capture therapy (BNCT) is a nuclear reaction-based tumor cell-selective particle irradiation method. High-dose methotrexate and whole-brain radiation therapy (WBRT) are the recommended treatments for primary central nervous system lymphoma (PCNSL). This tumor responds well to initial treatment but relapses even after successful treatment, and the prognosis is poor as there is no safe and effective treatment for relapse. In this study, we aimed to conduct basic research to explore the possibility of using BNCT as a treatment for PCNSL. Methods: The boron concentration in human lymphoma cells was measured. Subsequently, neutron irradiation experiments on lymphoma cells were conducted. A mouse central nervous system (CNS) lymphoma model was created to evaluate the biodistribution of boron after the administration of borono-phenylalanine as a capture agent. In the neutron irradiation study of a mouse PCNSL model, the therapeutic effect of BNCT on PCNSL was evaluated in terms of survival. Results: The boron uptake capability of human lymphoma cells was sufficiently high both in vitro and in vivo. In the neutron irradiation study, the BNCT group showed a higher cell killing effect and prolonged survival compared with the control group. Conclusions: A new therapeutic approach for PCNSL is urgently required, and BNCT may be a promising treatment for PCNSL. The results of this study, including those of neutron irradiation, suggest success in the conduct of future clinical trials to explore the possibility of BNCT as a new treatment option for PCNSL.

Smoking and incidence of insomnia: a systematic review and meta-analysis of cohort studies

OBJECTIVE

This study investigated the impact of smoking on the incidence of insomnia.

STUDY DESIGN

Systematic review and meta-analysis of cohort studies.

METHODS

PubMed, EMBASE, Web of Science, Cochrane Library, and OVID were searched through March 2020. Cohort studies reporting the effect of smoking on the incidence of insomnia were included. We quantitatively analyzed the basic framework and study characteristics and then pooled estimate effects with 95% confidence intervals (CIs) of outcomes of each included study using fixed-effects meta-analyses.

RESULTS

This systematic review included six cohort studies involving 12,445 participants. Quantitatively summarized results suggested that smoking could significantly increase the incidence of insomnia (odds ratio [OR]: 1.07, 95% CI: 1.02, 1.13). Regular smoking was significantly associated with the incidence of insomnia (OR = 1.07, 95% CI: 1.01, 1.13). As for occasional smokers and ex-smokers, the pooled analysis did not indicate a significant association (occasional smoker: OR = 2.09, 95% CI: 0.44, 9.95; ex-smoker; OR = 1.02, 95% CI: 0.67, 1.54). Subgroup analysis by age, gender ratio, and region showed a statistically significant relationship between smoking and the incidence of insomnia in specific groups.

CONCLUSIONS

Integrated longitudinal observational evidence identified smoking as a significant risk factor of insomnia. Considering the limited amount of available studies, more high-quality and prospective cohort studies of large sample sizes are needed to explore details of this association.

Photoneutron-induced damage reduction for cardiac implantable electronic devices using neutron-shielding sheets in high-energy X-ray radiotherapy: A phantom study

PURPOSE

To evaluate damage reduction in cardiac implantable electronic devices (CIEDs) caused by photoneutrons in high-energy X-ray radiotherapy using a neutron-shielding sheet (NSS).

METHODS

The NSS consists of a bolus with a thickness of 1 or 2 cm (Bls1 or Bls2) as a moderator and several absorbers (20%, 50%, or 80% B₄C silicone sheet [B₄C20, B₄C50, or B₄C80] or a 40% LiF silicone sheet [LiF40]). First, a linear accelerator (LINAC) with a water-equivalent phantom was modeled in the simulation and measured experimentally. Several NSSs were placed on the phantom, a Eu:LiCaAlF₆ scintillator was placed between the phantom and the NSS, and X-rays were irradiated. The relative counts (Cr = counts when placing the NSS or Bls2) were compared between the experiment and simulation. Second, CIED damage was evaluated in the simulation. The relative damage (Dr = damage when placing or not placing the NSS) was compared among all the NSSs. In addition, the γ-ray and leaking X-ray dose from B₄C was measured using a dosimetric film. After determining the optimal NSS combination, Dr value analysis was performed by changing the length of one side and the thickness.

RESULTS

The Cr values of the simulation and experiment agreed within a 30% percentage difference, except for Bare or LiF40-only. The Dr value was reduced by 43% when Bls2 + B₄C80 was applied. The photon dose was less than 5 cGy/1500 MU. The Dr values were smaller for the smaller lengths of one side of B₄C80 and decreased as the M-layer thickness increased.

CONCLUSIONS

The CIED damage induced by photoneutrons generated by a LINAC was effectively reduced by applying the optimal NSS.

T1rho mapping of cartilage and menisci in patients with hyperuricaemia at 3 T: a preliminary study

AIM

To compare and assess T_1rho values of the femorotibial cartilage compartments and subregional menisci in patients with hyperuricaemia at 3 T.

MATERIALS AND METHODS

Thirty-two patients were enrolled in the study and were subdivided into two subgroups: 15 healthy controls (three women, 12 men; mean age = 45.3 ± 10.9 years, age range 25-72 years) and 17 patients with asymptomatic hyperuricaemia (two women, 15 men; mean age = 44.4 ± 12.7 years, age range 26-77 years). All patients were evaluated using 3 T magnetic resonance imaging (MRI) using an eight-channel phased-array knee coil (transmit-receive). Wilcoxon's rank sum test and analysis of covariance (ANCOVA) were conducted to determine whether there were any statistically significant differences in the T_1rho values of the femorotibial cartilage compartments and subregional menisci between the two subgroups.

RESULTS

Lateral tibial cartilage (45.8 ± 2.9 ms) in the healthy subgroup had significantly lower (p<0.05) T_1rho values than those of all subcompartments of the femorotibial cartilage in the hyperuricaemia subgroup. The lateral femoral cartilage (LF) in hyperuricaemia (54.6 ± 3.9 ms) subgroup had significantly higher (p<0.05) T_1rho values than those of all subcompartments of the femorotibial cartilage except the LF in the healthy subgroup. Significantly higher (p<0.05) T_1rho values existed in the LF of the healthy (54.6 ± 4.7 ms) subgroup in comparison with those of all subcompartments of femorotibial cartilage except the LF in hyperuricaemia subgroup.

CONCLUSIONS

T_1rho values in certain compartments of the femorotibial cartilage in patients with hyperuricaemia are elevated compared to those in healthy patients presumably due to reduced proteoglycan content, to which particular attention should be paid when diagnosing and treating the patients with hyperuricaemia in a clinical setting.