CT number calibration audit in photon radiation therapy

BACKGROUND

Inadequate computed tomography (CT) number calibration curves affect dose calculation accuracy. Although CT number calibration curves registered in treatment planning systems (TPSs) should be consistent with human tissues, it is unclear whether adequate CT number calibration is performed because CT number calibration curves have not been assessed for various types of CT number calibration phantoms and TPSs.

PURPOSE

The purpose of this study was to investigate CT number calibration curves for mass density (ρ) and relative electron density (ρe ).

METHODS

A CT number calibration audit phantom was sent to 24 Japanese photon therapy institutes from the evaluating institute and scanned using their individual clinical CT scan protocols. The CT images of the audit phantom and institute-specific CT number calibration curves were submitted to the evaluating institute for analyzing the calibration curves registered in the TPSs at the participating institutes. The institute-specific CT number calibration curves were created using commercial phantom (Gammex, Gammex Inc., Middleton, WI, USA) or CIRS phantom (Computerized Imaging Reference Systems, Inc., Norfolk, VA, USA)). At the evaluating institute, theoretical CT number calibration curves were created using a stoichiometric CT number calibration method based on the CT image, and the institute-specific CT number calibration curves were compared with the theoretical calibration curve. Differences in ρ and ρe over the multiple points on the curve (Δρm and Δρe,m , respectively) were calculated for each CT number, categorized for each phantom vendor and TPS, and evaluated for three tissue types: lung, soft tissues, and bones. In particular, the CT-ρ calibration curves for Tomotherapy TPSs (ACCURAY, Sunnyvale, CA, USA) were categorized separately from the Gammex CT-ρ calibration curves because the available tissue-equivalent materials (TEMs) were limited by the manufacturer recommendations. In addition, the differences in ρ and ρe for the specific TEMs (ΔρTEM and Δρe,TEM , respectively) were calculated by subtracting the ρ or ρe of the TEMs from the theoretical CT-ρ or CT-ρe calibration curve.

RESULTS

The mean ± standard deviation (SD) of Δρm and Δρe,m for the Gammex phantom were -1.1 ± 1.2 g/cm3 and -0.2 ± 1.1, -0.3 ± 0.9 g/cm3 and 0.8 ± 1.3, and -0.9 ± 1.3 g/cm3 and 1.0 ± 1.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρm and Δρe,m for the CIRS phantom were 0.3 ± 0.8 g/cm3 and 0.9 ± 0.9, 0.6 ± 0.6 g/cm3 and 1.4 ± 0.8, and 0.2 ± 0.5 g/cm3 and 1.6 ± 0.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρm for Tomotherapy TPSs was 2.1 ± 1.4 g/cm3 for soft tissues, which is larger than those for other TPSs. The mean ± SD of Δρe,TEM for the Gammex brain phantom (BRN-SR2) was -1.8 ± 0.4, implying that the tissue equivalency of the BRN-SR2 plug was slightly inferior to that of other plugs.

CONCLUSIONS

Latent deviations between human tissues and TEMs were found by comparing the CT number calibration curves of the various institutes.

Epigenetic Regulation of Ameloblast Differentiation by HMGN Proteins

Dental enamel formation is coordinated by ameloblast differentiation, production of enamel matrix proteins, and crystal growth. The factors regulating ameloblast differentiation are not fully understood. Here we show that the high mobility group N (HMGN) nucleosomal binding proteins modulate the rate of ameloblast differentiation and enamel formation. We found that HMGN1 and HMGN2 proteins are downregulated during mouse ameloblast differentiation. Genetically altered mice lacking HMGN1 and HMGN2 proteins show faster ameloblast differentiation and a higher rate of enamel deposition in mice molars and incisors. In vitro differentiation of induced pluripotent stem cells to dental epithelium cells showed that HMGN proteins modulate the expression and chromatin accessibility of ameloblast-specific genes and affect the binding of transcription factors epiprofin and PITX2 to ameloblast-specific genes. Our results suggest that HMGN proteins regulate ameloblast differentiation and enamel mineralization by modulating lineage-specific chromatin accessibility and transcription factor binding to ameloblast regulatory sites.

Technical note: Point-by-point ion-recombination correction for accurate dose profile measurement in high dose-per-pulse irradiation field

BACKGROUND

Although flattening filter free (FFF) beams are commonly used in clinical treatment, the accuracy of dose measurements in FFF beams has been questioned. Higher dose per pulse (DPP) such as FFF beams from a linear accelerator may cause problems in dose profile measurements using an ionization chamber due to the change of the charge collection efficiency. Ionization chambers are commonly used for percent depth dose (PDD) measurements. Changes of DPP due to chamber movement during PDD measurement can vary the ion collection efficiency of ionization chambers. In the case of FF beams, the DPP fluctuation is negligible, but in the case of the FFF beams, the DPP is 2.5 ∼ 4 times larger than that of the FF beam, and the change in ion collection efficiency is larger than that of the FF beam. PDD profile normalized by maximum dose depth, 10 cm depth for example, may therefore be affected by the ion collection efficiency.

PURPOSE

In this study, we investigate the characteristics of the ion collection efficiency change depending on the DPP of each ionization chamber in the FFF beam. We furthermore propose a method to obtain the chamber- independent PDD by applying a DPP-dependent ion recombination correction.

METHODS

Prior to investigating the relationship between DPP and charge collection efficiency, Jaffe-plots were generated with different DPP settings to investigate the linearity between the applied voltage and collected charge. The absolute dose measurement using eight ionization chambers under the irradiation settings of 0.148, 0.087, and 0.008 cGy/pulse were performed. Applied voltages for the Jaffe-plots were 100, 125, 150, 200, 250, and 300 V. The ion recombination correction factor Pion was calculated by the two-voltage analysis (TVA) method at the applied voltages of 300 and 100 V. The DPP dependency of the charge collection efficiency for each ionization chamber were evaluated from the DPP- Pion plot. PDD profiles for the 10 MV FFF beam were measured using Farmer type chambers (TN30013, FC65-P, and FC65-G) and mini-type chambers (TN31010, TN31021, CC13, CC04, and FC23-C). The PDD profiles were corrected with ion recombination correction at negative and positive polar applied voltages of 100 and 300 V.

RESULTS

From the DPP-Pion relation for each ionization chamber with DPP ranging from 0.008 cGy/pulse to 0.148 cGy/pulse, all Farmer and mini-type chambers satisfied the requirements described in AAPM TG-51 addendum. However, Pion for the CC13 was most affected by DPP among tested chambers. The maximum deviation among PDDs using eight ionization chambers for 10 MV FFF was about 1%, but the deviation was suppressed to about 0.5% by applying ion recombination correction at each depth.

CONCLUSIONS

In this study, the deviation of PDD profile among the ionization chambers was reduced by the ion recombination coefficient including the DPP dependency, especially for high DPP beams such as FFF beams. The present method is particularly effective for CC13, where the ion collection efficiency is highly DPP dependent.

A virtual audit system for intensity-modulated radiation therapy credentialing in Japan Clinical Oncology Group clinical trials: A pilot study

PURPOSE

The Medical Physics Working Group of the Radiation Therapy Study Group at the Japan Clinical Oncology Group is currently developing a virtual audit system for intensity-modulated radiation therapy dosimetry credentialing. The target dosimeters include films and array detectors, such as ArcCHECK (Sun Nuclear Corporation, Melbourne, Florida, USA) and Delta4 (ScandiDos, Uppsala, Sweden). This pilot study investigated the feasibility of our virtual audit system using previously acquired data.

METHODS

We analyzed 46 films (32 and 14 in the axial and coronal planes, respectively) from 29 institutions. Global gamma analysis between measured and planned dose distributions used the following settings: 3%/3 mm criteria (the dose denominator was 2 Gy), 30% threshold dose, no scaling of the datasets, and 90% tolerance level. In addition, 21 datasets from nine institutions were obtained for array evaluation. Five institutions used ArcCHECK, while the others used Delta4. Global gamma analysis was performed with 3%/2 mm criteria (the dose denominator was the maximum calculated dose), 10% threshold dose, and 95% tolerance level. The film calibration and gamma analysis were conducted with in-house software developed using Python (version 3.9.2).

RESULTS

The means ± standard deviations of the gamma passing rates were 99.4 ± 1.5% (range, 92.8%-100%) and 99.2 ± 1.0% (range, 97.0%-100%) in the film and array evaluations, respectively.

CONCLUSION

This pilot study demonstrated the feasibility of virtual audits. The proposed virtual audit system will contribute to more efficient, cheaper, and more rapid trial credentialing than on-site and postal audits; however, the limitations should be considered when operating our virtual audit system.

Improvement of Crystal Identification Accuracy for Depth-of-Interaction Detector System with Peak-to-Charge Discrimination Method

In positron emission tomography (PET), parallax errors degrade spatial resolution. The depth of interaction (DOI) information provides the position in the depth of the scintillator interacting with the γ-rays, thus reducing parallax errors. A previous study developed a Peak-to-Charge discrimination (PQD), which can separate spontaneous alpha decay in LaBr₃:Ce. Since decay constant of GSO:Ce depends on Ce concentration, the PQD is expected to discriminate GSO:Ce scintillators with different Ce concentration. In this study, the PQD-based DOI detector system was developed, which can be processed online and implemented in PET. A detector was composed of four layers of GSO:Ce crystals and a PS-PMT. The four crystals were obtained from both the top and bottom of ingots with a nominal Ce concentration of 0.5 mol% and 1.5 mol%. The PQD was implemented on the Xilinx Zynq-7000 SoC board with 8ch Flash ADC to gain real-time processing, flexibility, and expandability. The results showed that the mean Figure of Merits in 1D between four scintillators are 1.5, 0.99, 0.91 for layers between 1st-2nd, 2nd-3rd, and 3rd-4th respectively, and the mean Error Rate in 1D between four scintillators are 3.50%, 2.96%, 13.3%, and 1.88% for layers 1, 2, 3, and 4, respectively. In addition, the introduction of the 2D PQDs resulted in the mean Figure of Merits in 2D greater than 0.9 and the mean Error Rate in 2D less than 3% in all layers.

Planning study: prone versus supine position for stereotactic body radiotherapy in prostate by CyberKnife

This study aimed to clarify the differences in radiotherapy dose characteristics and delivery efficiency between the supine and prone positions in patients with prostate cancer using the CyberKnife. The planning computed tomography (CT) and delineations of the prone position were obtained by rotating the supine CT images with delineations of 180° using image processing software. The optimization parameters for planning target volume (PTV) and organs at risk (OARs) were based on the prone position. The optimization parameters determined for the prone position were applied to the supine position for optimization and dose calculation. The dosimetric characteristics of the PTV and OARs, and delivery efficiency were compared between the two different patient positions. The plans in the prone position resulted in better PTV conformity index (nCI), rectum V90%, V80%, V75%, V50% and bladder V50%. A significant difference was observed in treatment time and depth along the central axis (dCAX) between the two plans. The mean treatment time per fraction and dCAX for the supine and prone positions were 20.9 ± 1.7 min versus 19.8 ± 1.3 min (P = 0.019) and 151.1 ± 33.6 mm versus 233.2 ± 8.8 mm (P < 0.001), respectively. In this study the prone position was found to improve dosimetric characteristics and delivery efficiency compared with the supine position during prostate cancer treatment with the CyberKnife.

Verification of patient‐setup accuracy using a surface imaging system with steep measurement angle

PURPOSE

We evaluate an SGRT device (Voxelan HEV-600 M/RMS) installed with Radixact, with the view angle of the Voxelan's camera at 74 degrees. The accuracy of Voxelan with this steep angle was evaluated with phantom experiments and inter-fractional setup errors of patients.

METHODS

In the phantom experiments, the difference between the measured values of Voxelan from the truth was evaluated for translations and rotations. The inter-fractional setup error between the setup using skin markers with laser localizer (laser setup: LS) and the setup using Voxelan (surface setup: SS) was compared for head and neck (N = 19), chest (N = 7) and pelvis (N = 9) cases. The inter-fractional setup error was calculated by subtracting from bone matching by megavoltage computed tomography (MVCT) as ground truth.

RESULTS

From the phantom experiments, the average difference between the measured values of Voxelan from the truth was within 1 mm and 1 degree. In all cases, inter-fractional setup error based on MVCT was not significantly different between LS and SS by Welch's t-test (P > 0.05). The vector offset of the LS for head and neck, chest, and pelvis were 6.5, 9.6, and 9.6 mm, respectively, and that of the SS were 5.8, 8.6, and 12.6 mm, respectively. Slight improvement was observed for the head and neck, and chest cases, however, pelvis cases were not improved because the umbilical region could not be clearly visualized as a reference.

CONCLUSION

The results show that SS in Voxelan with an installation angle of 74 degrees is equal to or better than LS.

Infants’ Prediction of Humanoid Robot’s Goal-Directed Action

Several studies have shown that infants anticipate human goal-directed actions, but not robot’s ones. However, the studies focusing on the robot goal-directed actions have mainly analyzed the effect of mechanical arms on infant’s attention. To date, the prediction of goal-directed actions in infants has not yet been studied when the agent is a humanoid robot. Given this lack of evidence in infancy research, the present study aims at analyzing infants’ action anticipation of both a human’s and a humanoid robot’s goal-directed action. Data were acquired on thirty 17-month-old infants, watching four video clips, where either a human or a humanoid robot performed a goal-directed action, i.e. reaching a target. Infants looking behavior was measured through the eye-tracking technique. The results showed that infants anticipated the goal-directed action of both the human and the robot and there were no differences in the anticipatory gaze behavior between the two agents. Furthermore, the findings indicated different attentional patterns for the human and the robot, showing a greater attention paid to the robot's face than the human’s face. Overall, the results suggest that 17-month-old infants may infer also humanoid robot’ underlying action goals.

Current status of countermeasures for ageing of nuclear power plants in Japan

This paper summarizes ageing countermeasure program of the nuclear power plants performed by the Japanese Government and industries and related activities, and describes current research program and utilization of the research results for the aged nuclear power plants. Regulatory bodies (NISA of METI: Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade and Industry') reviewed the ageing issues of nuclear power plants to enhance countermeasures for the aged plants. Nuclear Power Plant Life Engineering Center (PLEC) entrusted by NISA is carrying out the task relating to the aged plants.

Inflammatory Signaling and DNA Damage Responses after Local Exposure to an Insoluble Radioactive Microparticle

Simple Summary

A cesium-bearing microparticle (Cs-BMP) is an insoluble radioactive microparticle possessing high specific radioactivity, which was discovered after the incident at the Fukushima nuclear power plant. Due to their insoluble nature, such Cs-BMPs are assumed to adhere in the long term to normal tissue, leading to chronic local exposure. However, radiation risk due to the intake of internal exposure to radioactive cesium is conventionally estimated from the organ dose given by uniform exposure to soluble cesium. As such, it is critical to clarify the normal tissue effects posed by heterogeneous exposure to Cs-BMPs. This in vitro study reports on the relationship between the inflammatory responses and DNA damage induction during local exposure to a Cs-BMP.

Abstract

Cesium-bearing microparticles (Cs-BMPs) can reach the human respiratory system after inhalation, resulting in chronic local internal exposure. We previously investigated the spatial distribution of DNA damage induced in areas around a Cs-BMP; however, the biological impacts have not been fully clarified due to the limited amount of data. Here, we investigated the inflammatory signaling and DNA damage responses after local exposure to a Cs-BMP in vitro. We used two normal human lung cell lines, i.e., lung fibroblast cells (WI-38) and bronchial epithelial cells (HBEC3-KT). After 24 h exposure to a Cs-BMP, inflammation was evaluated by immunofluorescent staining for nuclear factor κB (NF-κB) p65 and cyclooxygenase 2 (COX-2). The number of DNA double-strand breaks (DSBs) was also detected by means of phospholylated histone H2AX (γ-H2AX) focus formation assay. Cs-BMP exposure significantly increased NF-κB p65 and COX-2 expressions, which were related to the number of γ-H2AX foci in the cell nuclei. Compared to the uniform (external) exposure to ¹³⁷Cs γ-rays, NF-κB tended to be more activated in the cells proximal to the Cs-BMP, while both NF-κB p65 and COX-2 were significantly activated in the distal cells. Experiments with chemical inhibitors for NF-κB p65 and COX-2 suggested the involvement of such inflammatory responses both in the reduced radiosensitivity of the cells proximal to Cs-BMP and the enhanced radiosensitivity of the cells distal from Cs-BMP. The data show that local exposure to Cs-BMP leads to biological effects modified by the NF-κB pathway, suggesting that the radiation risk for Cs-BMP exposure can differ from that estimated based on conventional uniform exposure to normal tissues.

Long working hours, depression and suicidality among OB/GYNs in Japan

Background

There is abundant evidence linking long working hours among physicians with adverse health effects; however, most studies have focused on medical residents. In Japan, obstetrician/gynaecologists (OB/GYNs) work the longest hours, yet no studies have investigated potential relationships between excessive overtime and depression and suicidal ideation within this population.

Aims

To investigate the relationship between long working hours and depression and suicidal ideation among OB/GYNs in Japan.

Methods

We administered a survey questionnaire to OB/GYNs and received 919 valid responses. Multivariate logistic regression was performed with depression and suicidal ideation as the outcome variables and number of working hours per week, gender, age, marital status, hospital type and geographical area type as the explanatory variables.

Results

Sixteen per cent of the participants were depressed, and 3% reported suicidal ideation. Working 100 or more hours per week increased the odds for both depression and suicidal ideation [odds ratio (OR): 2.08 (95% confidence interval {CI}: 1.07–4.05, P = 0.03); and OR: 7.03 (95% CI: 1.95–25.38, P &lt; 0.001), respectively].

Conclusions

The results suggest that the Japanese Government should vigorously promote physicians’ work-style reform, so that a lowered upper limit of overtime hours will be enforced from 2024 to improve physicians’ health and patients’ safety.

Prediction of target position from multiple fiducial markers by partial least squares regression in real-time tumor-tracking radiation therapy

The purpose of this work is to show the usefulness of a prediction method of tumor location based on partial least squares regression (PLSR) using multiple fiducial markers. The trajectory data of respiratory motion of four internal fiducial markers inserted in lungs were used for the analysis. The position of one of the four markers was assumed to be the tumor position and was predicted by other three fiducial markers. Regression coefficients for prediction of the position of the tumor-assumed marker from the fiducial markers' positions is derived by PLSR. The tracking error and the gating error were evaluated assuming two possible variations. First, the variation of the position definition of the tumor and the markers on treatment planning computed tomograhy (CT) images. Second, the intra-fractional anatomical variation which leads the distance change between the tumor and markers during the course of treatment. For comparison, rigid predictions and ordinally multiple linear regression (MLR) predictions were also evaluated. The tracking and gating errors of PLSR prediction were smaller than those of other prediction methods. Ninety-fifth percentile of tracking/gating error in all trials were 3.7/4.1 mm, respectively in PLSR prediction for superior-inferior direction. The results suggested that PLSR prediction was robust to variations, and clinically applicable accuracy could be achievable for targeting tumors.

Period1 gene expression in the olfactory bulb and liver of freely moving streptozotocin-treated diabetic mouse

Clock genes express circadian rhythms in most organs. These rhythms are organized throughout the whole body, regulated by the suprachiasmatic nucleus (SCN) in the brain. Disturbance of these clock gene expression rhythms is a risk factor for diseases such as obesity. In the present study, to explore the role of clock genes in developing diabetes, we examined the effect of streptozotocin (STZ)-induced high glucose on Period1 (Per1) gene expression rhythm in the liver and the olfactory bub (OB) in the brain. We found a drastic increase of Per1 expression in both tissues after STZ injection while blood glucose content was low. After a rapid expression peak, Per1 expression showed no rhythm. Associated with an increase of glucose content, behavior became arrhythmic. Finally, we succeeded in detecting an increase of Per1 expression in mice hair follicles on day 1 after STZ administration, before the onset of symptoms. These results show that elevated Per1 expression by STZ plays an important role in the aggravation of diabetes.

Fundamental study on quality assurance (QA) procedures for a real-time tumor tracking radiotherapy (RTRT) system from the viewpoint of imaging devices

PURPOSE

The real-time tumor tracking radiotherapy (RTRT) system requires periodic quality assurance (QA) and quality control. The goal of this study is to propose QA procedures from the viewpoint of imaging devices in the RTRT system.

METHODS

Tracking by the RTRT system (equips two sets of colored image intensifiers (colored I.I.s) fluoroscopy units) for the moving gold-marker (diameter 2.0 mm) in a rotating phantom were performed under various X-ray conditions. To analyze the relationship between fluoroscopic image quality and precision of gold marker coordinate calculation, the standard deviation of the 3D coordinate (σ3D [mm]) of the gold marker, the mean of the pattern recognition score (PRS) and the standard deviation of the distance between rays (DBR) (σDBR [mm]) were evaluated.

RESULTS

When tracking with speed of 10-60 mm/s, σDBR increased, though the mean PRS did not change significantly (p>0.05). On the contrary, the mean PRS increased depending on the integral noise equivalent quanta (∫NEQ) that is an indicator of image quality calculated from the modulation transfer function (MTF) as an indicator of spatial resolution and the noise power spectrum (NPS) as an indicator of noise characteristic.

CONCLUSION

The indicators of NEQ, MTF, and NPS were useful for managing the tracking accuracy of the RTRT system. We propose observing the change of these indicators as additional QA procedures for each imaging device from the commissioning baseline.

Oxygen enhancement ratios of cancer cells after exposure to intensity modulated x-ray fields: DNA damage and cell survival

Hypoxic cancer cells within solid tumours show radio-resistance, leading to malignant progression in fractionated radiotherapy. When prescribing dose to tumours under heterogeneous oxygen pressure with intensity-modulated radiation fields, intercellular signalling could have an impact on radiosensitivity between in-field and out-of-field (OF) cells. However, the impact of hypoxia on radio-sensitivity under modulated radiation intensity remains to be fully clarified. Here, we investigate the impact of hypoxia on in-field and OF radio-sensitivities using two types of cancer cells, DU145 and H1299. Using a nBIONIX hypoxic culture kit and a shielding technique to irradiate 50% of a cell culture flask, oxygen enhancement ratios for double-strand breaks (DSB) and cell death endpoints were determined. Thesein vitromeasurements indicate that hypoxia impacts OF cells, although the hypoxic impacts on OF cells for cell survival were dose-dependent and smaller compared to those for in-field and uniformly irradiated cells. These decreased radio-sensitivities of OF cells were shown as a consistent tendency for both DSB and cell death endpoints, suggesting that radiation-induced intercellular communication is of importance in advanced radiotherapy dose-distributions such as with intensity-modulated radiotherapy.

Quantification of Oscillatory Shear Stress from Reciprocating CSF Motion on 4D Flow Imaging

BACKGROUND AND PURPOSE

Oscillatory shear stress could not be directly measured in consideration of direction, although cerebrospinal fluid has repetitive movements synchronized with heartbeat. Our aim was to evaluate the important of oscillatory shear stress in the cerebral aqueduct and foramen magnum in idiopathic normal pressure hydrocephalus by comparing it with wall shear stress and the oscillatory shear index in patients with idiopathic normal pressure hydrocephalus.

MATERIALS AND METHODS

By means of the 4D flow application, oscillatory shear stress, wall shear stress, and the oscillatory shear index were measured in 41 patients with idiopathic normal pressure hydrocephalus, 23 with co-occurrence of idiopathic normal pressure hydrocephalus and Alzheimer-type dementia, and 9 age-matched controls. These shear stress parameters at the cerebral aqueduct were compared with apertures and stroke volumes at the foramen of Magendie and cerebral aqueduct.

RESULTS

Two wall shear stress magnitude peaks during a heartbeat were changed to periodic oscillation by converting oscillatory shear stress. The mean oscillatory shear stress amplitude and time-averaged wall shear stress values at the dorsal and ventral regions of the cerebral aqueduct in the idiopathic normal pressure hydrocephalus groups were significantly higher than those in controls. Furthermore, those at the ventral region of the cerebral aqueduct in the idiopathic normal pressure hydrocephalus group were also significantly higher than those in the co-occurrence of idiopathic normal pressure hydrocephalus with Alzheimer-type dementia group. The oscillatory shear stress amplitude at the dorsal region of the cerebral aqueduct was significantly associated with foramen of Magendie diameters, whereas it was strongly associated with the stroke volume at the upper end of the cerebral aqueduct rather than that at the foramen of Magendie.

CONCLUSIONS

Oscillatory shear stress, which reflects wall shear stress vector changes better than the conventional wall shear stress magnitude and the oscillatory shear index, can be directly measured on 4D flow MR imaging. Oscillatory shear stress at the cerebral aqueduct was considerably higher in patients with idiopathic normal pressure hydrocephalus.

An overview of the medical-physics-related verification system for radiotherapy multicenter clinical trials by the Medical Physics Working Group in the Japan Clinical Oncology Group-Radiation Therapy Study Group

The Japan Clinical Oncology Group-Radiation Therapy Study Group (JCOG-RTSG) has initiated several multicenter clinical trials for high-precision radiotherapy, which are presently ongoing. When conducting multi-center clinical trials, a large difference in physical quantities, such as the absolute doses to the target and the organ at risk, as well as the irradiation localization accuracy, affects the treatment outcome. Therefore, the differences in the various physical quantities used in different institutions must be within an acceptable range for conducting multicenter clinical trials, and this must be verified with medical physics consideration. In 2011, Japan's first Medical Physics Working Group (MPWG) in the JCOG-RTSG was established to perform this medical-physics-related verification for multicenter clinical trials. We have developed an auditing method to verify the accuracy of the absolute dose and the irradiation localization. Subsequently, we credentialed the participating institutions in the JCOG multicenter clinical trials that were using stereotactic body radiotherapy (SBRT) for lungs, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for several disease sites, and proton beam therapy (PT) for the liver. From the verification results, accuracies of the absolute dose and the irradiation localization among the participating institutions of the multicenter clinical trial were assured, and the JCOG clinical trials could be initiated.

Hyperuricemia impaired nitric oxide bioavailablity and deteriorated pulmonary arterial hypertension via a uric acid transporter, URATv1 in xanthine oxidoreductase (XOR)-independent manner

Background

Hyperuricemia occurs in approximately 80% in patients with pulmonary arterial hypertension (PAH) and is positively correlated with pulmonary arterial pressure (PAP). It has been reported that uric acid (UA) reduced endothelium derived nitric oxide (NO) production in porcine pulmonary arterial endothelial cells (PAEC). However, the effects of UA and xanthine oxidoreductase (XOR), catalytic enzyme of UA, on the development of PAH have not been fully elucidated.

Purpose

We examined the followings; (1) the effects of hyperuricemia on the endothelial function and the development of PAH in rats (2) the therapeutic effects of UA transporter inhibitor on PAH in rats, and (3) the role of XOR in PAH in mice.

Methods

We used normal and 5-wk Sugen5416/Hypoxia/Normoxia-exposed (SU/Hx/Nx) rats. Gene expression levels of URATv1, a UA transporter, were measured by RT-PCR. We determined the isometric tension of PA rings isolated from normal rats. The study with the isolated perfused lung preparation was performed in SU/HX/Nx rats. To investigate the chronic effect of UA on the development of PAH, hyperuricemia was induced by the administration of 2% oxonic acid (OA) in diet for 6-wk. Benzbromarone (BBR, 10mg/kg/day, diet, from weeks 0 to 5), a URATv1 transporter inhibitor, was administered in the SU/Hx/Nx-rats with or without 2%OA. To examine the role of XOR in PAH, XOR+/− and wild type (WT) mice were exposed to 3-wk Nx or Hx (10% O2).

Results

The mRNA of URATv1 was detected in the normal lungs. Isometric tension study showed that UA (8 mg/dl) inhibited acetylcholine-induced vasorelaxation. In perfused lung preparations, UA acutely increased estimated PVR in a dose-dependent manner (1.6–16.0mg/dl) with reducing cGMP levels in the lungs. BBR significantly attenuated the pressor response to UA. UA levels in the plasma and the lung tissues were significantly elevated in SU/Hx/Nx-rats with 2%OA (normal vs. vehicle vs. 2%OA, plasma: 0.24±0.01 vs. 0.80±0.14 and 1.44±0.17 mg/dl; lung tissues: 68±3 vs. 142±3 and 377±46 pmol/g tissue). They exhibited further elevation of right ventricle systolic pressure (RVSP) (31±2 vs. 72±6 vs. 101±3 mmHg) and Ea (a marker of RV afterload) (0.24±0.04 vs. 0.97±0.15 vs. 2.36±0.49 mmHg/μL) with the exacerbation of occlusive lesions of PAs. BBR had no changes in the UA levels in the plasma (1.93±0.30 mg/dL), but significantly reduced the UA levels in the lung tissues (101±10 pmol/g tissue) and attenuated the increase in RVSP (53±8mmHg) and Ea (0.21±0.05 mmHg/mL) in the SU/Hx/Nx-rats with 2%OA. On the other hand, BBR had no effects on RVSP (76±7 mmHg) and Ea (0.91±0.15 mmHg/mL) in the SU/Hx/Nx-rats without 2%OA. There were no significant differences in RVSP between XOR+/− mice with Hx and WT with Hx (26±2 vs. 26±2 mmHg).

Conclusions

Hyperuricemia itself impairs endothelial function and deteriorates PAH via URATv1 in a XOR-independent manner. UA can be a novel therapeutic target for PAH.

Funding Acknowledgement

Type of funding source: None

Comparison between optical frequency domain imaging and intravascular ultrasound in PCI guidance for Biolimus A9 eluting stent implantation

Background

It has been reported that intravascular ultrasound (IVUS) guided PCI reduced a risk of major adverse cardiac event compared to conventional angiography guided PCI, while comparison between IVUS-guided and optical frequency domain imaging (OFDI)-guided PCI specifically in long-term clinical outcomes (&gt;1 year) has been unexplored.

Purpose

We sought to compare imaging surrogates at 8 months and clinical outcomes beyond 1 year after drug-eluting stent implantation between IVUS and OFDI guidance.

Methods

The MISTIC-1 is a prospective, multi-centre, single-blinded, randomised-controlled, non-inferiority trial comparing OFDI-guided and IVUS-guided PCI using Biolimus A9 eluting Nobori stent. We enrolled patients with stable coronary artery disease who have symptoms or clinically relevant myocardial ischemia. Stent landing zones were selected in the most normal looking sites with largest lumen and without percentage plaque area &gt;50% in IVUS group while without lipidic plaque of &gt;2 quadrants or suggestive thin-cap fibroatheroma in OFDI group. Stent sizing was based on external elastic lamina (EEL) in IVUS group, while by taking 10% or 0.25mm larger than mean lumen diameter at reference sites in OFDI group. Stent optimisation with in-stent minimum lumen area ≥80% of the average lumen area at proximal and distal reference sites was encouraged in both groups. Primary efficacy endpoint is in-segment minimum lumen area (MLA) assessed by OFDI at 8 months. Secondary safety endpoint is a composite of cardiovascular death, target vessel myocardial infarction, or target lesion revascularisation. Based on the assumption that mean in-segment MLA at follow-up was 4.5mm2 with a standard deviation of 2.0mm2 in the control (IVUS) group and a non-inferiority limit of 1.2mm2 for OFDI group, sample size was estimated as 48 cases in each group with 5% type I error and 90% statistical power.

Results

Since June-2014 and August-2016, we prospectively enrolled 109 patients (mean age 70 years, male 78%) with 126 lesions. Baseline patient and lesion characteristics were well balanced and average nominal size and length of stent used did not differ between OFDI-guided and IVUS-guided PCI (3.0 and 19.1mm vs. 3.1 and 19.3mm, respectively). Post-procedural minimum stent area was 6.24mm2 in OFDI group and 6.72mm2 in IVUS group (p=0.20). At 8-month follow-up, in-segment MLA was 4.56mm2 in OFDI group and 4.13mm2 in IVUS group (P for non-inferiority &lt;0.001). During the follow-up (median 4.5 years [1654 days]), incidence rates of major adverse cardiac event were comparable between the two groups (7.4% in OFDI group and 7.3% in IVUS group, hazard ratio 0.96, 95% CI 0.24–3.83, p=0.95). No definite or probable stent thrombosis were documented in both groups.

Conclusion

OFDI-guided PCI demonstrated comparable results in achieving satisfactory imaging surrogates as well as long-term clinical outcomes after newer generation DES implantation as compared to IVUS-guided PCI.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Suzuken Memorial Foundation

Conceptual design of a collimator for the neutron emission profile monitor in JT-60SA using Monte Carlo simulations

Materials and structures of a collimator for a new neutron emission profile monitor in JT-60SA are examined through Monte Carlo simulations using the Monte Carlo N-Particle transport code. First, the shielding properties of various material combinations are compared in order to determine a combination with high shielding performances against both neutrons and gamma-rays. It is found that a collimator consisting of borated polyethylene and lead has a high shielding performance against neutrons. Moreover, a high shielding performance against gamma-rays is obtained when a lead pipe with a radial thickness of 0.01 m is inserted into a collimation tube. Second, we demonstrate that it is possible to improve the spatial resolution to a desired level by installing a thin tubular extension structure that fits into the limited space available between the main collimator block and the tokamak device. Finally, the collimator structures that meet both the targeted spatial resolutions (<10% of the plasma minor radius) and the targeted counting rate (10⁵ cps order) are discussed.

Five-year major adverse cardiac and cerebrovascular events of patients with lipid core abutting lumen (LCAL) on integrated-backscatter intravascular ultrasound undergoing PCI with current DES

Background

Percutaneous Coronary Intervention (PCI) using the new generation drug-eluting stent (DES) has been extremely reduced target lesion revascularization (TLR) in recent years. However, a high incidence of non-target lesion-related cardiovascular events in patients undergoing PCI is an important problem to be solved. According to the previous findings, patients with vulnerable plaques particularly have a high recurrence of cardiovascular events. Little studies, however, has been done to examine the relationship between plaque characteristics on intravascular imaging in a target lesion and non-target lesion-related cardiovascular events.

Purpose

The main objective of this study is to investigate the five-year major adverse cardiac and cerebrovascular events (MACCE) of patients with lipid core abutting lumen (LCAL) on integrated backscatter intravascular ultrasound (IB-IVUS) in a target lesion undergoing PCI with current DES.

Methods and results

Between February 2010 and September 2013, in total 780 patients with ischemic heart disease undergoing PCI, 166 target lesions in 166 consecutive patients with non-ST segment elevation acute coronary syndrome (NSTE-ACS) and stable angina pectoris (SAP) undergoing IVUS-guided PCI were studied.

Plaque characteristics in all target lesions were analyzed by three-dimensional IB-IVUS system using the mechanical IVUS catheter. Our previous study has found that LCAL which is defined as a lipid pool directly in contact with the lumen visualizes the thin fibrous cap of less than 75μm on optical coherence tomography (OCT). On the basis of this data, LCAL at minimal lumen area (MLA) site was identified.

In total, 39 patients had lesions with LCAL at MLA site (LCAL(+)), and 127 patients had those without LCAL (LCAL(−)).

The primary endpoint was defined as MACCE, including cardiovascular death, non-fatal myocardial infarction, non-fatal stroke and non-TLR for the new lesion during a median follow up of five years. The MACCE occurred significantly higher in the LCAL(+) than in the LCAL(−) (38.5% vs. 17.3%; p&lt;0.005). And the Kaplan-Meier estimates have shown that the cumulative incidence of MACCE was significantly higher in the LCAL(+) than in the LCAL(−) (log rank test, p=0.041). Additionally, after adjustment for confounders, gender, prior PCI and LCAL was the independent predictors for the MACCE of patients undergoing PCI with current DES.

Furthermore, after adding LCAL to a baseline model with established factors consisting of age, gender, diabetes mellitus, prior PCI and percentage lipid volume on IB-IVUS, the net reclassification (p&lt;0.002) and integrated discrimination improvement (p&lt;0.004) significantly improved compared to baseline model alone.

Conclusions

In this study, it has become clear that LCAL on IB-IVUS is likely to be a surrogate marker of MACCE in patients undergoing PCI with current DES.

Funding Acknowledgement

Type of funding source: None

The understanding of congruent and incongruent referential gaze in 17-month-old infants: an eye-tracking study comparing human and robot

Several studies have shown that the human gaze, but not the robot gaze, has significant effects on infant social cognition and facilitate social engagement. The present study investigates early understanding of the referential nature of gaze by comparing-through the eye-tracking technique-infants' response to human and robot's gaze. Data were acquired on thirty-two 17-month-old infants, watching four video clips, where either a human or a humanoid robot performed an action on a target. The agent's gaze was either turned to the target (congruent) or opposite to it (incongruent). The results generally showed that, independent of the agent, the infants attended longer at the face area compared to the hand and target. Additionally, the effect of referential gaze on infants' attention to the target was greater when infants watched the human compared to the robot's action. These results suggest the presence, in infants, of two distinct levels of gaze-following mechanisms: one recognizing the other as a potential interactive partner, the second recognizing partner's agency. In this study, infants recognized the robot as a potential interactive partner, whereas ascribed agency more readily to the human, thus suggesting that the process of generalizability of gazing behaviour to non-humans is not immediate.

Feasibility study on a novel tiny dosimeter using a barium titanate capacitor

In our laboratory we have confirmed that the capacitance of barium titanate-based capacitors changes due to radiation. Since a commercially available capacitor is very small and inexpensive, it may be used as a multidimensional dose meter in which a large number of capacitor elements are arranged, or may be embedded in the body and used as an in-vivo dose meter. In this study we examined the usefulness of a dosimeter using the capacitance change of a barium titanate capacitor. As a basic property, it was confirmed that the dose linearity was good. With regard to dose rate characteristics and response to fractionated irradiation, capacitance change due to aging affects measurement accuracy, but online measurement of capacitance change immediately before irradiation can be performed to correct aging effects during irradiation. By doing this, we confirmed that the dose rate characteristics and the response to fractionated radiation are improved.

[Real-time Lens Exposure Dose Measurement Using a Scintillator with Optical Fiber Dosimeter during Cardiac Catheter Operation]

In recent years, the exposure dose of the operator's eye lens during interventional radiology operations has become a problem. We therefore evaluated the feasibility of real-time lens dose measurement using scintillator with optical fiber (SOF) dosimeter. Given that the SOF dosimeter is calibrated for direct X-rays, we performed a calibration for scattered X-rays to investigate energy dependence and the accuracy of lens dose measurements. The detection limit was calculated using the Kaiser method. The SOF dosimeter and the radiophotoluminescence glass (RPLG) dosimeter were attached to the protective glasses worn by the operator, and the lens exposure dose of the operator during cardiac catheterization was measured. In the phantom experiment, the SOF dosimeter had an error rate of 5.45% based on the measured value of the ionization chamber dosimeter. The sensitivity characteristics of the SOF dosimeter were slightly reduced on the higher side of the effective energy. The difference in sensitivity was related to variations in the additional filter and energy dependency. The sensitivity difference was 18.5% at maximum. Furthermore, when the additional dose was displayed, the influence of noise on long-term measurement was considerable. Using the Kaiser method to obtain the detection limit, the accuracy of the integrated dose had SOF dosimeter error rates of 4.3% to 15.5% with respect to the integrated value of the RPLG dosimeter when calibrated by the ionization chamber dosimeter. The use of the SOF dosimeter allowed for the real-time visualization of the exposure status of the eye lens and measurements with a relatively high accuracy.

A self-reported measurement scale on a potential component of competency in the healthcare staff engaged in the prevention and control of non-communicable disease in Fiji

Background

According to the World Health Organization, an estimated 80% or more deaths in Pacific island countries, including Fiji, were related to non-communicable diseases (NCDs). Although competency-based approaches have been effective for developing healthcare workers’ capabilities, there are only a few reports on competency scales of healthcare workers for NCD prevention. We aimed to develop a self-reported measurement scale on a potential component of competency in the healthcare staff engaged in the prevention and control of NCDs in Fiji.

Methods

There were 378 Ministry of Health and Medical Services staff members working on NCD prevention and control in Fiji included in this study, which was a cross-sectional survey of social factors, working situation factors, and competency. Exploratory factor analysis was conducted to assess potential competency components, whereas Cronbach’s α coefficient and analysis of variance were used to assess the validity and reliability of the scale items, respectively. Multivariate regression analyses were conducted to analyze the respondents’ factor scores relative to social status and work situations.

Results

The factor analysis revealed 16 items that identified competency in four work types: 1) work management, 2) monitoring and evaluation, 3) community partnership, and 4) community diagnosis. The monitoring and evaluation roles were related to ethnic background, community partnership was related to religion, and community diagnosis was related to academic qualifications.

Conclusions

Based on the results, we developed a competency scale for the four work types. This scale can help healthcare workers engage in better management of residents with NCDs in Fiji.

P3388Five year outcomes of patients with lipid rich plaque detected three-dimensional Integrated-Backscatter intravascular ultrasound (IB-IVUS) in target lesion after second generation DES implantation

Background

Elective percutaneous coronary intervention (PCI) using second generation drug-eluting stent (DES) has been dramatically reduced restenosis rate. Recently, it has been reported that plaque characterization in nontarget lesion is associated with cardio-vascular events in ischemic heart disease patients undergoing elective PCI. However, it is unclear whether plaque characterization in target lesion is predictor of MACEs (major adverse cardiac events) after elective PCI.

Purposes

The aim of this study is whether plaque characterization detected integrated-backscatter intravascular ultrasound (IB-IVUS) in the target lesion is associated with MACEs in patients with PCI after second generation DES implantation.

Methods and results

Of 700 patients with ischemic heart disease, 552 patients were excluded for chronic totally occlusion, severe calcification hindering precise intracoronary imaging, tortuous lesions, ostial or left main stem lesions and ST-elevated myocardial infarction patients. Finally, 148 consecutive patients who consented to repeated IB-IVUS prior to undergoing elective PCI were recruited in the study.Plaque characterization in target lesion was identified for three-dimensional IB-IVUS technology using the mechanical IVUS catheter (ViewIT, 40 MHz, 2.5 Fr; Terumo, Tokyo, Japan). The median of percentage lipid volume in all target lesions was 47.6%. Furthermore, lipid rich plaque (LRP) group was defined as the lesions consisting of percentage lipid volume greater than the median. And, non-lipid rich plaque (non-LRP) group was defined as the lesions consisting of percentage lipid volume less than the median. MACEs were defined as cardiovascular death, target vessel myocardial infarction, target lesion revascularization and stent thrombosis. The median of follow up period was 60 months. Of the 148 patients, 106 patients had stable angina pectoris. The remaining 42 patients are acute coronary syndrome (NSTE-ACS). 74 patients were classified LRP groups and 74 patients were non-LRP groups. No significant differences were observed between the two groups with respect to age, sex and coronary risk factors. While plaque and vessel volume were greater in the LRP group (216.9±116.3mm3, p<0.001) than non-LRP group (322.5±144.0mm3, p p<0.001). Remodeling index was greater in LRP group (1.02±0.18) than non-LRP group (0.93±0.18, p<0.003). Although MACEs were no significant differences between the two groups, the number of MACEs tend to be more in patients with LRP group (8.1±27.4%) than small lipid group (2.7±16.3, p<0.147). Especially, cardiac death tend to be more in LRP group (6.7±25.2% than non-LRP group (1.3±11.6, p<0.096).

Conclusions

In conclusion, lipid rich plaque detected by three dimensional IB-IVUS system in target lesion with patients undergoing elective PCI may be associated with clinical outcomes for five years after second generation DES implantation.

Acknowledgement/Funding

None

P4691Chronic blockade of toll-like receptor 9 ameliorated pulmonary arterial hypertension by reducing perivascular inflammation in rats

Background/Introduction

Perivascular inflammation plays an important role in the pathogenesis of pulmonary arterial hypertension (PAH). Recent studies have demonstrated that damaged mitochondrial DNA induces sterile inflammation by activating toll-like receptor (TLR)9 in spontaneous hypertensive rats. However, it remains unclear whether TLR9 is involved in perivascular inflammation and subsequent development of PAH.

Purpose

The purpose of the present study is to investigate whether chronic inhibition of TLR9 can ameliorate monocrotaline (MCT)-induced PAH in rats.

Methods

Male Sprague-Dawley rats were injected with MCT (60 mg/kg). First, we conducted immunohistochemistory to examine which cell types express TLR9 in lungs of normal rats and MCT-exposed rats. Second, we extracted cell-free DNA from plasma of rats and amplified genes of COX2 by real-time PCR to detect circulating cell-free mitochondrial DNA, a ligand of TLR9. Third, the administration of a selective TLR9 inhibitor (E6446, 10mg/kg/day, drinking water) or non-selective TLR9 inhibitor (chloroquine: 50mg/kg/day, ip) started three days before MCT injection and sacrificed on day 21. We assessed hemodynamic data and histopathological analysis (EVG stain for medial wall thickness (MWT) in pulmonary arteries (outer diameter: 50 ∼ 100 μm) and CD68 for macrophage accumulation around pulmonary arteries (outer diameter: <50 μm)), and measured the levels of interleukin-6 (IL-6) in lungs by real time PCR. Finally, we investigated survival rate in the reversal protocol, where we started the administration of E6446 on day 14.

Results

TLR9 was expressed dominantly in pulmonary endothelial cells and macrophages in the lungs of both normal rats and MCT-exposed rats. Compared with normal rats, MCT-exposed rats showed increased gene expression of COX2 (0.048±0.001 vs. 0.052±0.001 expressed by 1/Ct) in plasma on day 14. MCT-exposed rats also had increased right ventricular systolic pressure (RVSP: 21±1 vs. 60±2 mmHg), total pulmonary vascular resistance index (TPRI: 0.07±0.01 vs. 0.43±0.02 mmHg/min/mL/kg), MWT (0.07±0.01 vs. 0.26±0,02) and accumulation of macrophages (1.6±0.3 vs. 20.0±1.7 cells/HPF) on day 21. In the prevention protocol, either E6446 or chloroquine significantly prevented the elevations of RVSP (49±4 or 48±3 mmHg) and TPRI (0.29±0.04 or 0.27±0.03 mmHg/min/mL/kg) with reducing MWT (0.18±0.01 or 0.18±0.01) and macrophage accumulation (9.7±1.3 or 9.8±2.5 cell/HPF) on day 21. In addition, these drugs significantly reduced the levels of IL-6 mRNA compared with MCT group (4.4±1.0 or 4.8±1.4 vs. 11.9±1.0). In the reversal protocol, the treatment of E6446 had significantly increased the survival rate (50 vs. 10%).

Conclusions

TLR9 largely contributes to the development of PAH by reducing perivascular inflammation. Inhibition of TLR9 could be a novel therapeutic target for PAH.

Relationship Between Tube Voltage and Physical Image Quality of Pulmonary Nodules on Chest Radiographs Obtained Using the Bone-Suppression Technique

RATIONALE AND OBJECTIVES

Image quality of chest radiographs is affected by tube voltage. This study aimed to clarify the relationship between tube voltage and physical image quality of pulmonary nodules on bone-suppressed chest radiographs.

MATERIALS AND METHODS

An anthropomorphic chest phantom and a spherical simulated nodule, with a 12-mm diameter and approximately +100 Hounsfield units were used. The lung field of the phantom was divided into three areas, based on the overlap with the ribs in the chest radiograph. Ten positions of the simulated nodule were defined in each area. One hundred and twenty chest radiographs were acquired using four tube voltages (70 kVp, 90 kVp, 110 kVp, and 130 kVp) for a total of 30 nodule positions and were processed to create bone-suppressed images. Differences in contrast and contrast-to-noise ratio (CNR) were analyzed for all pairs of the four tube voltages using a two-sided Wilcoxon signed-rank test.

RESULTS

In the area not overlapping with ribs, a statistically significant difference was observed only in contrast between tube voltage of 70 kVp and 90 kVp (p = 0.01). In the area overlapping with one or two ribs, the contrast and CNR tended to be higher at a lower tube voltage. In particular, the p values between the contrast at 70 kVp and that at the other three tube voltage settings were less than 0.01.

CONCLUSION

For a relatively dense nodule, the contrast and CNR in the bone-suppressed chest radiograph were significantly improved with lower tube voltage in the lung field overlapping with the ribs.

Identification of the Novel Tooth-Specific Transcription Factor AmeloD

Basic-helix-loop-helix (bHLH) transcription factors play an important role in various organs' development; however, a tooth-specific bHLH factor has not been reported. In this study, we identified a novel tooth-specific bHLH transcription factor, which we named AmeloD, by screening a tooth germ complementary DNA (cDNA) library using a yeast 2-hybrid system. AmeloD was mapped onto the mouse chromosome 1q32. Phylogenetic analysis showed that AmeloD belongs to the achaete-scute complex-like ( ASCL) gene family and is a homologue of ASCL5. AmeloD was uniquely expressed in the inner enamel epithelium (IEE), but its expression was suppressed after IEE cell differentiation into ameloblasts. Furthermore, AmeloD expression showed an inverse expression pattern with the epithelial cell-specific cell-cell adhesion molecule E-cadherin in the dental epithelium. Overexpression of AmeloD in dental epithelial cell line CLDE cells resulted in E-cadherin suppression. We found that AmeloD bound to E-box cis-regulatory elements in the proximal promoter region of the E-cadherin gene. These results reveal that AmeloD functions as a suppressor of E-cadherin transcription in IEE cells. Our study demonstrated that AmeloD is a novel tooth-specific bHLH transcription factor that may regulate tooth development through the suppression of E-cadherin in IEE cells.