[Development of Auto Dense-breast Classification on Mammography Images Using Image Similarity].

PURPOSE: In Japan, radiologists perform qualitative visual classification to define four categories of mammary gland density. However, an objective estimation of mammary gland density is necessary. To address this, we developed an automatic classification software using image similarity. METHODS: We prepared 741 cases of mediolateral oblique images (MLO) for evaluation, and they were diagnosed as normal among the mammography images taken at our hospital. Image matching was performed using the evaluation images and an image database for breast density determination. In this study, the image similarity used zero normalized cross-correlation (ZNCC) as an index. In addition, if the breast thickness is less than 30 mm and each breast density category ZNNC has the same value, the category is evaluated on the fat side. We compared the results of qualitative visual classification and automatic classification methods to assess consistency. RESULTS: The agreement with the subjective breast composition classification was 78.5%, and the weighted kappa coefficient was 0.98. One mismatched case was evaluated on the higher density side with the same ZNCC value between categories and a breast thickness greater than 30 mm. CONCLUSION: Image similarity provides an excellent estimation of quantification of breast density. This system could contribute to improving the efficiency of the mammography screening system.

Patient radiation exposure dose reduction using stent-enhanced image processing in percutaneous coronary intervention.

We investigated the reduction in patient radiation exposure dose during percutaneous coronary intervention (PCI) by stent enhancement processing. We examined the effects of dose reduction based on the image quality of stent enhancement processing using a purpose-built dynamic phantom. We evaluated the image contrast (IC) of the stent in stent-enhanced images (SVref), digital angiography (DA), and stent-enhanced images with a 20%, 40%, and 60% lower imaging doses (SV20, SV40, and SV60). We visually evaluated graininess and stent shape using the mean opinion score (MOS) and retrospectively evaluated the acquisition duration of stent enhancement in PCI cases; finally, we estimated the decrease in patient radiation exposure due to stent enhancement. The image contrast of SVref at phantom thicknesses of 20 cm was 51.25 ± 3.82, while the image contrast of DA was significantly reduced at 14.90 ± 1.57 (p < 0.05). We observed a significant decrease in the MOS of graininess in SV60 and MOS of stent shape in DA (p < 0.05). Furthermore, the average imaging duration for stent enhancement using PCI was 22.65 ± 7.43 s, and the maximum imaging duration was 68.07 s. We hypothesize that patient radiation exposure dose can be reduced by up to 60.17 mGy by lowering the imaging dose during the stent enhancement process. Stent enhancement processing improves the visibility of stent images, and can reduce radiation exposure by approximately 40% during confirmation imaging of stents. Our study contributes to the reduction of radiation exposure dose for operators and patients in PCI.

[Measurement of Average Glandular Dose Using Multiparameter X-ray Measuring Instrument].

The average glandular dose (AGD) is very important in the quality control of mammography. The AGD calculation requires measurements of half-value layer (HVL) and entrance surface air karma (ESAK). The HVL is measured by the Al-attenuation method using a non-energy-dependent ionization dosimeter. As the Al-attenuation method performs measurements using a succession of added filters, it requires lots of X-ray exposure and measurement time. In recent years, measuring instruments that can measure tube voltage, irradiation time, exposure dose, HVL, and other factors, at the same time, using one shot of X-rays have been developed. In this study, measurement of the AGD using multiparameter X-ray measuring instrument about rhodium (Rh) and tungsten (W) anode X-ray tubes. A comparative study was performed using standard ionization dosimeters. The error in measurements was as follows: HVL 5.8%, ESAK 3.3%, and AGD 2.9%. The AGD measurement using a multiparameter X-ray measuring instrument is simple and can significantly reduce the measurement time while maintaining accuracy.

[Evaluation of AEC Consistency in Digital X-ray Imaging Systems].

The Japan Network for Research and Information on Medical Exposures (J-RIME) established the diagnostic reference level (DRL) and is advancing optimization of radiation protection. We believe that the difference in the imaging dose between facilities may be due to the fact that automatic exposure control (AEC) adjustment is not unified among manufacturers. The consistency of AEC is specified in JIS 4751-2-54, but it is not applicable to digital X-ray imaging systems because it is for optical density of analog X-ray imaging systems. This article evaluates the consistency of AEC in digital X-ray imaging systems. The AEC consistency was compared with the AEC-estimated dose from the air kerma (KAEC) using the phosphor-based imaging plate placed at the back of the AEC detector. We measured the AEC tube voltage and subject thickness characteristics (tracking) of four types of digital X-ray imaging systems at three facilities. In the test of tube voltage characteristics, the average KAEC values at all tube voltages were 2.37±0.04 µGy for A system, 7.30±1.44 µGy for B system, 3.53±0.13 µGy for C system, and 5.70±0.18 µGy for D system. The relative errors were +2.6 to -1.8% for A system, +25.3 to -22.6% for B system, +5.2 to -1.4% for C system, and +2.5 to -4.4% for D system. In the subject thickness characteristics test, the average KAEC values for all Al thicknesses were 2.34±0.02 µGy for A system, 5.95±0.23 µGy for B system, 4.25±1.12 µGy for C system, and 5.03±1.27 µGy for D system. The relative errors were +1.0 to -0.9% for A system, +4.1 to -5.0% for B system, +40.5 to -28.1% for C system, and +19.7 to -42.9% for D system.

Evaluation of exposure factors of dual-energy contrast-enhanced mammography to optimize radiation dose with improved image quality.

Background: Dual-energy contrast-enhanced mammography (DECEM) is an advanced breast imaging technique of digital mammography. Purpose: To assess the total radiation dose received from complete DECEM using different combinations of exposure parameters for low- and high-energy images. Materials and methods: A dedicated phantom with three different concentrations of iodine inserts was used. Each iodine insert was 10 mm in diameter and concentration of 1.0 mgI/cm3, 2.0 mgI/cm3, and 4.0 mgI/cm3. The phantom was exposed at varying kVp levels. Mean glandular dose (MGD) was estimated. Contrast to noise ratio (CNR) and figure of merit (FOM) of the iodine inserts were used to assess the image quality. Results: The optimum CNR of the recombined images was obtained by using 28 kVp + 49 kVp tube voltage combination for 50 mm thickness, 50% fibroglandular phantom only with a 26% dose increase compared to the highest voltages (32 kVp + 49 kVp) that can be used for low energy (LE) and high energy (HE) imaging. The CNR value was increased with increasing iodine concentration (R 2 > 0.99). Conclusion: The use of as low as possible tube voltage for the LE imaging of standard 50% fibroglandular-50% adipose, 50 mm thickness breast while using the highest tube voltage for HE imaging has reduced the MGD while keeping optimum image quality.

An approach to dual-energy contrast-enhanced spectral mammography (DE-CESM) using a double layer filter: dosimetric and image quality assessment.

Dual-energy contrast-enhanced spectral mammography (DE-CESM) is a recently developed advanced technique in digital mammography that uses an iodinated intravenous contrast agent to assess tumor angiogenesis. The aim of this study was to investigate the diagnostic potential of DE-CESM recombined images in terms of radiation dose and image quality. A 50% fibroglandular-50% adipose, custom-made phantom with iodine inserts of 1.0 mgI cm-3, 2.0 mgI cm-3, 4.0 mgI cm-3was used for the estimation of mean glandular dose (MGD) and the image quality. Low-energy (LE) images were acquired with the W/Rh, W/Rh + 0.01 mm Cu and W/Rh + 0.5 mm Al while high energy images (HE) are acquired with the W/Rh, W/Rh + 0.06 mm Ba, W/Rh + 0.01 mm Cu, and W/Rh + 0.03 mm Ce anode filter combinations. The total MGD was reduced up to a maximum from 1.75 mGy to 1.45 mGy by using Rh + 0.01 mm Cu double-layer filter for both LE and HE imaging of 50 mm, standard 50% fibroglandular phantom compared to Rh single-layer filter with W target. The minimum total MGD reduction (1.69 mGy) was observed when Rh + 0.5 mm Al was used for LE and Rh + 0.06 mm Ba was used for HE exposure. The image quality was comparable with the single-layer filter. The use of W/Rh + 0.01 mm Cu or W/Rh + 0.5 mm Al as target/filter combination for LE exposure and W/Rh + 0.01 mm Cu for HE exposure can reduce the additional radiation dose delivered by DE-CESM without degrading the image quality.

[Examination of the Quality Control Items for Digital Breast Tomosynthesis System in Japan].

Mammography equipment attached to the digital breast tomosynthesis (DBT) system is widespread in Japan. However, there are no guidelines for quality control methods for DBT in Japan. Therefore, it is necessary to rapidly establish a performance evaluation procedure and a quality control procedure for DBT. In this study, we conducted basic experiments using DBTs of five companies (Canon Medical, Fujifilm Medical, GE Healthcare, Hologic, Siemens) already sold in Japan and examined feasible common items. We aimed to establish a quality control method for DBT in Japan. The measurement was performed based on the European Reference Organisation for Quality Assured Breast Screening and Diagnostic Services (EUREF) breast tomosynthesis quality control protocol, version 1.03. In this study, we tried to measure 18 items in DBT. We examined whether the 18 items could be measured using each device; it is not an evaluation of device performance based on the measured values. There were some management items that were difficult to implement due to the specifications of DBT, such as devices that required pressure on DBT operation, problems due to the shape of bucky, and devices that did not have stationary mode. There were also problems with measurement data; for example, devices could not retrieve projection data and reconstruction data. This study clarified points to be considered for establishing common quality control items. In the future, we will carefully refer to the recently published IEC 61223-3-6, consider international harmonization, and establish DBT guidelines customized for the Japanese market.

Establishment of regional diagnostic reference levels for digital mammography in Western Province of Sri Lanka.

The radiation dose to the breasts should be kept to a minimum as breast tissues are highly sensitive to radiation. In mammography, the mean glandular dose (MGD) is used to specify the patient dose. In this study, data on the MGD during diagnostic mammographic examinations was collected using the database from six digital mammography facilities available in the Western Province in Sri Lanka. Examinations involving breast pathology, breast implants, or compressed breast thicknesses (CBT) outside the range of 20-110 mm were excluded in this study. The mean MGD per breast was 3.50 mGy, with a mean CBT of 57 mm. The mean MGD per facility varies from 1.58 to 2.27 mGy, with overall 75th and 95th percentiles of 2.15 and 2.82 mGy, respectively. The 75th and 95th percentile MGD per image, for the average CBT of 57 ± 12 mm, were 2.00 and 2.65 mGy respectively. The 75th percentile value of the MGD is suggested for the Western Province and it depends on the specific CBT.

Effect of protective glasses on radiation dose to eye lenses during whole breast irradiation.

OBJECTIVES: The efficacy of radiotherapy for breast cancer has greatly improved owing to better irradiation methods. Radiotherapy aims to deliver therapeutic doses to predetermined target volumes while sparing surrounding healthy tissues. However, there are few reports on radiation exposure to eye lenses, and the recommended exposure limits to ocular lens have been substantially reduced in recent years. This study aimed to investigate the amount of radiation exposure to eye lenses using optically stimulated luminescence dosimeters (OSLDs) and determine whether wearing special protective devices to protect the eyes, as an organ at risk, during whole breast irradiation, is necessary. METHODS: This experiment used OSLDs on water-equivalent phantom to measure the change in scattered radiation dose due to the difference of irradiation field while using 4- and 6-MV photons of TrueBeam linear accelerator. Using a total treatment dose of 50 Gy, a target was positioned to approximate the breast, and a plan was formulated to deliver 2 Gy per treatment by tangential irradiation. The mean (SD) irradiation dose at the lens position outside the irradiation field was reported. RESULTS: The scattered radiation dose outside the irradiation field was more affected by the irradiation field size than by the radiation energy. The out-of-field irradiation dose with a larger field of view was higher than that with a smaller field of view. The use of 0.07- and 0.83-mm-thick lead shield protective glasses reduced the radiation dose by 56.1% (P < .001) and 55.6% (P < .001), respectively. CONCLUSIONS: In this experimental model, the amount of radiation the eye was exposed to during whole breast irradiation was determined by the distance of the eye from the radiation field edge and by wearing protective glasses. In clinical practice, the protection offered by eyeglasses may reduce the risk of long-term side effects and allow the use of higher intensive radiotherapy.

Dense-breast classification using image similarity.

This paper describes the auto-analysis of the mammary gland visualized on mammography images to eliminate the subjective evaluation error between physicians using pixel values and image similarity, including pattern recognition. The mammography images including the heterogeneously dense and extremely dense images were divided into two groups based on the result of the subjective breast classification as the dense breast, and non-dense breast. One hundred and thirty images obtained during screening were set as search images, and 101 evaluation images were classified using zero-mean normalized cross-correlation. Concerning the conventional method, we employed the variance histogram analysis method of Yamazaki et al. The concordance rate for the subjective breast classification result obtained using the conventional and proposed methods was 79.2% and 89.1%. The image similarity evaluation method, which analyzes the pattern of the pixel values, enabled the breast classification while eliminating ambiguity in the subjective breast classifications among physicians.

[Report Based on Fiscal 2015 Diagnostic X-ray Equipment Questionnaire Survey].

We have conducted a questionnaire survey every 5 years from 1974 to grasp the existing status of X-ray equipment. This time, we will report on the results of the fiscal 2015 diagnostic X-ray equipment questionnaire survey. Compared to the previous survey on X-ray equipment, there has been a progress in the introduction of inverter type X-ray generators and image receptor systems in digital systems. We think that this transition will be occurred when the X-ray equipment are updated. In addition, there has been an increase in digital breast tomosynthesis (DBT) and the use of tungsten anodes in the X-ray tubes of mammography apparatuses. X-ray equipment management was performed in many facilities. It seems that the importance of quality control of X-ray equipment is being realized. Constancy tests corresponding to digital systems were conducted at each facility. Maintenance by manufacturers has also increased. This is considered to be because the equipment management of digital systems has become difficult. We believe that it is necessary to continue the survey on the status of diagnostic X-ray equipment.

[Effect of Interspaces of Anti-scatter Grid on the Image Improvement Factor].

The standard general purpose of anti-scatter girds: JIS Z 4910: 2015 (IEC 60627: 2013) has been revised, with the new addition of an image improvement factor (Q) to the physical characteristic. Using aluminum (Al) and fiber-interspaced anti-scatter grids; we studied the meaning of Q by calculating each of the physical characteristics and assessing the image. The experimental method was based on JIS Z 4910: 2015. The two anti-scatter grids had a grid ratio of 12: 1 and a strip frequency of 40 cm-1. Assessment items consisted of grid exposure factor (B), grid selectivity (Σ), contrast improvement ratio (K), and Q. In addition, the contrast to noise ratio (CNR) and contrast-detail curve (CD-curve) were determined from the contrast-detail phantom image, and the inverse image quality figure (IQF) was then calculated from the CD-curve. Compared to the Al-interspaced anti-scatter grid, the fiber-interspaced anti-scatter grid had B at 0.87, Σ at 0.95, K at 0.99, and Q at 1.14. In the assessment of the contrast-detail phantom image, the fiber-interspaced anti-scatter grid had an IQF of 1.02 times and a CNR of approximately 1.24 times when compared to the Al interspaced anti-scatter grid. The fiber-interspaced anti-scatter grid was superior with respect to the B and Q of the physical characteristics and to the CNR of image quality assessment.

[Development of a simple measurement system for routine management of X-ray equipment].

Routine management of X-ray equipment is critically important, but due to the high cost of commercial management systems it is currently not practical to deploy this valuable instrumentation at every clinical facility. This led us to develop a simple measurement system for routine management purposes that can be deployed for around ¥100 thousand in materials. The system consists of an X-ray output meter, a clamp-type X-ray tube current meter (clamp meter), and a digital oscilloscope. Compared to a standard fluorescence meter, the X-ray output meter provides equivalent accuracy and reproducibility of X-ray tube voltage, X-ray tube current, and irradiation time changes, while also displaying the X-ray output time. The clamp meter must be periodically calibrated, however provides equivalent accuracy and reproducibility to a direct contact meter, while also displaying net X-ray tube current and loading time. Finally, the oscilloscope is able to estimate the waveform of X-ray tube voltage by monitoring each waveform, thus making it an extremely useful instrument for day-to-day management of X-ray equipment installed at clinical facilities.

[Report based on Fiscal 2010 Diagnostic X-ray Equipment Questionnaire Survey (conditions of X-ray units and similar equipment)].

On X-ray diagnostic technology, it is important to grasp a change of the X-ray high-voltage equipment and radiographic technique factors. The 1st questionnaire was performed in 1974, and it carried out after that every five years, and conducted 8th investigation. As a result, we requested 656 institutions and got a reply from 103 institutions. The response rate was 15.7%. For X-ray high-voltage equipment, the inverter-type device shifts to 83.6% from 73.4% of last time. X-ray high-voltage equipment will be shifted to inverter-type device the near future. For X-ray tube device, the target angle becomes more smaller than usual, and maximum anode heat content is increasing tendency. The spread of digital devices is being advanced, and especially the flat panel detector (FPD) increases in the devices. The spread of soft copy diagnoses is 73.8% for chest image diagnoses, and 49.5% for breast image diagnosis. For the device management, the ratio of institutions measured at purchase time was 91.2%. But, the ratio of institutions performed an invariability examination was 58.4%. It is required to grasp the performance of an X-ray equipment and peripheral equipment, and to perform accuracy control in order to obtain proper radiographic technique factors and imaging. In order to use it for the improvement in photography technology, we would like to continue to conduct this investigation periodically.