Characterization of microcalcification: can digital monitor zooming replace magnification mammography in full-field digital mammography?

The aim of this study was to compare the diagnostic accuracy and image quality of microcalcifications in zoomed digital contact mammography with digital magnification mammography. Three radiologists with different levels of experience in mammography reviewed 120 microcalcification clusters in 111 patients with a full-field digital mammography system relying on digital magnification mammogram (MAG) images and zoomed images from contact mammography (ZOOM) using commercially available zooming systems on monitors. Each radiologist estimated the probability of malignancy and rated the image quality and confidence rate. Performance was evaluated by sensitivity, specificity, positive predictive value, negative predictive value, and receiver operating characteristic (ROC) analysis. All three radiologists rated MAG images higher than ZOOM images for sensitivity with statistical significance (average value, 92% vs. 87%, P < 0.05) and performance by ROC analysis improved with MAG imaging. The confidence rate for diagnosis decision and the assessment of lesion characteristics were also better in MAG images than in ZOOM images with statistical significance (P < 0.0001). Digital magnification mammography can enhance diagnostic performance when characterizing microcalcifications. Images zoomed from digital contact mammography cannot serve as an alternative to direct magnification digital mammography. This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) (KRF-2007-313-E00363).     

Zooming method (× 2.0) of digital mammography vs digital magnification view (× 1.8) in full-field digital mammography for the diagnosis of microcalcifications

The purpose of this study was to determine whether the interpretation of microcalcifications assessed on images zoomed (× 2.0) from digital mammograms is at least equivalent to that from digital magnification mammography (× 1.8) with respect to diagnostic accuracy and image quality. Three radiologists with different levels of experience in mammography reviewed each full-field digital mammography reader set for 185 patients with pathologically proven microcalcification clusters, which consisted of digital magnification mammograms (MAGs) with a magnification factor of 1.8 and images zoomed from mammograms (ZOOM) with a zoom factor of 2.0. Each radiologist rated their suspicion of breast cancer in microcalcific lesions using a six-point scale and the image quality and their confidence in the decisions using a five-point scale. Results were analysed according to display methods using areas under the receiver operating characteristic curves (A_z value) for ZOOM and MAGs to interpret microcalcifications, and the Wilcoxon matched pairs signed rank test for image quality and confidence levels. There was no statistically significant difference in the level of suspicion of breast cancer between the ZOOM and MAG groups (A_z = 0.8680 for ZOOM; A_z = 0.8682 for MAG; p = 0.9897). However, MAG images were significantly better than ZOOM images in terms of visual imaging quality (p < 0.001), and the confidence level with MAG was better than with ZOOM (p < 0.001). In conclusion, the performance of radiologists in the diagnosis of microcalcifications using ZOOM was similar to that using MAGs, although image quality and confidence levels were better using MAGs.Magnification mammography produces better spatial resolution and signal-to-noise ratio than does contact mammography. It is well established as a valuable adjunct to contact mammography, especially for the diagnosis of microcalcifications, despite the additional radiation exposure and increased radiation dose because of the shorter distance between the breast and X-ray source during examination [1–4].However, with respect to full-field digital mammography (FFDM), a few studies using zoomed images from contact mammograms have recently been reported and, as a result, a debate has arisen over whether a digital zooming system of FFDM can replace the magnification view of digital mammography [5–7]. Whereas Fischer et al [5] reported that zoomed images of a digital contact mammogram were equivalent to direct magnification of FFDM for the interpretation of microcalcifications, our previous report suggested that magnification mammography yielded better sensitivity and receiver operating characteristic (ROC) analysis than did zoomed images [7]. However, that study compared images zoomed by a factor of 1.3 with images magnified by a factor of 1.8. Therefore, we wondered whether using a zooming factor comparable to a magnification factor of 1.8 would yield the same results.The purpose of this study was to determine whether the diagnostic accuracy and image quality of microcalcification assessments using images twice zoomed from contact mammograms were equivalent to those obtained using digital magnification mammography by a magnification factor of 1.8.     

Comparison of visibility of circumscribed masses on Digital Breast Tomosynthesis (DBT) and 2D mammography: are circumscribed masses better visualized and assured of being benign on DBT?

Objective

To compare the visibility of circumscribed masses on digital breast tomosynthesis (DBT) images and 2D mammograms and determine the usefulness of DBT for differentiation between benign and malignant circumscribed masses.

Methods

Seventy-one (19 malignant and 52 benign) mammographic well-circumscribed masses were included. Visibility of the masses and halo signs on DBT images were retrospectively compared with 2D mammograms. The effects of mammographic breast density on mass visibility were also evaluated.

Results

For DBT, 83% were superior and 17% were equivalent in visibility of the masses to that of 2D, and superiority of DBT was significantly enhanced in the high breast density group compared with the low breast density group (91% vs 68%, respectively, p = 0.016). Three lesions were only detected on DBT. There was no significant difference in the superiority of DBT for lesion visibility between malignant and benign masses. The halo sign was detected in 58% lesions on DBT and in 4% on 2D (p < 0.001).

Conclusion

Circumscribed masses were better visualized on DBT than on 2D mammograms, particularly in high-density breasts. The halo sign often appeared on DBT and gave a clearer mass margin. However, circumscribed masses on DBT are not assured of being benign.

Key Points

? Circumscribed masses were better visualized on breast tomosynthesis than on 2D mammography. ? Tomosynthesis visualized circumscribed masses better than 2D for all breast density categories. ? Halo signs often appeared on tomosynthesis and contributed to detect circumscribed margins. ? Circumscribed masses on tomosynthesis images are not assured of being benign lesions.

     

数字化断层融合(DBT)与全视野数字X线摄影(FFDM)引导乳腺病灶定位对比

【摘要】目的:比较数字化断层融合（DBT）及全视野数字X线摄影（FFDM）引导乳腺病灶定位的异同。方法:回顾性搜集DBT引导乳腺病灶定位患者55例,FFDM引导定位患者65例。两种成像方式引导分别计算病灶中心三维坐标,通过乳腺定位针对病灶定位。当定位针针尖与病灶中心距离≤2cm时认为定位满意。应用独立样本t检验对两种方式定位满意率、定位时间、病灶穿刺时间及患者所接受辐射剂量进行比较。结果：DBT引导病灶定位满意率55/58,高于FFDM满意率67/73;定位时间对比上DBT要低于FFDM（609.14s vs 760.25s,P<0.05）;DBT病灶穿刺时间294.09s,低于FFDM 482.58s（P<0.05）;患者DBT引导比FFDM接受更少辐射剂量（9.13 vs 13.67mGy,P<0.05）。两种成像方式对恶性病灶定位满意率均高于良性病灶（DBT：26/27 vs 29/31;FFDM：26/27 vs 41/46）。而恶性病灶定位时间、穿刺时间则低于良性病灶。结论：相比于FFDM引导乳腺病灶定位,DBT能提供准确病灶深度信息,病灶定位满意率更高、定位时间及辐射剂量更少。     

Breast cancer detection in digital breast tomosynthesis and digital mammography—a side-by-side review of discrepant cases

Objective:

To analyse discrepant breast cancer detection in digital breast tomosynthesis (DBT) and digital mammography (DM).

Methods:

From a previous detection study comparing DBT and DM, 26 discrepant cases were extracted, 19 detected by DBT only and 7 by DM only. An expert panel of three radiologists reviewed these cases and documented the level of discrepancy, lesion visibility, radiographic pattern and lesion conspicuity and assessed the reason for non-detection. Differences between groups were tested using the Wilcoxon rank sum test, the Kruskal–Wallis test and visual grading characteristics.

Results:

The proportion of lesion periphery in fatty tissue was statistically significantly larger, and there were significantly more spiculated masses in DBT compared with DM in the DBT only group (p = 0.018; p = 0.015). The main reasons for missing a lesion were poor lesion visibility when using DM and interpretative error when using DBT.

Conclusion:

Lesion visualization is superior with DBT, particularly of spiculated tumours. A major reason for non-detection in DBT seems to be interpretative error, which may be due to lack of experience.

Advances in knowledge:

Our findings suggest that DBT is better than DM in visualizing breast cancer and that non-detection when using DBT is related to interpretative error regarding clearly visible lesions.Although digital mammography (DM) is the standard technique for imaging examination of symptomatic females, as well as for screening, it is a well-established fact that the technique has important limitations in terms of breast cancer detection, especially in dense breasts, where the sensitivity has been reported as being as low as 30–60%.^1,2 The main reasons are the obscuring effect of fibroglandular tissue and certain cancer growth patterns, for example, invasive lobular carcinoma (ILC) that sometimes grows diffusely in the breast in a single-file pattern and produces little desmoplastic response.³ In recent years, digital breast tomosynthesis (DBT) has developed into a promising three-dimensional (3D) breast-imaging technique that takes advantage of multiple exposures at different angles, which enables reconstruction of thin slices into a 3D volume and reduces the degrading effect of superimposed tissue.^4,5 Data indicate that DBT is an important adjunct to conventional DM, as well as being a promising screening modality, with about 30% higher cancer detection rate than that of ordinary screening, when read in combination with DM.^5–8In an experimental clinical series in our institution, comparing the accuracy of one-view DBT with that of two-view DM, sensitivities of approximately 90% and approximately 79%, respectively, for cancer detection were found.⁹ In brief, the study included 185 symptomatic or asymptomatic females with subtle or negative findings on DM, but suspicious lesions on ultrasonography, yielding 89 females with 95 cancer lesions and 96 females with normal or benign findings. The females underwent standard assessment and one-view DBT. Five breast radiologists interpreted DBT and DM images independently in accordance with free-response receiver operating characteristic methodology,¹⁰ classifying findings in accordance with the American College of Radiology''s Breast Imaging Reporting and Data System (BI-RADS).¹¹ Cases of discrepant detection in DBT and DM form the basis of the current study.When introducing a new diagnostic method, it is important to evaluate not only its accuracy but also to define its advantages and limitations in terms of imaging characteristics.¹² The aim of this study was to reassess possible reasons for discrepant breast cancer detection in DBT vs DM by analysing detectability parameters and radiographic lesion characteristics, with the DBT and DM images displayed side by side.     

Can the size of microcalcifications predict malignancy of clusters at mammography?

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether the size of mammographically detected microcalcifications is predictive of malignancy. MATERIALS AND METHODS: Two hundred sixty mammograms showing clustered microcalcifications with proven diagnoses (160 malignant, 100 benign) were respectively reviewed by experienced mammographers. Lesions that were obviously benign in appearance were excluded from the study. A computer-aided diagnosis system digitized the lesions at 600 dpi, and the microcalcifications on the digital image were interactively defined by mammographers. Subsequently, three quantitative features that reflected the size of the microcalcifications-length, area, and brightness-were automatically extracted by the system. For each feature, the standard average of values obtained for individual calcifications within the cluster and the average with emphasis on extreme values (E) obtained in a single cluster were analyzed and matched with pathologic results. RESULTS: In the malignant group of cases, the mean values of the standard average length and area were significantly higher (P < .0001) than the mean values in the benign group. Distribution analysis demonstrated that an average length of more than 0.41 mm was associated with malignant lesions 77% of the time, while an average length of less than 0.41 mm was associated with benign lesions 71% of the time. The mean of the average length (E) and area (E) of microcalcifications within the cluster demonstrated an even higher discriminative power when compared with the standard average length and area. The average brightness, on the other hand, showed only a low discriminative power. CONCLUSION: Digital computerized analysis of mammographically detected calcifications demonstrated that the average length and area of the calcifications in benign clusters were significantly smaller than those in malignant clusters.     

Radiological assessment of breast density by visual classification (BI–RADS) compared to automated volumetric digital software (Quantra): implications for clinical practice

Objective

This study was done to assess breast density on digital mammography and digital breast tomosynthesis according to the visual Breast Imaging Reporting and Data System (BI–RADS) classification, to compare visual assessment with Quantra software for automated density measurement, and to establish the role of the software in clinical practice.

Materials and methods

We analysed 200 digital mammograms performed in 2D and 3D modality, 100 of which positive for breast cancer and 100 negative. Radiological density was assessed with the BI–RADS classification; a Quantra density cut-off value was sought on the 2D images only to discriminate between BI–RADS categories 1–2 and BI–RADS 3–4. Breast density was correlated with age, use of hormone therapy, and increased risk of disease.

Results

The agreement between the 2D and 3D assessments of BI–RADS density was high (K 0.96). A cut-off value of 21 % is that which allows us to best discriminate between BI–RADS categories 1–2 and 3–4. Breast density was negatively correlated to age (r =  ?0.44) and positively to use of hormone therapy (p = 0.0004). Quantra density was higher in breasts with cancer than in healthy breasts.

Conclusions

There is no clear difference between the visual assessments of density on 2D and 3D images. Use of the automated system requires the adoption of a cut-off value (set at 21 %) to effectively discriminate BI–RADS 1–2 and 3–4, and could be useful in clinical practice.     

Are digital images good enough? A comparative study of conventional film-screen vs digital radiographs on printed images of total hip replacement

The aim of this study was to evaluate the inter- and intra-observer variability and to find differences in diagnostic safety between digital and analog technique in diagnostic zones around hip prostheses. In 80 patients who had had a total hip replacement (THR) for more than 2 years, a conventional image and a digital image were taken. Gruens model of seven distinct regions of interest was used for evaluations. Five experienced radiologists observed the seven regions and noted in a protocol the following distances: stem–cement; cement–bone; and stem–bone. All images were printed on hard copies and were read twice. Weighted kappa, _w, analyses were used. The two most frequently loosening regions, stem–cement region 1 and cement–bone region 7, were closely analyzed. In region 1 the five observers had an agreement of 86.75–97.92% between analog and digital images in stem–cement, which is a varied _w 0.29–0.71. For cement–bone region 7 an agreement of 87.21–90.45% was found, which is a varied _w of 0.48–0.58. All the kappa values differ significantly from nil. The result shows that digital technique is as good as analog radiographs for diagnosing possible loosening of hip prostheses.     

Tumor accumulation of ε-poly-lysines-based polyamines conjugated with boron clusters

Boron Neutron Capture Therapy (BNCT) is one of the potent cancer radiotherapies using nuclear reaction between ¹⁰B atoms and the neutron. Whether BNCT will succeed or not depends on tumor selective delivery of ¹⁰B compounds. ε-Poly-L-lysine is a naturally occurring polyamine characterized by the peptide linkages between the carboxyl and ε-amino groups of L-lysine. Because of high safety ε-PLL is applied practically as a food additive due to its strong antimicrobial activity. In this study, we focus on a development of a novel polymeric delivery system for BNCT using biodegradable ε-PLL conjugated with ¹⁰B-containing clusters (BSH). This polymeric boron carrier will be expected to deliver safely and efficiently into tumor tissues based on Enhanced Permeability and Retention (EPR) effect.     

Is lower-dose digital fluorography diagnostically adequate compared with higher-dose digital radiography for the diagnosis of fallopian tube stenosis?

Purpose: In an effort to reduce patient radiation dose during selective fallopian tube catheterization, the diagnostic adequacy of fluoroscopic images was compared with digital radiographic images in both a phantom study and a clinical study. Methods: For the phantom study polyethylene tubes with inner diameters of 1.30, 0.95, 0.80, 0.57, and 0.45 mm were used. Randomly selected tubes with/without stenoses, recorded by digital radiographic and last-image hold fluoroscopic images, were presented to five blinded radiologists, and receiver-operating characteristic (ROC) analyses were performed. For the clinical study tubal visualization as well as detectability of stenoses and occlusions were analyzed in 14 women using a 2-way analysis of variance for nonrepeated measures. Results: The phantom study showed no significant differences between the two imaging techniques for 0.57-mm-diameter and larger tubes; in contrast, fluoroscopic images provided significantly lower detectability of stenoses in 0.45-mm-diameter tubes (p < 0.05). The clinical study showed inferior tubal visualization and diagnostic performance for fluoroscopic images. Conclusions: Although fluoroscopic images have inferior diagnostic capability in detection of tubal stenoses and occlusions, these images may be adequate for documenting tubal patency with spill into the peritoneal cavity.     

二维数字乳腺摄影(FFDM)及数字乳腺融合体层摄影(DBT)上的微钙化点簇的特点:DBT是否会低估微钙化点簇?多中心研究结果

摘要目的应用BI-RADS对比数字乳腺融合体层摄影(DBT)和二维数字乳腺摄影(FFDM)对微钙化点簇(MC)分类。方法本研究经机构伦理委员会批准,在3个研究中心进     

Does the digital signature of the DICOM standard meet the requirements of German law?

The DICOM standard offers the possibilities to generate electronic signatures, valid according to German laws. This enhances the reliability of the correlation between image and patient data. However, only so called qualified electronic signatures--conveniently issued by an accredited supplier--are permissible and not rejectable as evidence in German jurisdiction and are completely equivalent to the handwritten signatures. These qualified electronic signatures can be executed only by individuals, whereas the former are not applicable to technical apparatus like image generating modalities. In consequence, a modality is able to provide its pictures with a "common or advanced signature" solely. This limits the use of the digital signature of the DICOM standard for further applications, e.g. the verifiability within the teleradiology.     

The dynamic range of digital radiographic systems: dose reduction or risk of overexposure?

OBJECTIVES: To investigate the range of diagnostically acceptable digital radiographs and film as a function of exposure time, as well as the relationship to dose reduction and consequences for dental practice. METHODS: Five systems for intraoral radiography were used to take a series of radiographs, with increasing exposure times, of five different dry bone specimens. Seven observers evaluated the 25 series of radiographs. The observers had to determine which radiographs of each series were acceptable for dental diagnostics and which radiograph of each series they preferred. RESULTS: For Ektaspeed Plus film, the exposure time for the preferred radiograph was 0.52 s, with a range of diagnostically acceptable radiographs from 0.23-1.02 s. The preferred radiograph of the solid-state systems required less radiation than film (Sirona, 0.13 s; MPDx 0.35 s). The exposure range of these systems is narrow. In contrast, the exposure range of the phosphor plate systems is very wide. The preferred radiograph of the phosphor plate systems required high exposure (Digora, 1.21 s; Gendex DenOptix, 1.16 s). CONCLUSIONS: All digital systems require less exposure than film for diagnostically acceptable radiographs, but this is less obvious for preferred radiographs. Solid-state systems alert the dentist when a too long exposure time is used by a lack of image quality; phosphor plate systems, however, produce good quality radiographs even at high exposure times, which may result in an unnecessarily high dose.     

Does the insertion of more than one wire allow successful excision of large clusters of malignant calcification?

AIM: To determine whether the insertion of more than one localization wire for larger areas of malignant microcalcification reduces the need for re-excision. METHOD: This is a retrospective study of 101 cases of malignant calcifications preoperatively marked by one or more wires. Surgical and histopathology data were obtained from hospital records. Mammograms and specimen radiographs were evaluated without knowledge of the eventual outcome, i.e., whether further surgery was required or not. All cases had a preoperative diagnosis of malignancy. RESULT: In this study the group of patients in which two or more wires were inserted had mammographically larger lesions (p<0.000001) but did not have a greater chance of needing re-excision (p=0.822). Mammograms that demonstrated flecks of microcalcification outlying the main cluster were also more likely to require further surgery (p<0.01). Calcifications associated with high-grade ductal carcinoma in situ (DCIS) had three times the risk of requiring further surgery (p<0.01). However, as reported in other studies re-excision was not related to breast size (p=0.63) [Kollias J, Gill PG, Beamond B, Rossi H, Langlois S, Vernon-Roberts E. Clinical and radiological predictors of complete excision in breast-conserving surgery for primary breast cancer. Aust N Z J Surg 1998;68:702-6]. CONCLUSION: It was previously suggested that the risk of re-excision for DCIS is related to the size of the initial lesion [Cheng L, Al-Kaisi NK, Gordon NH, Liu AY, Gebrail F, Shenk RR. Relationship between the size and margins of ductal carcinoma in situ of the breast and residual disease. J Nat Cancer Inst 1997;89:1356-60]. However, in the present study larger clusters of microcalcification that have been 'bracketed' by two or more wires do not appear to have a greater requirement for re-excision. Grading of the malignant microcalcifications preoperatively may encourage the surgeon to take a wider margin. Careful examination of the mammograms at localization to include outlying flecks could help to reduce the need for further surgery.     

Measurement of breast density with digital breast tomosynthesis—a systematic review

Digital breast tomosynthesis (DBT) has gained acceptance as an adjunct to digital mammography in screening. Now that breast density reporting is mandated in several states in the USA, it is increasingly important that the methods of breast density measurement be robust, reliable and consistent. Breast density assessment with DBT needs some consideration since quantitative methods are modelled for two-dimensional (2D) mammography. A review of methods used for breast density assessment with DBT was performed. Existing evidence shows Cumulus has better reproducibility than that of the breast imaging reporting and data system (BI-RADS®) but still suffers from subjective variability; MedDensity is limited by image noise, whilst Volpara and Quantra are robust and consistent. The reported BI-RADs inter-reader breast density agreement (k) ranged from 0.65 to 0.91, with inter-reader correlation (r) ranging from 0.70 to 0.93. The correlation (r) between BI-RADS and Cumulus ranged from 0.54–0.94, whilst that of BI-RADs and MedDensity ranged from 0.48–0.78. The reported agreement (k) between BI-RADs and Volpara is 0.953. Breast density correlation between DBT and 2D mammography ranged from 0.73 to 0.97, with agreement (k) ranging from 0.56 to 0.96. To avoid variability and provide more reliable breast density information for clinicians, automated volumetric methods are preferred.Breast cancer accounts for approximately 23% of all cancers in females and is the most frequent cause of cancer deaths in females worldwide.^1–3 The exact aetiology of the disease is complex, but many risk factors have been documented in the literature amongst which is breast density.^4–7 Breast density refers to the proportion of the breast that is composed of fibroglandular tissue. Breasts with high density contain more epithelial and stromal cells and collagen, which are significant for tumorigenesis as well as tissue-specific progenitor cells that are at risk of transformation to cancer cells.^8,9 Studies have shown that breast density is a strong, modifiable and measureable risk factor for breast cancer.^10–13 Additionally, the masking effect from breast density reduces the performance of screening mammography and limits early detection and treatment of breast cancer.¹⁴ Encouragingly, breast density is reducible, and its reduction has been shown to mitigate breast cancer risk.¹³ Therefore, mammographic breast density measurement can be used for breast cancer risk prediction and personalization of breast cancer prevention and control strategies, such as the selection of females who may require breast density reduction interventions. It may also be used for selection of more appropriate imaging pathways for earlier detection of breast cancer.^5,13 Utilization of breast density for these purposes requires robust and consistent methods for its assessment.Breast density depicted by the radio-opaque areas on a mammogram can be assessed using qualitative and quantitative (semi-automated and automated) methods.^15–17 Qualitative methods assign breast density grades based on visual assessment of the relative proportions of dense tissue, fat and prominence of ducts and include breast imaging reporting and data system (BI-RADS®), visual analogue scale and Wolfe, Tabar and Boyd assessment methods.^15,18,19 Semi-automated methods use segmentation and thresholding techniques to quantify the percentage of dense tissue on a mammogram and include planimetry and interactive thresholding methods such as Cumulus and Madena.^20,21 Automated methods use mathematical, statistical and physical modelling to calculate breast density; such automated methods include computerized texture-based techniques, calibration approaches and dual X-ray absorptiometry.^22–24 Others are automated thresholding approaches, such as Autodensity and MedDensity,^25,26 and three physical model-based techniques: standard mammographic form (SMF), Volpara and Quantra.^27–29 Irrespective of the method of measurement, breast density has been shown to be a potent risk factor for breast cancer.Many studies on mammographic breast density measurement are based on film–screen mammography and digital mammography (DM), which produce two-dimensional (2D) images of a three-dimensional (3D) breast. Qualitative methods have been shown to be poorly reproducible with these modalities; they have wide inter-reader agreement with Kappa (k) values ranging from 0.37 to 0.91.^26,30 Quantitative methods have better reproducibility with these modalities; however, there are concerns that quantitative area measurement of breast density as percentage mammographic density (PMD) is not representative of the tissue at risk of breast cancer, and that it is more reasonable to measure the volume of only the fibroglandular tissue, which is more related to the dense tissue at risk instead of PMD.^16,31 Another concern is that volumetric breast density measurement with 2D mammography is limited owing to the absence of depth information in such mammograms;³¹ methods estimating mammographic breast density with 2D mammography attempt to take into account variation in breast tissue thickness by modelling; however, with all models, there are assumptions made that may not be necessarily correct for an individual patient.Digital breast tomosynthesis (DBT) has gained acceptance as a tool for imaging of the symptomatic breast and as an adjunct to DM in screening.^32,33 Breast density assessment with DBT needs some consideration since quantitative methods are modelled for 2D mammography. DBT is a 3D imaging modality utilizing the concept of conventional tomography but a limited angle of tube movement (11–60^°) to acquire depth information from the breast (Figure 1a,b).³⁴ With the removal of anatomical noise (superimposed skin and subcutaneous tissue) in DBT images, quantitatively assessed breast density is expected to be lower than DM. On the other hand, more dense tissue becomes apparent to a subjective reader and qualitatively assessed breast density with DBT is expected to be higher relative to DM. It is therefore important to have a standardized robust, reliable and reproducible assessment method to avoid variability in breast density measurement as this will impact on clinical decision-making for females undergoing breast screening. There are several contending methods (Figure 2), each of which has its own merits; this review briefly examines the links between breast density and breast cancer. It also examines methods that have been used for measurement of mammographic breast density with DBT to ascertain which can be considered the best approach.Open in a separate windowFigure 1.Principles of digital breast tomosynthesis: (a) tube rotations relative to the detector and (b) acquired image slices. Image courtesy of Hologic Inc.; Bedford, MA © 2011. All rights reserved.Open in a separate windowFigure 2.Methods of breast density measurement. BI-RADS®, breast imaging reporting and data systems; SMF, standard mammographic form.     

The role of the Pauli principle in the elastic scattering of α + O16 clusters

This work is mainly concerned with an applicability of the orthogonality condition model (OCM); which represents simply the effect of the Pauli principle in the strongly overlapping region in the interaction between α-particles and O¹⁶ nuclei for E_α = 20–32 MeV. The angular distributions are analysed. Good agreements are obtained especially at backward angles. The connection between the complex OCM and the effective surface potential model has been made confirming that the Pauli principle plays an important role in the scattering of α particles on O¹⁶.     

数字乳腺断层摄影(DBT)和2D乳腺X线在观察局限性肿块方面的比较:用DBT是否可以更好地观察肿块并判断良、恶性

正摘要目的比较乳腺数字断层摄影(DBT)和2D乳腺X线摄影对局限性肿块的显示,并确定DBT在鉴别局限性肿块良恶性上的价值。方法 71例(19例恶性和52例良性)乳     

Does digital radiography increase the number of intraoral radiographs? A questionnaire study of Dutch dental practices

OBJECTIVES: To compare the number of radiographs taken in general dental practices equipped with digital radiography vs conventional film-based radiography and to determine the reasons for any difference in numbers. METHODS: In a mail survey, 473 questionnaires were sent to Dutch General Dental Practitioners (GDPs) using digital radiography and 105 questionnaires were sent to GDPs using film. The questionnaire concerned the number of intraoral radiographs taken in the dental practice, as well as possible reasons to take more or fewer radiographs after conversion to digital radiography. RESULTS: The response rate was 73%. Users of a phosphor plate system on average take 42.8 radiographs per week and solid-state system users take 48.4 radiographs, whereas film users take on average only 32.5 radiographs per week. The need for more certainty about the planned or ongoing treatment as well as better diagnostics were the most important reasons for taking more radiographs. CONCLUSIONS: It seems that GDPs using a system for digital radiography are more inclined to take radiographs than dentists taking conventional radiographs. Although digital intraoral radiography requires 50-80% less radiation per exposure than film, it is likely that the effective dose reduction after converting from conventional to digital radiography is less than 25% owing to the greater numbers of radiographs taken.