Daniel Förnvik

Breast tomosynthesis: Accuracy of tumor measurement compared with digital mammography and ultrasonography.

Background: Mammographic tumor size measurement can be difficult because breast structures are superimposed onto a two-dimensional (2D) plane, potentially obscuring the tumor outline. Breast tomosynthesis (BT) is a 3D X-ray imaging technique in which low-dose images are acquired over a limited angular range at a total dose comparable to digital mammography (DM). These low-dose images are used to mathematically reconstruct a 3D image volume of the breast, thus reducing the problem of superimposed tissue. Purpose: To investigate whether breast cancer size can be more accurately assessed with breast tomosynthesis than with digital mammography and ultrasonography (US), by reducing the disturbance effect of the projected anatomy. Material and Methods: A prototype BT system was used. The main inclusion criterion for BT examination was subtle but suspicious findings of breast cancer on 2D mammography. Sixty-two women with 73 breast cancers were included. BT, DM, and US sizes were measured independently by experienced radiologists without knowledge of the pathology results, which were used as reference. Results: The tumor outline could be determined in significantly more cases with BT (63) and US (60) than DM (49). BT and US size correlated well with pathology (R=0.86 and R=0.85, respectively), and significantly better than DM size (R=0.71). Accordingly, staging was significantly more accurate with BT than with DM. Conclusion: The study indicates that BT is superior to DM in the assessment of breast tumor size and stage.

THE DIAGNOSTIC ACCURACY OF DUAL-VIEW DIGITAL MAMMOGRAPHY, SINGLE-VIEW BREAST TOMOSYNTHESIS AND A DUAL-VIEW COMBINATION OF BREAST TOMOSYNTHESIS AND DIGITAL MAMMOGRAPHY IN A FREE-RESPONSE OBSERVER PERFORMANCE STUDY

The purpose of the present study was to compare the diagnostic accuracy of dual-view digital mammography (DM), single-view breast tomosynthesis (BT) and BT combined with the opposite DM view. Patients with subtle lesions were selected to undergo BT examinations. Two radiologists who are non-participants in the study and have experience in using DM and BT determined the locations and extents of lesions in the images. Five expert mammographers interpreted the cases using the free-response paradigm. The task was to mark and rate clinically reportable findings suspicious for malignancy and clinically relevant benign findings. The marks were scored with reference to the outlined regions into lesion localization or non-lesion localization, and analysed by the jackknife alternative free-response receiver operating characteristic method. The analysis yielded statistically significant differences between the combined modality and dual-view DM (p < 0.05). No differences were found between single-view BT and dual-view DM or between single-view BT and the combined modality.

THE EFFECT OF REDUCED BREAST COMPRESSION IN BREAST TOMOSYNTHESIS: HUMAN OBSERVER STUDY USING CLINICAL CASES

The aim of this study was to investigate whether the compression force used with conventional mammography can be reduced with breast tomosynthesis (BT), without adversely affecting the visualisation of normal and pathological structures. Forty-five women were examined with BT using full (same as for 2D mammography) and half compression force. Both examinations were performed with the same acquisition parameters. A total of 103 paired structure images were evaluated according to specified image quality criteria. Three experienced radiologists participated in the study. They had to make a forced choice, i.e. choose the image they felt best fulfilled the image quality criteria. The results showed no evident difference in the image quality, indicating that BT may be performed with substantially less compression force compared with 2D mammography. A majority of the examined women felt that half compression was more comfortable than full compression.

Breast Cancer Screening With Tomosynthesis-Initial Experiences

Experiences gained so far using tomosynthesis for breast cancer screening will be reported. A short summary of results from preparatory studies will also be presented. The sensitivity and specificity of breast tomosynthesis (BT) will be compared with conventional two-dimensional digital mammography (DM) for breast cancer screening in a population-based study. Over 2000 women have been examined so far with BT and DM. The BT reading is significantly more time-consuming than the DM reading. Preparatory studies have shown that BT has a higher diagnostic precision and higher accuracy of size measurements and stage determination than DM. There is potential to use lower compression force with BT compared with DM, without decreasing the diagnostic accuracy. BT might play an important role in clinical as well as screening mammography. A large-scale population-based study to investigate BT as a screening modality is underway.

Breast compression in mammography: pressure distribution patterns

Background Breast compression is important in mammography in order to improve image quality, better separate tissue components, and reduce absorbed dose to the breast. In this study we use a method to measure and visualize the distribution of pressure over a compressed breast in mammography. Purpose To measure and describe the pressure distribution over the breast as a result of applied breast compression in mammography. Material and Methods One hundred and three women aged 40.7-74.3 years (median, 48.9 years) invited for mammographic screening consented to take part in this study. They were subjected to two additional breast compressions of the left breast (standard force and approximately 50% reduction). Pressure images of the compressed breast were obtained using force sensing resistor (FSR) sensors placed underneath the compression plate. Subjects rated their experience of pain on a visual analogue scale (VAS). Results Four pressure patterns were identified, fitting 81 of the 103 breasts, which were grouped accordingly. The remaining 22 breasts were found to correspond to a combination of any two patterns. Two groups (43 breasts) showed pressure mainly over the juxtathoracic part of the breast, had significantly greater breast thickness (P = 0.003) and had a lower mean pressure over dense tissue (P < 0.0001) than those with more evenly distributed pressure. Reducing compression force increased average breast thickness by 1.8 mm (P < 0.0001). Conclusion The distribution of pressure differed greatly between breasts. In a large proportion of breasts the compression plate did not provide optimal compression of the breast, the compression force being absorbed in juxtathoracic structures.

No evidence for shedding of circulating tumor cells to the peripheral venous blood as a result of mammographic breast compression.

This pilot study aimed to investigate whether mammographic compression procedures might cause shedding of tumor cells into the circulatory system as reflected by circulating tumor cell (CTC) count in peripheral venous blood samples. From March to October 2012, 24 subjects with strong suspicion of breast malignancy were included in the study. Peripheral blood samples were acquired before and after mammography. Enumeration of CTCs in the blood samples was performed using the CellSearch® system. The pressure distribution over the tumor-containing breast was measured using thin pressure sensors. The median age was 66.5xa0years (range, 51–87xa0years). In 22 of the 24 subjects, breast cancer was subsequently confirmed. The difference between the average mean tumor pressure 6.8xa0±xa05.3xa0kPa (range, 1.0–22.5xa0kPa) and the average mean breast pressure 3.4xa0±xa01.6xa0kPa (range, 1.5–7.1xa0kPa) was statistically significant (pxa0<xa00.001), confirming that there was increased pressure over the tumor. The median pathological tumor size was 19xa0mm (range, 9–30xa0mm). Four subjects (17xa0%) were CTC positive before compression and two of these (8xa0%) were also CTC positive after compression. A total of seven CTCs were isolated with a mean size of 8xa0×xa06xa0μm2 (range of the longest diameter, 5–12xa0μm). The study supports the view that mammography is a safe procedure from the point of view of tumor cell shedding to the peripheral blood.

Investigation of viewing procedures for interpretation of breast tomosynthesis image volumes: a detection-task study with eye tracking.

AbstractObjectivesTo evaluate the efficiency of different methods of reading breast tomosynthesis (BT) image volumes.MethodsAll viewing procedures consisted of free scroll volume browsing and three were combined with initial cine loops at three different frame rates (9, 14 and 25xa0fps). The presentation modes consisted of vertically and horizontally orientated BT image volumes. Fifty-five normal BT image volumes in mediolateral oblique view were collected. In these, simulated lesions were inserted, creating four unique image sets, one for each viewing procedure. Four observers interpreted the cases in a free-response task. Time efficiency, visual attention and search were investigated using eye tracking.ResultsHorizontally orientated BT image volumes were read faster than vertically when using free scroll browsing only and when combined with fast cine loop. Cine loops at slow frame rates were ruled out as inefficient.ConclusionsIn general, horizontally oriented BT image volumes were read more efficiently. All viewing procedures except for slow frame rates were promising when assuming equivalent detection performance.Key Points• Breast tomosynthesis is increasingly used for breast cancer detectionn • There is a benefit in reading breast tomosynthesis image volumes presented horizontallyn • Align image content to visual field, especially for dynamic 3D imagesn • Reading at slow frame rates was considered inefficient

The effect of breast positioning on breast compression in mammography: a pressure distribution perspective

The standard procedure at mammography is to compress the breast in order to improve image quality, better separate tissue components and reduce absorbed dose to the breast. Traditionally, compression guidelines have been based on applied force, rather than actual thickness reduction. Structures such as the pectoral muscle are stiffer than breast tissue and if compressed along with it, as in the MLO-projection, might absorb much of the applied force. This study investigated the difference in compression of breasts before and after they were repositioned to exclude 1 cm of the juxtathoracic part. Twenty-one women were included in the study. The distribution of compression pressure was measured using thin FSR (Force Sensing Resistor) pressure sensors attached to the compression paddle. Breast thickness and compression force were measured by the mammographic device. Compared to standard positioning the repositioned breasts were thinner by 4.4±2.3 mm (P < 0.001) (from 50.3 mm to 45.9 mm) and had a 12.3±24.5 cm2 (P = 0.032) larger area over which pressure was distributed (from 97.6 cm2 to 109.9 cm2), despite less of the breast being included in the projection. This indicates that the inclusion of the pectoral muscle and other juxtathoracic structures in the MLOprojection substantially affects pressure distribution and prevents proper compression of the breast. The results suggest that the exact positioning of the MLO-projection should be carefully evaluated in order to find a balance between breast compression and tissue inclusion.

Optimizing viewing procedures of breast tomosynthesis image volumes using eye tracking combined with a free response human observer study

The purpose of this study was to evaluate four different viewing procedures as part of improving viewing conditions of breast tomosynthesis (BT) image volumes. The procedures consisted of free scroll volume browsing, and a combination of initial cine loops at three different frame rates (9, 14 and 25 fps) terminated upon request followed by free scroll volume browsing. Fifty-five normal BT image volumes in MLO view were collected. In these, simulated lesions (20 masses and 20 clusters of microcalcifications) were randomly inserted, creating four unique image sets for each procedure. Four readers interpreted the cases in a random order. Their task was to locate a lesion, mark and assign a five level confidence scale. The diagnostic accuracy was analyzed using Jackknife Free Receiver Operating Characteristics (JAFROC). Time efficiency and visual search behavior were also investigated using eye tracking. The results indicate that there was no statistically significant difference in JAFROC FOM between the different viewing procedures, however the medium cine loop speed seemed to be the preferred viewing procedure in terms of total analyze time and dwell time.

Pressure distribution in mammography: compression of breasts with malignant tumor masses

The pressure distribution over a compressed breast is in general heterogeneous. In this study we investigated the pressure distribution over compressed breasts with tumor masses. Twenty-two women either recalled for work-up of findings suspicious for breast cancer in the screening program or with clinically suspected findings were included in the study. Twenty-one lesions turned out to be malignant and one benign. The distribution of compression pressure was measured using thin FSR (Force Sensing Resistor) pressure sensors attached to the compression plate. The pressure over the breast was ascertained by acquiring an x-ray image of the compressed breast with the pressure sensors present. The pressure data and the mammogram were used to create a composite image with pressure data displayed as a color overlay. The malignant tumor area generally matched an elevated pressure area and this pressure was generally higher than the pressure over surrounding parenchyma. In 11 out of 22 (50%) subjects the maximum pressure over the breast was located over the tumor. Only 4 out of 22 (18%) masses had a lower tumor mean pressure compared to the mean pressure over the breast (including one small < 10 mm tumor and one benign structure). The results suggest that tumors are stiffer, thus, absorbing more pressure compared to the surrounding parenchyma and that this property can be quantified. Refined pressure techniques could possibly be used to demonstrate the relative elasticity distribution in breast tissue, which might provide valuable differential diagnostic information.