The importance of early detection of calcifications associated with breast cancer in screening.

PURPOSE: The aim of this study was to assess how often women with undetected calcifications in prior screening mammograms are subsequently diagnosed with invasive cancer. METHODS: From a screening cohort of 63,895 women, exams were collected from 59,690 women without any abnormalities, 744 women with a screen-detected cancer and a prior negative exam, 781 women with a false positive exam based on calcifications, and 413 women with an interval cancer. A radiologist identified cancer-related calcifications, selected by a computer-aided detection system, on mammograms taken prior to screen-detected or interval cancer diagnoses. Using this ground truth and the pathology reports, the sensitivity for calcification detection and the proportion of lesions with visible calcifications that developed into invasive cancer were determined. RESULTS: The screening sensitivity for calcifications was 45.5%, at a specificity of 99.5%. A total of 68.4% (n = 177) of cancer-related calcifications that could have been detected earlier were associated with invasive cancer when diagnosed. CONCLUSIONS: Screening sensitivity for detection of malignant calcifications is low. Improving the detection of these early signs of cancer is important, because the majority of lesions with detectable calcifications that are not recalled immediately but detected as interval cancer or in the next screening round are invasive at the time of diagnosis.

The distribution of ductal carcinoma in situ (DCIS) grade in 4232 women and its impact on overdiagnosis in breast cancer screening.

BACKGROUND: The incidence of ductal carcinoma in situ (DCIS) has rapidly increased over time. The malignant potential of DCIS is dependent on its differentiation grade. METHODS: Our aim is to determine the distribution of different grades of DCIS among women screened in the mass screening programme, and women not screened in the mass screening programme, and to estimate the amount of overdiagnosis by grade of DCIS. We retrospectively included a population-based sample of 4232 women with a diagnosis of DCIS in the years 2007-2009 from the Nationwide network and registry of histopathology and cytopathology in the Netherlands. Excluded were women with concurrent invasive breast cancer, lobular carcinoma in situ and no DCIS, women recently treated for invasive breast cancer, no grade mentioned in the record, inconclusive record on invasion, and prevalent DCIS. The screening status was obtained via the screening organisations. The distribution of grades was incorporated in the well-established and validated microsimulation model MISCAN. RESULTS: Overall, 17.7 % of DCIS were low grade, 31.4 % intermediate grade, and 50.9 % high grade. This distribution did not differ by screening status, but did vary by age. Older women were more likely to have low-grade DCIS than younger women. Overdiagnosis as a proportion of all cancers in women of the screening age was 61 % for low-grade, 57 % for intermediate-grade, 45 % for high-grade DCIS. For women age 50-60 years with a high-grade DCIS this overdiagnosis rate was 21-29 %, compared to 50-66 % in women age 60-75 years with high-grade DCIS. CONCLUSIONS: Amongst the rapidly increasing numbers of DCIS diagnosed each year is a significant number of overdiagnosed cases. Tailoring treatment to the probability of progression is the next step to preventing overtreatment. The basis of this tailoring could be DCIS grade and age.

Experiences with a self-test for Dutch breast screening radiologists: lessons learnt.

PURPOSE: To evaluate a self-test for Dutch breast screening radiologists introduced as part of the national quality assurance programme. METHODS AND MATERIALS: A total of 144 radiologists were invited to complete a test-set of 60 screening mammograms (20 malignancies). Participants assigned findings such as location, lesion type and BI-RADS. We determined areas under the receiver operating characteristics (ROC) curves (AUC), case and lesion sensitivity and specificity, agreement (kappa) and correlation between reader characteristics and case sensitivity (Spearman correlation coefficients). RESULTS: A total of 110 radiologists completed the test (76%). Participants read a median number of 10,000 screening mammograms/year. Median AUC value was 0.93, case and lesion sensitivity was 91% and case specificity 94%. We found substantial agreement for recall (κ = 0.77) and laterality (κ = 0.80), moderate agreement for lesion type (κ = 0.57) and BI-RADS (κ = 0.45) and no correlation between case sensitivity and reader characteristics. CONCLUSION: Areas under the ROC curve, case sensitivity and lesion sensitivity were satisfactory and recall agreement was substantial. However, agreement in lesion type and BI-RADS could be improved; further education might be aimed at reducing interobserver variation in interpretation and description of abnormalities. We offered individual feedback on interpretive performance and overall feedback at group level. Future research will determine whether performance has improved. KEY POINTS: • We introduced and evaluated a self-test for Dutch breast screening radiologists. • ROC curves, case and lesion sensitivity and recall agreement were all satisfactory. • Agreement in BI-RADS interpretation and description of abnormalities could be improved. • These are areas that should be targeted with further education and training. • We offered individual feedback on interpretative performance and overall group feedback.

Variations in screening outcome among pairs of screening radiologists at non-blinded double reading of screening mammograms: a population-based study.

OBJECTIVES: Substantial inter-observer variability in screening mammography interpretation has been reported at single reading. However, screening results of pairs of screening radiologists have not yet been published. We determined variations in screening performances among pairs of screening radiologists at non-blinded double reading. METHODS: We included pairs of screening radiologists with at least 7,500 screening examinations per pair, obtained between 1997 and 2011. During 2-year follow-up, breast imaging reports, surgical reports and pathology results were collected of all referred women and interval cancers. Referral rate, cancer detection rate, positive predictive value and sensitivity were calculated for each pair. RESULTS: A total of 310,906 screening mammograms, read by 26 pairs of screening radiologists, were included for analysis. The referral rate ranged from 1.0 % (95 % CI 0.8 %-1.2 %) to 1.5 % (95 % CI 1.3 %-1.8 %), the cancer detection rate from 4.0 (95 % CI 2.8-5.2) to 6.3 (95 % CI 4.5-8.0) per 1,000 screens. The programme sensitivity and positive predictive value of referral ranged from 55.1 % (95 % CI 45.1 %-65.1 %) to 81.5 % (95 % CI 73.4 %-89.6 %) and from 28.7 % (95 % CI 20.8 %-36.6 %) to 49.5 % (95 % CI 39.7 %-59.3 %), respectively. CONCLUSION: We found significant variations in screening outcomes among pairs of screening radiologists at non-blinded double reading. This stresses the importance of monitoring screening results on a local scale. KEY POINTS: • Substantial inter-observer variability in screening mammography interpretation is known at single reading • Population-based study showed significant variations in outcomes among pairs of screening radiologists • Local monitoring and regular feedback are important to optimise screening outcome.

Immediate and delayed effects of mammographic screening on breast cancer mortality and incidence in birth cohorts.

BACKGROUND: Trend studies investigating the impact of mammographic screening usually display age-specific mortality and incidence rates over time, resulting in an underestimate of the benefit of screening, that is, mortality reduction, and an overestimate of its major harmful effect, that is, overdiagnosis. This study proposes a more appropriate way of analysing trends. METHODS: Breast cancer mortality (1950-2009) and incidence data (1975-2009) were obtained from Statistics Netherlands, 'Stg. Medische registratie' and the National Cancer Registry in the Netherlands for women aged 25-85 years. Data were visualised in age-birth cohort and age-period figures. RESULTS: Birth cohorts invited to participate in the mammographic screening programme showed a deflection in the breast cancer mortality rates within the first 5 years after invitation. Thereafter, the mortality rate increased, although less rapidly than in uninvited birth cohorts. Furthermore, invited birth cohorts showed a sharp increase in invasive breast cancer incidence rate during the first 5 years of invitation, followed by a moderate increase during the following screening years and a decline after passing the upper age limit. CONCLUSION: When applying a trend study to estimate the impact of mammographic screening, we recommend using a birth cohort approach.

Likelihood of early detection of breast cancer in relation to false-positive risk in life-time mammographic screening: population-based cohort study.

BACKGROUND: Women require balanced, high-quality information when making an informed decision on screening benefits and harms before attending biennial mammographic screening. PATIENTS AND METHODS: The cumulative risk of a false-positive recall and/or (small) screen-detected or interval cancer over 13 consecutive screening examinations for women aged 50 from the start of screening were estimated using data from the Nijmegen programme, the Netherlands. RESULTS: Women who underwent 13 successive screens in the period 1975-1976 had a 5.3% cumulative chance of a screen-detected cancer, with a 4.2% risk of at least one false-positive recall. The risk of being diagnosed with interval cancer was 3.7%. Two decades later, these estimates were 6.9%, 7.3% and 2.9%, respectively. The chance of detection of a small, favourable invasive breast cancer, anticipating a normal life-expectancy, rose from 2.3% to 3.7%. Extrapolation to digital screening mammography indicates that the proportion of false-positive results will rise to 16%. CONCLUSION: Dutch women about to participate in the screening programme can be reassured that the chance of false-positive recall in the Netherlands is relatively low. A new screening policy and improved mammography have increased the detection of an early screening carcinoma and lowering the risk of interval carcinoma.

Breast cancer risk prediction model: a nomogram based on common mammographic screening findings.

OBJECTIVES: To develop a prediction model for breast cancer based on common mammographic findings on screening mammograms aiming to reduce reader variability in assigning BI-RADS. METHODS: We retrospectively reviewed 352 positive screening mammograms of women participating in the Dutch screening programme (Nijmegen region, 2006-2008). The following mammographic findings were assessed by consensus reading of three expert radiologists: masses and mass density, calcifications, architectural distortion, focal asymmetry and mammographic density, and BI-RADS. Data on age, diagnostic workup and final diagnosis were collected from patient records. Multivariate logistic regression analyses were used to build a breast cancer prediction model, presented as a nomogram. RESULTS: Breast cancer was diagnosed in 108 cases (31 %). The highest positive predictive value (PPV) was found for spiculated masses (96 %) and the lowest for well-defined masses (10 %). Characteristics included in the nomogram are age, mass, calcifications, architectural distortion and focal asymmetry. CONCLUSION: With our nomogram we developed a tool assisting screening radiologists in determining the chance of malignancy based on mammographic findings. We propose cutoff values for assigning BI-RADS in the Dutch programme based on our nomogram, which will need to be validated in future research. These values can easily be adapted for use in other screening programmes. KEY POINTS: • There is substantial reader variability in assigning BI-RADS in mammographic screening. • There are no strict guidelines linking mammographic findings to BI-RADS categories. • We developed a model (nomogram) predicting the presence of breast cancer. • Our nomogram is based on common findings on positive screening mammograms. • The nomogram aims to assist screening radiologists in assigning BI-RADS categories.

Is DCIS breast cancer, and how do I treat it?

Ductal carcinoma in situ (DCIS) is a pre-invasive stage of breast cancer with a heterogeneous clinical behaviour. Since the introduction of mammographic screening programmes, the incidence of DCIS has shown a dramatic increase. Treatment should focus on the prevention of progression to invasive disease. If progression occurs, poorly differentiated DCIS frequently gives rise to grade III invasive breast cancer, whereas well differentiated DCIS more often recurs as grade I invasive disease. However, at present, validated diagnostic test are lacking to predict progression accurately. The majority of women with DCIS are suitable for breast conserving therapy. Obtaining clear surgical margins is the most important goal of a local excision. Radiotherapy is effective in reducing the risk of local recurrence with about 50 % in all subgroups of patients with DCIS. (Breast cancer specific) survival of women with DCIS is excellent, and radiotherapy does not further improve this. Future research should be directed in enabling to select women who have a high risk of--invasive--recurrence, so in which radiotherapy should be standard part of the breast conserving approach, and those women with a more indolent lesion, in which after surgery a watchful waiting approach can be followed.

The Breast Imaging Reporting and Data System (BI-RADS) in the Dutch breast cancer screening programme: its role as an assessment and stratification tool.

OBJECTIVES: To assess the suitability of the Breast Imaging Reporting and Data System (BI-RADS) as a quality assessment tool in the Dutch breast cancer screening programme. METHODS: The data of 93,793 screened women in the Amsterdam screening region (November 2005-July 2006) were reviewed. BI-RADS categories, work-up, age, final diagnosis and final TNM classification were available from the screening registry. Interval cancers were obtained through linkage with the cancer registry. BI-RADS was introduced as a pilot in the Amsterdam region before the nationwide introduction of digital mammography (2009-2010). RESULTS: A total of 1,559 women were referred to hospital (referral rate 1.7 %). Breast cancer was diagnosed in 485 women (detection rate 0.52 %); 253 interval cancers were reported, yielding a programme sensitivity of 66 % and specificity of 99 %. BI-RADS 0 had a lower positive predictive value (PPV, 14.1 %) than BI-RADS 4 (39.1 %) and BI-RADS 5 (92.9 %; P < 0.0001). The number of invasive procedures and tumour size also differed significantly between BI-RADS categories (P < 0.0001). CONCLUSION: The significant differences in PPV, invasive procedures and tumour size match with stratification into BI-RADS categories. It revealed inter-observer variability between screening radiologists and can thus be used as a quality assessment tool in screening and as a stratification tool in diagnostic work-up. KEY POINTS: • The BI-RADS atlas is widely used in breast cancer screening programmes. • There were significant differences in results amongst different BI-RADS categories. • Those differences represented the radiologists' degree of suspicion for malignancy, thus enabling stratification of referrals. • BI-RADS can be used as a quality assessment tool in screening. • Training should create more uniformity in applying the BI-RADS lexicon.

Increasingly strong reduction in breast cancer mortality due to screening.

BACKGROUND: Favourable outcomes of breast cancer screening trials in the 1970s and 1980s resulted in the launch of population-based service screening programmes in many Western countries. We investigated whether improvements in mammography and treatment modalities have had an influence on the effectiveness of breast cancer screening from 1975 to 2008. METHODS: In Nijmegen, the Netherlands, 55,529 women received an invitation for screening between 1975 and 2008. We designed a case-referent study to evaluate the impact of mammographic screening on breast cancer mortality over time from 1975 to 2008. A total number of 282 breast cancer deaths were identified, and 1410 referents aged 50-69 were sampled from the population invited for screening. We estimated the effectiveness by calculating the odds ratio (OR) indicating the breast cancer death rate for screened vs unscreened women. RESULTS: The breast cancer death rate in the screened group over the complete period was 35% lower than in the unscreened group (OR=0.65; 95% CI=0.49-0.87). Analysis by calendar year showed an increasing effectiveness from a 28% reduction in breast cancer mortality in the period 1975-1991 (OR=0.72; 95% CI=0.47-1.09) to 65% in the period 1992-2008 (OR=0.35; 95% CI=0.19-0.64). CONCLUSION: Our results show an increasingly strong reduction in breast cancer mortality over time because of mammographic screening.

Model-based measurements of the diameter of the internal carotid artery in CT angiography images.

PURPOSE: Computed tomography angiography (CTA) is often used to determine the degree of stenosis in patients that suffer from carotid artery occlusive disease. Accurate and precise measurements of the diameter of the stenosed internal carotid artery are required to make decisions on treatment of the patient. However, the inherent blurring of images hampers a straightforward measurement, especially for smaller vessels. The authors propose a model-based approach to perform diameter measurements in which explicit allowance is made for the blurring of structures in the images. Three features of the authors' approach are the use of prior knowledge in the fitting of the model at the site of the stenosis, the applicability to vessels both with circular and noncircular cross-section, and the ability to deal with additional structures close to the arteries such as calcifications. METHODS: Noncircular cross-sections of vessels were modeled with elliptic Fourier descriptors. When calcifications or other high-intensity structures are adjacent to the lumen, both the lumen and the high-intensity structures were modeled in order to improve the diameter estimates of the vessel. Measurements were performed in CT scans of a phantom mimicking stenosed carotids and in CTA scans of two patients with an internal carotid stenosis. In an attempt to validate the measurements in CTA images, measurements were also performed in three-dimensional rotational angiography (3DRA) images of the same patients. RESULTS: The validity of the approach for diameter measurements of cylindrical arteries in CTA images is evident from phantom measurements. When prior knowledge about the enhancement and the blurring parameter was used, accurate and precise diameter estimates were obtained down to a diameter of 0.4 mm. The potential of the presented approach, both with respect to the extension to noncircular cross-sections and the modeling of adjacent calcifications, appears from the patient data. The accuracy of the size estimates in the patient images could not be unambiguously established because no gold standard was available and the quality of the 3DRA images was often suboptimal. CONCLUSIONS: The authors have shown that the inclusion of a priori information results in accurate and precise diameter measurements of arteries with a small diameter. Furthermore, in patient data, the assumption of a circular cross-section often appears to be too simple. The extension to noncircular cross-sections and adjacent calcifications paves the way to realistic modeling of the carotid artery.

Intracranial CT angiography obtained from a cerebral CT perfusion examination.

CT perfusion (CTP) examinations of the brain are performed increasingly for the evaluation of cerebral blood flow in patients with stroke and vasospasm after subarachnoid hemorrhage. Of the same patient often also a CT angiography (CTA) examination is performed. This study investigates the possibility to obtain CTA images from the CTP examination, thereby possibly obviating the CTA examination. This would save the patient exposure to radiation, contrast, and time. Each CTP frame is a CTA image with a varying amount of contrast enhancement and with high noise. To improve the contrast-to-noise ratio (CNR) we combined all 3D images into one 3D image after registration to correct for patient motion between time frames. Image combination consists of weighted averaging in which the weighting factor of each frame is proportional to the arterial contrast. It can be shown that the arterial CNR is maximized in this procedure. An additional advantage of the use of the time series of CTP images is that automatic differentiation between arteries and veins is possible. This feature was used to mask veins in the resulting 3D images to enhance visibility of arteries in maximum intensity projection (MIP) images. With a Philips Brilliance 64 CT scanner (64 x 0.625 mm) CTP examinations of eight patients were performed on 80 mm of brain using the toggling table technique. The CTP examination consisted of a time series of 15 3D images (2 x 64 x 0.625 mm; 80 kV; 150 mAs each) with an interval of 4 s. The authors measured the CNR in images obtained with weighted averaging, images obtained with plain averaging, and images with maximal arterial enhancement. The authors also compared CNR and quality of the images with that of regular CTA examinations and examined the effectiveness of automatic vein masking in MIP images. The CNR of the weighted averaged images is, on the average, 1.73 times the CNR of an image at maximal arterial enhancement in the CTP series, where the use of plain averaging increases the CNR only with a factor of 1.49. The quality of the weighted averaged images approaches that of CTA images, although in the present study the image quality of CTA was not quite reached. The automatic masking of veins is effective and only small remnants of veins were sometimes present in the masked images. Weighted averaging makes it possible to create CTA images from a CTP examination with a CNR considerably higher than that of images with maximal arterial enhancement. The quality of the resulting images approaches that of CTA images and offers the additional advantages to automatically differentiate between arteries and veins.

[Revised practice guideline 'Screening and diagnosis of breast cancer']. / Richtlijn 'screening en diagnostiek van het mammacarcinoom' (herziening).

Revised practice guideline 'Screening and diagnosis of breast cancer' The evidence-based revision of the practice guideline 'Screening and diagnosis of breast cancer' was necessitated by new insights, for instance on the cost-effectiveness of screening modalities other than mammography. Mammography is the only screening modality that is recommended for the general population. In the Netherlands, women from 50-75 years of age are invited for screening. However, in view of the ongoing increase in the incidence of breast cancer and of the image quality advantages of radiological digitalization, a study on the decrease of the lower age limit--preferably 45 years--is recommended. Screening with MRI is indicated for carriers of breast cancer gene mutations. Evaluation of risk factors has resulted in a rearrangement of screening recommendations, based on relative risks (RRs): screening apart from the population screening is only recommended in case the RRis 4 or more and in patients with a positive family history in case of a RR of 2 or more. Additional risks require further genetic evaluation. The 'Breast imaging reporting and data system' (BI-RADS) is now recommended for both screening and diagnostic imaging. Its application has had an impact on the triple diagnostic approach, which has now evolved into a consensus between surgeon, radiologist and pathologist. Axillary ultrasound should be carried out ifa sentinel node procedure is being considered. MRI should be included if the cancer cannot be reliably delineated on mammography or ultrasound. The increased complexity of the diagnostic work-up often means that the final diagnosis is not arrived within one day. Every effort should be made to achieve this goal within 5 working days. Ned Tijdschr Geneeskd. 2008;I52:2336-9

Image quality of multisection CT of the brain: thickly collimated sequential scanning versus thinly collimated spiral scanning with image combining.

BACKGROUND AND PURPOSE: Routine CT of the brain is traditionally performed with sequential CT. We assessed whether sequential CT can be replaced with thinly collimated multisection spiral CT without loss of image quality. MATERIALS AND METHODS: An observer study was conducted using data from 23 patients who were scanned with both a sequential (collimation, 4 x 5 mm) and a spiral technique (collimation, 4 x 1 mm; pitch, 0.875). Each sequential image was registered with 4 combined spiral CT images at 1.2 mm distance. Two neuroradiologists blindly scored 232 image pairs on 6 aspects: streak artifacts, visualization of brain tissue near skull, visualization of hypoattenuated lesions, gray/white matter differentiation, image noise, and overall image quality. A 5-point scale (range, -2 to 2) was used to score the preferences. The 23 pairs of complete scans were scored likewise. In this case, no registration was performed. RESULTS: Virtually all mean scores were positive (ie, showed a preference for the spiral technique). For the comparison of image pairs, the preferences with respect to streak artifacts (mean score, 1.36), visualization of brain tissue near the skull (mean score, 0.69), and overall image quality (mean score, 0.95) were significant (P < .001). With respect to visualization of hypo-attenuated lesions, image noise, and gray/white matter differentiation (mean scores, 0.18, 0.27, and 0.13), the preferences for spiral CT were not significant. The preferences for the spiral technique were also present at the comparison of the complete scans. CONCLUSION: Thinly collimated multisection spiral CT of the brain with image combining is superior to thickly collimated sequential CT.

Removal of bone in CT angiography by multiscale matched mask bone elimination.

For clear visualization of vessels in CT angiography (CTA) images of the head and neck using maximum intensity projection (MIP) or volume rendering (VR) bone has to be removed. In the past we presented a fully automatic method to mask the bone [matched mask bone elimination (MMBE)] for this purpose. A drawback is that vessels adjacent to bone may be partly masked as well. We propose a modification, multiscale MMBE, which reduces this problem by using images at two scales: a higher resolution than usual for image processing and a lower resolution to which the processed images are transformed for use in the diagnostic process. A higher in-plane resolution is obtained by the use of a sharper reconstruction kernel. The out-of-plane resolution is improved by deconvolution or by scanning with narrower collimation. The quality of the mask that is used to remove bone is improved by using images at both scales. After masking, the desired resolution for the normal clinical use of the images is obtained by blurring with Gaussian kernels of appropriate widths. Both methods (multiscale and original) were compared in a phantom study and with clinical CTA data sets. With the multiscale approach the width of the strip of soft tissue adjacent to the bone that is masked can be reduced from 1.0 to 0.2 mm without reducing the quality of the bone removal. The clinical examples show that vessels adjacent to bone are less affected and therefore better visible. Images processed with multiscale MMBE have a slightly higher noise level or slightly reduced resolution compared with images processed by the original method and the reconstruction and processing time is also somewhat increased. Nevertheless, multiscale MMBE offers a way to remove bone automatically from CT angiography images without affecting the integrity of the blood vessels. The overall image quality of MIP or VR images is substantially improved relative to images processed with the original MMBE method.

Pressure-standardised mammography does not affect visibility, contrast and sharpness of stable lesions.

INTRODUCTION: A recent technological development allows pressure-standardised mammography by personalizing the compression force to the breast size and firmness. The technique has been shown to reduce pain and compression variability between consecutive exams, but also results in a slightly thicker compressed breast during exposure. This raises the question whether visibility, contrast and sharpness of lesions are affected? METHODS: Four experienced radiologists compared 188 stable lesions and structures including (clusters of) calcifications, (oil) cysts and lymph nodes that were visible in mammograms obtained in 2009 with a pain-tolerance limited 18 daN target force compression protocol, and in 2014/2015 obtained with a 10kPa (75mmHg) pressure-standardised compression protocol. Observers were blinded for all DICOM metadata and rated which of the randomly ordered, side by side presented images had better lesion visibility, contrast and sharpness, or whether they saw no difference. They also indicated which overall image they preferred, if any, and whether the non-preferred image was still adequate. Statistical non-inferiority is concluded when the lower limit of the 95% confidence interval of the 4-rater averaged 'new protocol better' proportions exceed the non-inferiority limit of 0.463. RESULTS: In 2014/2015, the compressions were significantly milder, with on average 17% (mediolateral oblique) to 29% (craniocaudal) lower forces. Breasts remained on average 2.4% (1.4mm) thicker. Dose was significantly lower (6.5%), which is explained by glandular atrophy. The 95% confidence interval lower limits are 0.479 for visibility, 0.473 for contrast, 0.488 for sharpness and 0.486 for preference, all exceeding the non-inferiority limit. Of the 60 non-preferred mammograms, multiple observers found only five to be inadequate: 4 obtained with the force protocol and 1 with the pressure protocol. CONCLUSION: Pain-reduced mammography with 10kPa pressure-standardised compression has non-inferior visibility, contrast and sharpness for stable lesions compared to pain-tolerance limited 18daN target force compression.

Shaving diffusion tensor images in discriminant analysis: a study into schizophrenia.

A technique called 'shaving' is introduced to automatically extract the combination of relevant image regions in a comparative study. No hypothesis is needed, as in conventional pre-defined or expert selected region of interest (ROI)-analysis. In contrast to traditional voxel based analysis (VBA), correlations within the data can be modeled using principal component analysis (PCA) and linear discriminant analysis (LDA). A study into schizophrenia using diffusion tensor imaging (DTI) serves as an application. Conventional VBA found a decreased fractional anisotropy (FA) in a part of the genu of the corpus callosum and an increased FA in larger parts of white matter. The proposed method reproduced the decrease in FA in the corpus callosum and found an increase in the posterior limb of the internal capsule and uncinate fasciculus. A correlation between the decrease in the corpus callosum and the increase in the uncinate fasciculus was demonstrated.

Observer variation in the evaluation of lumbar herniated discs and root compression: spiral CT compared with MRI.

Spiral CT is considered the best alternative for MRI in the evaluation of herniated discs. The purpose of this study was to compare radiological evaluation of spiral CT with MRI in patients suspected of herniated discs. 57 patients with lumbosacral radicular syndrome underwent spiral CT and 1.5 T MRI. Two neuroradiologists independently evaluated 171 intervertebral discs for herniation or "bulge" and 456 nerve roots for root compression, once after CT and once after MRI. We compared interobserver agreement using the kappa statistic and we performed a paired comparison between CT and MRI. For detection of herniated or bulging discs, we observed no significant difference in interobserver agreement (CT kappa 0.66 vs MRI kappa 0.71; p = 0.40). For root compression, we observed significantly better interobserver agreement at MRI evaluation (CT kappa 0.59 vs MRI kappa 0.78; p = 0.01). In 30 of 171 lumbar discs (18%) and in 54 of 456 nerve roots (12%), the observers disagreed on whether CT results were similar to MRI. In the cases without disagreement, CT differed from MRI in 6 discs (3.5%) and in 3 nerve roots (0.7%). For radiological evaluation of lumbar herniated discs, we found no evidence that spiral CT is inferior to MRI. For evaluating lumbar nerve root compression, spiral CT is less reliable than MRI.

Can the non-pre-whitening model observer, including aspects of the human visual system, predict human observer performance in mammography?

PURPOSE: In mammography, images are processed prior to display. Current methodologies based on physical image quality measurements are however not designed for the evaluation of processed images. Model observers (MO) might be suitable for this evaluation. The aim of this study was to investigate whether the non-pre-whitening (NPW) MO can be used to predict human observer performance in mammography-like images by including different aspects of the human visual system (HVS). METHODS: The correlation between human and NPW MO performance has been investigated for the detection of disk shaped objects in simulated white noise (WN) and clustered lumpy backgrounds (CLB), representing quantum noise limited and mammography-like images respectively. The images were scored by the MO and five human observers in a 2-alternative forced choice experiment. RESULTS: For WN images it was found that the log likelihood ratio (RLR2), which expresses the goodness of fit, was highest (0.44) for the NPW MO without addition of HVS aspects. For CLB the RLR2 improved from 0.46 to 0.65 with addition of HVS aspects. The correlation was affected by object size and background. CONCLUSIONS: This study shows that by including aspects of the HVS, the performance of the NPW MO can be improved to better predict human observer performance. This demonstrates that the NPW MO has potential for image quality assessment. However, due to the dependencies found in the correlation, the NPW MO can only be used for image quality assessment for a limited range of object sizes and background variability.

Force balancing in mammographic compression.

PURPOSE: In mammography, the height of the image receptor is adjusted to the patient before compressing the breast. An inadequate height setting can result in an imbalance between the forces applied by the image receptor and the paddle, causing the clamped breast to be pushed up or down relative to the body during compression. This leads to unnecessary stretching of the skin and other tissues around the breast, which can make the imaging procedure more painful for the patient. The goal of this study was to implement a method to measure and minimize the force imbalance, and to assess its feasibility as an objective and reproducible method of setting the image receptor height. METHODS: A trial was conducted consisting of 13 craniocaudal mammographic compressions on a silicone breast phantom, each with the image receptor positioned at a different height. The image receptor height was varied over a range of 12 cm. In each compression, the force exerted by the compression paddle was increased up to 140 N in steps of 10 N. In addition to the paddle force, the authors measured the force exerted by the image receptor and the reaction force exerted on the patient body by the ground. The trial was repeated 8 times, with the phantom remounted at a slightly different orientation and position between the trials. RESULTS: For a given paddle force, the obtained results showed that there is always exactly one image receptor height that leads to a balance of the forces on the breast. For the breast phantom, deviating from this specific height increased the force imbalance by 9.4 ± 1.9 N/cm (6.7%) for 140 N paddle force, and by 7.1 ± 1.6 N/cm (17.8%) for 40 N paddle force. The results also show that in situations where the force exerted by the image receptor is not measured, the craniocaudal force imbalance can still be determined by positioning the patient on a weighing scale and observing the changes in displayed weight during the procedure. CONCLUSIONS: In mammographic breast compression, even small changes in the image receptor height can lead to a severe imbalance of the applied forces. This may make the procedure more painful than necessary and, in case the image receptor is set too low, may lead to image quality issues and increased radiation dose due to undercompression. In practice, these effects can be reduced by monitoring the force imbalance and actively adjusting the position of the image receptor throughout the compression.