Evaluation of architectural distortion with contrast-enhanced mammography.

Architectural distortion (AD) is the third most common abnormality detected on mammograms. In the absence of an accurate non-invasive tool to evaluate ADs, clinical management often requires surgical excision for histological diagnosis. This problem is expected to worsen with the growing use of digital breast tomosynthesis (DBT) and the resultant increasing detection of ADs. There is therefore a great clinical need for a diagnostic imaging tool to complement non-enhanced mammography for the evaluation of AD. Contrast-enhanced mammography (CEM) is an emerging breast imaging method that uses contrast media and the principle of dual-energy subtraction to evaluate vascularity of suspicious breast lesions. CEM, a cost-effective alternative to breast magnetic resonance imaging (MRI), can be used to evaluate AD by juxtaposing CEM images with non-enhanced mammograms for comparison. In this review, the authors aim to provide readers with an overview of the interpretation of AD on CEM using imaging examples. Relevant imaging features of CEM and their respective significance will be matched with information from a literature review. Finally, the authors would like to highlight the added value of CEM in relevant clinical applications in the assessment of AD.

Statistical atlas-based morphological variation analysis of the asian humerus: towards consistent allometric implant positioning.

PURPOSE: Positioning existing humeral implants into Asian patients poses significant challenges due to the inconsistent statistical shapes between Western population and Asian population. Current humeral orthopedic fixation devices and implants have a generic shape and are not designed for Asian patients who exhibit different sizes and shapes compared to their Western counterparts for which present day designs have been based on. To address this problem, it is necessary to develop Asian-specific implants that accommodate the morphology of Asian humeri. Existing morphological studies of humeri in Asian populations are rare and most previous analyses are either based on the manual measurement of dry bones or the use of dual energy X-ray absorptiometry scans. The purpose of this pilot morphological study is to explore the characteristics of Asian humeri using statistical atlas-based analysis. METHODS: Forty-four CT scans of normal upper limbs were obtained from the National University Hospital, Singapore and used to construct statistical humerus atlases. The atlases were subsequently used to study the morphology of the humeri in an Asian population. Humeral shapes of different patient clusters were analyzed based on statistical shape models. Comparison between different clusters was conducted with regard to centerline, length, width and surface curvature. RESULTS: The statistical humerus atlases reflected the mean shape and modes of variation of humeri in an Asian population. Analyses based on these atlases indicated that curvature and shape of the internal humeral canal were similar in males and females while humeral length and width were greater in males. Most importantly, surface curvatures were explicitly different between clusters. CONCLUSION: Morphologic analysis based on statistical atlases is novel and useful to characterize the Asian humerus. The humerus demonstrates gender-specific morphology. This unique approach provides information that is useful to the clinician and biomedical engineer, not only in the modification of current or design of future humeral implants, but also in the precise dynamic positioning of Asian-specific humeral implants to Asian patients. Our findings support the need for further development of humeral implants, curvilinear robotics, and the questioning of whether gender-specific devices are necessary.

A power-law rheology-based finite element model for single cell deformation.

Physical forces can elicit complex time- and space-dependent deformations in living cells. These deformations at the subcellular level are difficult to measure but can be estimated using computational approaches such as finite element (FE) simulation. Existing FE models predominantly treat cells as spring-dashpot viscoelastic materials, while broad experimental data are now lending support to the power-law rheology (PLR) model. Here, we developed a large deformation FE model that incorporated PLR and experimentally verified this model by performing micropipette aspiration on fibroblasts under various mechanical loadings. With a single set of rheological properties, this model recapitulated the diverse micropipette aspiration data obtained using three protocols and with a range of micropipette sizes. More intriguingly, our analysis revealed that decreased pipette size leads to increased pressure gradient, potentially explaining our previous counterintuitive finding that decreased pipette size leads to increased incidence of cell blebbing and injury. Taken together, our work leads to more accurate rheological interpretation of micropipette aspiration experiments than previous models and suggests pressure gradient as a potential determinant of cell injury.

A re-look at an old disease: a multimodality review on gout.

Gout, the most common form of microcrystalline arthropathy has always interested radiologists. The diagnosis of gout is primarily based on clinical and laboratory findings; however, it has well known and characteristic radiographic manifestations. Radiographs remain the examination of choice in the diagnosis of joint involvement. Plain radiographs are less sensitive to early changes in gout than other imaging techniques. Recently, magnetic resonance imaging (MRI), ultrasound (US), and computed tomography (CT) have demonstrated an increasing role in early diagnosis of gouty arthritis, for assessing the extent of soft-tissue involvement and as problem-solving tools for diagnostically difficult cases. Cross-sectional imaging can also be used for guiding needle aspirations in patients with an acute attack of gout, which may simulate an infective process clinically. This pictorial review illustrates the main imaging features of gout on radiographs, MRI, CT, and ultrasound with the aim of helping the radiologist to make a confident diagnosis in radiographically typical cases and to serve as a problem-solving tool in cases that present a diagnostic dilemma.

Power-law rheology analysis of cells undergoing micropipette aspiration.

Accurate quantification of the mechanical properties of living cells requires the combined use of experimental techniques and theoretical models. In this paper, we investigate the viscoelastic response of suspended NIH 3T3 fibroblasts undergoing micropipette aspiration using power-law rheology model. As an important first step, we examine the pipette size effect on cell deformation and find that pipettes larger than ~7 µm are more suitable for bulk rheological measurements than smaller ones and the cell can be treated as effectively continuum. When the large pipettes are used to apply a constant pressure to a cell, the creep deformation is better fitted with the power-law rheology model than with the liquid drop or spring-dashpot models; magnetic twisting cytometry measurement on the rounded cell confirms the power-law behavior. This finding is further extended to suspended cells treated with drugs targeting their cytoskeleton. As such, our results suggest that the application of relatively large pipettes can provide more effective assessment of the bulk material properties as well as support application of power-law rheology to cells in suspension.

Adenoid cystic carcinoma of the breast.

Adenoid cystic carcinoma of the breast is a rare neoplasm that constitutes less than one percent of all mammary carcinomas. To date, there have been about 140 cases reported in the literature. It is a rare variant of adenocarcinoma that usually occurs in the salivary glands. In contrast to the aggressive nature of adenoid cystic carcinoma that occurs in the head and neck region, adenoid cystic carcinoma of the breast has a very favourable prognosis. Little has been published to date on its radiological features. We describe a 63-year-old woman with adenoid cystic carcinoma detected on mammography in our national breast screening programme, the radiological findings at presentation, the surgical management and a review of the literature.

Mechanical models for living cells--a review.

As physical entities, living cells possess structural and physical properties that enable them to withstand the physiological environment as well as mechanical stimuli occurring within and outside the body. Any deviation from these properties will not only undermine the physical integrity of the cells, but also their biological functions. As such, a quantitative study in single cell mechanics needs to be conducted. In this review, we will examine some mechanical models that have been developed to characterize mechanical responses of living cells when subjected to both transient and dynamic loads. The mechanical models include the cortical shell-liquid core (or liquid drop) models which are widely applied to suspended cells; the solid model which is generally used for adherent cells; the power-law structural damping model which is more suited for studying the dynamic behavior of adherent cells; and finally, the biphasic model which has been widely used to study musculoskeletal cell mechanics. Based upon these models, future attempts can be made to develop even more detailed and accurate mechanical models of living cells once these three factors are adequately addressed: structural heterogeneity, appropriate constitutive relations for each of the distinct subcellular regions and components, and active forces acting within the cell. More realistic mechanical models of living cells can further contribute towards the study of mechanotransduction in cells.

Design of interdigital transducers for crack detection in plates.

Interdigital transducers (IDT) for non-destructive evaluation (NDE) of cracks in plates are designed based on an analytical model established previously. Key considerations include mode selectivity, excitation strength, collimation of wave and cost. The advantage of mode selectivity of IDT over PZT patch is presented both analytically and experimentally. Effects of parameters, namely finger spacing, width, length, number of fingers, and the size of IDT, on the excitation strength and mode selectivity are considered. This led to the design of a mobile double-sided IDT as an efficient device where excitation strength is strong and focused. The device was fabricated in-house using commercially available piezoelectric ceramics and used to develop a procedure for accurate identification of the direction and extent of cracks in plates. Three aluminum plates, one with a linear deep crack, another with a piecewise linear shallower crack and the third with a curved crack, were used to illustrate the accuracy and efficiency of both the proposed device and procedure for effective NDE.

Clinics in diagnostic imaging (85). Mandible osteoradionecrosis complicated by infection.

Mandibular osteoradionecrosis is a rare but well-known complication that may be seen in patients with head and neck tumours following radiation therapy. A 42-year-old man presented with painful soft tissue swelling and a discharging sinus over the right mandible. Radiographs showed osteolytic destruction. Computed tomography confirmed bony destruction and fragmentation, as well as signs of soft tissue infection. The diagnosis of mandible osteoradionecrosis complicated by infection was confirmed by biopsy and surgically. The clinical and imaging features of osteoradionecrosis are highlighted.

Breath-hold fast recovery fast spin echo versus conventional non-breath-hold fast spin echo T2-weighted MR imaging of focal liver lesions.

INTRODUCTION: We compare the breath-hold fast recovery fast spin echo (BHFRFSE) T2-weighted and non-breath-hold fast spin echo (NBHFSE) T2-weighted sequences in image quality and lesion characterisation of focal liver lesions. MATERIALS AND METHODS: Fat-suppressed T2-weighted magnetic resonance (MR) images obtained with the 2 sequences (BHFRFSE and NBHFSE) in 79 patients with 113 liver lesions were analysed retrospectively. The image quality and nature of the lesions were evaluated by 2 experienced radiologists. RESULTS: Based on receiver operating characteristic curve analysis, lesion characterisation was comparable for both sequences. The image quality of BHFRFSE was significantly better than that of NBHFSE. The NBHFSE missed 4 malignant lesions while BHFRFSE missed 2 malignant lesions. CONCLUSION: BHFRFSE performs similarly to NBHFSE in image quality and liver lesion characterisation.

Carcinoma of the cervix: role of MR imaging.

Staging is of paramount importance in cancer management. In cervical carcinoma, it is performed using the clinical International Federation of Gynaecology and Obstetrics (FIGO) staging system. However, besides some inherent inaccuracies, it does not include important prognostic factors such as tumour size, which may help determine treatment strategies. These shortcomings of the clinical FIGO staging system underline the importance of accurate imaging evaluation of cervical carcinoma. Although magnetic resonance (MR) imaging is not officially incorporated into current staging work-up assessment, it has been shown by a number of studies to be the most reliable imaging modality in the evaluation of cervical cancer and in treatment planning. It has the advantages of direct tumour visualisation, accurate assessment of the depth of stromal invasion and tumour volume, and lymph node evaluation. In this article, the utility of MR imaging in the evaluation of cervical carcinoma is reviewed.

Radiologists' detection of mammographic abnormalities with and without a computer-aided detection system.

The aim of this study was to to evaluate the role of a computer-aided program (CAD) in assisting detection of mammographic lesions by radiologists not specifically trained in mammography and its potential utility in breast screening. Mammograms were evaluated by radiologists not specifically trained in mammography first without, and then with, the CAD. Finally, the mammograms were evaluated by experienced mammographers who formed the reference standard. Two hundred and ninety four breasts were studied. In 257 breasts (87.4%), the CAD system did not help with the detection of abnormalities. It assisted radiologists in detecting abnormalities in 21 breasts (7.1%) with potential for detecting abnormalities in a further 13 breasts (4.4%). Only in three cases (1%) did it cause confusion in interpretation. There is overall increased sensitivity in detecting mammographic abnormalities with the aid of the CAD system from 74.4 to 87.2%, which is statistically significant. However, it failed to detect suspicious abnormalities in 71 breasts (24.1%). The CAD system improved detection of suspicious mammographic abnormalities by radiologists who are not specifically trained in mammography. However, there is also a substantial failure to detect suspicious mammographic features that cautions against over-reliance on the system, emphasizing its role as a second reader at best.

Clinics in diagnostic imaging (72). Superior labral anterior-posterior (SLAP) tear.

The lesions at and around the superior glenolabral junction of the shoulder have gained considerable attention since its description in 1990. A 31-year-old Chinese woman with a superior labral anterior-posterior (SLAP) tear is reported. The MR arthrogram findings were confirmed at surgery. The classification and mechanisms of SLAP lesions, and the role of MR arthrography in the diagnosis of glenolabral lesions are discussed.

Clinics in diagnostic imaging (77). Pes anserine bursitis.

Many cystic lesions occur around the knee and may produce overlapping clinical features, rendering the clinical diagnosis difficult. A 50-year-old woman presented with a soft tissue swelling on the medial aspect of her right knee. The diagnosis of pes anserine bursitis was made, based on typical MR imaging features. Cystic masses occurring in and around the knee, such as bursae and recesses, meniscal and ganglion cysts, and benign and malignant soft tissue masses that may mimic cysts, are classified and described. The role of MR imaging in making an accurate diagnosis and distinguishing among the various masses is discussed.

Abdominal coarctation and Alagille syndrome.

Structural cardiac defects such as peripheral pulmonary stenosis are well-described in Alagille syndrome (AS), which is transmitted in an autosomal dominant inheritance. The genetic defect, with incomplete penetrance and variable expression, is localized to the short arm of chromosome 20. Abdominal coarctation is an uncommon congenital anomaly, with a spectrum of symptoms that may range from hypertension, intermittent claudication to abdominal pain. The association of abdominal coarctation with AS is rarely described. We report such a patient who also had aberrations of the visceral vascular supply involving the celiac, splenic, and superior mesenteric arteries. The indications to treat the coarctation, and in the context of a patient with AS, in whom liver transplantation may be contemplated at some stage, merit discussion.

Cardiac manifestations in tuberous sclerosis: a 10-year review.

OBJECTIVE: Tuberous sclerosis is a genetic disorder with multisystem involvement. The aim of this study was to focus primarily on the cardiac aspects of this condition. METHOD: This review included 10 children with tuberous sclerosis presenting to our department during a 10-year period. RESULTS: From our data, 80% were found to have cardiac involvement. There was an equal prevalence of neurologic complications. CONCLUSIONS: Cardiac tumours and seizures were the most common problems encountered. Whereas most patients had no symptoms referable to the cardiovascular system and required no active intervention, many of those with neurologic involvement needed appropriate treatment.