Metasurfaces with Asymmetric Optical Transfer Functions for Optical Signal Processing.

Metasurface thin films created from arrays of structured optical elements have been shown to perform spatial filtering of optical signals. To extend their usefulness it is important that the symmetry of their response with changes to the in-plane wave vector k_{p}→-k_{p} can be tailored or even dynamically tuned. In this Letter we use a general theory of metasurfaces constructed from nondiffracting arrays of coupled metal particles to derive the optical transfer function and identify the physical properties essential for asymmetry. We validate our theory experimentally showing how the asymmetric response of a two-dimensional (planar) metasurface can be optically tuned. Our results set the direction for future developments of metasurfaces for optical signal processing.

Excitation of bound plasmons along nanoscale stripe waveguides: a comparison of end and grating coupling techniques.

In this paper we excite bound long range stripe plasmon modes with a highly focused laser beam. We demonstrate highly confined plasmons propagating along a 50 µm long silver stripe 750 nm wide and 30 nm thick. Two excitation techniques were studied: focusing the laser spot onto the waveguide end and focusing the laser spot onto a silver grating. By comparing the intensity of the out-coupling photons at the end of the stripe for both grating and end excitation we are able to show that gratings provide an increase of a factor of two in the output intensity and thus out-coupling of plasmons excited by this technique are easier to detect. Authors expect that the outcome of this paper will prove beneficial for the development of passive nano-optical devices based on stripe waveguides, by providing insight into the different excitation techniques available and the advantages of each technique.

Kramers-Kronig-constrained variational dielectric fitting and the reflectance of a thin film on a substrate.

A test was made of the ability of Kramers-Kronig-constrained variational dielectric fitting to extract the optical conductivity of a thin film from reflectance data containing structure due to both thin film and substrate. The reflectance of a series of well-characterized thin films of SrRu(x)Mg(1-x)O(3) and SrRu(x)O(3) with a variety of thicknesses (approximately 56-300 nm) and dc resistivities (approximately 250-2200 micro Omega cm) was measured. The low frequency values of the extracted optical conductivities agree with the dc measurements, however, removal of features due to the substrate improves with increasing film thickness.

Encysted spermatic cord hydroceles: a report of three cases in adults and a review of the literature.

A hydrocele of the spermatic cord, which results from aberrant closure of the processus vaginalis, is an asymptomatic entity detected incidentally on computed tomography (CT)scans performed for other clinical indications. There are two variations of a spermatic cord hydrocele: the "encysted" variety that does not communicate with the peritoneal cavity, and the "funicular" variety that does communicate with the peritoneal cavity. The encysted type can be confused with an inguinal mass (lymphadenopathy, hernias), and also primary tumors of the cord. We reviewed CT scans for all three adults and ultrasound images for one patient. Confirmation of spermatic cord hydrocele was made by surgery in one case, and CT and follow-up CT in two cases. Our findings indicate that a mass of the spermatic cord, showing fluid attenuation by CT and an avascular,anechoic appearance with sound transmission by ultrasound in an otherwise asymptomatic patient or even in those with an underlying malignancy, should prompt the radiologist to consider the diagnosis of spermatic cord hydrocele. This may eliminate the need for unnecessary, highly invasive procedures such as biopsy or surgical exploration.

Geometric optics method for surface plasmon integrated circuits.

A fully-analytic expression is derived for the phase of reflection of surface plasmons at a semi-infinite boundary. We apply this phase of reflection result in the geometric optics method to calculate the properties of surface plasmon stripe waveguides. Comprehensive vectorial numerical computations are compared with the analytic method to show that it is accurate. The loss of the surface plasmon stripe waveguide is calculated using the geometric optics approach, which is also found to be in close agreement with numerical computations. The geometric optics approach may be used to obtain accurate results for other surface plasmon structures, such as microdisk or ring resonators, with greater efficiency and physical intuition than numerical computation.

Case report: Calcifying fibrous pseudotumour of the adrenal gland.

Calcifying fibrous pseudotumour is a distinct pathological entity usually occurring in the soft tissue of the extremities, trunk, axilla, pleura, mediastinum and peritoneum. This report describes the hitherto unreported occurrence of this tumour of the adrenal gland in a 10-year-old girl whose imaging findings closely resembled a neuroblastoma. This entity is a potential pitfall in diagnosing adrenal neuroblastoma.

Childhood cancers: hepatoblastoma.

Hepatoblastoma is the most common primary liver tumor in children, accounting for just over 1% of pediatric cancers. The etiology is unknown, but it has been associated with Beckwith-Weidemann syndrome, familial adenomatosis polypi, and low birth weight. The primary treatment is surgical resection, however, chemotherapy plays an important role by increasing the number of tumors that are resectable. The prognosis for patients with resectable tumors is fairly good, however, the outcome for those with nonresectable or recurrent disease is poor.

Hepatocellular carcinoma and intrahepatic peripheral cholangiocarcinoma: enhancement patterns with quadruple phase helical CT--a comparative study.

PURPOSE: To define the hemodynamic features of hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma by using quadruple phase helical computed tomography (CT) and determine the value of this information in characterizing tumors. MATERIALS AND METHODS: Helical CT of the liver was performed in 45 patients with newly diagnosed HCC or peripheral cholangiocarcinoma. Scans were obtained before and 25 seconds, 70 seconds, and 2-6 minutes after the start of the contrast material injection. The intensity and spatial distribution of contrast material uptake were evaluated during all phases. Time-attenuation curves were established for each lesion. Relative attenuation and lesion conspicuity were assessed. A diagnostic confidence level was assigned to each lesion. RESULTS: In the majority of HCC lesions, a single, early peak of enhancement followed by a continuous decrease in tumor attenuation over time was seen. The greatest tumor conspicuity occurred during the delayed phase. In cholangiocarcinoma, tumor attenuation increased during the delayed phase. In the majority of lesions, the greatest tumor conspicuity was seen during the portal venous phase. In both tumor types, the diagnostic confidence level improved when the delayed phase was used. CONCLUSION: The variation over time in the intensity of contrast enhancement in HCC and cholangiocarcinoma differs sufficiently to make this a useful diagnostic criterion. The delayed phase is particularly important because it amplifies this difference.

Thymic sarcoma in childhood.

Sarcoma of the thymus is exceedingly rare, especially in children. We report a case of thymic sarcoma in a child, including the imaging findings which have not been previously described.

Osteosarcoma metastatic to the pancreas in young patients.

Two rare cases of pancreatic metastases from osteosarcoma are reported. Metastatic spread occurred after treatment with chemotherapy. This unusual phenomenon represents an alternation in the natural history of osteosarcoma with increased long-term survival of patients who are successfully treated with chemotherapy.

Merkel cell carcinoma of the skin: imaging and clinical features in 93 cases.

Clinical, pathological and imaging data for 93 patients with Merkel cell carcinoma were reviewed. Median survival duration from the date of diagnosis was estimated using the Kaplan-Meier product-limit method. Survival durations of patients with no metastastic disease, with regional lymph node metastasis only and with distant metastases were compared using the Cox-Mantel log-rank test. The median age for patients with Merkel cell carcinoma was 70 years (range 35-91 years). The tumour occurred in 71 men and 22 women. The most common primary site was the head and neck region (64 patients), followed by the extremities (21 patients) and the trunk (10 patients). Median survival duration for the whole group was 33 months (range 2-140 months). Imaging studies of the primary sites were available for 10 patients and of metastatic sites for seven patients. Sonograms of the primary skin lesions showed single or multicentric hypoechoic nodules arising from the dermis and growing into the subcutaneous tissues. CT scans showed single or multiple minimally enhancing soft tissue nodules, in two instances associated with lytic bone erosion. The metastatic lesions were moderately hypoechoic on sonography and target-shaped with or without ring-enhancement on CT. Imaging studies have a limited role in diagnosis of the clinically evident primary skin lesions, but may be helpful in the assessment of the depth of the invasion and are crucial in the evaluation of regional and distant metastatic disease. If regional adenopathy is found then CT of the chest, abdomen and pelvis may be in order.

Imaging of superficial soft-tissue infections: sonographic findings in cases of cellulitis and abscess.

The variation in the sonographic appearances of superficial soft-tissue infections probably reflects a continuous process that leads from soft-tissue edema, seen in cellulitis, to a fully developed abscess and that depends on the type of infection or the immune status of the host. We describe the sonographic findings seen in this process and the variable appearance of abscesses, with emphasis on scanning techniques that facilitate the diagnosis of liquefaction.

Importance of dynamic assessment of the soft tissues in the sonographic diagnosis of echogenic superficial abscesses.

Superficial abscesses evaluated by ultrasonography may occasionally be isoechoic relative to the surrounding inflamed tissues and without mass effect, preventing diagnosis by morphologic criteria alone. We present a simple and effective method to detect such abscesses. In three cases, gentle repetitive pressure of the inflamed tissue revealed the liquefied nature of abscesses that otherwise would have been overlooked.

Mesenchymal hamartoma of the chest wall in infants and children: a clinicopathological study of five patients.

Mesenchymal hamartoma of chest-wall is a rare benign lesion that has varied histological characteristics and usually occurs during early infancy. We report the histological characteristics of mesenchymal hamartoma found in five patients aged respectively 25 days, 5 months, 8 months, and 4 and 8 years at presentation. Two patients presented with respiratory distress, two with an asymptomatic chest-wall mass, and one with a deformity of the left chest wall. Surgical resection was performed on four patients and a biopsy only in one patient. Overall, the tumors were well delineated, lobulated, tan to reddish in color, and on section showed blood-filled cystic spaces with interspersed small islands of cartilage and fibrous tissue. Histological analyses demonstrated mixtures of bone trabeculae with spindle-cell stroma, chondroblast-like proliferation, mature and immature hyaline cartilage, and aneurysmal bone cyst formation. All patients are alive and well without evidence of disease. Despite the alarming clinical and histologic presentation, mesenchymal hamartoma of the chest wall is a non-neoplastic benign lesion.

Sonography of the scrotum after orchiectomy: normal and abnormal findings.

Sonography is the primary imaging technique for evaluating the scrotal contents. In this pictorial essay, we illustrate a range of normal and abnormal sonographic findings in patients after orchiectomy, including the appearances of the normal postorchiectomy space, acute and subacute hematomas, recurrent neoplasm, second primary tumor in the remaining testis, and testicular prostheses.

Cystic retroperitoneal lymphangioma: CT, ultrasound and MR findings.

A case of cystic retroperitoneal lymphangioma complicated by hemorrhage is reported in a 7-year-old boy who presented with an abdominal mass. The mass which was partially obstructing the ureter was successfully resected. The imaging findings with emphasis on MR features are described.

Sonographic findings in Richter's hernia.

Richter's hernia can present as a diagnostic challenge because of its usually small size and eccentric bowel wall involvement with limited luminal compromise. This article describes a case of Richter's hernia in the femoral canal and illustrates its sonographic features.