Fiber Bragg gratings in hole-assisted multicore fiber for space division multiplexing.

In this Letter we present, for the first time to our knowledge, the results of fiber Bragg grating (FBG) inscription in a novel microstructured multicore fiber characterized by seven single-mode isolated cores. A clear Bragg reflection peak can be observed in all of the 7 cores after one inscription process with a KrF nanosecond laser in a Talbot interferometer set up. We furthermore perform a numerical analysis of the effective refractive indices of the particular modes and compare it with the FBG inscription results. An experimental analysis of the strain and temperature sensitivities of all of the Bragg peaks is also included.

Higher-order rocking filters induced mechanically in fibers with different birefringence dispersion.

We studied the transmission characteristics of higher-order rocking filters induced mechanically in birefringent microstructured fibers and standard elliptical core fibers with varying spectral dependence of phase modal birefringence. We demonstrated the effect of birefringence dispersion on polarization mode coupling induced by a point-like force. We also investigated the spectral dependence of the resonance depth and force-induced resonance wavelength shift in mechanical rocking filters. The observed phenomena were explained by a numerical model linking the spectral dependence of the polarization mode coupling coefficient with the dispersion of intrinsic fiber birefringence and applied force.

Sensing and transmission characteristics of a rocking filter fabricated in a side-hole fiber with zero group birefringence.

We report on sensing and transmission characteristics of rocking filters fabricated in a silica side-hole fiber with group birefringence changing its sign at certain wavelength (λ(G = 0)), which corresponds to parabolic-like spectral dependence of beat length. Unusual birefringence dispersion of the side-hole fiber is induced by an elliptical germanium doped core located in a narrow glass bridge between two holes. Rocking filters fabricated in such a fiber have two resonances of the same order located on both sides of λ(G = 0). The sensitivity of both resonances has an opposite sign, which makes it possible to double the response of the rocking filter by applying the differential interrogation scheme. We demonstrate that in this way a pressure sensitivity of the rocking filter can be enlarged to 132 nm/MPa. We also show that by fabricating the rocking filter with a period close to maximum beat length a coupling between polarization modes can be obtained in a broad band reaching 240 nm.

Fabrication of multiple Bragg gratings in microstructured polymer fibers using a phase mask with several diffraction orders.

We demonstrate for the first time a possibility of fabrication of Bragg gratings in polymer microstructured fibers with multiple reflection peaks by using He-Cd laser (λ = 325 nm) and a phase mask with higher diffraction orders. We experimentally studied the growth dynamics of the grating with the primary Bragg peak at λ(B) = 1555 nm, for which we also observed good quality peaks located at λ(B)/2 = 782 nm and 2λ(B)/3 = 1040 nm. Temperature response of all the Bragg peaks was also investigated. Detailed numerical simulations of the interference pattern produced by the phase mask suggests that the higher order Bragg peaks originate from interference of UV beams diffracted in ± 1st, ± 2nd orders. We also demonstrated the grating with the reflection peak at λ(B)/2 = 659 nm, which is the shortest Bragg wavelength ever reported for polymer microstructured fibers. This peak was observed for the grating with primary Bragg wavelength at λ(B) = 1309 nm.

Sensing characteristics of the rocking filters in microstructured fibers optimized for hydrostatic pressure measurements.

We report on the sensing characteristics of rocking filters fabricated in two microstructured fibers with enhanced polarimetric sensitivity to hydrostatic pressure. The filter fabricated in the first fiber shows a very high sensitivity to pressure ranging from 16.2 to 43.4 nm/MPa, depending on the resonance order and features an extremely low cross-sensitivity between pressure and temperature 28 ÷ 89 × 10(3) K/MPa. The filter fabricated in the second fiber has an extreme sensitivity to pressure ranging from -72.6 to -177 nm/MPa, but a less favorable cross-sensitivity between pressure and temperature of 1.05 ÷ 3.50 × 10(3) K/MPa. These characteristics allow using the rocking filters for pressure measurements with mbar resolution.

Application of continuous wavelet transform for determination of fiber birefringence.

Measurements of the group-birefringence dispersion of a microstructured optical fiber using the wavelength-scanning technique are reported. Resulting interferograms are processed using the continuous wavelet transform. We discuss application of this approach for determination of birefringence of few-mode fibers and show that with careful analysis it is possible to determine birefringence dispersion of the higher-order modes in optical fibers.

Intermodal interferometer for strain and temperature sensing fabricated in birefringent boron doped microstructured fiber.

We present a compact in-line fiber interferometric sensor fabricated in a boron doped two-mode highly birefringent microstructured fiber using a CO(2) laser. The intermodal interference arises at the fiber output due to coupling between the fundamental and the first order modes occurring at two fiber tapers distant by a few millimeters. The visibility of intermodal interference fringes is modulated by a polarimetric differential signal and varies in response to measurand changes. The proposed interferometer was tested for measurements of the strain and temperature, respectively, in the range of 20-700 °C and 0-17 mstrain. The sensitivity coefficients corresponding to fringe displacement and contrast variations are equal respectively for strain -2.51 nm/mstrain and -0.0256 1/mstrain and for temperature 16.7 pm/°C and 5.74×10(-5) 1/°C. This allows for simultaneous measurements of the two parameters by interrogation of the visibility and the displacement of interference fringes.

Splenic and perisplenic involvement in acute pancreatitis: determination of prevalence and morphologic helical CT features.

PURPOSE: The purpose of this work was to determine the prevalence and morphologic helical CT features of splenic and perisplenic involvement in patients with acute pancreatic inflammatory disease in correlation with the severity of the pancreatitis. METHOD: One hundred fifty-nine contrast-enhanced helical CT scans of 100 consecutive patients with acute pancreatitis were reviewed retrospectively and independently by three observers. CT scans were scored using the CT severity index (CTSI): Pancreatitis was graded as mild (0-2 points), moderate (3-6 points), and severe (7-10 points). Interobserver agreement for both the CTSI and the presence of splenic and perisplenic involvement was calculated (K statistic). Correlation between the prevalence of complications and the degree of pancreatitis was estimated using the Fisher exact test. RESULTS: The severity of pancreatitis was graded as mild (n = 59 scans), moderate (n = 82 scans), and severe (n = 18 scans). Splenic and perisplenic abnormalities detected included perisplenic inflammatory fluid collections (95 scans, 58 patients), narrowing of the splenic vein (35 scans, 25 patients), splenic vein thrombosis (31 scans, 19 patients), splenic infarction (10 scans, 7 patients), and subcapsular hemorrhage (2 scans, 2 patients). No cases of splenic artery pseudoaneurysm formation, intrasplenic venous thrombosis, intrasplenic pseudocysts, or abscesses were detected. The interobserver agreement range for scoring the degree of pancreatitis and the overall presence of abnormalities was 75.5-79.2 and 71.7-100%, respectively. A statistically significant difference between the presence of abnormalities and the severity of pancreatitis was observed (p < 0.001). CONCLUSION: Splenic vein thrombosis (19%) and splenic infarction (7%) are relatively common CT findings in association with acute pancreatitis. The CTSI proves to be accurate in predicting these complications as there is a statistically significant correlation between the prevalence of these complications and the severity of pancreatitis.

Characterization of focal hepatic lesions with ferumoxides-enhanced T2-weighted MR imaging.

OBJECTIVE: The purpose of this study was to evaluate whether ferumoxides-enhanced MR imaging of focal hepatic lesions provides distinctive signal intensity and lesion-to-liver contrast changes for benign and malignant lesions, helping to further characterize and differentiate these lesions. MATERIALS AND METHODS: Data analysis was performed on 70 patients, with previously identified focal hepatic lesions, who underwent MR imaging of the liver before and after IV administration of ferumoxides (10 micromol Fe/kg). Lesions analyzed with pathologically proven diagnoses included metastases (n = 40), hepatocellular carcinoma (n = 11), cholangiocarcinoma (n = 6), hemangioma (n = 4), focal nodular hyperplasia (n = 6), and hepatocellular adenoma (n = 3). Response variables measured and statistically compared included the percentage of signal-intensity change and lesion-to-liver contrast. RESULTS: Focal nodular hyperplasia showed significant signal intensity loss on ferumoxides-enhanced T2-weighted images (mean, -43%+/-6.7%, p < 0.01). All other lesion groups showed no statistically significant change in signal intensity on ferumoxides-enhanced T2-weighted images, although signal intensity loss was seen in some individual hepatocellular adenomas (mean, -6.6%+/-24.0%) and hepatocellular carcinomas (mean, -3.3%+/-10.3%). All lesions, with the exception of hepatocellular carcinoma, had a marked increase in lesion-to-liver contrast on ferumoxides-enhanced T2-weighted images, which was statistically significant for metastases and hemangioma (p < 0.02). CONCLUSION: Focal nodular hyperplasia shows significant decrease in signal intensity on ferumoxides-enhanced T2-weighted images, which may aid in the differentiation of focal nodular hyperplasia from other focal hepatic lesions. Other lesions, namely, hepatocellular adenoma and carcinoma, can have reticuloendothelial uptake, but usually to a lesser degree than that of focal nodular hyperplasia.

Durable cure of mucormycosis involving allograft and native lungs.

Among the spectrum of fungi causing disease in lung allograft recipients, fungi in the order Mucorales represent uncommon pathogens. Lung transplant patients, however, often possess more than one risk factor for development of life-threatening mucormycosis. We describe a unique case of pulmonary mucormycosis involving both the allograft and the native lungs, in a single lung transplant recipient with steroid-induced diabetes. Extended intravenous amphotericin B and oral fluconazole therapy, reduction of immunosuppression, and blood glucose control achieved a durable cure without the need for surgical intervention. Early diagnosis with prompt initiation of multiagent antifungal therapy, prolonged continuation of antifungal therapies, and amelioration of contributing conditions are important elements of the treatment strategy that led to successful resolution of the infection.

A simple method for obtaining original data from published graphs and plots.

OBJECTIVE: To describe a method for deriving original data values from scanned images of graphs and scatterplots published in the medical literature. CONCLUSION: The procedure is simple, reproducible, and relatively error free (when performed carefully). This method is useful in converting published graphic material into numeric data for various uses when the original data are unavailable directly from the authors.

Renal and perirenal space involvement in acute pancreatitis: spiral CT findings.

BACKGROUND: This study was conducted to estimate the prevalence and morphologic computed tomographic (CT) features of renal and perirenal space abnormalities in acute pancreatitis in correlation with the severity of pancreatitis. METHODS: One hundred fifty-nine contrast-enhanced CT scans of 100 consecutive patients with acute pancreatitis were retrospectively and independently reviewed by three observers. All CT images were obtained using contrast-enhanced helical CT (collimation width = 5 mm, table increment = 7 mm/s, reconstruction interval = 5 mm, scan delay time = 30-50 s). Additional maximized images (field of view = 260 mm) of the perirenal space were available for review. All CT scans were scored with the CT Severity Score Index: pancreatitis was graded as mild (0-2 points), moderate (3-6 points), and severe (7-10 points). Interobserver agreement for both the severity score and the presence of renal and perirenal involvement was calculated. Correlation between the prevalence of complications and the degree of pancreatitis was estimated. RESULTS: CT scans were graded as mild (n = 59), moderate (n = 82), and severe (n = 18). Abnormalities detected included perirenal stranding (n = 37 patients, 26 bilateral), perirenal fluid collections (n = 10 patients, one bilateral), ureteral encasement (n = 2 patients), renal vein thrombosis (n = 1 patient), and renal parenchymal abnormalities (n = 1 patient). The interobserver agreement range for scoring the degree of pancreatitis and the overall presence of abnormalities was 75.5-79.2% and 59.8-100%, respectively. Except for stranding of the perirenal fat, no statistically significant differences between the presence of abnormalities and the severity of pancreatitis (moderate or severe) was observed with Fisher's exact test. Also, no preferential left-sided localization of complications was observed. CONCLUSIONS: The incidence of renal and perirenal complications from acute pancreatitis is higher than previously estimated (7%). We found no significant correlation between the prevalence of major complications and the severity of pancreatitis. These findings are important because these complications may have an impact on therapeutic strategy and can affect prognosis.

Perineal angiomyofibroblastoma: CT and MR findings with pathologic correlation.

We present a case of a perineal angiomyofibroblastoma (AMFB) arising in the right perirectal fossa in a middle-aged woman, documented with CT and MRI. Compounding the rarity of the entity, this case is unique as it is the first radiological report illustrating the CT and MR features of this recently clinicopathologically described neoplasm.

Pediatric liver neoplasms: a radiologic-pathologic correlation.

Only 1-2 % of all pediatric tumors occur in the liver. Two thirds of these tumors are malignant and almost all of the tumors cause clinical symptoms due to their mass effects. Besides the poor prognosis in most of the malignant tumors, for further treatment the origin and nature of the neoplasm has to be known. Due to the mostly unimpeded growth into the peritoneal cavity, the origin of the tumors is primarily often unclear and can non-invasively only be determined by advanced imaging techniques. The display of the macro- and microhistological key features of primary pediatric liver neoplasms, including hepatoblastoma (HB), infantile hemangioendothelioma (IHE), mesenchymal hamartoma (MH), undifferentiated (embryonal) sarcoma (UES), and hepatocellular carcinoma (HCC), together with their imaging representation by ultrasound, computed tomography, and magnetic resonance imaging, may deepen the understanding of the underlying pathology and its imaging appearance. Furthermore, in many cases sufficient information may be provided not only to differentiate benign from malignant tumors, but also to guide for adequate treatment.

Bilateral adrenal cystic lymphangiomas in nevoid basal cell carcinoma (Gorlin-Goltz) syndrome: US, CT, and MR findings.

We present a case of bilateral adrenal cystic lymphangioma in a patient with the Gorlin-Goltz syndrome. This case is unique as it is the first illustrated case (US, CT, and MR findings) of a cystic lymphangioma arising within the adrenal gland. In addition, the coexistence of cystic adrenal lymphangioma with the Gorlin-Goltz syndrome has not been described previously.

Pulmonary mucosa-associated lymphoid tissue lymphoma: CT and pathologic findings.

OBJECTIVE: The objective of this study was to determine the CT findings in pulmonary mucosa-associated lymphoid tissue lymphoma and to correlate these CT findings with histologic specimens. CONCLUSION: In the 11 patients reviewed, the most common CT appearance of pulmonary mucosa-associated lymphoid tissue lymphoma was consolidation with air bronchograms, correlating histologically with a cellular lymphocytic infiltrate expanding the interstitium and compressing adjacent alveoli, producing air bronchograms.

New formula for quantification of pleural effusions from computed tomography.

The authors develop a method to accurately and easily estimate the volume of pleural effusions with computed tomography (CT). In 15 patients with either simple or loculated pleural effusions (14 right-sided and 11 left-sided), routine helical CT examinations of the thorax were obtained. Two experienced radiologists visually estimated the volume of the effusions. Three-dimensional reconstructions of the pleural effusions were performed from the helical CT examinations, and the volumes of the effusions were calculated. Effusion volumes were also estimated using the formula d2 x l (d = greatest depth of the effusion on a single CT image, l = greatest length of the effusion). The computer calculated the estimated volumes and they were then statistically compared. The coefficient of correlation between the estimation by measurement and calculated volumes of all effusions was 0.908 (p<0.0001) for the right side, and 0.849 for the left side (p<0.002). Excluding the loculated effusions, the coefficient of correlation was 0.969 for the right side and 0.949 for the left side (p<.001). The volume estimation by visual inspection was also correlated to the calculated volumes (0.84 on the left and 0.85 on the right, p<0.008), but resulted in a consistent overestimation by 300 ml to 500 ml. Although pleural effusion volumes can be estimated by visual inspection with good correlation, some overestimation is consistently seen. Use of the formula d2 x l readily enables estimation of pleural effusion volume from CT, from two simple measurements. This formula-based method of volume estimation provides an accurate and easily measured means of estimation that is readily obtained from routine CT of the chest.

Radiation effective doses to patients undergoing abdominal CT examinations.

PURPOSE: To determine the radiation effective dose to adult and pediatric patients undergoing abdominal computed tomographic (CT) examinations. MATERIALS AND METHODS: Technique factors were obtained for three groups of randomly selected patients undergoing abdominal CT examinations: 31 children aged 10 years or younger; 32 young adults aged 11-18 years; and 36 adults older than 18 years. The radiographic techniques, together with the measured cross sections of patients, were used to estimate the total energy imparted to each patient. Each value of energy imparted was subsequently converted into the corresponding effective dose to the patient, taking into account the mass of the patient. RESULTS: All abdominal CT examinations were performed at 120 kVp with a section thickness of approximately 7 mm for all sizes of patients. The mean number of CT sections increased from 22.0 for children to 31.5 for adults, and the mean quantity of x radiation in milliampere-seconds increased from 220 mAs for children to 290 mAs for adults. The mean values (+/- SD) of energy imparted were 72.1 mJ +/- 24.4 for children, 183.5 mJ +/- 44.8 for young adults, and 234.7 mJ +/- 89.4 for adults. The corresponding mean values of patient effective dose were 6.1 mSv +/- 1.4 for children, 4.4 mSv +/- 1.0 for young adults, and 3.9 mSv +/- 1.1 for adults. CONCLUSION: Values of energy imparted to patients undergoing abdominal CT examinations were a factor of three higher in adults than in children, but the corresponding patient effective doses were 50% higher in children than in adults.

Magnetic resonance epidurography with gadolinium-DTPA.

The aim of this study was to evaluate and describe MRI epidurography as a new imaging tool. Five volunteers and one patient were investigated with MR epidurography after injection of 20 ml Gd-DPTA solution (1:250/1 ml Gd-DPTA/250 ml normal saline). Magnetic resonance epidurography is possible. With fat-suppression techniques, the contrast between Gd-DPTA solution in the epidural space and surrounding soft tissue proved adequate. Using the multiplanar capability of MRI with MR epidurography coronal and sagittal projections similar to conventional epidurography, axial slices comparable to CT epidurography can be obtained. Magnetic resonance epidurography is superior to conventional and CT epidurography. Presently, due to high costs as compared with conventional and CT epidurography, MRI is not suitable for the routine monitoring of peridural catheters, but it may have a place in the future with decreasing costs for MRI and for the evaluation of patients with spine pathology, especially in describing epidural processes.