Dietary fibre linked to decreased inflammation in overweight minority youth.

OBJECTIVE: The objective of this study was to examine the relationship between diet and inflammation, and adiposity in minority youth. DESIGN AND METHODS: The study was designed as a cross-sectional analysis of 142 overweight (≥85th body mass index percentile) Hispanic and African-American adolescents (14-18 years) with the following measures: anthropometrics, adiposity via magnetic resonance imaging, dietary intake via 24-h dietary recalls, and inflammation markers from fasting blood draws utilizing a multiplex panel. Partial correlations were estimated and analysis of covariance (ancova) models fit to examine the relationship among dietary variables, inflammation markers and adiposity measures with the following a priori covariates: Tanner stage, ethnicity, sex, total energy intake, total body fat and total lean mass. RESULTS: Inference based on ancova models showed that the highest tertile of fibre intake (mean intake of 21.3 ± 6.1 g d(-1) ) vs. the lowest tertile of fibre intake (mean intake of 7.4 ± 1.8 g d(-1) ) was associated with 36% lower plasminogen activator inhibitor-1 (P = 0.02) and 43% lower resistin (P = 0.02), independent of covariates. Similar results were seen for insoluble fibre. No other dietary variables included in this study were associated with inflammation markers. CONCLUSIONS: These results suggest that increases in dietary fibre could play an important role in lowering inflammation and therefore metabolic disease risk in high-risk minority youth.

Determinants of renal volume in autosomal-dominant polycystic kidney disease.

The Consortium of Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP) recently showed that renal enlargement in autosomal-dominant polycystic kidney disease mimicked exponential growth. We determined the effects of cyst initiation rate, total number, and growth rate on the time-dependent change of total cyst volume (TCV). Mathematical models with equations integrating cyst surface area, volume, and an invariant growth rate constant were used to compute the time-dependent change in volume of solitary and multiple cysts. Multiple expanding cysts increased TCV in an exponential-like pattern even when individual cysts formed at different rates or exhibited different but constant growth rates. TCV depended on the rate of cyst initiation and on the total number of cysts; however, the compounding effect of exponential-like growth was the most powerful determinant of long-term cyst expansion. Extrapolation of TCV data plots for individual subjects back to an age of 18 predicted TCV values within an established range. We conclude that cysts started early in life were the main contributor to eventual TCV while their growth rate primarily determined renal size; although the rate of formation and the ultimate number of cysts also contributed. The good fit between the exponential models and the extrapolated CRISP data indicates that the TCV growth rate is a defining trait for individual patients and may be used as a prognostic marker.

Volumetric determination of progression in autosomal dominant polycystic kidney disease by computed tomography.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive renal enlargement and renal failure. We evaluated sequential radiocontrast-enhanced computed tomography (CT) scans to determine the rate of kidney enlargement in patients with ADPKD. METHODS: Ten adult patients with ADPKD (4 men and 6 women) with initial serum creatinine levels 0.05), and 185 +/- 52 mL (P < 0.01), respectively. In 19 individual spherical cysts selected in six patients, the mean initial volume was 15.0 +/- 7.2 mL (range 1.1 to 137 mL), and the average rate of volume increase was 0.52 +/- 0.21 mL/month (P < 0.025, range 0.02 to 4.15 mL/month). In five patients who eventually required dialysis, 11.2 years after the initial CT scan, the initial cyst/kidney volume ratio (combined for both kidneys) exceeded 0.43; four patients with lower cyst/kidney volume ratios had serum creatinine levels <1.5 mg/dL, 8.7 years after the initial CT scan. CONCLUSIONS: On the basis of this preliminary survey of archival material, we conclude that conventional contrast-enhanced CT scans can be used to quantitate volume components of progression in ADPKD. The rates of individual kidney and cyst enlargement are highly variable within and between patients, but overall, the values increase over time. The volume fraction of kidneys comprised of cysts may be a useful indicator of ADPKD progression.

Comparison of a cathode-ray-tube and film for display of computed radiographic images.

The goal of the study was to compare a cathode-ray-tube (CRT) digital display with film by using task-dependent image quality assessment methods. Contrast-detail analysis was utilized. Human observers performed a simple detection task, specifically, detecting a pillbox target in a uniform Poisson field, using either film or a digital display that employed a CRT monitor. Observers performed equally well on both film and CRT when the window settings of the digital display were established subjectively by a radiologist. Changing the window settings of the digital display to match the average background luminance of a film-illuminator combination decreased the luminance contrast of the targets and observer performance was reduced, though these effects were probably not linked. The "gold standard" film had lower luminance contrast than the CRT displayed images, yet observer performance was never lower for film than for the CRT. Therefore we concluded that luminance contrast was not a limiting factor for observer performance in this study. The CRT monitor changed fairly rapidly after it was calibrated. During a period of six months the gamma of the display increased from 1.82 to 2.42 and the maximum luminance decreased from 319 to 228 cd/m2. Low luminance output demonstrated a larger percentage decrease (approximately equal to 85%) than high luminance output (approximately equal to 29%) over the same time period. These observations suggest that standard window settings should be reviewed from time to time to ensure that the display is used optimally. No special look-up table setup such as perceptual linearization was used.

The effects of lossy compression on the detection of subtle pulmonary nodules.

We examined the ability of radiologists to detect pulmonary nodules in computed radiographic (CR) chest images subjected to lossy image compression. Low-contrast 1-cm diameter targets simulating noncalcified pulmonary nodules were introduced into clinical images and presented to ten radiologists in a series of two-alternative forced-choice (2AFC) observer experiments. The percentages of correct observer responses obtained while viewing noncompressed images (1:1) were compared with those obtained for the same images compressed 7:1, 16:1, 44:1, and 127:1. The images were compressed using a standard full-frame discrete cosine transform (DCT) technique. The degree of compression was determined by quantizing Fourier components in various frequency channels and then Huffman encoding the result. The data show a measurable decline in performance for each compression ratio. Through signal-to-noise ratio (SNR) analysis, we found that the reduction in performance was due primarily to the compression algorithm that increased image noise in the frequency channels of the signals to be detected.

The transverse plane evolution of the most common adolescent idiopathic scoliosis deformities. A cross-sectional study of 181 patients.

STUDY DESIGN: The transverse plane evolution of the most common idiopathic deformities was studied using a cross-sectional database of 181 patients whose deformities were visualized by precise three-dimensional techniques. OBJECTIVE: The objective was to test the hypothesis that for all common idiopathic scoliosis deformities evolution occurs as a torsion, the apex vertebra translating away from the upper end vertebra and at the same time angulating in a clockwise arc for right apex deformities and a counterclockwise arc for left apex deformities. SUMMARY OF BACKGROUND DATA: Perdriolle and Vidal proposed this hypothesis in 1987, which explained observations we had made in 1983 and which was partially supported in thoracic curves in our 1992 study. METHODS: Deformities were characterized as single thoracic major, thoracic major and thoracolumbar or lumbar minor, double thoracic and thoracolumbar or lumbar major, and single thoracolumbar or lumbar major curves. The dependent variable studied was the coronal plane regional angular (Cobb) deformity. The independent variables studied were the lateral and anteroposterior translation of the apex vertebra in relation to the upper end vertebra, and the transverse plane translation and angulation of the apex vertebra in relation to the upper end vertebra. For the model or hypothesis to be true, the apex vertebra to upper end vertebra transverse plane translational distance and angular relationship should increase as the Cobb angle increases. RESULTS: In relation to the upper end vertebra, the apex vertebra always translated laterally, almost always was accompanied by transverse plane translation increase, and usually was accompanied by transverse plane angulation increase. Anteroposterior translation was minimal, but for thoracolumbar and lumbar curves it tended to be posterior. CONCLUSION: The theory that these deformities evolve as torsions, with the apex vertebra translating away from the upper end vertebra and at the same time following a clockwise angular pathway to the upper end vertebra of right apex curves and a counterclockwise angular pathway for left apex curves is supported. Compensatory thoracolumbar and lumbar curves evolve in the same manner as major curves.

Contrast-detail analysis of image degradation due to lossy compression.

A contrast-detail (CD) experiment was performed to study the effect of lossy compression on computed radiographic (CR) images. Digital CR images of a phantom were compressed by quantizing the full-frame discrete cosine transform and Huffman encoding the result. Since low-contrast detectability is directly linked to an important radiological task, namely, the detection of noncalcified pulmonary nodules in adult chest radiographs, the goal of the study was to quantify any loss in low-contrast detectability due to compression. Compression ratios varied significantly among compressed images, despite the use of fixed compression parameters; detectability could be specified by a single parameter of a CD curve; there was no significant reduction in detectability for an average compression ratio of 11:1; and, there was a statistically significant degradation in detectability for an average compression ratio of 125:1.

Comparison of the low-contrast detectability of a screen-film system and third generation computed radiography.

Contrast-detail (CD) analysis was used to compare the low-contrast detectability of computed radiography (CR) and screen-film (SF) as applied to the task of adult chest radiography. A phantom was constructed and imaged using the same exposure factors throughout all experiments. Within-observer variance, between-observer variance, and image sample variance were calculated and used to estimate the standard error for each experiment. The results of these CD experiments agreed with the predictions of the Rose model. Observers performed equally well for low-contrast target detection using CR and SF.

Backscatter coefficient estimation using array transducers.

This paper describes an extension of our broadband method for estimating backscatter coefficients from random media to include data from array transducers. Four different transducer designs have now been considered: oneand two-dimensional linear arrays, annular arrays, and single-element focused pistons commonly used in mechanical sector scanners. The analysis shows that if the backscatter echo spectrum is properly normalized, the shape of the piezoelectric elements affects only the magnitude and not the frequency dependence of the backscatter coefficient estimates. Experimental data were acquired using laboratory and clinical imaging instrumentation to verify the analysis. We compared backscatter coefficients measured as a function of frequency from well-defined scattering media that were obtained using a 1-D linear array and focused piston transducers. Instrument-independent results were found that matched theoretical predictions within the measurement error between 2 and 12 MHz. We conclude from this study that accurate backscatter coefficient estimates may be easily obtained using current clinical imaging instrumentation.

Image calibration of laser digitizers, printers, and gray-scale displays.

Laser film digitizers, interactive gray-scale monitors, and laser film printers are necessary to transmit digital image information. These devices must be standardized so that hard- and soft-copy images are as similar as possible. Standardization of appropriate calibration procedures is necessary to attain this goal. Radiographs are converted into digital data representations by a laser film digitizer. These representations (and those obtained with other modalities) are transferred to a laser film printer or to an interactive monitor with gray-scale display. To obtain the best gray-level fidelity, printer output optical densities should be identical to those of the input film. Laser printers should be calibrated regularly to ensure uniform results. A gray-scale controller functions as an adjunct to the host computer and can automate the calibration process. Gray-scale controller functions may someday be incorporated into an accelerator or array-processor board.

Enhancement of storage phosphor plate images: a C-language program.

A C-language software program has been developed for emulating the image enhancement processing of a storage phosphor plate system. This software has been implemented on a VAX 3400 computer. There are 2,100 lines of C-language code in the program. There are seven parameters used to specify the degree of enhancement. The software is being implemented on a single accelerator board.

Computed radiography in musculoskeletal imaging: state of the art.

Computed radiography is a 2K x 2K x 10 bit digital radiographic system that replaces the film-screen combination with a photo-stimulable phosphor plate. The advantages of this relatively new technology include linear detector response, improved detector efficiency, and digital processing capabilities. Musculoskeletal applications benefit significantly from these attributes, which result clinically in the ability to reduce both radiation dose and number of exposures. Studies of observers' performance have shown no statistically significant difference in diagnostic accuracy between film-screen and computed radiographic musculoskeletal images. Computed radiography is particularly useful in the evaluation of the musculoskeletal system in traumatized patients with portable radiographs, spine radiographs, scoliosis studies, and depiction of soft-tissue abnormalities. Limitations include change in image format and size, high cost, decreased spatial resolution, restricted throughput, increased perception of noise, and new artifacts that must be recognized. Spatial resolution limitations of computed radiography in identification of fine detail information can be improved by using magnification techniques. Radiation dose reduction with an exposure decrease of 25-50% can be achieved without loss of diagnostic accuracy, although this depends on the examination and the abnormality. An interactive workstation is important in the use of a computed radiographic system with capabilities to adjust display parameters to best depict images and disease. We conclude that computed radiography is an alternative to film-screen radiography without significant differences in diagnostic quality in the evaluation of musculoskeletal images.

Conventional screen/film vs reduced exposure photostimulable phosphor plate imaging in lower extremity venography: an ROC analysis.

Half-exposure phosphor plates used in venography substantially reduce the total X-ray exposure to a patient while increasing the chance that all images will be of excellent diagnostic quality. Simultaneous half-exposure phosphor plate and full-exposure conventional screen/film venograms were obtained of 35 patients and compared by using receiver operating characteristic (ROC) analysis. The area under the ROC curve ranged from 0.67 to 0.78 for conventional films and 0.68 to 0.91 for phosphor plates. Group performances on conventional films vs phosphor plates were not statistically different. No statistically significant difference in individual performance with the two techniques was seen in seven of the eight interpreters at the 95% confidence level. The eighth interpreter performed significantly better with phosphor plates than with conventional films. Interpreters with and without specific experience in phosphor plate venography were grouped separately, and performance of the two groups was compared in each technique. No difference in performance was found between the groups when interpreting conventional venograms, but, when interpreting phosphor plate venograms, the group with specific experience performed significantly better than they had with conventional venograms, and significantly better than the other group did at interpreting either conventional or phosphor plate venograms. We conclude that phosphor plate venograms made at a 50% reduction in X-ray exposure are equal to, and may surpass, conventional screen/film venograms for diagnosing acute venous thrombosis of the calf and thigh. We recommend expanding the indications for phosphor plate radiography to include contrast venography of the lower extremities.

Chest radiography: comparison of high-resolution digital displays with conventional and digital film.

This study was performed to compare the performances of observers using three display formats for chest radiography. The display formats were conventional radiographs, digitized radiographs (2,048 X 2,048 X 12 bits) printed on laser film, and digitized radiographs (2,048 X 2,048 X 12 bits) displayed on a high-resolution (2,560 X 2,048 X 12-bit) gray-scale display. The test set for the study consisted of 163 cases. Sixty-four of the cases were normal, whereas the 99 remaining cases demonstrated one or more common radiographic abnormalities. Nine abnormalities were selected for analysis: costophrenic angle blunting, interstitial disease, atelectasis, pneumothorax, parenchymal mass, consolidation, obstructive disease, hilar/mediastinal mass, and apical scarring. Six experienced general radiologists participated in the evaluation. Receiver operating characteristic curves were generated for each abnormality and display format. The results indicate that, while the three display formats are equivalent for the detection of some abnormalities, detectable differences in observer performance may be seen even at 2,048 X 2,048 X 12 bits for the detection of obstructive disease, pneumothorax, interstitial disease, and parenchymal masses.

Nondisplaced fractures: spatial resolution requirements for detection with digital skeletal imaging.

Fifty-six radiographs of nondisplaced or minimally displaced fractures of the extremities and an equal number of studies with normal findings were selected and digitized to produce spatial resolution varying from 5.75 to 0.72 line pairs per millimeter (1p/mm), corresponding to pixel sizes ranging from 0.08 to 0.64 mm. The conventional and digitized images were evaluated by 10 radiologists, who gave their decision confidence on a graded scale. Receiver operating characteristic analyses were performed from these data to compare the digital images with the conventional radiographs. There was a progressive improvement in observer performance as the pixel size decreased. A pixel size greater than 0.16 mm (2.88 1p/mm) resulted in a significant loss of diagnostic accuracy in comparison with conventional radiographs. Specific fractures in which a larger pixel size adversely affected the evaluation included torus injuries, corner fractures in child abuse, minimal avulsion injuries, and fractures that demonstrated only trabecular disruption.

Image data compression in magnification hand radiographs.

A study was conducted on the use of an irreversible compression technique, Fourier quantization, to reduce the amount of digital data needed for an image. The effect of image compression was studied in radiographs obtained to diagnose subperiosteal bone resorption. Magnification radiographs of 44 hands were digitized to an array size of 4,096 X 4,096 X 12 bits. Selected subregions containing a single middle phalanx were compressed and reconstructed. A subset of the resultant 12-bit uncompressed and 8-, 7-, and 6-bit compressed images were read by four radiologists whose responses were analyzed with receiver operating characteristic (ROC) techniques. There were 81 images used in the ROC analysis, of which 48 were normal and 33 showed subperiosteal resorption. No statistically significant loss of diagnostic quality was detected for 8- or 7-bit compressed images, with average compression ratios of 16:1 and 28:1, respectively. Diagnostic quality was lost with 6-bit images, with an average compression ratio of 107:1.

Digital image-management networks: problems in implementation.

The apparent advantages of a DIMS are often cited by those involved in medical information-management research. The promise of a high-speed electronic image-management system that could increase a department's patient throughput and improve patient care is most attractive. Every major manufacturer of medical imaging equipment has a group working to develop such systems. Many problems remain to be solved before such systems can be acquired, installed, and made operational. This paper has summarized the significant technical problems yet to be solved.

High-resolution digital x-ray detector utilizing a discrete array of CdWO4 scintillators and a self-scanned photodiode array.

A high-resolution x-ray detector array for x-ray imaging is described. It consists of a discrete array of CdWO4 scintillators and a Reticon 1024S photodiode array with a fiber-optic faceplate. The scintillator elements measure 0.099 X 3 X 4 mm and are bonded together with aluminum foil separators to minimize light crossover. Detective quantum efficiency (DQE) of individual detector channels was 0.38. Systematic variations between channels were substantial. With only a simple correction for between channel variations, DQE for the entire array was 0.04. Evaluation of the edge response function of the array showed that resolution is similar to a detector whose line spread function is Gaussian with a standard deviation of 0.172 mm.