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PubMed1969

The spatial selectivity of the visual cells of the cat.

1. Micro-electrode recordings have been made from single units in the visual cortex of the cat, during stimulation by moving grating patterns generated on a cathode ray tube.2. The responses of the units have been measured in terms of either the frequency of impulses, or the contrast sensitivity, and expressed as a function of the spatial frequency of the grating pattern.3. The amplitude of the responses recorded from cortical cell bodies was dependent upon the orientation of the moving grating, and for these units the stimulus was always presented at the preferred orientation. The response amplitude of other units did not depend upon the orientation of the grating stimulus, and these are believed to be the terminations of geniculate fibres.4. The high spatial frequency end of the response function measured in terms of the contrast sensitivity could be well fitted by an exponential function. Subtraction of the blank count from the impulse frequency data gave a curve fitted by the same exponential function. The low frequency end was less consistent.5. The spatial frequency at which this exponential function had fallen by one log. unit was taken to specify the position of the unit's response in the spatial frequency spectrum. For all units these values cover a range of four octaves of spatial frequency (from 0.18 to 3.8 cycles per degree).6. It is suggested that these neurophysiological results support psychophysical evidence for the existence in the visual system of channels, each selectively sensitive to a narrow band of spatial frequencies.

Animals↗
PubMed1980

The contrast sensitivity, spatial resolution and velocity tuning of the cat's optokinetic reflex.

1. Optokinetic nystagmus has been evoked from two cats using horizontally moving vertical grating patterns with sinusoidally modulated wave forms (mean luminance 8.5 cd/m2). Eye movements were recorded by DC electro-oculography. 2. The velocity 'tuning' of the slow phase response was measured for high-contrast (0.8) gratings with spatial frequencies ranging from 0.18 to 2.8 cycles/deg. Irrespective of spatial frequency, the gain of slow phase tracking always declined as the stimulus velocity exceeded 5-8 deg/sec. 3. The effect of variations in grating contrast on the gain of slow phase tracking was investigated for spatial frequencies ranging from 0.04 to 2.8 cycles/deg. These gratings always moved at a velocity of 3 deg/sec. Reductions in grating contrast produced a fall in the gain of slow phase tracking. At any given contrast, the extent of the fall in gain depended on spatial frequency. At no value of spatial frequency was an optokinetic response demonstrable when the contrast fell below 0.02. 4. The above results have been used to derive the threshold contrast for evoking an optokinetic response at each spatial frequency tested. A contrast sensitivity function is plotted from these threshold contrasts, and this is compared with previous estimates of the cat's contrast sensitivity function derived from measurements of visual discrimination and cortical evoked potentials.

Animals↗
PubMed1981

Spatial contrast sensitivity of cells in the lateral geniculate nucleus of the rat.

1. The responses to visual stimuli of cells in the dorsal lateral geniculate nucleus of the rat were recorded with micro-electrodes. 2. Maps made with small spots of light showed that most units had concentrically organized receptive fields. Some units gave 'on-off' responses to spots flashed anywhere within the receptive field. These units were not directionally selective. 3. By the use of grating patterns as stimuli, units with concentrically organized receptive fields could be divided into groups that showed linear or non-linear spatial summation. Those unit showing linear spatial summation behaved like the 'X' cells of the cat, those showing non-linear summation like 'Y' cells. 4. 'On-off' units showed non-linear spatial summation of a kind that readily distinguished them from Y cells. 5. Measurements of spatial contrast sensitivity made with moving gratings showed, for both X and Y cells, peak sensitivities for spatial frequencies between 0.05 and 0.09 c/deg X and Y cells were not distinguished by their preferred spatial frequencies at any eccentricity.

Action Potentials↗
PubMed1981

The development of spatial-frequency selectivity in kitten striate cortex.

1. Single units were recorded in the striate cortex of kittens aged between 2 and 12 weeks. Contrast sensitivity measurements made using moving sinusoidal gratings were used to construct spatial-frequency tuning curves. 2. In young kittens cells had low sensitivities, responded only to low spatial frequencies and were unselective for spatial frequency. In addition 30% of the cells recorded in the youngest kittens were unresponsive to visual stimuli. 3. Sensitivity improved to near-adult values within 5-6 weeks. 4. Best spatial frequency improved more gradually, so that even in the oldest kittens best spatial frequencies were lower than adult values. 5. Selectivity for spatial frequency, considered both in terms of the numbers of selective cells and the narrowness of their tuning curves, improved rapidly, and reached adult values within the first 6 weeks. 6. These results are discussed in relation to other developmental studies.

Age Factors↗
PubMed1982

Correlation between the preferred orientation and spatial frequency of neurones in visual areas 17 and 18 of the cat.

1. In seventy-six penetrations through areas 17 and 18 of the cat, neurones were regularly sampled at intervals of 100 micrometers and preferred orientation, optimal spatial frequency and resolving power were determined for each neurone in response to drifting sinusoidal gratings. 2. As already shown for area 17, in tangential penetrations through area 18, whenever the preferred orientation rotates progressively from cell to cell, the optimal spatial frequency tends to remain constant. 3. A statistical analysis on 1574 cells in areas 17 and 18 showed that for pairs of cells separated 200-300 micrometers along a track the difference in preferred orientation delta alpha and the difference in optimal spatial frequency delta f are not randomly distributed: cell pairs with small delta alpha are most likely to have large delta f and vice versa. 4. These findings indicate that in areas 17 and 18 neurones with the same optimal frequency are aligned along a direction orthogonal to the orientation columns. 5. The optimal spatial frequency, resolving power and the velocity cut-off were averaged for cells from different penetrations located in the same cortical layer or sublayer of area 18: mean optimal spatial frequency and acuity are highest in layer IV and lowest in layers II and V, while the velocity cut-off is highest in layers II and V and lowest in layer IV. 6. Our data suggest that the layering of cells according to optimal spatial frequency is a more subtle subdivision than the six histological layers.

Action Potentials↗
PubMed1984

Spatial and temporal contrast sensitivities of neurones in lateral geniculate nucleus of macaque.

The discharges of single neurones in the parvocellular and magnocellular laminae of the macaque's lateral geniculate nucleus (l.g.n.) were recorded with glass-insulated tungsten micro-electrodes. Linearity of spatial summation was examined using the test devised by Hochstein & Shapley (1976). 2 of 272 parvocellular units and 6 of 105 magnocellular units showed clearly non-linear spatial summation. A quantitative index of non-linearity did not suggest the existence of a distinct 'non-linear' class of magnocellular unit. Spatial contrast sensitivity to moving gratings was measured by a tracking procedure in which contrast was adjusted to elicit a reliable modulation of discharge. With the exception of cells that were driven by blue-sensitive cones, measurements of contrast sensitivity did not reveal distinct subgroups of parvocellular units. All had low sensitivity, and those with receptive fields in the fovea could resolve spatial frequencies of up to 40 cycles deg-1. Magnocellular units had substantially higher sensitivity, but poorer spatial resolution. The higher sensitivities of magnocellular units led to their giving saturated responses to stimuli of high contrast. Responses of parvocellular units were rarely saturated by any stimulus. At any one eccentricity the receptive fields of parvocellular units had smaller centres than did those of magnocellular units. Receptive fields of magnocellular units driven by the ipsilateral eye had larger receptive fields than did those driven by the contralateral eye. Parvocellular units were most sensitive to stimuli modulated at temporal frequencies close to 10 Hz; magnocellular units to stimuli modulated at frequencies nearer 20 Hz. The loss of sensitivity as temporal frequency fell below optimum was more marked in magnocellular than parvocellular units. Changes in temporal frequency altered the shapes of the spatial contrast sensitivity curves of both parvocellular and magnocellular units. These changes could be explained by supposing that centre and surround have different temporal properties, and that the surround is relatively less sensitive to higher temporal frequencies.

Action Potentials↗
PubMed1987

Interhemispheric transfer of visual information in humans: spatial characteristics.

1. The problem of the interhemispheric transfer of visual information in humans has been approached psychophysically, making use of a visual discrimination task that shows a clear left field advantage and is subject to the phenomenon of perceptual learning. 2. For this task (discrimination of complex gratings differing only by the relative spatial phase of their harmonic components) there is a left field advantage and a lack of interhemispheric transfer of learning effects at all spatial frequencies tested for stimuli removed at least 5 deg from either side of the vertical meridian. 3. For stimuli close to the vertical meridian, the left field advantage disappears and there is a complete transfer of learning effects, provided the fundamental spatial frequency is 2 cycles/deg or lower. 4. At higher spatial frequencies the left field advantage is maintained and the learning effects do not transfer from one visual hemifield to the other, even at +/- 0.5 deg from the vertical meridian, unless the contrast is very high. 5. The transfer of learning effects obtained for spatial frequencies of 2 cycles/deg or lower is peculiar to regions placed close to the vertical meridian and symmetrically located on either side of it. No transfer is obtained between non-overlapping regions on the same side of the vertical meridian. 6. These findings are consistent with an interhemispheric transfer of visual information, preferential for low spatial frequencies and high contrasts, in agreement with that found for callosal transfer in the cat (Berardi, Bisti & Maffei, 1987).

Corpus Callosum↗
PubMed1990

Spatial organization of the bipolar cell's receptive field in the retina of the tiger salamander.

1. The spatial properties of rods, horizontal cells and bipolar cells were studied by intracellular recording in the isolated, perfused retina of the tiger salamander, Ambystoma tigrinum. Low stimulus intensities were used in order to keep cell responses close to, or within, their linear intensity/response range. 2. Spatial properties of bipolar cell receptive fields, measured while perfusing with normal Ringer solution, were compared with those measured during exposure to agents that eliminated the bipolar cells' receptive field surround (RFS). In this way, the spatial properties of the receptive field centre (RFC) and those of the RFS could be characterized independently. 3. To a good approximation, the contribution to the horizontal cell's response of unit area of its receptive field declined exponentially with distance from the centre of the receptive field. The (apparent) length constant describing this decay was 200 microns. The one-dimensional length constant of the horizontal cell syncytium was thus 248 microns. The variation of response amplitude with the radius of a centred circular stimulus was consistent with this finding. 4. This was true also of the RFCs of bipolar cells. The one-dimensional length constant of the RFC of off-centre bipolar cells averaged 124 microns. That of the RFC of on-centre cells averaged 62 microns though values were more variable, the RFCs of some on-centre cells being comparable to those of off-centre cells. These values were independent of the class of photoreceptor driving the bipolar cell. 5. The large size of the RFCs of off-centre cells and many on-centre cells cannot by explained by light scatter within the retina or by voltage spread within the rod syncytium. We proposed that off-centre cells are tightly coupled in a syncytium. On-centre cells, on average, are less tightly coupled. 6. The spatial properties of the bipolar cell's RFS were consistent with the notion that the RFS represents a convolution of the horizontal cell's receptive field and the bipolar cell's RFC. 7. The spatial properties of bipolar cell receptive fields were reconstructed from the measured properties of their RFCs and the measured properties of horizontal cell receptive fields. Under the conditions of our experiments, the bipolar cell's response could be described by a linear difference between a component generated by the RFC and a component generated by the RFS. 8. The spatial filtering characteristics of the bipolar cells were calculated from our data.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1996

Spatial frequency tuning of orientation-discontinuity-sensitive corticofugal feedback to the cat lateral geniculate nucleus.

1. The influence of spatial frequency on the inhibitory component of the effects mediated by feedback from the visual cortex has been examined in X and Y cells in the A laminae of the feline dorsal lateral geniculate nucleus (dLGN). Experiments utilized a concentric, bipartite visual stimulus centered over the receptive fields of the cells studied. The responses of dLGN cells to selective stimulation of receptive field centre (with the inner window) were compared with those to stimulation of centre and surround mechanisms (both inner and outer window), with the stimuli either in or out of orientation alignment. 2. With these same stimuli, layer VI cells in the visual cortex showed a marked increase in response magnitude when the inner and outer components of the stimulus were in orientation alignment, and presented at the preferred orientation. In the case of dLGN X and Y cells we observed an enhancement of the surround antagonism of the centre response when the inner and outer sections of the stimulus were in orientation alignment. 3. The effects of varying spatial frequency on these responses were examined in dLGN cells in the presence of corticofugal feedback. With the stimulus sections in orientation alignment, surround stimulation produced a powerful and significant reduction in the response to stimulation of centre mechanism alone with the most marked effects for stimuli in the range 0.1-0.85 cycles per degree (c.p.d.). The reduction produced by surround stimulation in the range 0.1-0.5 c.p.d. was notably more potent in X cells than in Y cells. 4. The responses to the same stimuli were examined in dLGN cells with the corticofugal feedback inactivated. Comparison of data from cells studied with and without feedback revealed a significant decrease in surround-mediated attenuation of the centre response in Y cells for spatial frequencies in the range 0.1-0.85 c.p.d. For X cells the decrease in strength of the surround antagonism was also clear and significant but only seen in the range 0.1-0.5 c.p.d. 5. The influence of the orientation alignment of inner and outer stimulus sections revealed a marked difference between cells studied with and without feedback. In the presence of feedback fully aligned stimuli enhanced surround antagonism of centre responses for spatial frequencies in the range 0.1-0.5 c.p.d., in X and Y cells. In the absence of corticofugal feedback this alignment effect was essentially eliminated. 6. These data show that surround antagonism of the centre response is influenced by orientation alignment of the stimulus sections at low spatial frequencies and in the presence of corticofugal feedback. They support a cortically driven enhancement of the inhibitory mechanisms reinforcing surround mechanisms in the dLGN. We propose that feedback enhances a low spatial frequency cut-off in the dLGN, that this effect is maximal for a continuous iso-orientated contour, but diminished whenever there is an orientation discontinuity. The hyperpolarizing influence underlying this effect may contribute to the recently described synchronizing influence of the direct corticofugal contacts onto relay cells. We suggest feedback of the cortical level of analysis refines the transfer of the visual input at geniculate level in a stimulus-context-dependent fashion.

Animals↗
PubMedDate not supplied

Optical coherence tomography speckle reduction by a partially spatially coherent source.

Speckle in optical coherence tomography (OCT) images originates in the high spatial coherence of incident light that enables interference of light backscattered from spatially heterogenous tissue specimens. We report results of a numerical simulation and an experiment to test speckle reduction using a partially spatially coherent source. A Gaussian-Schell model for a partially spatially coherent source is used in the OCT simulation. For the experiment, such a source was generated by a spatially coherent boardband light source and a multimode fiber. The advantage of using a multimode fiber in combination with a broadband source is the large number of photons per coherence volume. To illustrate speckle reduction with a partially spatially coherent source, we record low-coherence interferograms of a scattering surface using single-mode and multimode source fibers. Interferograms recorded using a single-mode source fiber are indicative of those observed using conventional OCT. Speckle in OCT images recorded using a multimode source fiber is substantially reduced.

Algorithms↗
PubMed1994

A spatial-frequency dependent quantum accounting diagram and detective quantum efficiency model of signal and noise propagation in cascaded imaging systems.

The detective quantum efficiency (DQE) is a system parameter that can be used to accurately describe image noise transfer characteristics through many imaging systems. A simpler approach used by some investigators, particularly when evaluating new ideas and system designs, is to describe the system as a series of cascaded stages. Each stage may correspond to either an increase in the number of quanta (e.g., conversion from x-ray to optical quanta in a radiographic screen), or a loss (a detection or coupling probability). The number of secondary quanta at each stage per incident primary quantum is given by the product of all preceding gains, and can be displayed graphically for convenient interpretation. The stage with the fewest quanta is called the "quantum sink," limiting the pixel signal-to-noise ratio to less than the square root of the number of quanta per pixel. This conventional zero-spatial-frequency "quantum accounting diagram" (QAD), however, neglects the spatial spreading of secondary quanta and can seriously underestimate image noise. It is shown that this problem is avoided with the introduction of a spatial-frequency dependent QAD, expressed as the product of the gains and squared modulation-transfer functions (MTF) of each stage. A generalized expression is developed for the DQE of a cascaded imaging system that is dependent only on the gain, gain Poisson excess (related to the variance), and MTF, of each stage. A direct relationship is then shown to exist between the DQE and values in the QAD. The QAD of a hypothetical system consisting of a charge-coupled device camera and a scintillating screen is evaluated as an illustrative example. The conventional zero-frequency analysis suggests two quantum sinks occur with approximately equal importance: one in the number of x rays, and one in the number of optical quanta. The spatial-frequency dependent analysis, however, shows the optical quantum sink becomes severe and dominates at nonzero frequencies. The necessary increase in gain or optical numerical aperture required to prevent the optical quantum sink for spatial frequencies of interest is determined from the QAD analysis. The visual impact of this nonzero spatial-frequency quantum sink is shown in images generated using a Monte Carlo simulation of the cascading process.

Algorithms↗
PubMed2005

Spatial unmasking of birdsong in human listeners: energetic and informational factors.

Spatial unmasking describes the improvement in the detection or identification of a target sound afforded by separating it spatially from simultaneous masking sounds. This effect has been studied extensively for speech intelligibility in the presence of interfering sounds. In the current study, listeners identified zebra finch song, which shares many acoustic properties with speech but lacks semantic and linguistic content. Three maskers with the same long-term spectral content but different short-term statistics were used: (1) chorus (combinations of unfamiliar zebra finch songs), (2) song-shaped noise (broadband noise with the average spectrum of chorus), and (3) chorus-modulated noise (song-shaped noise multiplied by the broadband envelope from a chorus masker). The amount of masking and spatial unmasking depended on the masker and there was evidence of release from both energetic and informational masking. Spatial unmasking was greatest for the statistically similar chorus masker. For the two noise maskers, there was less spatial unmasking and it was wholly accounted for by the relative target and masker levels at the acoustically better ear. The results share many features with analogous results using speech targets, suggesting that spatial separation aids in the segregation of complex natural sounds through mechanisms that are not specific to speech.

Acoustic Stimulation↗
PubMed2006

Efficient array beam forming by spatial filtering for ultrasound B-mode imaging.

This paper proposes an efficient array beam-forming method using spatial matched filtering (SMF) for ultrasonic imaging. In the proposed method, ultrasonic waves are transmitted from an array subaperture with fixed transmit focus as in conventional array imaging. At receive, radio frequency echo signals from each receive channel are passed through a spatial matched filter that is constructed based on the system transmit-receive spatial impulse response. The filtered echo signals are then summed without time delays. The filter concentrates and spatially registers the echo energy from each element so that the pulse-echo impulse response of the summed output is focused with acceptably low side lobes. Analytical beam pattern analysis and simulation results using a linear array show that this spatial filtering method can improve lateral resolution and contrast-to-noise ratio as compared with conventional dynamic receive focusing (DRF) methods. Experimental results with a linear array are consistent but point out the need to address additional practical issues. Spatial filtering is equivalent to synthetic aperture methods that dynamically focus on both transmit and receive throughout the field of view. In one common example of phase aberrations, the SMF method was degraded to a degree comparable to conventional DRF methods.

Computer Simulation↗
PubMed2004

Modification of spatial distribution of 2,4-dichlorophenoxyacetic acid degrader microhabitats during growth in soil columns.

Bacterial processes in soil, including biodegradation, require contact between bacteria and substrates. Knowledge of the three-dimensional spatial distribution of bacteria at the microscale is necessary to understand and predict such processes. Using a soil microsampling strategy combined with a mathematical spatial analysis, we studied the spatial distribution of 2,4-dichlorophenoxyacetic acid (2,4-D) degrader microhabitats as a function of 2,4-D degrader abundance. Soil columns that allowed natural flow were percolated with 2,4-D to increase the 2,4-D degrader abundance. Hundreds of soil microsamples (minimum diameter, 125 microm) were collected and transferred to culture medium to check for the presence of 2,4-D degraders. Spatial distributions of bacterial microhabitats were characterized by determining the average size of colonized soil patches and the average number of patches per gram of soil. The spatial distribution of 2,4-D degrader microhabitats was not affected by water flow, but there was an overall increase in colonized patch sizes after 2,4-D amendment; colonized microsamples were dispersed in the soil at low 2,4-D degrader densities and clustered in patches that were more than 0.5 mm in diameter at higher densities. During growth, spreading of 2,4-D degraders within the soil and an increase in 2,4-D degradation were observed. We hypothesized that spreading of the bacteria increased the probability of encounters with 2,4-D and resulted in better interception of the degradable substrate. This work showed that characterization of bacterial microscale spatial distribution is relevant to microbial ecology studies. It improved quantitative bacterial microhabitat description and suggested that sporadic movement of cells occurs. Furthermore, it offered perspectives for linking microbial function to the soil physicochemical environment.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2026

Spatial habitat radiomics predicts tertiary lymphoid structure status and identifies an IDO1+ migratory dendritic cell axis in breast cancer.

BACKGROUND: Tertiary lymphoid structures (TLS) are spatially organized immune niches associated with therapeutic response and favorable outcomes in breast cancer (BC). However, TLS assessment currently relies on invasive tissue-based analyses, and the biological mechanisms underlying imaging-based TLS prediction remain poorly understood. METHODS: We developed and validated a spatial heterogeneity-based radiomic TLS signature (shTLS) using dynamic contrast-enhanced MRI to non-invasively predict TLS status across multicenter BC cohorts. Spatial habitat radiomics were used to capture intratumoral and peritumoral immune-related heterogeneity. Integrated multi-omics analyses, including transcriptomics, pathomics, genomics, single-cell RNA sequencing, immunohistochemistry, and multiplex immunofluorescence, were performed to biologically interpret shTLS-defined subgroups. Functional drug-sensitivity assays were conducted to assess therapeutic implications. RESULTS: The shTLS model achieved robust predictive performance across independent cohorts and molecular subtypes. High shTLS scores were associated with immune-inflamed tumors characterized by spatially clustered activated T cells and dendritic cells (DCs). In contrast, shTLS-low tumors exhibited an immunosuppressive spatial niche with peripheral accumulation of CD4+ PD-1+ T cells and plasma cells, increased immune-tumor separation, and enhanced inflammatory and immunoregulatory signaling. An indoleamine 2,3-dioxygenase 1 (IDO1)-associated immunoregulatory program was observed in the shTLS-low tumors, which appeared to be preferentially expressed by LAMP3+CCR7+ migratory DCs. Pharmacologic inhibition of IDO1 enhanced chemotherapy and CDK4/6 inhibitor sensitivity in vitro. CONCLUSION: This study establishes spatial radiomics as a non-invasive approach to decode TLS-associated immune ecosystems and supports the presence of an IDO1-associated immunosuppressive phenotype, providing biological insight and translational rationale for patient stratification and future combination strategies.

Humans↗
PubMed2000

Spatial memory impairment in patients after tumour resection: evidence for a double dissociation.

Human spatial memory can be divided into multiple, partly separate cognitive processes. In this study, object location memory was studied using a set of tasks that assessed three different spatial memory aspects: positional memory, object location binding, and a combined process. Also, maze learning and spatial span memory were measured. Ten patients who had undergone intracranial tumour resection participated, and their individual results were compared with control data from 24 healthy subjects. Four patients showed selective spatial memory impairments; two patients were impaired at positional memory, and two other patients were impaired on object location binding and the combined process. This double dissociation provides further evidence for the notion that object location memory is not a unitary system, but consists of at least two separate mechanisms. In addition, spatial memory problems were predominantly present in the patients with lesions in either the right hemisphere or in the parietal lobe. These results are in agreement with previous findings on the involvement of the right hemisphere and the posterior parietal cortices in spatial processing.

Adult↗
PubMed2005

Differentiation of benign from malignant solid breast masses: conventional US versus spatial compound imaging.

PURPOSE: To compare prospectively the diagnostic performance of radiologists who used conventional ultrasonography (US) with that of radiologists who used spatial compound imaging for the differentiation of benign from malignant solid breast masses. MATERIALS AND METHODS: The study was approved by the institutional review board, and informed consent was obtained. Before excisional or needle biopsy was performed, conventional US and spatial compound images were obtained in 67 patients (age range, 25-67 years; mean age, 45 years) with 75 solid breast masses (21 cancers and 54 benign lesions). Three experienced radiologists who did not perform the examinations independently analyzed US findings and indicated the probability of malignancy. Results were evaluated with kappa statistics and receiver operating characteristic (ROC) analysis. RESULTS: For US findings, the presence of calcifications was the most discordant feature (kappa = 0.372) between conventional US and spatial compound imaging, followed by echotexture (kappa = 0.439), boundary echo (kappa = 0.496), orientation (kappa = 0.518), echogenicity (kappa = 0.523), shape (kappa = 0.526), margin (kappa = 0.569), and posterior acoustic transmission (kappa = 0.669). The area under the ROC curve for conventional US was 0.79 for reader 1, 0.88 for reader 2, and 0.82 for reader 3, and the area under the ROC curve for spatial compound imaging was 0.85 for reader 1, 0.88 for reader 2, and 0.89 for reader 3. The partial area index for conventional US was 0.29 for reader 1, 0.69 for reader 2, and 0.39 for reader 3, and the partial area index for spatial compound imaging was 0.29 for reader 1, 0.65 for reader 2, and 0.39 for reader 3. The difference between the diagnostic performances of the two techniques was not significant (P > .05). CONCLUSION: The performance of the radiologists with respect to the characterization of solid breast masses was not significantly improved with spatial compound imaging.

Adult↗
PubMed2001

Scaphoid fractures: evaluation with high-spatial-resolution US initial results.

PURPOSE: To evaluate the diagnostic accuracy of high-spatial-resolution ultrasonography (US) in the diagnosis of scaphoid fractures. MATERIALS AND METHODS: In 72 hours after acute wrist trauma, 15 consecutive patients were examined for possible scaphoid fractures clinically and with conventional radiographs, including scaphoid views. Thereafter, high-spatial-resolution US was performed by two experienced radiologists blinded to the results of the previously performed investigations. High-spatial-resolution US of the scaphoid bones was performed from the palmar, lateral, and dorsal directions in the longitudinal and transverse planes. US findings indicative of a scaphoid fracture were cortical discontinuity and/or periosteal elevation. Finally, magnetic resonance (MR) images (short inversion time inversion-recovery, T1- and T2*-weighted) (ie, the standard) of the affected wrist were obtained and evaluated for a possible scaphoid fracture by two radiologists in consensus. RESULTS: Nine of 15 patients had scaphoid fractures. Seven (78%) of nine patients had positive findings at high-spatial-resolution US and five (56%) had such findings at conventional radiography (ie, four occult scaphoid fractures), with an accuracy of 87% and 73%, respectively. Two (50%) of four radiographically occult scaphoid fractures were depicted with high-spatial-resolution US. Sonographic findings of scaphoid fractures were either cortical discontinuity (n = 4), periosteal elevation (n = 2), or a combination of these two findings (n = 1). CONCLUSION: High-spatial-resolution US is a reliable diagnostic tool for the evaluation of occult scaphoid fractures and should be considered an adequate alternative diagnostic tool prior to computed tomography or MR imaging.

Adolescent↗