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PubMed2006

Aperture collimation correction and maximum-likelihood image reconstruction for near-field coded aperture imaging of single photon emission computerized tomography.

Coded aperture (CA) imaging originally developed in X-ray astronomy has not been widely used in nuclear medicine due to the decoding complexity of near-field CA images. In this paper, we present a near-field CA imaging technique and image reconstruction method for high sensitivity and high resolution single photon emission computerized tomography (SPECT). Our approach makes three contributions. First, a correction method for the aperture collimation effect is used to eliminate the near-field artifacts without dual acquisitions of mask and anti-mask images. Second, a maximum-likelihood expectation-maximization (MLEM) deconvolution method is used to restore CA images. Finally, a new MLEM-based algorithm is used to partially reconstruct three-dimensional (3-D) objects from a single projection of CA images. Experiments conducted using a dual-head SPECT system equipped with a parallel-hole collimator and a CA module show a tenfold increase in count sensitivity and significant improvement in image resolution with CA collimation as compared to parallel-hole collimation. Experiments conducted using the same dual-head SPECT system equipped with a pinhole collimator show that when the object is closer to the pinhole collimator the CA image resolution is only slightly inferior to the pinhole collimated image. We found that the MLEM deconvolution method provides an inherent nonnegativity constraint on pixel values and remarkably reduces background activities of CA images. The MLEM reconstruction algorithm for CA images is capable of reconstructing 3-D objects from a single projection and can be potentially extended to full 3-D SPECT reconstruction for CA images.

Algorithms↗
PubMed2001

Power motion imaging can improve image quality in stress conditions with tachycardia.

BACKGROUND: Stress echocardiographic studies are useful, but the evaluation of wall motion is sometimes suboptimal. The recently developed technique of power motion imaging can enhance mobile tissue definition. HYPOTHESIS: The study was undertaken to determine whether power motion imaging improves endocardial definition during tachycardia compared with conventional two-dimensional (2-D) imaging. METHODS: Twenty pigs were studied during pacing rates of 100, 120, and 150 beats/min. We compared power motion imaging with standard 2-D imaging using systolic thickening visualization (STV) scores (3 = excellent definition of systolic thickening approximately 0 = total lack of visualization of systolic thickening) at each heart rate. We calculated the sum of the scores of 22 left ventricular segments as the overall STV score, and also calculated the sum of the scores in 10 parasternal segments and 12 apical segments separately. RESULTS: The overall STV scores in both imaging methods were similar at 100 beats/min, but scores for power motion imaging were significantly higher than those of usual 2-D imaging at 120 and 150 beats/min. Using power motion imaging, the overall STV scores were similar as heart rate was increased; however, while using standard 2-D imaging, STV scores were significantly decreased as heart rate was increased. Findings were analyzed separately by parasternal and apical images. Especially in the parasternal images, the scores were significantly increased as heart rate was increased using power motion imaging. CONCLUSIONS: We conclude that power motion imaging improves the detection of endocardial border in stress condition with tachycardia, and thus this modality is useful for stress echocardiography.

Animals↗
PubMedDate not supplied

Diagnostic value of gadopentetate dimeglumine for 1.5-T MR imaging of musculoskeletal masses: comparison with unenhanced T1- and T2-weighted imaging.

Three magnetic resonance (MR) imaging techniques (T1-weighted, T2-weighted, and T1-weighted gadopentetate dimeglumine--enhanced) were compared in 32 consecutive MR imaging studies of 26 patients with suspected musculoskeletal masses. T2-weighted images were superior to T1-weighted enhanced images with respect to detection and definition of lesions in 12% of cases (n = 4) and were equal in 88% of cases (n = 28). T2-weighted images were also superior to T1-weighted images in 38% of cases (n = 12). In no cases were T1-weighted enhanced images superior to T2-weighted images. In two cases, T1-weighted images were superior to both T1-weighted enhanced and T2-weighted images. The authors conclude that gadopentetate dimeglumine did not provide much value in lesion detection above that obtained with T2-weighted images. They also conclude that T1-weighted images were occasionally superior to T1-weighted enhanced images and T2-weighted images because of loss of definition between fat and lesion on the latter.

Adolescent↗
PubMed2001

The efficacy of technetium-99m ciprofloxacin (Infecton) imaging in suspected orthopaedic infection: a comparison with sequential bone/gallium imaging.

Technetium-99m ciprofloxacin (Infecton) has recently become established as a new radiopharmaceutical for the imaging of infection. This study was performed to determine the value of Infecton imaging in demonstrating orthopaedic infection and to compare the results with bone/gallium imaging. Twenty-two patients (12 female, 10 male; mean age 51.7+/-16.8 years) with suspected orthopaedic infective conditions were included in the study. The patients underwent three scintigraphic studies in the following sequence: 740 MBq 99mTc-methylene diphosphonate (MDP) three-phase bone scintigraphy; at least 2 days later, 370 MBq Infecton scan at 1-4 h; and finally, 185 MBq gallium-67 scintigraphy. 67Ga imaging could not be performed on four patients. All images were blindly interpreted by two independent observers. The final diagnosis was made by consensus when the readings were different. Interpretation of the early and late Infecton images was made separately, with visual findings being classified according to a four-grade scale (0, +, ++, +++). Images graded 0 and +, and also those regions which showed a decrease in uptake grade on late images as compared with early images, were classified as negative for infection; grades ++ and +++ were classified as positive. Bone/gallium images were considered positive when the images were spatially incongruent or when gallium uptake was more intense than that of 99mTc-MDP. The diagnosis was confirmed by intraoperative microbiological or histological findings, or by the presence of gross purulence. The sensitivity of Infecton imaging was found to be 85%, the specificity 92% and the accuracy 88%, as compared to figures of 78%, 100% and 90%, respectively, for bone/gallium imaging. Although the two modalities showed a similar clinical yield, the easy availability of Infecton and the short investigation time make Infecton imaging the better option for the detection of orthopaedic infection.

Arthritis, Infectious↗
PubMed2003

Multiplanar and 3D imaging of the central airways: comparison of image quality and radiation dose of single-detector row CT and multi-detector row CT at differing tube currents in dogs.

PURPOSE: To compare in an animal model the image quality of multiplanar reformation and three-dimensional (3D) reconstruction images of the central airways by using single-detector row computed tomography (CT) and multi-detector row CT at varied tube currents and to compare radiation dose. MATERIALS AND METHODS: Five dogs each underwent five consecutive helical CT examinations (one single-detector row CT examination at 240 mA and four multi-detector row CT examinations at 240, 120, 40, and 20 mA), with 0.8-second gantry rotation time. Multiplanar reformation and 3D reconstruction images were created from each of the 25 CT acquisitions. The images were randomized and blindly reviewed with consensus agreement by three radiologists who graded image quality by using a five-point scale. In a separate review, the three radiologists independently used a four-point scale to rank the comparative image quality of the multi-detector row CT 3D images, while blinded to specific tube currents. The radiation doses were measured for each type of scan, and the relative radiation dose length products that were normalized to single-detector row CT values were used to compare radiation doses of the various CT techniques. Statistical analysis was performed with the Wilcoxon signed-rank test and the Friedman analysis of variance test. RESULTS: Image quality was consistently ranked higher for multi-detector row CT images than for single-detector row CT images (P =.03). Although there were no distinguishable differences between images obtained with multi-detector row CT at 240, 120, or 40 mA, images obtained with 20 mA were given a significantly (P =.04) lower relative rank (mean, 2.4) than those obtained with higher tube currents (mean, 1.4-1.7). Multi-detector row CT radiation doses were 1.64, 0.82, 0.27, and 0.14 (for 240-, 120-, 40-, and 20-mA multi-detector row CT, respectively) relative to the dose for 240-mA single-detector row CT. CONCLUSION: Multi-detector row CT is superior to single-detector row CT for multiplanar and 3D imaging of the central airways. Substantial dose reductions can be made, while maintaining high image quality.

Animals↗
PubMed1991

GRASE (gradient- and spin-echo) MR imaging: a new fast clinical imaging technique.

A novel technique of magnetic resonance (MR) imaging, which combines gradient-echo and spin-echo (GRASE) technique, accomplishes T2-weighted multisection imaging in drastically reduced imaging time, currently 24 times faster than spin-echo imaging. The GRASE technique maintains contrast mechanisms, high spatial resolution, and image quality of spin-echo imaging and is compatible with clinical whole-body MR systems without modification of gradient hardware. Image acquisition time is 18 seconds for 11 multisection body images (2,000/80 [repetition time msec/echo time msec]) and 36 seconds for 22 brain images (4,000/104). With a combination of multiple Hahn spin echoes and short gradient-echo trains, the GRASE technique overcomes several potential problems of echo-planar imaging, including large chemical shift, image distortions, and signal loss from field inhomogeneity. Advantages of GRASE over the RARE (rapid acquisition with relaxation enhancement) technique include faster acquisition times and lower deposition of radio-frequency power in the body. Breath holding during 18-second GRASE imaging of the upper abdomen eliminates respiratory-motion artifacts in T2-weighted images. A major improvement in T2-weighted abdominal imaging is suggested.

Abdomen↗
PubMed1991

Thallium reinjection after stress-redistribution imaging. Does 24-hour delayed imaging after reinjection enhance detection of viable myocardium?

BACKGROUND: Thallium reinjection immediately after conventional stress-redistribution imaging improves the detection of viable myocardium, as many myocardial regions with apparently "irreversible" thallium defects on standard 3-4-hour redistribution images manifest enhanced thallium uptake after reinjection. Because the 10-minute period between reinjection and imaging may be too short, the present study was designed to determine whether 24-hour imaging after thallium reinjection provides additional information regarding myocardial viability beyond that obtained by imaging shortly after reinjection. METHODS AND RESULTS: We studied 50 patients with chronic stable coronary artery disease undergoing exercise thallium tomography, radionuclide angiography, and coronary arteriography. Immediately after the 3-4-hour redistribution images were obtained, 1 mCi thallium was injected at rest, and images were reacquired at 10 minutes and 24 hours after reinjection. The stress, redistribution, reinjection, and 24-hour images were then analyzed qualitatively and quantitatively. Of the 127 abnormal myocardial regions on the stress images, 55 had persistent defects on redistribution images by qualitative analysis, of which 25 (45%) demonstrated improved thallium uptake after reinjection. At the 24-hour study, 23 of the 25 regions (92%) with previously improved thallium uptake by reinjection showed no further improvement. Similarly, of the 30 regions determined to have irreversible defects after reinjection, 29 (97%) remained irreversible on 24-hour images. These findings were confirmed by the quantitative analysis. The mean normalized thallium activity in regions with enhanced thallium activity after reinjection increased from 57 +/- 13% on redistribution studies to 70 +/- 14% after reinjection but did not change at 24 hours (71 +/- 14%). In regions with irreversible defects that were unaltered by reinjection, mean regional thallium activity did not differ from the reinjection to the 24-hour studies (57 +/- 17% and 58 +/- 17%, respectively). Twenty-four-hour imaging after reinjection showed improvement in only four of 35 irreversible regions (involving three of the 50 patients). CONCLUSIONS: These data indicate that thallium reinjection at rest after 3-4 hours of redistribution provides most of the clinically relevant information pertaining to myocardial viability in regions with apparently irreversible thallium defects. Hence, thallium reinjection may be used instead of 24-hour imaging in most patients in whom a persistent thallium defect is observed on conventional redistribution images.

Coronary Angiography↗
PubMed2005

Effectiveness of flexible noise control image processing for digital portal images using computed radiography.

The purpose of this study was to evaluate the clinical efficacy of flexible noise control (FNC) image processing in off-line computed radiography (CR) portal images. An observer study was designed to compare FNC with multiobjective frequency processing (MFP) in images acquired using a CR portal imaging device (CRPID). The image processing of MFP and FNC used the same data and required no additional irradiation of patients, and all images were printed on 10-bit grey-level dry laser film. Four radiation technologists and one oncologist served as observers and evaluated 40 sets of images for three different treatment sites: brain, lung and pelvis. Six to 10 anatomical landmarks were selected from each treatment site. Each observer was asked to rate each landmark in terms of its clinical visibility and rate the ease of making the pertinent verification in the MFP- and FNC-processed images. In the ratings of the visibility of landmarks and for the verification of treatment ports, FNC-processed images were more visible than MFP-processed images except for several landmarks in the anteroposterior (AP) pelvis such as the pubic symphysis. The visibility of landmarks in FNC-processed images was comparable with that in MFP-processed images. The verification of treatment ports using the CRPID with FNC was generally achievable. In conclusion, this study suggests that FNC is effective for image processing of CR portal images.

Algorithms↗
PubMed2003

Quality of digital pre-implant tomography: comparison of film-screen images with storage phosphor images at normal and low dose.

OBJECTIVES: The aim of this pilot study was to compare the image quality of a storage phosphor system with that of conventional film-screen in pre-implant conventional tomography, and to test the influence of radiation dose on image quality in the storage phosphor system. METHODS: Cross-sectional conventional tomographic images (Scanora) technique) were obtained on 11 patients with film-screen and with storage phosphor image plates (Digora) PCT) at normal and low doses. Ten observers graded the visibility of anatomical structures of importance for implant planning. A three-step rating scale was used, where -1 =worse, 0=equal and 1=better than the reference image. RESULTS: Although image quality was graded as equally good in the majority (59%) of images, the storage phosphor system scored significantly lower than film-screen (-0.37 vs 0.00, respectively) for all the images. Low dose storage phosphor images were rated significantly lower (-0.21) than normal dose images (0.00). CONCLUSIONS: In the majority of patients, anatomic structures of importance for implant planning are visualized equally well on storage phosphor and film-screen images. However, where differences do exist, storage phosphor images score lower than film-screen images. Dose reduction in the storage phosphor system had a negative influence on image quality.

Adult↗
PubMed2003

Coronary artery calcium scoring using ECG-gated multidetector CT: effect of individually optimized image-reconstruction windows on image quality and measurement reproducibility.

OBJECTIVE: We studied the effect of using individually optimized image-reconstruction windows on image quality and measurement reproducibility in coronary artery calcium scoring using ECG-gated multidetector CT (MDCT). SUBJECTS AND METHODS: In 50 patients, the coronary arteries were investigated twice with ECG-gated MDCT with 500-msec rotation time. Per scan, three sets of images were reconstructed, respectively, at an image-reconstruction window of 40%, 50%, and 60% of the R-R interval. Image quality was assessed, and the optimal image-reconstruction window per scan and per coronary territory was determined. The interscan variability of calcium mass measurements was calculated for different strategies (use of fixed image-reconstruction window [40%, 50%, or 60%] versus individually optimized image-reconstruction window). RESULTS: A significant improvement in image quality was obtained by selecting the best of three reconstructed data sets (mean image quality score, 4.4 vs 3.7; p < 0.001). Even with individually optimized image-reconstruction window values, we obtained high values for interscan variability (mean +/- SD, 27% +/- 22% vs 31% +/- 35% with a fixed image-reconstruction window). CONCLUSION: The use of individually optimized image-reconstruction windows leads to a significant improvement in image quality. However, interscan variability of calcium mass measurements remains high.

Aged↗
PubMedDate not supplied

Comparison of transaxial source images and 3-plane, thin-slab maximal intensity projection images for the diagnosis of coronary artery stenosis with using ECG-gated cardiac CT.

OBJECTIVE: We wanted to compare the transaxial source images with the optimized three plane, thin-slab maximum intensity projection (MIP) images from electrocardiographic (ECG)-gated cardiac CT for their ability to detect hemodynamically significant stenosis (HSS), and we did this by means of performing a receiver operating characteristic (ROC) analysis. MATERIALS AND METHODS: Twenty-eight patients with a heart rate less than 66 beats per minute and who were undergoing both retrospective ECG-gated cardiac CT and conventional coronary angiography were included in this study. The contrast-enhanced CT scans were obtained with a collimation of 16 x 0.75-mm and a rotation time of 420 msec. The transaxial images were reconstructed at the mid-diastolic phase with a 1-mm slice thickness and a 0.5-mm increment. Using the transaxial images, the slab MIP images were created with a 4-mm thickness and a 2-mm increment, and they covered the entire heart in the horizontal long axis (4 chamber view), in the vertical long axis (2 chamber view) and in the short axis. The transaxial images and MIP images were independently evaluated for their ability to detect HSS. Conventional coronary angiograms of the same study group served as the standard of reference. Four radiologists were requested to rank each image with using a five-point scale (1 = definitely negative, 2 = probably negative, 3 = indeterminate, 4 = probably positive, and 5 = definitely positive) for the presence of HSS; the data were then interpreted using ROC analysis. RESULTS: There was no statistical difference in the area under the ROC curve between transaxial images and MIP images for the detection of HSS (0.8375 and 0.8708, respectively; p > 0.05). The mean reading time for the transaxial source images and the MIP images was 116 and 126.5 minutes, respectively. CONCLUSION: The diagnostic performance of the MIP images for detecting HSS of the coronary arteries is acceptable and this technique's ability to detect HSS is comparable to that of the transaxial source images.

Adult↗
PubMed1989

[Clinical trial of 111In-antimyosin antibody imaging: (3) Comparison with 99mTc-pyrophosphate imaging].

Clinical value of 111In-antimyosin monoclonal antibody F ab (AM) was compared with 99mTc-pyrophosphate (PYP) in 13 patients with myocardial infarction and 3 patients with myocarditis. Following PYP injection, PYP imaging was performed 3 hours later. Immediately after PYP imaging, AM was administrated and AM images were obtained 48 hours later. Abnormal accumulation in the infarcted myocardium was observed in 11 patients (85%) on AM images but only in 3 patients (23%) on PYP images. All patients within 8 days after the onset of infarction showed abnormal uptake on both images. Of 5 patients with 1 to 2 weeks after the onset of infarction, abnormal uptake was observed in all of them on AM images but only in one of them on PYP imaging. Furthermore, of 6 patients with more than 2 weeks after the onset, AM imaging showed abnormal uptake in 4 (67%) but PYP imaging did not show abnormal uptake in any of them. Similarly. Of 3 patients with myocarditis, diffuse uptake in the myocardium ws observed in 2 of them on AM images but none of them showed abnormal uptake on PYP images. We conclude that AM imaging is a useful means for identifying not only acute stages but also subacute stages of myocardial necrosis where PYP imaging did not show any abnormality.

Adult↗
PubMed1999

Diagnostic and therapeutic consequences of repeat brain imaging and follow-up vascular imaging in stroke patients.

BACKGROUND AND PURPOSE: Recently, the diagnostic and therapeutic importance of repeat radiologic imaging in stroke patients has been questioned. The aim of this study was to show the therapeutic and diagnostic consequences of both repeat brain imaging and follow-up vascular imaging in this group of patients. METHODS: Neuroradiologic images and reports as well as clinical records of 317 patients (209 men and 108 women; mean age, 63 years) were reviewed retrospectively to determine the number of modifications made to the diagnosis and therapeutic regimen and to the classification of neuroradiologic findings. RESULTS: Two hundred thirty-eight repeat imaging procedures were performed in 171 patients. Of these, 76 were vascular imaging examinations (11 CT angiograms, 13 MR angiograms, 52 digital subtraction angiograms) and 162 were cross-sectional brain imaging studies (54 MR images, 108 CT scans). Forty of the 76 vascular imaging procedures and 77 of the 162 repeat cross-sectional brain imaging studies led to important diagnostic modifications with consequences for the patients' therapy and prognosis. CONCLUSION: Our study establishes that vascular imaging methods as well as cross-sectional brain imaging used as repeat imaging procedures in stroke patients can have important diagnostic and therapeutic consequences. We believe that repeat imaging in selected subgroups will be cost-effective.

Angiography, Digital Subtraction↗
PubMed2000

Transmission imaging for registration of ictal and interictal single-photon emission tomography, magnetic resonance imaging and electroencephalography.

A method developed for registration of ictal and interictal single-photon emission tomography (SPET), magnetic resonance imaging (MRI) and electroencephalography (EEG) is described. For SPET studies, technetium-99m ethyl cysteinate dimer (ECD) was injected intravenously while the patient was monitored on video-EEG to document the ictal or interictal state. Imaging was performed using a triple-head gamma camera equipped with a transmission imaging device using a gadolinium-153 source. The images (128x128 pixels, voxel size 3.7x3.7x3.6 mm3) were reconstructed using an iterative algorithm and postfiltered with a Wiener filter. The gold-plated silver electrodes on the patient's scalp were utilized as markers for registration of the ictal and interictal SPET images, as these metallic markers were clearly seen on the transmission images. Fitting of the marker sets was based on a non-iterative least squares method. The interictal SPET image was subtracted from the ictal image after scaling. The T1-weighted MPRAGE MR images with voxel size of 1.0x1.0x1.0 mm3 were obtained with a 1.5-T scanner. For registration of MR and subtraction SPET images, the external marker set of the ictal SPET study was fitted to the surface of the head segmented from MR images. The SPET registration was tested with a phantom experiment. Registration of ictal and interictal SPET in five patient studies resulted in a 2-mm RMS residual of the marker sets. The estimated RMS error of registration in the final result combining locations of the electrodes, subtraction SPET and MR images was 3-5 mm. In conclusion, transmission imaging can be utilized for an accurate and easily implemented registration procedure for ictal and interictal SPET, MRI and EEG.

Adolescent↗
PubMed2002

Factor analysis of medical image sequences improves evaluation of first-pass MR imaging acquisitions for myocardial perfusion.

RATIONALE AND OBJECTIVES: Factor analysis of medical image sequences (FAMIS) applied to gadolinium chelate-enhanced subsecond magnetic resonance (MR) imaging was evaluated as a postprocessing method for assessing myocardial perfusion in coronary artery disease (CAD). MATERIALS AND METHODS: To assess the accuracy of motion correction, five normal volunteers underwent MR imaging at rest. Thirteen patients with well-documented CAD and no myocardial infarction underwent MR imaging at rest and after dipyridamole administration. After motion correction, a single myocardial tissue factor (FAMISt) image was obtained with FAMIS for each raw MR imaging series acquisition. To evaluate how FAMIS could improve the analysis of these acquisitions, five readers visually assessed myocardial perfusion with FAMISt and raw MR images, and a multicase, multireader receiver operating characteristic analysis was performed. RESULTS: FAMISt images significantly improved detection of the perfusion defects when compared with raw MR images (P = .002). Areas under the receiver operating characteristic curves ranged from 0.84 to 0.93 with FAMISt images and from 0.48 to 0.85 with raw MR images. CONCLUSION: FAMIS applied to first-pass MR imaging series provided myocardial perfusion images that improve the objective assessment of myocardial perfusion in patients with CAD.

Adult↗
PubMed2001

Investigation of a direct conversion flat panel imager for portal imaging.

Flat-panel based x-ray imaging is an emerging new technology that could be used to significantly improve the quality of on-line portal imagers. There are two types of flat panel imagers: direct and indirect conversion. Previous experimental work on flat panel detectors for portal imaging application used indirect-conversion imagers. In this paper, a direct-conversion amorphous-selenium flat panel imager is investigated for application in portal imaging. The imager has an active imaging area of 14 in. X 17 in., i.e., 3072 X 2560 pixels each with dimensions 139 microm X 139 microm. The spatial frequency dependent detective quantum efficiency of the imager has been measured for a 6 MV beam and found to be amongst the best area detectors investigated for on-line portal imaging. Effects of changing pixel size, as well as possible improvements to both the image quality and convenience of operation are discussed. Comparison with an indirect conversion flat panel imager is also included.

Diagnostic Imaging↗
PubMed1986

Optimization of signal-to-noise ratio in calculated T1 images derived from two spin-echo images.

A simplified model relating signal intensity in an MR image to spin-lattice relaxation time (T1), repetition time (TR), number of signal averages and the average tip angle (-alpha) of the protons within the slice has been developed. This model has been used to select the optimal repetition times of two spin-echo images for a fixed total imaging time to maximize signal to noise in calculated T1 images. Theoretical predictions of T1 are virtually identical to spectroscopically measured values, and the relative noise (delta T1) in T1 images calculated from two measured spin-echo images is in good agreement with the theoretically predicted values of delta T1/T1. This model predicts that: (a) for a T1 of approximately 500 ms, the least T1 image noise is obtained with one of the spin-echo images collected with a TR of 400-500 ms. The longer the TR of the other spin-echo image, the lower the T1 image noise, but past a TR of approximately 1400 ms, T1 image signal/noise is optimized for the same total imaging time by increasing the number of averages in the shorter TR spin-echo image rather than increasing the TR of the second spin-echo image. (b) The error is reduced and the optimum TR1 is reduced as -alpha is increased from 63 to 90 degrees. (c) For a range of T1, optimal selection of TR1 and TR2 based on an intermediate value of T1, results in relatively little increase over optimal values in delta T1/T1 for the entire T1 range.

Humans↗
PubMed1992

What an image depicts depends on what an image means.

Previous research has shown that subjects visually imaging the classical ambiguous figures have great difficulty in reconstruing these images. To explain this finding, we propose that subjects' construal of their image strongly influences what is depicted in the image, leading to the inclusion of some aspects of an imaged figure and the exclusion of others. Thus, images of (supposedly) ambiguous figures may literally omit information necessary for the reconstrual. To test this claim, we asked subjects to form an image of the duck/rabbit figure, and then to compare their image to drawings that departed slightly from the original figure. We hypothesized that subjects would have a clear image of the side of the figure they understood as the "face" (the left side if the image is understood as a duck, the right side for the rabbit). Conversely, subjects would have only a vague image of the "back" of the head. Consequently, in comparing their image to test stimuli, subjects should be able to detect variations in the contour of the "face," but not in the contour of the "back" of the animal's head. These predictions were confirmed, strongly suggesting that the construal of an image does dictate what is depicted within the image.

Attention↗