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PubMed2003

The effect of perceptual distinctiveness on the prospective and retrospective components of prospective memory in young and old adults.

In two experiments, the effect of perceptual distinctiveness of cues on prospective memory performance was examined. Young and older adults completed a visual search task with embedded prospective memory instructions. On each trial, participants were asked to indicate the position of a target letter in a letter string, unless either of two letters previously identified as prospective memory cues was presented. Each prospective cue was associated with a specific response. Perceptual distinctiveness was manipulated by spatially displacing a single letter. The prospective component (successful detection of the cue) and the retrospective memory component (recalling the correct response when a cue is detected) were measured separately. Perceptual displacement of cues modulated performance of the prospective component but not the retrospective component. Young adults successfully detected a larger proportion of cues (prospective component) than older adults. However, there were minimal effects of age and no effect of cue displacement on participants' ability to recall the intention once they detected a cue (retrospective component performance). Results are discussed within the context of current theoretical models of prospective memory.

Adolescent↗
PubMed2000

Retrospective shading correction based on entropy minimization.

Shading is a prominent phenomenon in microscopy, manifesting itself via spurious intensity variations not present in the original scene. The elimination of shading effects is frequently necessary for subsequent image processing tasks, especially if quantitative analysis is the final goal. While most of the shading effects may be minimized by setting up the image acquisition conditions carefully and capturing additional calibration images, object-dependent shading calls for retrospective correction. In this paper a novel method for retrospective shading correction is proposed. Firstly, the image formation process and the corresponding shading effects are described by a linear image formation model, which consists of an additive and a multiplicative parametric component. Secondly, shading correction is performed by the inverse of the image formation model, whose shading components are estimated retrospectively by minimizing the entropy of the acquired images. A number of tests, performed on artificial and real microscopical images, show that this approach is efficient for a variety of differently structured images and as such may have applications in and beyond the field of microscopical imaging.

Alloys↗
PubMed2003

Retrospective and prospective persistent activity induced by Hebbian learning in a recurrent cortical network.

Recordings from cells in the associative cortex of monkeys performing visual working memory tasks link persistent neuronal activity, long-term memory and associative memory. In particular, delayed pair-associate tasks have revealed neuronal correlates of long-term memory of associations between stimuli. Here, a recurrent cortical network model with Hebbian plastic synapses is subjected to the pair-associate protocol. In a first stage, learning leads to the appearance of delay activity, representing individual images ('retrospective' activity). As learning proceeds, the same learning mechanism uses retrospective delay activity together with choice stimulus activity to potentiate synapses connecting neural populations representing associated images. As a result, the neural population corresponding to the pair-associate of the image presented is activated prior to its visual stimulation ('prospective' activity). The probability of appearance of prospective activity is governed by the strength of the inter-population connections, which in turn depends on the frequency of pairings during training. The time course of the transitions from retrospective to prospective activity during the delay period is found to depend on the fraction of slow, N-methyl-d-aspartate-like receptors at excitatory synapses. For fast recurrent excitation, transitions are abrupt; slow recurrent excitation renders transitions gradual. Both scenarios lead to a gradual rise of delay activity when averaged over many trials, because of the stochastic nature of the transitions. The model reproduces most of the neuro-physiological data obtained during such tasks, makes experimentally testable predictions and demonstrates how persistent activity (working memory) brings about the learning of long-term associations.

Animals↗
PubMed2000

[Value of retrospective assessment of the Epworth Sleepiness Scale after long-term CPAP therapy in obstructive sleep apnea disorder]].

BACKGROUND: Daytime-sleepiness is the main symptom of the obstructive sleep apnoea syndrome. Standarized questionnaires (e.g. the Epworth sleepiness scale = ESS) have become useful diagnostic tools. In this study we investigated wether there is a difference between the estimation of initial "pre-treatment" daytime sleepiness (by ESS) compared to the retrospective ESS score after implementation of CPAP therapy. PATIENTS AND METHODS: We included 46 patients (RDI 39/h +/- 20.2, CPAP pressure 8 cm/H2O +/- 1.7, daily use of 5.8 h +/- 1.8, RDI with CPAP 7.6/h +/- 5.3). We examined the ESS score before CPAP-therapy (ESS-base) in comparison to the retrospective estimation of the initial conditions after one year of CPAP-therapy (ESS-retro). RESULTS: There was no statistical significant difference between ESS base (11.7 +/- 4.6) and ESS-retro (12.7 +/- 5.2). ESS decreased to 5.4 +/- 3.7 by CPAP-therapy (p < 0.01). CONCLUSION: From a chronological point of view ESS is a consistent parameter of daytime sleepiness. Hence, the retrospective estimation of pre-CPAP ESS can be considered as a useful diagnostic tool.

Adult↗
PubMed2003

[Quantification of cardiac function with multislice spiral CT using retrospective EKG-gating: comparison with MRI].

PURPOSE: To quantify left ventricular function derived from retrospectively ECG-gated multislice spiral CT (MSCT) data sets in comparison to MRI. MATERIALS AND METHODS: In 16 patients (14 males, 2 females, mean age 56.8 +/- 11.5 years), retrospectively ECG-gated MSCT angiography of the coronary arteries and breath-hold steady state free precession cine MRI were performed. From MSCT data-sets, 20 axial image series were reconstructed every 5 % of the RR interval. Multiplanar images were reformatted in the short axis orientation from axial images. End-systolic and end-diastolic images were selected. From these images end-systolic volume (ESV), end-diastolic volume (EDV) and stroke volume (SV) as well as the ejection fraction (EF) and myocardial mass (MM) were determined using the Simpson's method and compared with MRI. Furthermore, image quality was assessed for both imaging modalities using a four point grading scale. RESULTS: All parameters were found to have an excellent correlation between MSCT and MRI data (Pearson's correlation coefficient 0.95 - 0.99), without clinically relevant differences between both modalities. On average, the difference between both methods was 0.5 ml for ESV, 0.8 ml for EDV, 1.3 ml for SV, 0.9 % for EF and 2.3 g for MM. Image quality was slightly better for MRI (1.5 +/- 0.65) than for MSCT (1.64 +/- 0.74). CONCLUSION: Retrospectively ECG-gated MSCT angiography can not only visualize the coronary arteries but also enables precise quantification of the left ventricular function from the same MSCT data set.

Aged↗
PubMed2004

Retrospectively ECG-gated multi-detector row CT of the chest: does ECG-gating improve three-dimensional visualization of the bronchial tree?

PURPOSE: To determine the impact of retrospectively ECG-gated multi-detector row CT (MDCT) on three-dimensional (3D) visualization of the bronchial tree and virtual bronchoscopy (VB) as compared to non-ECG-gated data acquisition. MATERIALS AND METHODS: Contrast-enhanced retrospectively ECG-gated and non-ECG-gated MDCT of the chest was performed in 25 consecutive patients referred for assessment of coronary artery bypass grafts and pathology of the ascending aorta. ECG-gated MDCT data were reconstructed in diastole using an absolute reverse delay of - 400 msec in all patients. In 10 patients additional reconstructions at - 200 msec, - 300 msec, and - 500 msec prior to the R-wave were performed. Shaded surface display (SSD) and virtual bronchoscopy (VB) for visualization of the bronchial segments was performed with ECG-gated and non-ECG-gated MDCT data. The visualization of the bronchial tree underwent blinded scoring. Effective radiation dose and signal-to-noise ratio (SNR) for both techniques were compared. RESULTS: There was no significant difference in visualizing single bronchial segments using ECG-gated compared to non-ECG-gated MDCT data. However, the total sum of scores for all bronchial segments visualized with non-ECG-gated MDCT was significantly higher compared to ECG-gated MDCT (P < 0.05). The summary scores for visualization of bronchial segments for different diastolic reconstructions did not differ significantly. The effective radiation dose and the SNR were significantly higher with the ECG-gated acquisition technique (P < 0.05). CONCLUSION: The bronchial tree is significantly better visualized when using non-ECG-gated MDCT compared to ECG-gated MDCT. Additionally, non-ECG-gated techniques require less radiation exposure. Thus, the current retrospective ECG-gating technique does not provide any additional benefit for 3D visualization of the bronchial tree and VB.

Adult↗
PubMed2006

Investigation of retrospective respiratory gating techniques for acquisition of thin-slice 4D-Multidetector-computed Tomorgraphy (MDCT) of the lung: Feasibility study in a large animal model.

Respiratory gated 3D-MDCT acquisition of the whole chest over time (4D-MDCT) allow retrospective reconstruction of raw data at any point of the respiratory cycle might be beneficial in severely ill or sedated patients. Aim of this feasibility study was to investigate 2 prototype devices as input for retrospective respiratory gating in order to calculate lung volumes (LVs) and mean lung densities (MLDs) over time. Sixteen-row MDCT data were acquired in 5 ventilated pigs using a laser sensor and charge-coupled devine (CCD) camera and retrospectively reconstructed at every 10% of the respiratory cycle. Semiautomatic segmentation of the 3D data sets was performed, and LV and MLD were calculated. Data acquisition was successful in all cases. The mean difference of LV between maximum inspiration and expiration was 246 and 240 mL (laser and CCD, respectively). The mean difference of MLD between inspiration and expiration was 70 (laser) and 67 (CCD) HU. The lowest MLD was found at the beginning of the respiratory cycle (0%) for laser, and at 90% for CCD. Both gating devices allowed for reliable 4D-MDCT image acquisition. No differences were found for calculated LV and MLD, whereas the respiratory cycle was more precisely detected using the laser based gating device.

Animals↗
PubMed2002

Higher-order retrospective revaluation in human causal learning.

Previous studies demonstrated that participants will retrospectively adjust their ratings about the relation between a target cue and an outcome on the basis of information about the causal status of a competing cue that was previously paired with the target cue. We demonstrate that such retrospective revaluation effects occur not only for target cues with which the competing cue was associated directly, but also for target cues that were associated indirectly with the competing cue. These second-order and third-order retrospective revaluation effects are compatible with certain implementations of the probabilistic contrast model and with a modified, extended comparator model, but cannot be explained on the basis of a revised Rescorla-Wagner model or a revised SOP model.

Adult↗
PubMed2003

Can we rely on retrospective pain assessments?

The objective of this paper was to study whether subjects in a workplace setting are able to assess the intensity of musculoskeletal pain retrospectively for a period of 3 months. The intensity of average pain and maximum pain in eight anatomic regions was assessed on a numeric rating scale. The results of 12 consecutive weekly pain recordings were compared with a final retrospective assessment of pain intensity covering the same 3-month period (119 subjects). The degree of agreement was good or excellent. The subjects were able to distinguish between the worst complaints and average complaints, and the subjective perception of aggravations or improvements corresponded to the direction of a change in score. Current complaint status slightly influenced the memory of pain. The reproducibility of the questionnaire was also assessed and showed kappa coefficients between 0.44 and 0.91 (36 subjects). The results suggest that subjects are able to accurately recall and rate the severity of pain or discomfort for a period of 3 months. These findings are of practical importance in epidemiologic studies, because they imply that retrospective reports on pain intensity are sufficiently reliable.

Adult↗
PubMedDate not supplied

Retrospective registration of PET and MR brain images: an algorithm and its stereotactic validation.

OBJECTIVE: We present a validation study of an algorithm for retrospective registration of PET and MR brain images. MATERIALS AND METHODS: This algorithm involves two steps. In the first step, the two volumes are reformatted by aligning their interhemispheric fissure planes (midsagittal plane). In the second step, the corresponding planes parallel to the midsagittal plane are further aligned in the reformatted volumes to produce a 3D rigid body registration of the two original volumes. It is an efficient algorithm because both steps are performed in 2D spaces, and in each step only a small number of landmarks are required. A user-friendly system has been implemented to facilitate easy and fast processing of registration and reformatting of image volumes. The accuracy of this algorithm is validated using clinical scans of neurosurgical patients with a stereotaxic frame attached to their skull. The frame-based stereotaxic system provides an effective method for transforming image coordinates from different image volumes into a common coordinate system. This common coordinate system is used for assessing the spatial correspondence of each pixel in the registered image volumes. Validation using the stereotaxic image volumes enables objective estimation of retrospective registration accuracy. RESULTS: Analysis of 11 MR/PET image pairs indicates that our registration method not only is efficient but also provides adequate accuracy for most clinical evaluation of PET studies. CONCLUSION: We have implemented and validated an efficient algorithm for retrospective registration of PET and MR brain images.

Adult↗
PubMed1993

Coping behaviour and degree of discrepancy between retrospective and prospective self-ratings of change in quality of life in type 1 diabetes mellitus.

Quality of life and metabolic control were examined in 74 adults with Type 1 diabetes mellitus in 1988. Sixty-six of the persons were followed up in 1990 with the aim of studying more closely the subgroup that showed a 'major' discrepancy between 'retrospective' and 'prospective' quality of life change ratings. 'Prospective' quality of life change was defined as the difference in assessed quality of life status between 1990 and 1988. 'Retrospective' quality of life change was assessed directly by subjects in 1990 covering the same time period. Data on quality of life, well-being, sociodemographics and metabolic control were collected on both occasions. Recent life-change events and long-term complications were also recorded in 1990. Subjects with 'major' discrepancy reported greater retrospective quality of life improvement, higher quality of life, and greater well-being, as well as lesser occurrence of negative and greater occurrence of positive recent life-change events, than did those with 'minor' discrepancy, despite their exhibiting poorer metabolic control and a higher prevalence of incipient nephropathy. The results are discussed in terms of possible coping and defence strategies.

Adaptation, Psychological↗
PubMed2006

Treatment of headaches in the ED with lower cervical intramuscular bupivacaine injections: a 1-year retrospective review of 417 patients.

OBJECTIVE: The primary objective of this retrospective chart review is to describe 1 year's experience of an academic emergency department (ED) in treating a wide spectrum of headache classifications with intramuscular injections of 0.5% bupivacaine bilateral to the spinous process of the lower cervical vertebrae. BACKGROUND: Headache is a common reason that patients present to an ED. While there are a number of effective therapeutic interventions available for the management of headache pain, there clearly remains a need for other treatment options. The intramuscular injection of 1.5 mL of 0.5% bupivacaine bilateral to the sixth or seventh cervical vertebrae has been used to treat headache pain in our facility since July 2002. The clinical setting for the study was an academic ED with an annual volume of over 75,000 patients. METHODS: We performed a retrospective review of over 2805 ED patients with the discharge diagnosis of headache and over 771 patients who were coded as having had an anesthetic injection between June 30, 2003 and July 1, 2004. All adult patients who had undergone paraspinous intramuscular injection with bupivacaine for the treatment of their headache were gleaned from these 2 larger databases and were included in this retrospective chart review. A systematic review of the medical records was accomplished for these patients. RESULTS: Lower cervical paraspinous intramuscular injections with bupivacaine were performed in 417 patients. Complete headache relief occurred in 271 (65.1%) and partial headache relief in 85 patients (20.4%). No significant relief was reported in 57 patients (13.7%) and headache worsening was described in 4 patients (1%). Overall a therapeutic response was reported in 356 of 417 patients (85.4%). Headache relief was typically rapid with many patients reporting complete headache relief in 5 to 10 minutes. Associated signs and symptoms such as nausea, vomiting, photophobia, phonophobia, and allodynia were also commonly relieved. CONCLUSION: Our observations suggest that the intramuscular injection of small amounts of 0.5% bupivacaine bilateral to the sixth or seventh cervical spinous process appears to be an effective therapeutic intervention for the treatment of headache pain in the outpatient setting.

Adult↗
PubMed1980

Psychogenic psychoses. A retrospective study with special reference to clinical course and prognosis.

The study comprises a retrospective evaluation of case records of 220 patients admitted for the first time with psychogenic psychosis with special reference to clinical course and prognosis within a period of 13--14 years. The reliability of the diagnosis at the time of the first admission is about 60% when the evaluation is based on positive criteria for psychosis. If the psychogenic psychoses are divided into subgroups, the reliability of the diagnosis of psychogenic affective psychoses is about 30%, whereas it is over 90% for psychogenic confusional psychoses and psychogenic paranoid psychoses. If subsequent cases of other functional psychoses (manic-depressive psychosis and schizophrenia) are subtracted, the diagnostic reliability is 50% (111 of 220 cases), which represents the number of retrospectively verified psychogenic psychoses. The frequency of recurrence of psychogenic psychosis was 18% (40), corresponding to 36% of psychogenic psychoses verified by retrospective evaluation (111 of 220 cases). The recurrences were mainly homologous, as heterologous recurrences developed only among the psychogenic affective psychoses (slightly less than half of the recurrences in question). Schizophrenia developed in only 10% (23), and subsequent episodes of manic-depressive psychosis occurred in 8% (18). The stability of psychogenic psychosis on recurrence of functional psychosis was 49% expressed in relation to all subsequent cases of functional psychosis. The over-all prognosis for the psychogenic/reactive psychosis is thus good as regards subsequent mental disease. Chronic functional psychosis (schizophrenia) developed in only 10% (and in less than 20% if the prognosis is assessed on the basis of the reliability of the diagnosis at the time of the first admission (about 60%)). However, in the group of psychogenic/reactive psychoses as a whole an overmortality of 100% was observed in the course of the 14 years, highest in the younger age groups.

Adult↗
PubMed2006

Reducing respiratory motion artifacts in positron emission tomography through retrospective stacking.

Respiratory motion artifacts in positron emission tomography (PET) imaging can alter lesion intensity profiles, and result in substantially reduced activity and contrast-to-noise ratios (CNRs). We propose a corrective algorithm, coined "retrospective stacking" (RS), to restore image quality without requiring additional scan time. Retrospective stacking uses b-spline deformable image registration to combine amplitude-binned PET data along the entire respiratory cycle into a single respiratory end point. We applied the method to a phantom model consisting of a small, hot vial oscillating within a warm background, as well as to 18FDG-PET images of a pancreatic and a liver patient. Comparisons were made using cross-section visualizations, activity profiles, and CNRs within the region of interest. Retrospective stacking was found to properly restore the lesion location and intensity profile in all cases. In addition, RS provided CNR improvements up to three-fold over gated images, and up to five-fold over ungated data. These phantom and patient studies demonstrate that RS can correct for lesion motion and deformation, while substantially improving tumor visibility and background noise.

Algorithms↗
PubMed2001

Detection of coronary artery stenoses by contrast-enhanced, retrospectively electrocardiographically-gated, multislice spiral computed tomography.

BACKGROUND: Multislice spiral computed tomography (MSCT) with retrospectively ECG-gated image reconstruction permits coronary artery visualization. We investigated the method's ability to identify high-grade coronary artery stenoses and occlusions. METHODS AND RESULTS: A total of 64 consecutive patients were studied by MSCT (4x1 mm cross-sections, 500-ms rotation, table feed 1.5 mm/rotation, intravenous contrast agent, retrospectively ECG-gated image reconstruction). All coronary arteries and side branches with a luminal diameter >/=2.0 mm were assessed concerning evaluability and the presence of high-grade stenoses (>70% diameter stenosis) or occlusions. Results were compared with quantitative coronary angiography. Of 256 coronary arteries (left main, left anterior descending, left circumflex and right coronary artery, including their respective side branches), 174 could be evaluated (68%). In 19 patients (30%), all arteries were evaluable. Artifacts caused by coronary motion were the most frequent reason for unevaluable arteries. Overall, 32 of 58 high-grade stenoses and occlusions were detected by MSCT (58%). In evaluable arteries, 32 of 35 lesions were detected, and the absence of stenosis was correctly identified in 117 of 139 arteries (sensitivity, 91%; specificity, 84%). If analysis was extended to all stenoses with >50% diameter reduction, sensitivity was 85% (40 of 47) and specificity was 76% (96 of 127). CONCLUSIONS: MSCT with retrospective ECG gating permits the detection of coronary artery stenoses with high accuracy if image quality is sufficient, but its clinical use may presently be limited due to degraded image quality in a substantial number of cases, mainly due to rapid coronary motion.

Aged↗
PubMed2001

An evaluation of the use of retrospectively acquired preoperative AOFAS clinical rating scores to assess surgical outcome after elective foot and ankle surgery.

The use of retrospectively acquired preoperative AOFAS rating scores in clinical research to assess the outcomes of elective foot and ankle surgery has not been validated. The data obtained utilizing this methodology may misrepresent the results and lead to spurious conclusions. This investigation compared preoperative AOFAS Ankle-Hindfoot scores obtained before and after surgery from patients who had undergone elective surgery to determine if retrospectively acquired scores match those collected prospectively. Only two out of 47 patients (4%) recalled identical AOFAS scores. The mean difference between the preoperative scores (preoperative score obtained after surgery minus preoperative score obtained before surgery) was -5.3 points. Fifteen patients (32%) had preoperative scores that differed by 20 points or more. Kappa statistics found little agreement among the five elements that comprised the two preoperative scores when responses obtained before and after surgery were compared to one another. The results suggest that preoperative clinical rating scores obtained after elective surgery are a poor predictor of the patient's preoperative condition and that studies which employ retrospectively acquired preoperative AOFAS clinical rating scores may overestimate the benefit of surgery.

Adult↗
PubMed2006

Three-dimensional drip infusion CT cholangiography in patients with suspected obstructive biliary disease: a retrospective analysis of feasibility and adverse reaction to contrast material.

BACKGROUND: Computed Tomography Cholangiography (CTC) is a fast and widely available alternative technique to visualise hepatobiliary disease in patients with an inconclusive ultrasound when MRI cannot be performed. The method has previously been relatively unknown and sparsely used, due to concerns about adverse reactions and about image quality in patients with impaired hepatic function and thus reduced contrast excretion. In this retrospective study, the feasibility and the frequency of adverse reactions of CTC when using a drip infusion scheme based on bilirubin levels were evaluated. METHODS: The medical records of patients who had undergone upper abdominal spiral CT with subsequent three-dimensional rendering of the biliary tract by means of CTC during seven years were retrospectively reviewed regarding serum bilirubin concentration, adverse reaction and presence of visible contrast media in the bile ducts at CT examination. In total, 153 consecutive examinations in 142 patients were reviewed. RESULTS: Contrast media was observed in the bile ducts at 144 examinations. In 110 examinations, the infusion time had been recorded in the medical records. Among these, 42 examinations had an elevated bilirubin value (>19 micromol/L). There were nine patients without contrast excretion; 3 of which had a normal bilirubin value and 6 had an elevated value (25-133 micromol/L). Two of the 153 examinations were inconclusive. One subject (0.7%) experienced a minor adverse reaction - a pricking sensation in the face. No other adverse effects were noted. CONCLUSION: We conclude that drip infusion CTC with an infusion rate of the biliary contrast agent iotroxate governed by the serum bilirubin value is a feasible and safe alternative to MRC in patients with and without impaired biliary excretion. In this retrospective study the feasibility and the frequency of adverse reactions when using a drip infusion scheme based on bilirubin levels has been evaluated.

Journal Article↗
PubMed2003

Adoption of retrospective Medicare maximization billing practices by state Medicaid home care programs.

Home care services funded by Medicare and Medicaid grew rapidly throughout most of the 1990s. During this period some state Medicaid programs transferred costs for home care claims to the Medicare program to reduce their liability and increase beneficiary access to Medicare coverage. This article reports the findings of the first national study of these Medicare maximization billing practices for home care services. Primary data were collected to determine which states conduct retrospective Medicare billing practices and the amounts recovered from Medicare. Our analysis indicates that seven states recovered as much as dollar 265 million from Medicare in state and federal dollars during the 1990s. Ratios of recovered expenditures-to-costs incurred for retrospective billing practices conducted in Connecticut, New York, and Massachusetts are between 5:1 and 7:1. While retrospective billing practices may aid states in reducing Medicaid outlays and potentially help dual Medicare beneficiaries gain coverage for their home care claims, they increase Medicare expenditures for home care at a time of concern for the long-term financial viability of Medicare and illustrate the need for reforming our national long-term care financing policy.

Costs and Cost Analysis↗