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1.
BACKGROUND AND PURPOSE: The role of single-photon emission CT (SPECT) in the prognosis of cerebral infarction is controversial, but most studies report that SPECT using a variety of radiopharmaceutical agents gives useful prognostic information. Only one study has questioned whether acute perfusion deficits independently add to a valid clinical prognostic score. This study was limited to middle cerebral artery territory infarcts and was negative. We present data on the prognostic utility of SPECT using 99mTc-hexamethylpropyleneamine oxime (HMPAO) in cerebral infarction, unselected by site. METHODS: Fifty consecutive unselected patients admitted to the hospital with acute cerebral infarction, of whom 10 died and 7 withdrew, had SPECT performed serially at onset and at 1 week and 3 months after stroke onset using 99mTc-HMPAO and the NOVO 810 dedicated high-resolution head tomograph. Clinical severity at presentation and outcome was measured with the Canadian Neurological Scale and the Barthel Index. Infarct volumes were measured from both the SPECT and CT scans. The data for the 43 subjects who completed the study or died were evaluated to determine the most powerful prognostic measures. Predictors were the Canadian Neurological Scale score at onset and 1 week, the Barthel Index at 1 week, the CT infarct volume typically done between 3 and 7 days after stroke onset, and the infarct volumes at the first and second SPECT. Outcome measures were the Canadian Neurological Scale score and Barthel Index score at 3 months, scored as zero for those patients who died. RESULTS: The clinical prognostic indicators correlated with the outcome measures, with coefficients between .617 and .821 (P < .0006 in all cases). The Canadian Neurological Scale score measured at 1 week was the best of these. Infarct volumes measured from SPECT correlated less well (coefficients between -.518 and -.683, P < .0019 in all cases). CT infarct volume was the poorest predictor. Although SPECT infarct volumes predicted outcome, they did so less well than clinical examination. Spontaneous infarct reperfusion did not affect outcome. CONCLUSIONS: Although the measurement of infarct volume on SPECT using 99mTc-HMPAO provides a predictor of stroke outcome, it is not a better predictor than the Canadian Neurological Scale score.  相似文献   

2.
A. S. Kaufman (1994) recommends that the Symbol Search, an optional subtest to the WISC-III, be substituted for Coding in the calculation of WISC-III Performance and Full Scale IQ scores. Conversion tables have been published for use with American norms. The authors provide conversion tables for the Canadian-normed WISC-III. The standardization sample consisted of a representative group of 1,100 English-speaking Canadian children. The conversion tables are provided. These tables allow Canadian WISC-III examiners to substitute Symbol Search for Coding in the calculation of the Performance and Full Scale IQ scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

3.
This study equates the physical functioning subscales of the Medical Outcomes Study Short Form 36 (SF36) and the Louisiana State University Health Status Instruments (LSU HSI). Data from the SF36's 10-item physical functioning scale, the PF10, and the LSU HSI's 29-item Physical Functioning Scale (PFS), were fit to separate and mixed Rasch rating scale models. Data were provided by a convenience sample of 285 patients waiting for appointments in a public hospital general medicine clinic. Difficulty estimates for a subset of similar items from the two instruments were highly correlated (.95), indicating that the items from the two scales are working together to measure the same variable. The measures from the two equated instruments correlate .80 (.86 when disattenuated for error). Of the two instruments, the PFS's error is lower, model fit is better, and reliability coefficients are higher. Both instruments measure physical functioning, and can do so in a common unit of measurement. Conversion tables are provided for transforming raw scores from either instrument into the common metric.  相似文献   

4.
BACKGROUND AND PURPOSE: We used transcranial magnetic stimulation of the motor cortex to evaluate the functional state of corticospinal pathways innervating the first dorsal interosseous muscle of the hand in 26 patients suffering from a first-ever ischemic stroke in the middle cerebral artery territory. METHODS: All patients had complete hand palsy and were tested within the first 24 hours from stroke onset. Patients were also tested clinically with the MRC, Rankin, and National Institutes of Health (NIH) stroke scales at day 1 and with MRC and NIH scales and the Barthel Index at day 14. Electrophysiological testing was repeated at day 14. Patients were divided into three subgroups according to the amplitude of the maximal response (motor evoked potential [MEP]) evoked at day 1. RESULTS: After 2 weeks, all 6 patients with initial MEPs > 5% maximum motor response (Mmax) showed some first dorsal interosseous muscle motor function recovery, whereas 19 of 20 patients with initially absent or small (< 5% Mmax) MEPs were left with complete hand palsy. There were strong positive correlations between MEP amplitude at day 1 and MRC and Barthel Index scores at day 14. However, measurement of central motor conduction time proved to be of little prognostic value. CONCLUSIONS: We conclude that early-performed transcranial magnetic stimulation is a valuable prognostic tool for motor recovery from stroke and that relatively preserved MEP amplitude shortly after stroke is a better prognostic factor than normal central motor conduction time.  相似文献   

5.
The stroke patient is acutely ill within minutes of symptom onset. Typically, he or she is awake and thus requires a focal neurologic exam to evaluate vision, movement, sensation and language. With the advent of acute stroke treatments that need to be rapidly implemented, it is critical that the nurse be able to assess patients and relay the information accurately and efficiently to other members of the health care team. Performing and documenting the awake stroke exam in the most efficient and useful manner is key to the nursing care of the stroke patient. The National Institutes of Health Stroke Scale (NIHSS) is a systematic assessment tool designed to measure the neurologic deficits most often seen with acute stroke patients. Originally designed as a research tool, it is a nonlinear ordinal scale, with possible scores ranging form 0-42. Exam performance has been timed to take 5-8 minutes. Use of the NIHSS includes documentation of neurologic status and outcome, data collection for planning safe nursing care and standardization of information exchanges between nurse caregivers and other health care professionals.  相似文献   

6.
This study was designed to assess the return to work, the poststroke depression and the quality of life after a cerebral infarction in young adults and was conducted on 71 consecutive young patients (aged 15-45 years) affected by a cerebral infarct who were hospitalized for the first time and discharged at least 1 year before the study. Data about risk factors, etiology, side and territory of stroke, social characteristics of the patient (age, sex, profession, educational level, family situation), poststroke seizures, recurrent stroke, other vascular events, and deaths were collected. Neurological deficits were graded with the National Institutes of Health (NIH) Stroke Scale. Poststroke depression (PSD) was quantified using the DSM-IIIR criteria and the Montgomery Asberg Depression Rating Scale. Outcomes were rated with the Ranking Scale, the Barthel Index and the Glasgow Outcome Scale. Quality of life was assessed with the Sickness Impact Profile. Follow-up information was obtained by interview and neurological examination. Follow-up information was obtained in 65 patients at a mean of 31.7 +/- 13.0 (range 12-59) months, as 2 patients died and 4 were lost to follow-up and were thus excluded from this study. Poststroke seizures occurred in 7 patients (10.8%) and recurrent strokes in 4 patients (6.2%), but none were fatal. The outcome after stroke among survivors was usually good, since more than two-thirds of the patients (69.8%) reported no problem, 11.1% moderate handicap and one-fifth major handicap. Forty-six patients (73%) returned to work: the time period ranging from several days after stroke to 40 months, with a mean of 8 months. However, adjustments in their occupation were necessary for 12 patients (26.1%). PSD was common, since 48.31% of the patients were classified as depressed. PSD was associated with the localization of the infarct (carotid territory), a severe disability, a bad general outcome, and an absence of return to work. Their opinion about their quality of life was negative among approximately 30% of the patients, especially in emotional and alertness behaviors. social interaction, recreation and pastimes. The general outcome after cerebral infarct in young adults is usually good. However, the risk of a PSD is high, and only half of the patients had returned to their previous work. A remaining psychosocial handicap and depression of sexual activity impaired the quality of life. In multivariate analysis, a low NIH score at admission is a significant predictor for return to work, the absence of PSD, and a good quality of life.  相似文献   

7.
OBJECTIVES: (1) To determine whether and how outcome measurements in the ECASS trial are influenced by a shorter time window (0-3 vs. 3-6 h) between onset of symptoms and start of thrombolytic therapy using recombinant tissue plasminogen activator (rt-PA) in acute ischemic stroke. (2) To discuss the results of the ECASS 0- to 3-hour cohort with the results of the National Institute of Neurological Disorders and Stroke Study (NINDSS). DESIGN AND ANALYSIS: Analysis of the 0- to 3-hour and the 3- to 6-hour cohort in accordance with the ECASS protocol. Comparative analysis of the ECASS and NINDSS results following the NINDSS protocol using dichotomized endpoints. MAIN OUTCOME MEASURES: Primary endpoints: modified Rankin Scale, Barthel Index; secondary endpoints: combined Barthel/Rankin, long-term Scandinavian Stroke Scale, National Institutes of Health Stroke Scale, mortality at 30 and 90 days, occurrence of intracranial hemorrhage. NINDS trial endpoint: favorable outcome as defined in the NINDS trial. RESULTS: In ECASS, 87 patients were randomized within 3 h of stroke onset. Differences in favor of rt-PA treatment can be found for all primary and secondary outcome measures in the ECASS 0- to 3-hour cohort, except for mortality at day 30, which is somewhat higher in the rt-pA-treated group. However, due to the small sample size, the differences do not reach statistical significance. Early infarct signs (as defined by the ECASS protocol) are found as early as 2 h after stroke onset. Parenchymal hemorrhages are found significantly more often among rt-PA-treated patients. The results in the ECASS 0- to 3-hour cohort fit well with the results in NINDSS. CONCLUSION: Data from the 3-hour ECASS cohort support the efficacy of early thrombolytic therapy in acute hemispheric stroke patients. Comparing bleeding complications between the ECASS and NINDSS is difficult because of differences in the definition and occurrence of hemorrhagic events.  相似文献   

8.
BACKGROUND AND PURPOSE: We performed a retrospective analysis of the prognostic factors in patients treated with local intra-arterial thrombolysis (LIT). The purpose of this study was to evaluate the safety and efficacy of LIT using urokinase in patients with acute ischemic stroke of the anterior or posterior circulation and to determine the influence of clinical and radiological parameters on outcome. METHODS: Forty-three patients were treated with LIT using urokinase (median dose, 0.75x10(6) IU). The median National Institutes of Health Stroke Scale (NIHSS) score at hospital admission was 18 (range, 9 to 36). Nine patients had occlusions of the internal carotid artery (ICA), 23 of the middle cerebral artery (MCA), 1 of the anterior cerebral artery, and 10 of the basilar artery (BA). Outcome was assessed after 3 months and classified as good for Rankin Scale (RS) scores of 0 to 3 and poor for RS scores of 4 or 5 and death. RESULTS: Nine patients (21%) recovered to RS scores 0 or 1, 17 (40%) to scores of 2 or 3, and 7 (16%) to scores of 4 or 5. Ten patients (23%) died. Outcome was good in 17 patients (80%) with MCA occlusions, in 3 patients (33%) with ICA, and in 5 patients (50%) with BA occlusions. Good outcome was associated with an initial NIHSS score of <20 (P<0.001), improvement by 4 or more points on NIHSS score within 24 hours (P=0.001), and vessel recanalization (P=0.02). Recanalization was more likely if LIT was started within 4 hours (P=0.01). Symptomatic cerebral hemorrhage occurred in 2 patients (4.7%). CONCLUSIONS: LIT was most efficacious in patients with MCA and BA occlusions when the initial NIHSS score was less than 20 and when treated within 4 hours. It is of limited value in patients with distal ICA occlusions.  相似文献   

9.
OBJECTIVE: To conduct a pilot trial of mild intraoperative hypothermia during cerebral aneurysm surgery. METHODS: One hundred fourteen patients undergoing cerebral aneurysm clipping with (n = 52) (World Federation of Neurological Surgeons score < or =III) and without (n = 62) acute aneurysmal subarachnoid hemorrhage (SAH) were randomized to normothermic (target esophageal temperature at clip application of 36.5 degrees C) and hypothermic (target temperature of 33.5 degrees C) groups. Neurological status was prospectively evaluated before surgery, 24 and 72 hours postoperatively (National Institutes of Health Stroke Scale), and 3 to 6 months after surgery (Glasgow Outcome Scale). Secondary outcomes included postoperative critical care requirements, respiratory and cardiovascular complications, duration of hospitalization, and discharge disposition. RESULTS: Seven hypothermic patients (12%) could not be cooled to within 1 degrees C of target temperature; three of the seven were obese. Patients randomized to the hypothermic group more frequently required intubation and rewarming for the first 2 hours after surgery. Although not achieving statistical significance, patients with SAH randomized to the hypothermic group, when compared with patients in the normothermic group, had the following: 1) a lower frequency of neurological deterioration at 24 and 72 hours after surgery (21 versus 37-41%), 2) a greater frequency of discharge to home (75 versus 57%), and 3) a greater incidence of good long-term outcomes (71 versus 57%). For patients without acute SAH, there were no outcome differences between the temperature groups. There was no suggestion that hypothermia was associated with excess morbidity or mortality. CONCLUSION: Mild hypothermia during cerebral aneurysm surgery is feasible in nonobese patients and is well tolerated. Our results indicate that a multicenter trial enrolling 300 to 900 patients with acute aneurysmal SAH will be required to demonstrate a statistically significant benefit with mild intraoperative hypothermia.  相似文献   

10.
Minnesota Multiphasic Personality Inventory—2 profile differences between patients with a discharge diagnosis of schizophrenia (n?=?42) vs. depression (n?=?42) were investigated. Multivariate analyses of variance indicated significant multivariate effects associated with diagnosis for the basic validity and clinical scales and for the content scales. The depression group obtained significantly higher mean scale scores on Scales 2 (Depression), 4 (Psychopathic Deviate), 7 (Psychasthenia), O (Social Introversion), Anxiety, Depression (DEP), and Social Discomfort. In an attempt to replicate work by Y. S. Ben-Porath, J. N. Butcher, & J. R. Graham (1991), a stepwise multiple regression analysis was performed to predict diagnosis, with similar findings obtained. Scale 2 was identified as the 1 significant clinical scale predictor. Two content scales, DEP and Bizarre Mentation, were identified as contributing significantly to prediction beyond Scale 2. When the order of the analysis was reversed, none of the basic clinical and validity scales contributed beyond prediction afforded by the content scales. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

11.
Cross-sectional data from a representative sample of the general population in Japan were analyzed to test the validity of Japanese SF-36 Health Survey scales as measures of physical and mental health. Results from psychometric and clinical tests of validity were compared. Principal components analyses were used to test for the hypothesized physical and mental dimensions of health and the pattern of scale correlations with those components. To test the clinical validity of SF-36 scale scores, self-reports of chronic medical conditions and the Zung Self-Rating Depression Scale were used to create mutually exclusive groups differing in the severity of physical and mental conditions. The pattern of correlations between the SF-36 scales and the two empirically derived components generally confirmed hypotheses for most scales. Results of psychometric and clinical tests of validity were in agreement for the Physical Functioning, Role-Physical, Vitality, Social Functioning, and Mental Health scales. Relatively less agreement between psychometric and clinical tests of validity was observed for the Bodily Pain, General Health, and Role-Emotional scales, and the physical and mental health factor content of those scales was not consistent with hypotheses. In clinical tests of validity, the General Health, Bodily Pain, and Physical Functioning scales were the most valid scales in discriminating between groups with and without a severe physical condition. Scales that correlated highest with mental health in the components analysis (Mental Health and Vitality) also were most valid in discriminating between groups with and without depression. The results of this study provide preliminary interpretation guidelines for all SF-36 scales, although caution is recommended in the interpretation of the Role-Emotional, Bodily Pain, and General Health scales pending further studies in Japan.  相似文献   

12.
BACKGROUND AND PURPOSE: Early identification of acute stroke patients at risk of fatal brain swelling is necessary to facilitate implementation of aggressive therapies. Initial clinical, laboratory, and CT characteristics that may be used as selection criteria were analyzed to determine predictors of herniation and neurological death. METHODS: Data from the placebo arm of the Lubeluzole-International-9 trial were reviewed to identify patients with fatal brain edema. Early clinical, laboratory, and radiographic parameters were evaluated in a case-control design. Initial CT scans were analyzed for early ischemic abnormalities by 2 blinded investigators. RESULTS: Twenty-three patients died from brain swelling, with minimum baseline National Institutes of Health Stroke Scale (NIHSS) scores of 20 (n=12; mean, 23.2+/-1.8) with left and 15 (n=11; mean, 17.6+/-2.2) with right hemispheric infarctions (P=0. 0001). A sample of 112 subjects with comparably severe strokes, but who did not die from brain swelling, was selected from the remaining population according to the same NIHSS scores. Among clinical and laboratory characteristics, nausea/vomiting within 24 hours after onset (odds ratio [OR], 5.1; 95% CI, 1.7 to 15.3; P=0.003) and 12-hour systolic blood pressure >/=180 mm Hg (OR, 4.2; 95% CI, 1.4 to 12.9; P=0.01) were independently associated with fatal brain swelling. Among radiographic factors, only hypodensity of >50% of the middle cerebral artery territory on initial CT scan was an independent predictor (OR, 6.1; 95% CI, 2.3 to 16.6; P=0.0004). CONCLUSIONS: Patients with baseline NIHSS score >/=20 with left or >/=15 with right hemispheric infarctions within 6 hours of symptom onset who also have nausea/vomiting or >50% middle cerebral artery territory hypodensity are at high risk for developing fatal brain swelling.  相似文献   

13.
This study was designed to examine the scale quality of our newly developed short behavior scale and to identify its role in predicting the functional outcome of stroke patients. The short behavior scale consists of six items that assess cognitive function related to the daily behavioral status of a patient in activities of daily living and exercise. It can be scored quickly through observation of a patient's behavior. We assessed 190 stroke inpatients, who had a mean age of 61 years. The mean days and length of stay from onset were 47.3 and 138.2, respectively. We examined internal consistency with the Cronbach's alpha coefficient. Interrater reliability was tested by having two examiners evaluate 30 patients independently. We studied how the short behavior scale correlated with the admission Functional Independence Measure, Mini-Mental State Examination scores, and speech and visuospatial functions. We also studied how the short behavior scale contributed to the prediction of discharge Functional Independence Measure raw scores with stepwise multiple regression analysis. In another group of 116 patients, we cross-validated our predictive equation. The Cronbach's alpha coefficient was 0.88. The intraclass correlation coefficient was 0.84 for total score. The short behavior scale correlated significantly with cognitive Functional Independence Measure scores and Mini-Mental State Examination scores. We could explain 70.8% of the variance of discharge Functional Independence Measure scores from the Short Behavior Scale, days from onset to admission, age, speech scores, and admission Functional Independence Measure scores. Stability of the predictive equation was shown in cross-validation to a second sample of 116 patients. In conclusion, our newly developed short behavior scale proved reasonable and would be useful to enhance the precision of outcome prediction in stroke rehabilitation.  相似文献   

14.
Three scales, the Fake Bad Scale, the Fake Good Scale, and the Fake Bad-Fake Good scales were developed and evaluated with respect to their capacity to detect response manipulation on the Multiple Affect Adjective Check List-Revised. Cutting scores for each scale were cross-validated in two samples consisting of three groups: (1) college students simulating either "fake good" or "fake bad," (2) college students under standard instructions, and (3) psychiatric patients. Cutting scores on the three scales were compared with cutting scores established for the MAACL-R Dysphoria and Positive Affect plus Sensation Seeking. Analysis indicated that these scales were more accurate than the Positive Affect plus Sensation Seeking and the Dysphoria scales in detecting response manipulation.  相似文献   

15.
BACKGROUND and PURPOSE: The purpose of this study was to report our experience with percutaneous transluminal angioplasty (PTA) of intracranial arteries in acute stroke patients who were resistant to intra-arterial thrombolysis alone. METHODS: PTA was performed within 6 hours from symptom onset in 13 acute stroke patients in whom no hypodensity areas were observed on initial CT. PTA was classified into 3 categories: immediate (3 patients), delayed (3 patients), and rescue (7 patients) angioplasty. Treatment results in the PTA group for 9 cases of middle cerebral artery (MCA) occlusion were compared with those in the thrombolysis alone group for 12 cases of thrombotic MCA occlusion. RESULTS: Technical success rates for immediate, delayed, and rescue angioplasty were 100%, 100%, and 71%, respectively, and that of angioplasty for the MCA was 100%. Ten patients (77%) showed improvement in the National Institutes of Health (NIH) stroke score after treatment. Improvement in NIH stroke scores in the PTA group for MCA occlusion was greater than that in the thrombolysis alone group (P<0.01). Nine patients (69%) had an excellent, good, or fair outcome 3 months after treatment. In 9 patients who had follow-up angiography 1 month after treatment, no restenosis or reocclusion was demonstrated. There were no symptomatic complications during or after treatment. CONCLUSIONS: This limited study demonstrates the technical feasibility of angioplasty for intracranial arteries in acute ischemic stroke and suggests that angioplasty may be an effective option for improving the success rate of recanalization and preventing reocclusion of the MCA. The present results encourage us to perform further clinical trials in a larger number of patients to assess the efficacy of this procedure.  相似文献   

16.
Objective: Adaptation to prisms displacing the visual scene rightward is a therapeutic tool for left unilateral spatial neglect (USN). We aimed at comparing the effects of the classic adaptation procedure (repeated pointing toward visual targets, control treatment, C), with those of a novel adaptation method, involving ecological visuomotor activities (experimental treatment, E). Method: In 10 right-brain-damaged USN patients, each treatment was given for 1 week, with a crossover design, for a total of 20 sessions, twice per day. USN was assessed by cancellation, reading, and drawing tasks, and by a standardized scale. Neurological severity was assessed by the National Institutes of Health (NIH) stroke scale (Brott et al., 1989), disability by the Functional Independence Measure (FIM) scale. Results: The 2-week treatments (EC, CE) were equally effective, improving both USN, confirming previous reports (Frassinetti, Angeli, Meneghello, Avanzi, & Làdavas, 2002) and, importantly, disability. The improvement was independent of baseline performance, duration of disease, and neurological severity. Recovery took place after the first week, continued in the second week, and was stable at the follow-up of 3 months. The improvement of USN, measured by cancellation performance, and, in part, that of disability, measured through the FIM scale, were mediated by the size of the leftward aftereffects, suggesting a causal relationship between prism exposure and recovery. The E protocol was better tolerated. Conclusions: Daily life visuomotor activities, associated with prism exposure, are a useful tool for rehabilitating USN patients. This new treatment may widen the compliance with prism exposure treatments and their feasibility within home-based programs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

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19.
BACKGROUND AND PURPOSE: To assess the prevalence of depressive symptoms, their clinical correlates, and the effects of depressive symptoms on stroke recovery, a relatively unselected, well-diagnosed cohort of consecutive stroke survivors was followed prospectively. METHODS: Consecutive admissions to a regional stroke center who met World Health Organization and National Institute of Neurological Disorders and Stroke criteria for stroke were eligible. Subarachnoid hemorrhage and brain stem strokes were excluded. Patients underwent CT, single-photon emission CT, and standardized neurological and cognitive examinations at entry. At 3 months and 1 year after stroke, depressive symptoms were assessed with the Montgomery Asberg Depression Rating Scale (MADRS) and the Zung Self-Rating Depression Scale (SDS). Functional outcome was measured with the Functional Independence Measure, and handicap was assessed by the Oxford Handicap Scale. RESULTS: We assessed 436 patients at entry (mean +/- SD age, 74.9 +/- 11.6 years). There were 150 patients available for assessment at 3 months and 136 at 1 year. Marked depressive symptoms were noted in 22% (SDS) to 27% (MADRS) at 3 months and 21% (SDS) to 22% (MADRS) at 1 year. Patents with marked depressive symptoms had more neurological impairment (P<.008), were more likely to be female (P<.05), and were more likely to have previous histories of depression (P<.03). There was no relationship between depressive symptoms and age, lesion volume, or side of lesion. Depressive symptoms were correlated with functional outcome (r = -.31, P<.0001) and handicap (r = .41, P<.0001) at 3 months and 1 year (r= -.28, P<.001; r = .35, P<.0001). CONCLUSIONS: Depressive symptoms and functional outcome are correlated. In view of the prevalence of depressive symptoms in this population, diagnosis and treatment of depression are important in optimizing recovery.  相似文献   

20.
This paper was presented in part by V. L. Snoeyink as the Simon W. Freese Lecture at the 2002 Canadian Society of Civil Engineers/Environmental and Water Resources Institute of ASCE Environmental Engineering Conference in Niagara Falls, Ontario, Canada, July 22, 2002. The interactions of corroded iron pipe surfaces with water are of importance because they can lead to serious water quality degradation and material deterioration. A conceptual model has been developed in this paper to describe the formation and growth of iron scales, and their reactions that lead to colored water problems. Most corrosion scales have characteristic structural features, such as a loosely held top surface layer, a shell-like layer(s), and a porous core. According to this model corrosion scales are expected to grow from inside the scale via the corrosion reaction, i.e., the conversion of iron metal to ferrous ion. The average oxidation state of iron increases with distance from the pipe wall. The scale structure and scale reactions permit the ferrous iron to be released to the bulk water, where it undergoes conversion to particulate ferric iron, which is the cause of colored water. Scale structure and composition play important roles in the reactions of iron scales that lead to iron release, and water quality control to decrease the porosity of the scale is an important means of reducing iron release. It is anticipated that the conceptual model presented here will be used as a basis for changing water quality to minimize colored water formation, and as a guide for further research.  相似文献   

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