Correlation between diffusion- and perfusion-weighted MRI and neurological deficit measured by the Scandinavian Stroke Scale and Barthel Index in hyperacute subcortical stroke (< or = 6 hours).

OBJECTIVE: We used combined diffusion-weighted (DWI) and perfusion-weighted (PWI) MRI to characterize hyperacute infarctions within 6 h of symptom onset with special reference to subcortical infarctions, and investigated the relation between perfusion-diffusion mismatch volume and functional outcome. MATERIAL AND METHODS: Twenty-two patients presenting with symptoms of acute stroke underwent DWI and PWI within 6 h of symptom onset, and follow-up MRI 30 days later. Twelve of these had a subcortical infarction on acute DWI. Lesion volumes were measured by acute DWI and PWI as well as chronic T(2)-weighted MRI (T2WI). Clinical severity was measured by the Scandinavian Stroke Scale (SSS) and the Barthel Index (BI). RESULTS: In the 12 patients with subcortical infarctions, PWI and especially DWI correlated strongly with acute and chronic neurological SSS score, as well as with final infarct volume. Furthermore, a hyperacute PWI/DWI mismatch in this subgroup predicted lesion growth. There was a weaker correlation between acute DWI/PWI and neurological score among all 22 patients, and patients with a PWI/DWI mismatch larger than 100 ml had a significantly larger lesion growth and a poorer outcome than patients with a smaller mismatch. CONCLUSIONS: Subcortical infarctions may represent a sizeable subgroup of acute stroke patients. Also subcortical infarctions may have a PWI/DWI mismatch and therefore may respond to neuroprotective/thrombolytic therapy. Hyperacute DWI may reflect the acute clinical status and predict the outcome in patients with subcortical infarction.

Viability thresholds of ischemic penumbra of hyperacute stroke defined by perfusion-weighted MRI and apparent diffusion coefficient.

BACKGROUND AND PURPOSE: The penumbra of ischemic stroke consists of hypoperfused, but not irreversibly damaged, tissue surrounding the ischemic core. The purpose of this study was to determine viability thresholds in the ischemic penumbra, defined as the perfusion/diffusion mismatch in hyperacute stroke, by the use of diffusion- and perfusion-weighted MRI (DWI and PWI, respectively). METHODS: DWI and PWI were performed in 11 patients 1.63. Higher sensitivity and accuracy in predicting outcome of the penumbra were obtained from the rCBF maps compared with the rCBV and MTT maps. The initial rCBV and apparent diffusion coefficient ratios did not differentiate between the part of the penumbra that recovered and the part that progressed to infarction. The mean rCBF ratio was optimal in distinguishing the parts of the penumbra recovering or progressing to infarction. CONCLUSIONS: The thresholds found in this study by combined DWI/PWI might aid in the selection of patients suitable for therapeutic intervention within 6 hours. However, these hypothesized thresholds need to be prospectively tested at the voxel level on a larger patient sample before they can be applied clinically.

Prediction of tissue survival after middle cerebral artery occlusion based on changes in the apparent diffusion of water.

OBJECT: In this study the authors tested the hypothesis that the estimate of the apparent diffusion coefficient (ADC) of water is a reliable pathophysiological index of the viability of ischemic brain tissue. METHODS: Cerebral blood flow (CBF) and the cerebral metabolic rates of oxygen and glucose (CMRO2 and CMRglc, respectively) were measured using positron emission tomography (PET) scanning before and after permanent middle cerebral artery occlusion (MCAO) or reperfusion in pigs. The ADC value, which was measured using diffusion-weighted magnetic resonance (DW MR) imaging was compared with physiological variables obtained by PET scanning and with histological findings. After both permanent MCAO and reperfusion, the decrease in the ADC was significantly correlated with decrease in the CMRO2 and CMRglc. The infarction coincided with a CMRO2 threshold of 50% of the value measured on the contralateral side. Thus, an ADC value of 80% or 75% of the contralateral value reflected the CMRO2 threshold after permanent MCAO or reperfusion, respectively. On DW MR images, lesions with ADC values above 80% of the contralateral value are potentially reversible until 6 hours after MCAO, whereas lesions with ADC values below 75% of the contralateral value are irreversible as early as 2 hours after MCAO. CONCLUSIONS: The ADC of water provides a reliable pathophysiological index for tailoring therapy to the condition of individual stroke patients in clinical practice.

[MR scanning in acute apoplexy]. / MR-scanning ved akut apopleksi.

MR is increasingly used as a diagnostic tool in stroke management, especially since new and acute treatments are now available. This article describes the new MR sequences used in the scanning of stroke patients. A scanning protocol is suggested and our preliminary experiences with acute MR scanning of stroke patients are presented. Pros and cons are discussed.

Relationship between residual cerebral blood flow and oxygen metabolism as predictive of ischemic tissue viability: sequential multitracer positron emission tomography scanning of middle cerebral artery occlusion during the critical first 6 hours after stroke in pigs.

OBJECT: The authors tested the hypothesis that oxygen metabolism is the key factor linking the long-term viability of ischemic brain tissue to the magnitude of residual blood flow during the first 6 hours following a stroke. METHODS: Eleven anesthetized pigs underwent a series of positron emission tomography studies to measure cerebral blood flow (CBF) and metabolism before and for 7 hours after the animals were subjected to permanent middle cerebral artery (MCA) occlusion. The extent of collateral blood supply was assessed using angiography. Abnormal metabolism of the ischemic tissue progressed as a function of time in inverse proportion to the magnitude of residual CBF, and the volume of the infarct grew in inverse proportion to the residual blood supply. Ten hours after occlusion of the MCA, the infarct topographically matched the tissue with a cerebral metabolic rate of oxygen consumption below 50% of values measured on the contralateral side. This was also the threshold for the decline of the oxygen extraction fraction below normal, which was critical for the prediction of nonviable ischemic tissue. Mildly ischemic tissue (CBF > 30 ml/100 g/min) did not reach the cerebral metabolic rate of oxygen threshold of viability during the first 6 hours after MCA occlusion; moderately ischemic tissue (CBF 12-30 m1/100 g/ min) reached the threshold of viability in 3 hours; and severely ischemic tissue (CBF < 12 ml/100 g/min) remained viable for less than 1 hour. CONCLUSIONS: The relationship between the residual CBF and both oxygen metabolism and extraction is critical to the evolution of metabolic deficiency and lesion size after stroke.

Cerebral blood flow and blood volume measured by magnetic resonance imaging bolus tracking after acute stroke in pigs: comparison with [(15)O]H(2)O positron emission tomography.

BACKGROUND AND PURPOSE: Early and accurate assessments of cerebral ischemia allow therapy to be tailored to individual stroke patients. We examined the feasibility of using a novel method for measuring cerebral blood flow (CBF) of ischemic tissue based on MRI after middle cerebral artery occlusion (MCAO). Moreover, the regional correlations between CBF and cerebral blood volume (CBV) were investigated in the regions with acute ischemic stroke. METHODS: CBF and CBV were measured before and after MCAO or reperfusion by positron emission tomography (PET) in 13 pigs. Just after the PET scans, CBF and CBV were measured by MR bolus tracking and were compared with results obtained by PET at 6 hours after permanent MCAO or reperfusion. The infarction was verified histologically. RESULTS: The MR method yielded parametric CBF and CBV maps with tissue contrast in good agreement with parametric PET images, which demonstrated hypoperfused and hyperperfused areas after MCAO or reperfusion. Both MRI and PET technology showed that CBF values below 60% of the contralateral value induced a reduction of CBV, which committed the tissue to infarction. CONCLUSIONS: The novel MR method provides accurate measurement of CBF and CBV in acute stroke and hence gives useful information for planning the appropriate therapeutic intervention.

Esophageal rings and strictures. Manometric characteristics in patients with food impaction.

PURPOSE: The purpose was to investigate the manometric characteristics in patients with lower esophageal rings or strictures with special reference to food impaction. MATERIAL AND METHODS: The material comprised 344 patients (158 female and 186 male). Lower esophageal rings or strictures were diagnosed radiologically by the full column technique. Manometry was performed with triple lumen catheters connected to a hydraulic capillary system and external transducers. RESULTS: Forty patients had rings, and 21 patients strictures. The reference group comprised 283 patients. Dysphagia was seen most frequently in patients with rings. Food impaction was seen only in patients with rings or strictures, whereas chest pain and heartburn appeared with the same incidence in all 3 groups. Non-specific motor disorders were seen most frequently in patients with strictures, but as delayed esophageal emptying with no influence on the tendency to food impaction. Only ring diameter, but not stricture diameter, was of any significance with a higher incidence of food impaction in patients with narrow rings. CONCLUSION: Radiology rather than manometry should be the first diagnostic step in patients with benign dysphagia suffering from food impaction.

NC100150-enhanced 3D-SPGR MR angiography of the common carotid artery in a pig vascular stenosis model. Quantification of stenosis and dose optimization.

PURPOSE: NC100150 is a new type of ultra-small iron oxide (USPIO) blood pool agent. The aim of this study was to compare NC100150-enhanced MR angiography (MRA) to time-of-flight (TOF) MRA, phase-contrast (PC) MRA, and digital subtraction angiography (DSA) in experimental stenoses in pigs, and furthermore to determine the optimal dose of the contrast agent. MATERIAL AND METHODS: An experimental stenosis of the right and left common carotid artery (CCA) was applied surgically in 6 Yorkshire pigs. DSA was performed as the gold standard, followed by 3D-TOF, 3D-PC, and NC100150-enhanced MRA. RESULTS: Eleven stenoses of the CCA were successfully applied. The degree of the stenosis, determined by NC100150-enhanced MRA, did not differ significantly from DSA, whereas TOF and PC MRA underestimated it. The image quality of the NC100150-enhanced MRA was superior to both TOF and PC MRA. The optimal dose of NC100150 was 5-6 mg Fe/kg, since higher doses did not further increase signal-to-noise ratio or contrast-to-noise ratio. There was a linear relationship between blood relaxation rate and contrast dose. CONCLUSION: NC100150-enhanced MRA has the potential for quantification of carotid stenoses and provides an alternative to DSA. The optimal dose of NC100150 was 5-6 mg Fe/kg.

CBF and CBV measurements by USPIO bolus tracking: reproducibility and comparison with Gd-based values.

The authors measured cerebral blood flow (CBF) and cerebral blood volume (CBV) by bolus tracking of a novel ultrasmall superparamagnetic iron oxide (USPIO) contrast agent (NC100150) and compared absolute and relative perfusion measurements with those obtained by a standard gadolinium-based contrast agent. They found a linear correlation between the two methods. A dose of 0.4 mg Fe/kg body weight was found to produce a signal drop similar to that of a standard 0.2 mmol/kg gadodiamide injection using spin-echo echoplanar imaging (SE-EPI) at 1.0 T. The measurements showed a high degree of reproducibility of repeated absolute as well as relative CBF and CBV values, lending further hope to the possibility of using magnetic resonance bolus tracking for routine CBF and CBV measurements. Finally, the authors present their initial experience with high-resolution, non-EPI CBV maps obtained from steady-state levels of an intravascular superparamagnetic contrast agent.

Simultaneous measurement of stiffness and energy absorptive properties of articular cartilage and subchondral trabecular bone.

The purpose of this study was to develop a method for simultaneous measurement of the mechanical properties of articular cartilage and underlying trabecular bone. Cylindrical bone-cartilage specimens from human cadaver knees were tested under non-destructive axial compression. The specimens wer mounted in a cage by three screws fixed to the subchondral bone plate to create a reference plane between the cartilage and the bone. Each test was carried out as a single test cycle between a 0.12 MPa (4 N) pre-stress and 0.5 per cent bone strain. Twenty conditioning cycles were performed prior to each test cycle. In order to determine the reproducibility of the test method, the test procedure was repeated after turning the cage through 90 degrees. The specimens were then kept at +5 degrees C for 24 hours, and the procedure was repeated. The normalized stiffness and energy absorptive properties were calculated from each test cycle. No significant difference was found between the results obtained on the first and on the second day. Both days the stiffness of cartilage was significantly larger during the second test, indicating that 20 conditioning cycles may not provide a viscoelastic steady state.

[Local recurrence after organ saving kidney tumor surgery]. / Lokale Rezidive nach organerhaltender Nierentumorchirurgie.

Although excellent survival rates for nephron-sparing surgery in mandatory indications (solitary kidney, bilateral renal neoplasms) have been documented, parenchymasparing surgery in elective indications (normal contralateral kidney) is a point of controversy. Local tumor recurrence is the most important argument against this approach. From January 1971 to December 1989, 107 patients suffering from renal cell carcinoma in solitary kidneys or bilateral renal carcinoma underwent nephron-sparing surgery. Thirteen patients (12%) suffered from local recurrence between 4 and 112 months after tumor resection. A high proportion of these recurrences were seen within the first 2 years after resection, followed by a almost linear increase thereafter. Thus-there are possibly two different entities for local recurrence. A correlation between tumor grade and interval from resection to local recurrence could be found, with a long average interval for grade 1 tumors--longer than the published follow-up times for patients undergoing elective tumor resections. Although most of the patients described in this report do not fulfil the surgical criteria for elective resection, we cannot recommend parenchyma-sparing surgery in elective indications.

Tensile and compressive properties of cancellous bone.

The relationship between the mechanical properties of trabecular bone in tension and compression was investigated by non-destructive testing of the same specimens in tension and compression, followed by random allocation to a destructive test in either tension or compression. There was no difference between Young's modulus in tension and compression, and there was a strong positive correlation between the values (R = 0.97). Strength, ultimate strain and work to failure was significantly higher in tensile testing than in compressive testing.

[Causes of hypertension following kidney transplantation with special reference to arterial stenoses]. / Ursachen der Hypertonie nach Nierentransplantation unter besonderer Berücksichtigung arterieller Stenosen.

Hypertension is regarded as a significant complication in renal transplant recipients. Its frequency was 48,1% after cadaver donor and 40,6% after living donor transplantation. The etiology is multifactorial. A correlation could be demonstrated between blood pressure and graft function or presence or absence of the diseased kidneys while no influence was found with regard to steroid dosage in patients with long term graft function. After 575 renal transplantations with 147 angiographies arterial stenoses were observed in nine patients (1,6%) and corrected surgically.

[Report of experiences with therapy of kidney injuries]. / Erfahrungsbericht über die Therapie des Nierentraumas.

Of 510 traumatic renal injuries analyzed for the period 1960-1982, 95 patients demonstrated an injury of grade I-V according to the classification of Küster[11]. 88 patients were treated by surgery, 73 had immediate exploration. 15 patients in whom surgery became necessary after a trial of non operative management demonstrated much more complications than those managed by early operative intervention. Nephrectomy had to be performed in 8 of these 15 patients. The value of early excretory urography, ultrasound and sometimes of CT in the diagnosis of renal injuries is discussed. Arteriography and retrograde pyelography are only useful in very selected cases.