Regional measurements of pulmonary edema by using magnetic resonance imaging

A three-dimensional magnetic resonance imaging (MRI) method to measure pulmonary edema and lung microvascular barrier permeability was developed and compared with conventional methods in nine mongrel dogs. MRIs were obtained covering the entire lungs. Injury was induced by injection of oleic acid (0.021-0.048 ml/kg) into a jugular catheter. Imaging followed for 0.75-2 h. Extravascular lung water and permeability-related parameters were measured from multiple-indicator dilution curves. Edema was measured as magnetic resonance signal-to-noise ratio (SNR). Postinjury wet-to-dry lung weight ratio was 5.30 +/- 0.38 (n = 9). Extravascular lung water increased from 2.03 +/- 1.11 to 3.00 +/- 1.45 ml/g (n = 9, P < 0.01). Indicator dilution studies yielded parameters characterizing capillary exchange of urea and butanediol: the product of the square root of equivalent diffusivity of escape from the capillary and capillary surface area (D1/2S) and the capillary permeability-surface area product (PS). The ratio of D1/2S for urea to D1/2S for butanediol increased from 0.583 +/- 0.027 to 0.852 +/- 0.154 (n = 9, P < 0.05). Whole lung SNR at baseline, before injury, correlated with D1/2S and PS ratios (both P < 0.02). By using rate of SNR change, the mismatch of transcapillary filtration flow and lymph clearance was estimated to be 0.2-1.8 ml/min. The filtration coefficient was estimated from these values. Results indicate that pulmonary edema formation during oleic acid injury can be imaged regionally and quantified globally, and the results suggest possible regional quantification by using three-dimensional MRI.     

Gadolinium-enhanced magnetic resonance angiography of abdominal blood vessels

Contrast enhanced (CE) magnetic resonance angiography (MRA) provides high resolution angiograms within 20-40 sec. The technique is based on the acquisition of heavily T1-weighted three-dimensional (3D) gradient-echo data sets (FISP) with ultrashort echo-(< 2ms) and repetition times (< 5 ms) during arterial phase of an intravenously injected bolus of a T1-shortening agent such as Gd-DTPA. For MR-angiography of abdominal vessels CE-MRA is better suited than "time-of flight" (TOF) and phase-contrast (PC) MRA because motional artifacts can be obviated with breath-held acquisitions. We have optimised the technique and evaluated its potential for angiography of the abdominal aorta and its branches as well as the portal vein and its tributaries. Whilst CE-MRA provides reliable diagnostic accuracy in the aorta and the proximal sections of its branches, small peripheral arteries cannot be assessed accurately. The portal vein and its tributaries can often be depicted better with CE-MRA than with conventional angiography but, like conventional angiography, CE-MRA is hampered by slow and reversed flow, conditions under which TOF or "true FISP" MRA may perform bst. We have also investigated FLASH-echo-planar imaging (EPI) hybrid techniques, a further technical development which due to shorter acquisition times of 12-15 sec. allows semi-dynamic imaging of the arterial and venous phase and provide better vessel contrast due to the use of fat-suppression.     

Hypertensive intra-arterial chemotherapy for endometrial carcinoma assessed by transvaginal Doppler ultrasound and magnetic resonance imaging

We examined the effectiveness of hypertensive intra-arterial chemotherapy for endometrial carcinoma using transvaginal Doppler ultrasound and magnetic resonance imaging. Angiotensin II, 100 mg cisplatin, and 40 mg doxorubicin were prescribed for 8 patients with endometrial carcinoma (3 stage Ia; 3 stage Ib; 2 stage II). The resistance index (RI) was obtained for intratumoral blood flow velocity waveforms by transvaginal Doppler ultrasound and changes in RI (delta RI: differences before and after chemotherapy) were calculated. The tumor volume (TV) was also evaluated, based on the T2-weighted image of magnetic resonance imaging (MRI). The decrease in tumor size [DR-T: (TV before chemotherapy--TV after chemotherapy)/TV before chemotherapy x 100] was determined. RI measurements did not correlate with TV, either before or after chemotherapy. The delta RI varied from 0.007 to 0.615 (mean: 0.207) and DR-T varied from 20.1% to 65.0% (mean: 45.5%). The correlation between delta RI and DR-T [DR-T = 23.5 + 167.2 (delta RI)-165.6 (delta RI)2; R2 = 0.772, p < 0.05] was significant. Therefore, we confirmed the effectiveness of hypertensive intra-arterial chemotherapy for endometrial carcinoma using both transvaginal Doppler ultrasound and MRI.     

Quantification of optic nerve blood flow changes using magnetic resonance imaging

PURPOSE: To evaluate the possibilities of magnetic resonance imaging (MRI) for quantification of pharmacologically induced changes in optic nerve microcirculation. METHOD: T2-weighted MRI sequences were used to image the eye, optic nerve, and frontal cortex in rats. Two sets of control images before and one set during Gd (DTPA) infusion were recorded. Blood flow values for two regions of the optic nerve (an anterior part, including the optic nerve head, and a more posterior part) and the frontal cortex were calculated by image analysis from the change in signal intensity, as already reported for cerebral blood flow. For each rat, a control experiment before drug administration and a second experiment 30 minutes after subcutaneous injection of either placebo (n = 7), timolol (n = 7), or SDZ GLC-756, a dopamine D-1 antagonist and D-2 agonist (n = 7), were carried out in a double-blind fashion. RESULTS: Mean basal blood flow values were found between 29.4 and 45.6 ml/100 g per minute in the anterior part of the optic nerve, 38.3 and 42.9 ml/100 g per minute in the posterior part of the optic nerve, and 68.0 and 75.0 ml/100 g per minute in the frontal cortex. Placebo and timolol did not cause significant changes. SDZ GLC-756 significantly increased blood flow by 238% +/- 65% in the anterior part and by 87% +/- 40% in the posterior part of the optic nerve. CONCLUSIONS: These results suggest that MRI provides quantification of optic nerve blood flow and that dopaminergic substances increase optic nerve blood flow.     

Assessment of cerebral blood flow reserve using functional magnetic resonance imaging

Imaging of activated brain areas based on changes of blood deoxyhemoglobin levels is now possible with MRI. Acetazolamide (ACZ) increases cerebral blood flow (CBF) without changing cerebral oxygen consumption; this results in signal changes observed in gradient echo MR images from the areas with an increase in CBF. We assessed signal changes after ACZ application in seven healthy subjects with a conventional 1.5-T MRI scanner. The susceptibility-sensitized three-dimensional fast low-angle shot (FLASH) sequence was used to visualize signal changes induced by ACZ. We analyzed anatomic localization of different ranges of detected signal changes. ACZ caused significant signal changes in the gray matter and at the edge of the cerebral cortex, the latter corresponding to draining surface veins. No significant differences were seen among different brain areas within the same slice. Using the maximal intensity projection technique, we were able to partially separate signal changes originating in draining veins from signal originating in the gray matter microvasculature. Signal changes from the microvessels reflect cerebrovascular reserve. Blood-oxygen-level-dependent (BOLD) based MRI can evaluate CBF reserve with high spatial and temporal resolution. To assess cerebrovascular reserve, it is necessary to separate signal changes originating in large vessels from signal from brain microvasculature.     

Three-vessel study of cerebral blood flow using phase-contrast magnetic resonance imaging: effect of physical characteristics

The development of phase-contrast magnetic resonance imaging (P-C MRI) provides a noninvasive method for measurement of volumetric blood flow (VFR). We performed P-C MRI to study the effects of physical characteristics on cerebral blood flow. VFR of the left and right internal carotid arteries and basilar artery were measured using P-C MRI and total cerebral blood flow (tCBF) was calculated by summing up the VFR values in the three vessels. Moreover, we investigated the changes in these blood flows as influenced by age, head size, height, weight, body surface area, and handedness. The blood flows were 142 +/- 58 ml/min (mean +/- standard deviation) in the basilar artery; and 229 +/- 86 ml/min in the left, and 223 +/- 58 ml/min in the right internal carotid artery; and tCBF was 617 +/- 128 ml/min. Significant increases were observed in head size-related change of VFR in the basilar artery (p = .028) and height-related change of tCBF (p = .045). The other characteristics did not significantly influence any VFR. The results suggest that head size and height may reflect CBF, and that these effects should be considered when changes of CBF are diagnosed. Phase-contrast MRI is useful for a noninvasive and rapid analysis of cerebral VFR and has potential for clinical use.     

Value of Doppler blood flow velocity measurements in peripheral percutaneous laser-assisted angioplasties

PURPOSE: The aim of the study was to establish the prognostic value and clinical implications of blood flow velocity measurements by Doppler guide wires during peripheral laser-assisted percutaneous transluminal angioplasty (PTLA). METHODS: 39 patients presenting with symptomatic peripheral arterial obstructive disease underwent angiography and blood flow velocity assessment by Doppler guide wire (0.018") prior to and following PTLA. Both quantitative angiography (QCA) for measurement of luminal diameters and Doppler assessment of maximum peak velocities (MPV) were performed 2 cm proximal, over and 2 cm distal to stenoses. The results were compared with the following clinical endpoints: 1. Short-term clinical improvement by AHA-criteria during first follow-up examination and 2. criteria for patency suggested by Rutherford [12] within 1 year (1-22 months). RESULTS: Angiography demonstrated initial success of PTLA in all patients. Relative diameter stenosis decreased from 70 +/- 0.04% to 17 +/- 0.05%. Mean clinically category improved from 2.7 +/- 0.1 to 1.2 +/- 0.1 following intervention. Mean grade of clinical improvement was 2.8 +/- 0.1. 22/39 patients demonstrated event-free follow-up examinations. Doppler measurements of MPV post PTLA in the proximal reference segment correlated with clinical outcome. MPV > or = 90 cm/s was associated with good primary success, unlimited walking capacity and event-free follow-up. MPV > or = 70 cm/s predicted an improvement of short-term clinical outcome by 2 grades (predictive value 80%). MPV < 70 cm/s was associated with both minor primary clinical improvement (+/- 0, +1) and increased incidence of restenosis during follow-up. CONCLUSION: Following PTLA, MPV adds information to angiographic success. MPV > or = 90 cm/s in a proximal reference segment following PTLA predicts good clinical outcome, whereas MPV < 70 cm/s is associated with minor primary clinical success and increased rates of restenosis.     

Congenital muscular torticollis: magnetic resonance imaging and ultrasound diagnosis

According to figures published by the College of Health, 34,837 patients were waiting for in-patient plastic surgery treatment nationwide in 1986. By 1989 this number had increased to 40,085--an increase of 15%. Out of this waiting list, nearly 2000 patients were waiting in Manchester in 1990. Increasing public concern over the length of surgical waiting lists forced the Government to allocate extra resources to reduce both waiting lists and waiting times. We have reviewed the extra work done on a waiting list initiative scheme in Manchester in one year, from 1 August 1990 to 31 July 1991. The waiting list was reduced by 932 patients in one year. The attendance rate of the patients for surgery was excellent and the patients in general were very grateful for having had the treatment. The problems associated with setting us such schemes are enormous and are discussed in detail, with alternative suggestions for preventing waiting lists from building up again in future.     

Fetal intracranial hemorrhage. Imaging by ultrasound and magnetic resonance imaging

OBJECTIVE: To describe the magnetic resonance imaging (MRI) findings associated with fetal intracranial hemorrhage and to compare them with ultrasound findings. STUDY DESIGN: In four pregnancies complicated by fetal intracranial hemorrhage, fetal imaging was carried out using T2-weighted fast spin echo sequences and T1-weighted fast low angle shot imaging sequences and by transabdominal ultrasonography. RESULTS: An antepartum diagnosis of hemorrhage was made by ultrasound in one case and by MRI in two. Retrospectively, the hemorrhagic area could be identified from the MRI images in an additional two cases and from the ultrasound images in one case. In the cases of intraventricular hemorrhage, the MRI signal intensity in the T1-weighted images was increased in the hemorrhagic area as compared to the contralateral ventricle and brain parenchyma. In a case with subdural hemorrhage, T2-weighted MRI signals from the hemorrhagic area changed from low-to high-intensity signals during four weeks of follow-up. Better imaging of the intracranial anatomy was possible by MRI than by transabdominal ultrasonography. CONCLUSION: MRI can be used for imaging and dating fetal intracranial hemorrhages. Variable ultrasound and MRI findings are associated with this complication, depending on the age and location of the hemorrhage.     

Striatopallidal and thalamic dystonia. A magnetic resonance imaging anatomoclinical study

The effects of manual and a new mechanical chest compression device (Heartsaver 2000) during prolonged CPR with respect to haemodynamics and outcome were tested in a prospective, randomized, controlled experimental trial during ventricular fibrillation in 12 dogs of 9-13 kg body weight after 1 min of cardiac arrest. During the first 10 min of CPR the dogs were resuscitated according to the Basic Life Support (BLS) algorithm, followed by 20 min of Advanced Life Support (ALS) algorithm. After 30 min of CPR both manual and mechanical CPR groups were resuscitated following a standardized ALS protocol. During CPR, coronary perfusion pressure and end tidal CO2 were greater with mechanical CPR. All animals were successfully resuscitated and neurological deficit scores were not different. The CPR trauma score was less in the mechanical group. Mechanical external chest compression provided better haemodynamics than the manual technique, though outcome did not differ. Both optimally performed manual and mechanical techniques produce flow sufficient to maintain organ viability for 30 min of CPR after a 1 min arrest interval.     

Characterization of blood flow turbulence with pulsed-wave and power Doppler ultrasound imaging

Blood turbulence downstream of a concentric 86 percent area reduction stenosis was characterized using absolute and relative Doppler spectral broadening measurements, relative Doppler velocity fluctuation, and Doppler backscattered power. Bidimensional mappings of each Doppler index were obtained using a 10 MHz pulsed-wave Doppler system. Calf red cells suspended in a saline solution were used to scatter ultrasound and were circulated in an in vitro steady flow loop model. Results showed that the absolute spectral broadening was not a good index of turbulence because it was strongly affected by the deceleration of the jet and by the shear layer between the jet and the recirculation zones. Relative Doppler spectral broadening (absolute broadening divided by the frequency shift), velocity fluctuation, and Doppler power indices provided consistent mapping of the centerline axial variation of turbulence evaluated by hot-film anemometry. The best agreement between the hot-film and Doppler ultrasound methods was however obtained with the Doppler back-scattered power. The most consistent bidimensional mapping of the flow characteristics downstream of the stenosis was also observed with the Doppler power index. The relative broadening and the velocity fluctuation produced artifacts in the shear layer and in the recirculation zones. Power Doppler imaging is a new emerging technique that may provide reliable in vivo characterization of blood flow turbulence.     

Local staging of esophageal cancer using endoscopic magnetic resonance imaging: prospective comparison with endoscopic ultrasound

Thyroid cancer is associated with abnormal thyroid peroxidase (TPO) expression as shown by abolition of immunodetection by monoclonal antibody 47 (Mab 47). The purpose of this study was to determine the relation of this abnormality with differentiation and proliferative potential of follicular tumors evaluated by analyzing thyroglobulin (TG) expression and proliferative cell nuclear antigen (PCNA) index. TPO, TG, and PCNA immunostaining were performed in a series of 30 thyroid follicular tumors ranging from adenoma to invasive carcinoma. Our findings confirmed that TPO abnormalities and PCNA index were correlated with malignancy, and that PCNA as well as TPO could be used to determine the growth potential of follicular proliferations in fine-needle aspirates. The most discriminant parameter was the ratio between the percentage of Mab-47 and PCNA positive cells. Ratios under 0.6 were correlated with malignancy in 90% of the cases, with only 3 cases of atypical adenomas being misdiagnosed as carcinomas. An inverse correlation was found between TPO and PCNA expression, but TG, which persisted at high levels in several actively growing follicular carcinomas, did not appear directly linked to cellular proliferation. These findings confirm that, unlike a decrease in TG synthesis that merely reflects the progressive loss of differentiation occurring in high-grade proliferations, alteration of TPO is an early marker of thyroid follicular tumors, closely related to acceleration of tumor growth in the first stages of malignant transformation.     

Cine magnetic resonance imaging study of blood flow and wall motion of the aortic arch

The aortic arch has 3D distortions in the transverse arch in the axial view, and we previously reported that this distortion is a risk factor in the pathogenesis of arch aneurysms. In this study, we evaluated blood flow and movement of the aortic arch. In 10 healthy young volunteers, ECG-gated cine magnetic resonance imaging was carried out in the axial plane of the transverse arch, the coronal plane of the ascending arch, and the long axial plane along the entire arch. 1. Left anterolateral movements around the midpoint of the transverse arch in the systolic phase were observed in all of the men (6.3 +/- 1.59 mm) and women (4.8 +/- 0.73 mm). 2. A jet flow was detected in the systolic phase along the right side of the aortic wall. At the top of the plane, this jet flow turned to the left in a clockwise rotation in the anterior view. 3. In the long axial plane, a turbulent flow in the systolic phase was observed distal to the left subclavian arterial orifice in 6 of the 7 cases. In conclusion, this turbulent flow and left anterolateral wall motion of the transverse arch are due to anatomical three-dimensional distortion of the transverse arch. We propose that these phenomena may be important risk factors in the pathogenesis of arch aneurysms.     

A study of radiation necrosis and edema in the canine brain using positron emission tomography and magnetic resonance imaging

Evidence derived from sequence comparisons and the genomic organization of the murine Antennapedia-class homeobox gene clusters suggest that they arose from a primordial cluster through a process of gene duplication and divergence followed by cluster duplication. A large chromosomal domain surrounding the ancestral homeobox cluster also appears to have been duplicated and has remained relatively stable since the divergence of humans and rodents. To test the extent of the duplicated chromosomal domain, we have initiated physical mapping studies of the regions surrounding the four murine homeobox clusters using pulsed-field gel electrophoresis and yeast artificial chromosome cloning. In this study, we present a long-range restriction map of mouse chromosome 11 spanning 1500 kb in the region surrounding the Hox-b cluster. We have determined that the gene for the nerve growth factor receptor is tightly linked to the Hox-b complex and is located within 50 kb of the Hox-b 1 gene at the 3' end of the cluster. Four yeast artificial chromosomes have been isolated and characterized by the polymerase chain reaction, long-range restriction mapping, and Southern blotting. Two clones of 150 and 300 kb contain the entire Hox-b cluster and the nerve growth factor receptor gene. A 440-kb clone contains the 3' end of the Hox-b cluster, the nerve growth factor receptor gene, and extends downstream. A 210-kb clone contains the 5' end of the Hox-b cluster and extends upstream. These clones confirm the pulsed-field restriction map of uncloned mouse DNA and represent a contig of approximately 600 kb of cloned material from mouse chromosomes 11.     

Reproducibility of color Doppler imaging in orbital vessels

The purpose of this study was to evaluate the short-term reproducibility, the long-term reproducibility, and the reproducibility of the measurements made between two different examiners of blood-flow velocity in extraocular vessels using color Doppler imaging (CDI). In a group of 10 healthy volunteers, measurements of the peak-systolic velocity (PSV), end-diastolic velocity (EDV), and resistivity index (RI) in the ophthalmic artery and the central retinal artery as well as one lateral and one medial short posterior ciliary artery were performed. The best intraindividual reproducibility, expressed as the relative error, was found for the PSV and RI measured in the ophthalmic artery (OA; PSV 5.9%, RI 3.1%) and the central retinal artery (CRA; PSV 7.7%, RI 4.7%). The PSV and RI determined in the posterior ciliary arteries were less reproducible but as much so as the EDV measured in the OA (11.8%) and CRA (19.9%). No systematic trend could be found between the first and second measurements. However, the long-term fluctuation was considerable high. Measurements of PSVs showed good concurrence between the two observers in all four vessels measured. The EDVs and RIs differed statistically significantly between the two observers. This difference was most pronounced in the posterior ciliary arteries.     

Variations in human corpus callosum do not predict gender: A study using magnetic resonance imaging.

Controversy exists in the neuropsychological literature concerning the existence of gender-associated differences in cognitive functioning and in hemispheric lateralization of cognitive functions. A recent study, based on 14 brains obtained at autopsy, reported sex differences in the splenium of the human corpus callosum and suggested that the larger splenium in females reflects less hemispheric lateralization, or "specialization," than the male brain for visuospatial functions. Our measurements of the human corpus callosum using magnetic resonance images of 37 living subjects failed to confirm reported sex differences in the splenium. A marginally significant sex-related difference in minimum body width and an age-related decrease in anteroposterior distance were found. Most striking were the large variations in callosal size and shape among individuals regardless of age or gender. Existing knowledge of the functions of the corpus callosum does not permit correlations between variations in callosal size and shape and variations in cognitive functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessment of oropharyngeal distance in children using magnetic resonance imaging

Matrix proteolysis is thought to play a crucial role in several stages of tumor progression, including angiogenesis, and the invasion and metastasis of tumor cells. We investigated the specific role of gelatinase A (matrix metalloproteinase 2) on these events using gelatinase A-deficient mice. In these mice, tumor-induced angiogenesis was suppressed according to dorsal air sac assay. When B16-BL6 melanoma cells or Lewis lung carcinoma cells were implanted intradermally, the tumor volumes at 3 weeks after implantation in the gelatinase A-deficient mice decreased by 39% for B16-BL6 melanoma and by 24% for Lewis lung carcinoma (P < 0.03 for each tumor). The number of lung colonies of i.v. injections fell by 54% for B16-BL6 melanoma and 77% for Lewis lung carcinoma (P < 0.014 and P < 0.0015, respectively). These results indicated that host-derived gelatinase A plays an important role in angiogenesis and tumor progression, suggesting the usefulness of gelatinase A inhibitors for anticancer chemotherapy.     

Cerebral blood flow velocity in acute schizophrenic patients. A transcranial Doppler ultrasonography study

Arg-Gly-Asp (RGD) motif mediates cell adhesion as a major determinant in interactions of disintegrins with cell surface receptors. In order to obtain a mutant trypsin with both high affinity to integrins and retained proteolytic activity, RGDS and RGD were inserted into a rigid turn region and a flexible loop of trypsin, respectively. Wild type trypsin and substituted mutant trypsins, 37RGDS and 77RGD, were expressed in E. coli and purified. Kinetic properties, autolytic stability as well as platelet aggregation inhibitory activity of both 37RGDS and 77RGD were determined. 37RGDS and 77RGD give retained proteolytic activities of 34% and 87%, respectively, and both become less stable to autolysis. 37RGDS shows an obvious inhibition rate of 29% for platelet aggregation and 77RGD gives a rather weak rate of 14% at the same protein concentration of 3.5 microM, while the wild type trypsin shows no inhibitory activity.     

Evaluation of hilar pulmonary vessels using magnetic resonance angiography (MRA)

OBJECTIVE: To assess the relationship between ethnicity and decision-makers expressing healthcare wishes in a group of frail older persons enrolled in the Program of All-inclusive Care for the Elderly (PACE). DESIGN: A retrospective chart review of 1193 participants in the PACE program. SETTING: Program of All-inclusive Care for the Elderly, a comprehensive managed care demonstration program serving frail older participants at 10 sites across the nation. PARTICIPANTS: A total of 1193 older adults, all of whom met state criteria for nursing home level of care. Three hundred were non-Hispanic whites, 364 were black, 156 were Hispanic, and 288 were Asian. MEASUREMENTS: Demographic characteristics of the patients and the presence or absence of an alternative decision-maker; the characteristics of alternative decision-makers included the relationship to the participant as recorded in the patient's medical record. RESULTS: Ninety-one percent of white patients expressed their own healthcare wishes in contrast to only 85% of Hispanic, 83% of Asian, and 67% of black patients. An alternative decision-maker was identified for about 15% of Asians and Hispanics and for one-third of blacks, but only about 8% of whites had an alternative decision-maker. Black and Hispanic patients were most likely to have a daughter as an alternative decision-maker, Asians were most likely to have a son, and whites patients were most likely to have a spouse as an alternative decision-maker. Blacks, particularly black men, were the most likely to have a relative other than a spouse or child as an alternative decision-maker. CONCLUSIONS: In this population, we found significant ethnic variation in the person identified to be the decision-maker in a group of frail older people. Ethnic variation reflected sociodemographic as well as cultural differences. However, there are important limitations to this study, and caution should be used in extrapolating the results to other populations or in attributing the results to ethnicity alone. An awareness of cross-cultural patterns in identified or de facto decision-makers can be significant for healthcare workers when they approach patients and their families about issues surrounding end of life decisions.     

In vivo study of halothane hepatotoxicity in the rat using magnetic resonance imaging and 31P spectroscopy

Using magnetic resonance imaging (MRI) and spectroscopy (MRS), in vivo halothane hepatotoxicity was assessed in male Wistar rats. With 1.5% halothane in 100 or 20% O2, an edematous region, characterized by increased intensity on T2 weighted images and an increase in regional tissue water content (rho water), was seen proximal to the hepatic portal vein in the liver. Both spin-lattice relaxation (T1) and spin-spin relaxation (T2) increased in this region, relative to distal regions of the liver. Similarly, a high signal intensity on proton density weighted images was observed in this area. As halothane anaesthesia progressed, a decrease in the adenosine triphosphate-inorganic phosphate ratio (ATP/Pi) and an increase in the phosphomonoester-phosphodiester (PME/PDE) ratio was detected in the liver. In addition, intracellular pH decreased and intracellular free magnesium concentration [Mg2+] increased with time of exposure. Excessive vacuolation, ribosomal disappearance from rough endoplasmic reticulum, mitochondrial swelling and fragmentation of smooth endoplasmic reticulum were observed by transmission electron microscopy (TEM) in samples from the edematous region of the liver.