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David K W Yeung

Publications and source records attributed to David K W Yeung.

At least 19 recordsLinked to original sources
PubMed2006

Vertebral marrow fat content and diffusion and perfusion indexes in women with varying bone density: MR evaluation.

PURPOSE: To prospectively study the relationship among vertebral marrow fat content, marrow diffusion indexes, and marrow and erector spinae muscle perfusion indexes in female subjects with varying bone mineral density. MATERIALS AND METHODS: Institutional study approval and informed consent were obtained. Dual x-ray absorptiometry, proton magnetic resonance (MR) spectroscopy, diffusion-weighted MR imaging, and dynamic contrast material-enhanced MR imaging of the lumbar spine and erector spinae muscle were performed in 110 women (mean age, 73 years; range, 67-84 years). Marrow fat content, marrow apparent diffusion coefficient (ADC), and perfusion indexes (maximum enhancement and enhancement slope) of marrow and erector spinae muscle were compared among three bone density groups (normal, osteopenic, and osteoporotic). The t test comparisons and Pearson correlations were applied. RESULTS: Seven subjects were excluded, which yielded a final cohort of 103 subjects: 18 with normal bone density, 30 with osteopenia, and 55 with osteoporosis. Vertebral marrow fat content was significantly increased in the osteoporotic group (67.8% +/- 8.5 [standard deviation]) when compared with that of the normal bone density group (59.2% +/- 10.0, P = .002). Vertebral marrow perfusion indexes were significantly decreased in the osteoporotic group (enhancement slope, 1.10%/sec +/- 0.51) compared with those of the osteopenic group (1.45%/sec +/- 0.51, P = .01) and normal bone density group (1.70%/sec +/- 0.52, P < .001). Erector spinae muscle perfusion indexes did not decrease as bone density decreased. The ADC of vertebral marrow did not change with bone density. CONCLUSION: The subjects experienced a decrease in vertebral marrow maximum enhancement and enhancement slope and an increase in marrow fat content as bone density decreased. The reduction in perfusion indexes occurred only within the vertebral body and not in the paravertebral tissues supplied by the same artery.

Absorptiometry, Photon↗
PubMed2006

Changes of brain activity in the aged SAMP mouse.

This study investigates characteristics of aging in the central nervous system of the senescence accelerated prone mice (SAMP8). We examined 3 and 10-months old senescence-accelerated-prone mice (SAMP8) for functional and molecular changes in their brains, specifically in the hippocampus and somatosensory cortex. There was no statistically significant increase in the apoptosis indicators as revealed by Western Blotting for BAD and TUNEL experiments. However, the functional magnetic resonance imaging showed an increase in the area of BOLD images from the 3-month old to the 10-months old SAMP mice upon the application of tail stimulus. These results demonstrated a lack of neuronal deaths but an increase in the activated brain area with age.

Aging↗
PubMed2006

Diffusion tensor imaging (DTI) of rodent brains in vivo using a 1.5T clinical MR scanner.

PURPOSE: To evaluate the feasibility of using a clinical 1.5T MR scanner to perform magnetic resonance (MR) diffusion tensor imaging (DTI) on in vivo rodent brains and to trace major rodent neuronal bundles with anatomical correlation. MATERIALS AND METHODS: Two normal adult Sprague Dawley (SD) rats were anesthetized and imaged in a 1.5T MR scanner with a microscopic coil. DTI was performed at a resolution of 0.94 mm x 0.94 mm x 0.5 mm (reconstructed to 0.47 mm x 0.47 mm x 0.5 mm, with b-factors of 600 seconds/mm2 and 1000 seconds/mm2) and a higher resolution of 0.63 mm x 0.63 mm x 0.5 mm (reconstructed to 0.235 mm x 0.235 mm x 0.5 mm, with a b-factor of 1500 seconds/mm2). The fiber-tracking results were correlated with corresponding anatomical sections stained to visualize neuronal fibers. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) of the neuronal fibers were measured and compared with results in published reports. RESULTS: Several major neuronal fiber tracts, including the corticospinal cord, corpus callosum, and anterior commissure, were identified in all DTI data sets. Stained anatomical sections obtained from the rats confirmed the location of these fibers. The ADC values (0.6-0.8 +/- 10(-3) mm2/second) of the fibers were similar to published figures. However, the FA values (0.3-0.35) were lower than those obtained in previous studies of white matter in rodent spinal cord. CONCLUSION: We have demonstrated the feasibility of using a 1.5T clinical MR scanner for neuronal fiber tracking in rodent brains. The technique will be useful in rodent neuroanatomy studies. Further investigation is encouraged to verify the FA values generated by DTI with such techniques.

Animals↗
PubMed2006

Bilateral frontal activation associated with cutaneous stimulation of elixir field: an FMRI study.

Elixir Field, or Dan Tian, is the area where energy is stored and nourished in the body according to traditional Chinese medicine (TCM). Although Dan Tian stimulation is a major concept in Qigong healing and has been practiced for thousands of years, and while there are some recent empirical evidence of its effect, its neurophysiological basis remains unknown. We used functional magnetic resonance imaging (fMRI) to study brain activations associated with external stimulation of the lower Elixir Field in ten normal subjects, and compared the results with the stimulation of their right hands. While right-hand stimulation resulted in left postcentral gyrus activation, stimulation of the lower Elixir Field resulted in bilateral activations including the medial and superior frontal gyrus, middle and superior temporal gyrus, thalamus, insula, and cingulate gyrus. These findings suggest that stimulation of the Elixir Field is not only associated with activation of the sensory motor cortex but also with cortical regions that mediate planning, attention, and memory.

Adult↗
PubMed2005

Vertebral bone mineral density, marrow perfusion, and fat content in healthy men and men with osteoporosis: dynamic contrast-enhanced MR imaging and MR spectroscopy.

PURPOSE: To prospectively use hydrogen 1 (1H) magnetic resonance (MR) spectroscopy and dynamic contrast material-enhanced MR imaging to measure vertebral body marrow fat content and bone marrow perfusion in older men with varying bone mineral densities as documented with dual x-ray absorptiometry (DXA). MATERIALS AND METHODS: This study had institutional review board approval, and all participants provided informed consent. DXA, 1H MR spectroscopy, and dynamic contrast-enhanced MR imaging of the lumbar spine were performed in 90 men (mean age, 73 years; range, 67-101 years). Vertebral marrow fat content and perfusion (maximum enhancement and enhancement slope) were compared for subject groups with differing bone densities (normal, osteopenic, and osteoporotic). The t test was used for comparisons between groups, and the Pearson test was used to determine correlation between marrow fat content and perfusion indexes. RESULTS: Eight subjects were excluded, yielding a final cohort of 82 subjects (mean age, 73 years; range, 67-101 years) that included 42 subjects with normal bone density (mean T score, 0.8 +/- 1.1 [standard deviation]), 23 subjects with osteopenia (mean T score, -1.6 +/- 0.4), and 17 subjects with osteoporosis (mean T score, -3.2 +/- 0.5). Vertebral marrow fat content was significantly increased in subjects with osteoporosis (mean fat content, 58.23% +/- 7.8) (P = .002) or osteopenia (mean fat content, 55.68% +/- 10.2) (P = .034) compared with that in subjects with normal bone density (50.45% +/- 8.7). Vertebral marrow perfusion indexes were significantly decreased in osteoporotic subjects (mean enhancement slope, 0.78%/sec +/- 0.3) compared with those in osteopenic subjects (mean enhancement slope, 1.15%/sec +/- 0.6) (P = .007) and those in subjects with normal bone density (mean enhancement slope, 1.48%/sec +/- 0.7) (P < .001). CONCLUSION: Subjects with osteoporosis have decreased vertebral marrow perfusion and increased marrow fat compared with these parameters in subjects with osteopenia. Similarly, subjects with osteopenia have decreased vertebral marrow perfusion and increased marrow fat compared with these parameters in subjects with normal bone density.

Absorptiometry, Photon↗
PubMed2005

Segmentation of nasopharyngeal carcinoma (NPC) lesions in MR images.

PURPOSE: An accurate and reproducible method to delineate tumor margins from uninvolved tissues is of vital importance in guiding radiation therapy (RT). In nasopharyngeal carcinoma (NPC), tumor margin may be difficult to identify in magnetic resonance (MR) images, making the task of optimizing RT treatment more difficult. Our aim in this study is to develop a semiautomatic image segmentation method for NPC that requires minimal human intervention and is capable of delineating tumor margins with good accuracy and reproducibility. METHODS AND MATERIALS: The segmentation algorithm includes 5 stages: masking, Bayesian probability calculation, smoothing, thresholding and seed growing, and finally dilation and overlaying of results with different thresholds. The algorithm is based on information obtained from the contrast enhancement ratio of T1-weighted images and signal intensity of T2-weighted images. The algorithm is initiated by the selection of a valid anatomical seed point within the tumor by the user. The algorithm was evaluated on MR images from 7 NPC patients and was compared against the radiologist's reference outline. RESULTS: The algorithm was successfully implemented on all 7 subjects. With a threshold of 1, the average percent match is 78.5 +/- 3.86 (standard deviation) %, and the correspondence ratio is 66.5 +/- 7%. DISCUSSION: The segmentation algorithm presented here may be useful for diagnosing NPC and may guide RT treatment planning. Further improvement will be desirable to improve the accuracy and versatility of the method.

Algorithms↗
PubMed2005

Osteoporosis is associated with increased marrow fat content and decreased marrow fat unsaturation: a proton MR spectroscopy study.

PURPOSE: To use proton magnetic resonance spectroscopy ((1)H-MRS) to evaluate vertebral marrow fat, and to determine whether bone density correlates with fat content and fat unsaturation levels in postmenopausal women. MATERIALS AND METHODS: Fifty-three women (mean age = 70 years) underwent dual energy x-ray absorptiometry and (1)H-MRS, and 12 young female controls (mean age = 28 years) underwent (1)H-MRS of the lumber spine. Water and lipid peak amplitudes were measured to calculate fat content and fat unsaturation index. Spearman's correlation tests and a t-test comparison of means were applied. RESULTS: (1)H-MRS was successful in 15 normal, 15 osteopenic, and 20 osteoporotic subjects, and in all controls. Marrow fat content was significantly elevated in osteoporotic (65.5% +/- 10%) and osteopenic (63.5% +/- 9.3%) subjects compared to normal subjects (56.3% +/- 11.2%) and young controls (29% +/- 9.6%). The fat unsaturation index was significantly decreased in osteoporotic (0.091 +/- 0.013) and osteopenic (0.097 +/- 0.014) subjects compared to normal subjects (0.114 +/- 0.016) and young controls (0.127 +/- 0.031). A good inverse correlation was observed between the fat content and the unsaturation index (r(s) = -0.53, P < 0.0001). CONCLUSION: Osteoporosis is associated with increased marrow fat. As marrow fat increases, saturated lipids appear to increase preferentially to unsaturated lipids.

Adipose Tissue↗
PubMed2005

In vivo 1H MR spectroscopy of thyroid carcinoma.

To determine if proton magnetic resonance spectroscopy (1H MRS) of thyroid carcinoma is feasible and to determine if 1H MRS spectra of malignant tumors differ from that of normal thyroid tissue. We performed 1H MRS at 1.5 T at echo-times (TE) 136 and 272 ms to examine eight patients with thyroid cancer (primary tumour or nodal metastasis) larger than 1 cm3 in size and five volunteers with normal thyroids. Spectra acquired from six primary tumors (three anaplastic carcinomas, two papillary carcinomas and one follicular carcinoma) and two nodes (two papillary carcinoma metastases) were analyzed in the time-domain using a non-linear least squares fitting algorithm with incorporation of prior knowledge. Choline (3.2 ppm) was identified in all solid carcinomas with a mean choline/creatine of 4.3 at TE 136 ms and 5.4 at TE 272 ms. Ratios for malignant tumors at TE 136 ms ranged from 1.6 in well differentiated follicular carcinoma to 9.4 in anaplastic carcinoma. No choline was detected in normal thyroid tissues. Our results showed that 1H MRS is a feasible technique for the evaluation of malignant thyroid tumors larger than 1 cm3 and that proton spectra of malignant tumors differ from that of normal thyroid tissue.

Adolescent↗
PubMed2005

Salivary gland tumors at in vivo proton MR spectroscopy.

PURPOSE: To prospectively evaluate whether proton magnetic resonance (MR) spectroscopy can be used to characterize salivary gland tumors (SGTs). MATERIALS AND METHODS: Ethics committee approval and informed consent were obtained. Hydrogen 1 ((1)H) MR spectroscopy was performed with echo times of 136 and 272 msec at 1.5 T in both SGTs and normal parotid glands. Spectra were analyzed in the time domain by using prior knowledge in the fitting procedure to obtain peak amplitudes of choline (Cho), creatine (Cr), and unsuppressed water. Mean Cho/Cr and Cho/water ratios for each subgroup of SGTs were obtained, and results were compared by using a nonparametric t test. RESULTS: Successful spectra were acquired in 56 patients (35 men, 21 women; mean age, 56 years) with a total of nine malignant tumors and 47 benign SGTs (24 Warthin tumors, 22 pleomorphic adenomas, one oncocytoma). At an echo time of 136 msec, Cho/Cr ratios were obtained in 26 (47%) of 55 spectra, with a mean value (+/- standard deviation) of 1.73 +/- 0.47, 5.49 +/- 1.86, 3.46 +/- 0.84, and 2.45 for malignant tumors, Warthin tumors, pleomorphic adenomas, and oncocytoma, respectively. Differences were significant between Warthin tumors and pleomorphic adenomas (P = .028) and between benign SGTs and malignant tumors (P < .001). At an echo time of 272 msec, Cho/Cr ratios were obtained in 16 (30%) of 53 spectra, with a mean value of 2.27 +/- 0.69, 6.92 +/- 1.47, and 3.67 +/- 1.23 for malignant tumors, Warthin tumors, and pleomorphic adenomas, respectively. Differences were also significant between Warthin tumors and pleomorphic adenomas (P = .041) and benign SGTs and malignant tumors (P = .004). There was a significant difference in mean Cho/water ratio for Warthin tumors versus pleomorphic adenomas at echo times of 136 msec (P = .003) and 272 msec (P = .002) but not for benign SGTs versus malignant tumors. CONCLUSION: (1)H MR spectroscopy may be used to characterize SGTs, but a larger study is required to validate these initial results.

Adult↗
PubMed2005

Phosphorus-31 MR spectroscopy in pediatric liver transplant recipients: a noninvasive assessment of graft status with correlation with liver function tests and liver biopsy.

OBJECTIVE: Noninvasive in vivo hepatic phosphorus-31 MR spectroscopy has recently been shown to provide information about hepatic functional status. We sought to show the correlation of phosphorus-31 MR spectroscopy with blood biochemistry and liver biopsy results in pediatric patients after liver transplantation. MATERIALS AND METHODS: Eleven pediatric transplant recipients (eight with good graft function, two with chronic hepatitis, and one with acute rejection) and four healthy control subjects were studied with in vivo 31P MR spectroscopy. Ratios of phosphomonoesters (PME) to total phosphorus (TP), phosphodiester (PDE) to TP, nucleotide triphosphates (NTP), inorganic phosphate (Pi), and intracellular acid-base status (pH) were measured. Liver function test (n = 11) and biopsy (n = 3) results were obtained for correlation with spectroscopic findings. RESULTS: The eight patients with good graft function displayed spectral profiles similar to those of the healthy subjects, and no significant difference in the metabolic ratios of these patients compared with the control subjects was detected. Three patients with abnormal liver function and biopsy-proven hepatic complications showed elevated PME/TP ratios when compared with those of both the control subjects and the group with good graft function. CONCLUSION: Phosphorus-31 MR spectroscopy is a feasible technique for the noninvasive assessment of host-related complications in pediatric patients after liver transplantation. Our preliminary data suggest that the technique may be integrated with MRI for the investigation of impaired liver function in transplant recipients when neither a biliary complication nor a vascular complication is identified.

Adolescent↗
PubMed2004

Bone marrow diffusion in osteoporosis: evaluation with quantitative MR diffusion imaging.

PURPOSE: To determine the diffusion of vertebral body marrow with quantitative MR diffusion imaging and to examine whether differences exist between subjects with postmenopausal osteoporosis and premenopausal control subjects. MATERIALS AND METHODS: A total of 44 consecutive women (mean age, 70 years) with documented bone mineral density (BMD) measured by dual energy x-ray absorptiometry (T-score) and 20 normal subjects (mean age, 28 years) were examined with echo-planar diffusion imaging at 1.5 T using b values of 0, 20, 40, 60, 80, 100, 200, 300, 400, and 500 seconds/mm2. Extravascular diffusion (D) and apparent diffusion coefficient (ADC) were calculated and results from both groups compared. RESULTS: Both D and ADC values tended to decrease with decreasing BMD. Mean D values were significantly lower in postmenopausal women with reduced BMD (0.42 +/- 0.12 x 10(-3) mm2/second) than normal premenopausal women (0.50 +/- 0.09 x 10(-3) mm2/second). Mean ADC values were significantly lower both in subjects with reduced BMD (0.41 +/- 0.10 x 10(-3) mm2/second) and normal BMD (0.43 +/- 0.08 x 10(-3) mm2/second) compared to normal controls (0.49 +/- 0.07 x 10(-3) mm2/second). CONCLUSION: Accumulation of fatty bone marrow associated with osteoporosis is reflected by a decrease in D and ADC. Diffusion imaging may prove useful in the study of osteoporosis.

Adult↗
PubMed2004

Relationship between lesion size and signal enhancement on subtraction fat-suppressed MR imaging of the breast.

OBJECTIVE: To investigate the relationship between size and whole lesion enhancement of breast neoplasms. MATERIALS AND METHODS: Fat-suppressed subtraction MRI was performed in 94 breast lesions (44 malignant, 50 benign) with pathologically confirmed diagnoses. Of these, all malignant lesions and 31 of the 50 benign lesions showed enhancement. The degree of enhancement was quantified by using an ROI tracing around the whole lesion and calculated as the percentage increase in signal intensity between the corresponding precontrast and postcontrast images. RESULTS: The 44 malignant lesions showed enhancement percentage of 38.3% to 186.4% (mean 109.9%), and the 31 benign lesions showed enhancement percentage of 12.8% to 180.2% (mean 79.5%). The difference is statistically significant (P = .002). In 54 small lesions (28 malignant, 26 benign) with enhancing pixel areas of <300 mm(2) corresponding to a diameter of approximately 19.5 mm, an enhancement exceeding 75% of baseline separated malignant lesions (mean enhancement 116.7%) from benign ones (mean enhancement 72.8%) (P = .0001). This gave a sensitivity of 100% and a specificity of 69%, a positive predictive value of 78%, negative predictive value of 100% and an accuracy of 85% in using >75% enhancement increase in detecting malignancy in small (<300 mm(2)) enhancing lesions. CONCLUSION: The high sensitivity in the detection of small malignant lesions suggests a potential for the method to be used in assessment of small enhancing breast lesions.

Adult↗
PubMed2004

In vivo proton MR spectroscopy of primary and nodal nasopharyngeal carcinoma.

BACKGROUND AND PURPOSE: The aim of this study was to determine the feasibility of performing in vivo proton ((1)H) MR spectroscopy of nasopharyngeal carcinoma (NPC) and to document the (1)H spectrum of this cancer. METHODS: Twenty-seven patients with NPC lesions >1 cm(3) underwent localized (1)H MR spectroscopy performed at 1.5 T. Water-suppressed spectra from both primary tumors (nine cases) and metastatic nodes (18 cases) were obtained at TE 136 and 272. Spectra were analyzed in the time domain by using a nonlinear least squares fitting algorithm with incorporation of previous knowledge. Choline (Cho)/creatine (Cr) ratios for primary NPC and metastatic nodes were calculated and compared. Spectra from normal neck muscle of five volunteers were acquired as control data. RESULTS: (1)H MR spectroscopy was successfully obtained in seven (78%) of nine primary tumors and 16 (89%) of 18 metastatic nodes. Intense lipid signals in the range of 0.89 to 2.02 ppm were observed in 95% of spectra at TE 136 and 91% of spectra at TE 272. At TE 136, Cho/Cr for metastatic nodes (5.3 +/- 1.6) was significantly higher than the ratio for primary (2.6 +/- 0.5) NPC lesions (P =.02). Cho/Cr ratios for NPC lesions were higher than those for normal neck muscles, for which values ranged from 0 to 0.97 and 0 to 1.1 at TE 136 and 272, respectively. CONCLUSION: (1)H MR spectroscopy is a feasible technique for the evaluation of NPC tumors >1 cm(3). Cho/Cr ratios for the lesions were high compared with those for normal neck muscle.

Adult↗
PubMed2003

White matter and cerebral metabolite changes in children undergoing treatment for acute lymphoblastic leukemia: longitudinal study with MR imaging and 1H MR spectroscopy.

PURPOSE: To assess the development of white matter and cerebral metabolite changes during and after treatment in children with acute lymphoblastic leukemia. MATERIALS AND METHODS: Twenty-three children (10 boys, mean age of 6.3 years; 13 girls, mean age of 6.6 years) with acute lymphoblastic leukemia were examined prospectively with magnetic resonance (MR) imaging and MR spectroscopy at 0, 8, and 20 weeks and 1, 2, and 3 years after diagnosis. White matter changes were diagnosed on the basis of hyperintense abnormalities on T2-weighted MR images. Single-voxel hydrogen 1 MR spectroscopy results from the right frontoparietal region of 21 children who received intravenous high-dose methotrexate were analyzed for cerebral metabolite changes. Multilevel models were used to assess the change in metabolites from baseline levels at subsequent follow-up. RESULTS: At 20 weeks, MR spectroscopy showed a significant reduction (P <.05) of mean N-acetylaspartate to choline ratio and increase in mean choline to creatine ratio (P <.05) in the children given high-dose methotrexate. This decline in N-acetylaspartate to choline ratio subsequently reversed and increased, possibly because of normal age-related brain maturation. Seventeen of 21 (81%) children showed metabolite changes at MR spectroscopy, while five of 22 (23%) showed white matter changes at MR imaging at 20 weeks. One more child developed white matter changes at 32 weeks. The associated changes resolved or reduced with time. CONCLUSION: MR spectroscopy demonstrated metabolite changes in the brain after high-dose methotrexate treatment in the absence of structural white matter abnormalities at MR imaging. MR spectroscopy might thus be a more sensitive method of monitoring the effects of high-dose methotrexate in the brain.

Adolescent↗
PubMed2003

Diffusion-weighted MRI in shaken baby syndrome.

We present the characteristic CT and MRI findings of a 2-month-old girl with shaken baby syndrome. Diffusion-weighted MR imaging performed 8 days after the insult established the presence of injury to the white matter in the corpus callosum and subcortical white matter in the temporo-occipito-parietal region. Diffusion-weighted MR imaging is valuable in the diagnostic work-up of suspected shaken baby syndrome, as injury to the white matter can be demonstrated days after the injury.

Diagnosis, Differential↗
PubMed2003

Characterization of lesions of the breast with proton MR spectroscopy: comparison of carcinomas, benign lesions, and phyllodes tumors.

OBJECTIVE: Proton MR spectroscopy is a recently described technique with high sensitivity and specificity for differentiating breast carcinoma from benign lesions. We evaluated the possible relationship between spectroscopy results and the tumor proliferative index, angiogenesis, and HER2/neu oncogene overexpression. SUBJECTS AND METHODS. We prospectively evaluated 19 breast carcinomas, 21 benign breast lesions (including 18 fibroadenomas, one fibrocystic change, one hamartoma, and one papilloma), and six phyllodes tumors (four benign, two of borderline malignancy) using proton MR spectroscopy. All lesions were larger than 1.5 cm. Tumor Ki-67 proliferative index, tumor angiogenesis, and HER2/neu oncogene overexpression were evaluated by immunohistochemistry of the histologic material. RESULTS: Spectroscopy findings were positive in 17 (89%) of 19 carcinomas but negative for all benign lesions and phyllodes tumors (sensitivity, 89%; specificity, 100%). Significantly higher levels were obtained for all biologic parameters in carcinomas compared with benign lesions and phyllodes tumors. HER2/neu oncogene overexpression was present in 37% of carcinomas but not in other lesions. The two false-negative findings of breast carcinoma showed similar Ki-67 proliferative index and microvessel density compared with the remaining carcinomas, but both cases were negative for HER2/neu overexpression. CONCLUSION: Proton MR spectroscopy is useful in the in vivo characterization of breast masses when the lesion exceeds 1.5 cm in maximal dimension. Spectroscopy is unable to reveal benign breast lesions and phyllodes tumors of benign and borderline malignancy. We suggest that a false-negative spectroscopic result may be related to an absence of HER2/neu overexpression in carcinoma of the breast.

Adult↗
PubMed2002

Metabolic control patterns in acute phase and regenerating human liver determined in vivo by 31-phosphorus magnetic resonance spectroscopy.

OBJECTIVE: To elucidate the metabolic changes occurring within hepatocytes during acute phase reaction and liver regeneration. SUMMARY BACKGROUND DATA: The metabolic events occurring within the liver during the hepatic stress response are poorly understood. The authors used in vivo 31-phosphorus magnetic resonance spectroscopy to study hepatic metabolism after surgical trauma with and without loss of liver cell mass. METHODS: Three groups were studied: five patients undergoing partial hepatectomy; five patients in whom laparotomy and colonic resection was performed; and five patients treated by thyroidectomy. Hepatic metabolism was evaluated by 31-phosphorus magnetic resonance spectroscopy before surgery and serially thereafter on postoperative days 2, 4, 6, 14, and 28. Estimation of liver volume by magnetic resonance imaging and blood sampling for biochemistry were performed at the same time points. RESULTS: The authors found that alterations in hepatocyte phospholipid metabolism occurred after surgery that were correlated with changes in circulating acute phase proteins. Liver regeneration after hepatectomy was also associated with a derangement in energy metabolism, measured by a decrease in the ratio of ATP to its hydrolysis product inorganic phosphate. The depleted energy status was mirrored in biochemical indices of liver function, and restitution paralleled the course of restoration of hepatic cell mass. CONCLUSIONS: These findings indicate that changes in liver metabolism after surgery reflect the magnitude of tissue injury and the quantity of functioning liver cells. Acute phase responses dominate the initial recovery period at the expense of less important endergonic functions. When liver parenchyma is lost, the acute phase reaction is maintained and further supported by a rapid replenishment of hepatocytes, which can even be considered a continuation of acute phase physiology. Modulation of liver function within the framework of overall hepatic energy economy is one mechanism for matching energy supply with increased demands during these processes.

Acute-Phase Reaction↗