Renal corticomedullary metabolite gradients during graded arterial occlusion: a localized 31P magnetic resonance spectroscopy study

In order to investigate the role of the outer medulla in acute ischemic renal failure (Epstein FH, Balaban RS, Ross BD: Redox state of cytochrome aa3 in isolated perfused rat kidney. Am J Physiol 1982;243: F356-F363), the distribution of ATP in the in vivo porcine kidney and its relationship to Na transport and to ischemia was examined by using localized 31P magnetic resonance spectroscopy. Renal cortex (ATP) was higher than medulla. Reduction in Na transport produced by partial renal arterial occlusion ("hypofiltration"), resulted in a 13% increase in the ATP/Pi ratio of the whole kidney (from 2.61 +/- 0.26 to 2.96 +/- 0.27; P less than 0.03). This increase was accounted for by a statistically significant increase in (ATP) in the cortex, with medulla contributing to an insignificant extent. Further occlusion of the renal artery to reduce GFR to zero ("hypoperfusion") resulted in a 70% fall in ATP/Pi ratio. (ATP) was reduced most in the cortex, but pH fell equally in cortex and medulla. After release of arterial occlusion, cortical ATP recovered less completely than medulla ATP. Intracellular pH and Pi were restored in both cortex and medulla. It was concluded that cortex and medulla contribute equally to the pattern of disordered energy metabolism in acute renal failure. Sparing of ATP during hypofiltration may reflect the reduced energy requirements of active Na transport.     

Localized 31P magnetic resonance spectroscopy of large pediatric brain tumors

Fourteen children aged 1 week to 16 years, with a variety of large or superficial brain tumors, underwent localized in vivo 31P magnetic resonance spectroscopy of their tumor. Quantitative spectral analysis was performed by measuring the area under individual peaks using a computer algorithm. In eight patients with histologically benign tumors the spectra were considered to be qualitatively indistinguishable from normal brain. The phosphocreatine/inorganic phosphate ratio (PCr/Pi) averaged 2.0. Five patients had histologically malignant tumors; qualitatively, four of these were considered to have abnormal spectra, showing a decrease in the PCr peak. The PCr/Pi ratio for this group averaged 0.85, which was significantly lower than that seen in the benign tumor group (p less than 0.05). No difference between the two groups was seen in adenosine triphosphate or phosphomonoesters. It is concluded that a specific metabolic "fingerprint" for childhood brain tumors may not exist, but that some malignant tumors show a pattern suggestive of ischemia.     

Differentiation between renal cortex and medulla in the response to hypotension using localized 31P magnetic resonance spectroscopy

Experiments were designed to test the hypothesis that renal medulla is more sensitive to hypoxia than is the cortex. Using the one-dimensional phase encoding technique to perform 31phosphorus magnetic resonance spectroscopy in a perfused porcine kidney preparation, cortex and medulla were differentiated on the basis of the unique resonance at 3 ppm found only in medulla. Hypotension-induced hypoxia reduced total renal oxygen consumption by 60%, and urine flow by 44%. Nonlocalized 31P MRS spectra showed that [ATP]/[Pi] ratio fell by 40%, and intrarenal pH by 0.1 unit. Virtually all of these changes could be accounted for by changes in the renal cortex, where initial [ATP]/[Pi] was higher than in medulla (1.16 vs. 0.68). In medulla [ATP]/[Pi] fell only 29% (n.s. versus control) and pH remained unchanged during hypotension. Thus the cortex appears to be more sensitive to hypoxia in this preparation, and observations fail to support the proposed hypothesis. They are consistent, however, with the greater capacity of medulla for anaerobic glycolysis. Localized 31P MRS provides improved noninvasive metabolic assessment of cold-preserved kidneys.     

Post-polio fatigue: a 31P magnetic resonance spectroscopy investigation.

Changes in high energy phosphates (HEP) and intramuscular pH during exercise were measured in 17 patients with post-polio fatigue and in 28 healthy controls using 31P magnetic resonance spectroscopy (MRS). Subjects performed a dynamic hand grip exercise at low and high intensity. Mean changes in the HEP and pH showed no significant differences between the groups, although the post-polio group's response was highly variable. Six patients showed evidence of a lower lactate accumulation during the high intensity exercise when compared with controls. These data suggest that the whole body fatigue experienced by polio survivors is not related to any systemic metabolic abnormality.     

Image-guided 31P magnetic resonance spectroscopy of normal and transplanted human kidneys

Image-guided 31-phosphorus magnetic resonance spectroscopy (MRS) was used to obtain spatially localized 31P spectra of good quality from healthy normal human kidneys and from well-functioning renal allografts. A surface coil of 14 cm diameter was used for acquiring phosphorus signals solely from a volume-of-interest located within the kidney. To determine the effects of kidney transplantation on renal metabolism, patients with well functioning allografts were studied. Little or no phosphocreatine in all spectra verifies the absence of muscle contamination, and is consistent with proper volume localization. The intensity ratio of phosphomonoesters (PME) to adenosine triphosphate (ATP) resonances in transplanted kidneys (PME/ATP = 1.1 +/- 0.4) was slightly elevated (P = 0.2) compared to that of healthy normal kidneys (PME/ATP = 0.8 +/- 0.3). The inorganic phosphate (Pi) to ATP ratio was similar in the two groups (Pi/ATP = 1.1 +/- 0.1 in transplanted kidneys vs. 1.2 +/- 0.6 in normal kidneys). Acid/base status, as evidenced from the chemical shift of Pi, was the same in both normal controls and transplanted kidneys. Despite the practical problems produced by organ depth, respiratory movement, and tissue heterogeneity, these results demonstrate that image-guided 31P MR spectra can reliably be obtained from human kidneys.     

Magnetic resonance imaging and 31P magnetic resonance spectroscopy for evaluating focal cerebral ischemia

Recent advances in magnetic resonance (MR) imaging and MR spectroscopy (MRS) allow the noninvasive in vivo study of a variety of anatomical, physiological, and biochemical alterations that may occur in different cerebral pathologies. The authors have investigated the use of MR imaging and MRS to monitor the evolution of experimental focal cerebral ischemia in rats. Permanent focal cerebral ischemia was induced in 36 rats, and 12 normal rats were used as a control group. Changes in high-energy phosphate metabolites were followed in vivo using MRS during the 1st hour and at 3 and 6 hours after ischemic insult. Changes in vivo MR images were evaluated at 1, 3, 6, 12, and 24 hours after ischemic insult. Significant decreases (p less than 0.05) in phosphocreatine/inorganic phosphate ratios and intracellular pH values occurred immediately after the induction of ischemia. The presence of an infarcted area seen on MR images was a constant finding at 3 hours after ischemic insult, and was well defined and localized at 12 and 24 hours. The location of areas of infarction seen on MR images correlated well with areas identified histopathologically. The T1 and T2 MR relaxation times were significantly increased 3 hours after ischemic insult and remained prolonged for at least 24 hours. The results show that MR imaging is a sensitive method to measure cerebral infarction, and that MRS is a sensitive measure of changes that occur in the early phases of ischemia, perhaps when cellular changes may still be reversible. At 3 and 6 hours after the ischemic insult, however, 31P-MRS spectra may appear to be "normal" despite the presence of well-documented areas of infarction.     

肝细胞癌31P磁共振波谱诊断价值的初步研究

目的利用31P磁共振波谱(magnetic resonance spectroscopy,MRS)分析肝细胞癌与正常肝组织的磷脂和能量代谢特点。方法16例正常人(对照组)及10例肝细胞癌患者(观察组)纳入本研究,对照组既往无肝病史,生化检查确认无异常,肝细胞癌患者经病理检查证实,用Sonata1.5T磁共振仪行31P-MRS检查,对磷酸单脂、磷酸单脂/β-三磷酸腺苷、磷酸单脂/磷酸二脂指标作独立样本t检验。结果对照组和观察组的上述3个指标均值分别为0.71±0.19、0.33±0.16、0.37±0.12和3.13±0.53、1.88±0.2、2.27±0.42,两组比较差异有统计学意义(P<0.05)。结论31P-MRS能够无创性鉴别肝细胞癌与正常肝组织的代谢改变,可以对肝细胞癌进行早期诊断。     

磁共振尿路水成像对诊断上尿路梗阻病变的价值

目的：探讨磁共振尿路水成像(MRU)对诊断上尿路梗阻病变的价值。方法：回顾分析了52例上尿路梗阻患者的MRU的临床资料。结果：52例患者经过MRU检查均能显示梗阻的部位，50例与手术后诊断或治疗后明确的诊断相符合，2例误诊。结论：MRU能准确地显示尿路梗阻病变的部位和大小，具有无创伤、无痛苦、无辐射、不需造影剂及多平面成像能力等特点，比临床上常用的B超、静脉肾盂造影、逆行肾盂造影等检查具有一定的优越性。     

Long-term assessment of posttransplant renal prognosis with 31 P magnetic resonance spectroscopy.

BACKGROUND: 31P-magnetic resonance spectroscopy (MRS) has been widely used to study pretransplantation renal viability, and although some had discussed posttransplant renal viability, no one has examined long-term posttransplant renal prognosis. We discuss the use of 31P-MRS to assess the long-term prognosis from the time when MRS was performed. METHODS: We studied 20 patients with renal allografts. 1.5 Tesla clinical magnetic resonance imaging (MRI) and 15 cm surface coil was used for 31P-MRS. Localized 31P-MRS was done using image selected in vivo spectroscopy (ISIS) method. Individual peaks were fitted by Lorenzian line-shapes with a least square method and peak area ratios were calculated. RESULTS: A beta-adenosine triphosphate/inorganic phosphate (beta-ATP/Pi) ratio >1.2 had sensitivity of 92.8%, specificity of 100%, and accuracy of 95% for predicting 3-year renal survival; a beta-ATP/Pi ratio >1.2 had sensitivity of 90.9%, specificity of 66.7%, and accuracy of 76.9% for predicting 5-year renal survival. We compared 31P-MRS spectra data between the survived group and failed group. The survived group had significantly higher beta-ATP/Pi, alpha-ATP/Pi, and phosphodiester (PDE)/Pi ratios than the failed group. CONCLUSIONS: We discussed the beta-ATP/Pi value as a parameter for predicting long-term survival of a transplanted kidney from the time when MRS was performed. A value above 1.2 suggests a high probability of 3-year renal survival, whereas a value over 2.5 indicates that the transplanted kidney could survive over 5 years. 31P-MRS may be useful for predicting long-term survival of transplanted kidneys, but additional studies are needed.     

Cardioplegia and ischemia in the canine heart evaluated by 31P magnetic resonance spectroscopy

BACKGROUND: Warm continuous blood cardioplegia provides excellent protection, but must be interrupted by ischemic intervals to aid visualization. We hypothesized that (1) as ischemia is prolonged, the reduced metabolic rate offered by cooling gives the advantage to hypothermic cardioplegia; and (2) prior cardioplegia mitigates the deleterious effects of normothermic ischemia. METHODS: Isolated cross-perfused canine hearts underwent cardioplegic arrest followed by 45 minutes of global ischemia at 10 degrees C or 37 degrees C, or 45 minutes of normothermic ischemia without prior cardioplegia. Left ventricular function was measured at baseline and during 2 hours of recovery. Metabolism was continuously evaluated by phosphorus-31 magnetic resonance spectroscopy. RESULTS: Adenosine triphosphate was 71% +/- 4%, 71% +/- 7%, and 38% +/- 5% of baseline at 30 minutes, and 71% +/- 4%, 48% +/- 5%, and 39% +/- 6% at 42 minutes of ischemia in the cold ischemia, warm ischemia, and normothermic ischemia without prior cardioplegia groups, respectively. Left ventricular systolic function, left ventricular relaxation, and high-energy phosphate levels recovered fully after cold cardioplegia and ischemia. Prior cardioplegia delayed the decline in intracellular pH during normothermic ischemia initially by 9 minutes, and better preserved left ventricular relaxation during recovery, but did not ameliorate the severe postischemic impairment of left ventricular systolic function, marked adenosine triphosphate depletion, and creatine phosphate increase. Left ventricular distensibility decreased in all groups. CONCLUSIONS: When cardioplegia is followed by prolonged ischemia, better protection is provided by hypothermia than by normothermia. Prior cardioplegia confers little advantage on recovery after prolonged normothermic ischemia but delays initial ischemic metabolic deterioration, which would contribute to the safety of brief interruptions of warm cardioplegia.     

Clinical applicability of human in vivo localized phosphorus-31 magnetic resonance spectroscopy of bone and soft tissue tumors

Background: Magnetic resonance imaging (MRI) is of restricted value for the in vivo characterization of tumor types. The applicability of phosphorus-31 (³¹P) magnetic resonance spectroscopy (MRS) in the diagnosis of bone and soft tissue tumors is unknown. Methods: A total of 191 consecutive patients (85 females and 106 males; mean age 41 years, range 1–80) with a well-defined bone or soft tissue tumor on MRI were analyzed for additional³¹P spectroscopy. Histology and/or cytology was obtained from all tumors. Because of low sensitivity of the³¹P nucleus and the contamination of surrounding tissue, only large, superficially located tumors accessible to the surface coil could be accepted for MRS. Results: Twenty-one patients (11%) could be included in the study. From this remaining group only 12 studies (57%) produced spectra with well resolved phosphorus peaks and an acceptable signal-to-noise ratio. However, these spectra did not allow differentiation between the benign and malignant nature of the lesions. The other 9 studies showed spectra with poor signal intensities and/or poorly defined peaks, making tumor differentiation impossible. Conclusion: Only 6% of the bone and soft tissue tumors produced well defined spectra, which implies that localized³¹P MRS cannot be considered as a routine technique in the diagnostic and treatment evaluation of bone and soft tissue tumors.The results of this study were presented at the 46th Annual Cancer Symposium of The Society of Surgical Oncology, Los Angeles, California, March 18–21, 1993.     

31P nuclear magnetic resonance study of intrahepatic energy metabolism in acute liver failure

Changes in phosphorus metabolites and intracellular pH in acute liver failure induced by D-galactosamine (GAL) were evaluated non-destructively and continuously using 31P-NMR spectroscopy. Furthermore, changes in these parameters under ischemia were also examined. GAL(1.0g/kg) was injected intravenously to male Wistar rats. NMR measurements in perfused livers were performed with a GX-270FT NMR spectrometer (JEOL). Typical changes in 31P-NMR spectra were observed after GAL administration. ATP levels decreased to 57.4 +/- 12.4% at 12 hours and to 65.4 +/- 7.7% at 24 hours after the administration compared with that in control rats. Pi levels increased remarkably to 632.1 +/- 76.4% at 3 hours and recovered to 127.5 +/- 22% at 24 hours. NAD+/NADH and UDP-sugar levels gradually increased to 253.5 +/- 33.4 and 456.3 +/- 60.9%, respectively, at 24 hours. In GAL treated livers, ATP levels fell rapidly and Pi levels rose correspondingly during ischemia, and they rapidly recovered by reperfusion. The intracellular pH decreased to 7.16 +/- 0.032 from 7.38 +/- 0.065 at 3 hours after GAL administration. However, significant changes in pH were not observed until 24 hours. In GAL treated livers, slight changes in pH were observed under ischemia. These results indicate that 31P-NMR is a useful method to evaluate the damage of acute liver failure, and to diagnose liver diseases involving the intrahepatic energy metabolism.     

31P nuclear magnetic resonance of rat pancreatic grafts

This study investigates whether phosphate metabolite concentrations and intracellular pH alter in early acute rejection of rat pancreatic allografts. In vitro biochemical assays, in vitro 31P nuclear magnetic resonance spectroscopy, and in vivo 31P NMR spectroscopy of the grafts were compared. Duct-ligated, vascularized rat pancreatic isografts and allografts were transplanted onto the infrarenal aorta of the recipients with inferior vena cava venous drainage. In order to obtain reproducible acute rejection, allografting was performed across a major histocompatibility barrier. For the in vitro experiments freeze-clamped graft extracts were prepared and analyzed for adenosine triphosphate concentration by fluorimetry, then placed in an 8.5 Tesla vertical bore magnet. 31P NMR spectra were recorded using a Bruker AM 360 spectrometer operating at 145.7 MHz for 31P. Spectra were acquired from nontransplanted controls; 3-day, 5-day, and 1-month posttransplant isografts, and 3-day and 5-day posttransplant allografts. All grafts examined were functioning satisfactorily. The ATP content of the extracts was significantly lower in the 3- and 5-day allografts than the respective isografts. Invasive in vivo 31P NMR spectra were recorded using surface coils adjacent to the grafts from functioning 5-day posttransplant isografts and allografts (i.e., 3 days prior to an expected elevation in blood sugar from acute rejection in the allografts). The ATP/inorganic phosphate ratios and pH from the in vivo spectra were significantly lower in the allografts than in the isografts. It is concluded that changes in intracellular metabolism occur early in the process of acute rejection and that 31P NMR spectroscopy may provide a means of diagnosing this before current methods.     

Assessment of renal viability by phosphorus-31 magnetic resonance spectroscopy

To assess the applicability of phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in the analysis of renal transplant viability and preservation techniques with respect to pre-transplant ischemia, we studied two rat groups. Twenty-five rat kidneys were subjected to various time increments of warm ischemia (Group A), and 31P-MRS was performed on each kidney at time intervals of up to 72 hours during simple hypothermic storage. We correlated findings of 31P-MRS with simultaneous findings of electron microscopic (EM) ultrastructural viability parameters (in Group A) and subsequent survival and renal function in 30 rats (Group B) subjected to similar amounts of variable ischemia. Intracellular phosphorus metabolite levels were nondestructively monitored by 31P-MRS via spectral peaks of NAD, sugar monophosphates (SP), and inorganic phosphate (Pi). We concluded: SP/Pi and NAD/Pi ratios decay in a time-dependent manner for both warm and cold ischemia, although this process is much slower during cold storage; EM viability parameters correlate with the development of acute tubular necrosis (irreversible damage) versus nonviability (gross cell death) on a qualitative basis only; and 31P-MRS enables a quantitative assessment of renal viability and ischemic renal damage and can predict the degree of acute tubular necrosis and post-ischemic renal function. 31P-MRS is potentially a noninvasive, nondestructive method of assessing viability during simple hypothermic storage of the rat kidney. Preliminary evidence shows that this MRS method can be applied to human kidney viability studies for clinical renal transplantation and urologic research concerning renal preservation.     

Phosphorus-31 magnetic resonance spectroscopy of cerebral ischemia in cats

The energy metabolism of the brain was measured in three types of ischemic models in the cat using phosphorus-31 magnetic resonance spectroscopy. The cerebral ischemia was produced as follows. In Group 1, two balloons were inflated in the left subclavian artery and the brachiocephalic trunk. In Group 2, the left middle cerebral artery was occluded through a transorbital approach. A combination of the two was employed in Group 3. Phosphorus-31 magnetic resonance spectra were obtained serially during 2 hours of ischemia. Immediately after occlusion, peaks of phosphocreatine and adenosine triphosphate decreased, whereas the peak of inorganic phosphate increased and split in two. Intracellular pH determined by chemical shift of the inorganic phosphate peak decreased. These changes were more pronounced in Group 3 when compared with the other groups. Histological study showed no infarction in Group 1 and infarcted areas in Groups 2 and 3. The size of the infarcted area in Group 3 was larger than that in Group 2. These results suggest that the model of middle cerebral artery occlusion potentiated with the occlusion of the brachiocephalic trunk and the left subclavian artery by balloon catheters is a reliable stroke model and that phosphorus-31 magnetic resonance spectroscopy is useful to understand the pathophysiological state of cerebral ischemia in vivo.     

急性上尿路结石梗阻的影像学分析

目的：探讨超声、腹部平片（ＫＵＢ）、静脉尿路造影（ＩＶＵ）对急性输尿管结石梗阻的诊断价值。方法：回顾性分析３５２例急性输尿管结石梗阻患者的Ｂ超、利尿性Ｂ超、ＫＵＢ、ＩＶＵ的诊断结果。结果：对肾积水的诊断,常规Ｂ超诊断率８３．２％（２９３／３５２）,而５９例可疑病例利尿性Ｂ超的诊断率７９．７％（４７／５９）,利用常规Ｂ超加利尿Ｂ超检查,对梗阻性肾积水的诊断率９６．６％（３４０／３５２）;对输尿管结石     

MRU诊断上尿路梗阻性疾病的价值

目的 探讨磁共振尿路造影（MRU）诊断上尿路梗阻性疾病的意义。方法 59例上尿路梗阻性疾病患者接受检查，MRU为冠状位快速自旋回波T2加权像。结果 所有病例MRU尿路梗阻部位及扩张状况均显示良好，其中54例经手术或病理确诊，仅2例术前MRU误诊。结论 MRU作为一种非侵袭性、无辐射损伤和不需造影剂的新技术，对上尿路梗阻性疾病的定位及定性诊断具有特殊价值，是一种可供选择的有临床实用价值的尿路成像方法。     

Forebrain ischemia in diabetic and nondiabetic BB rats studied with 31P magnetic resonance spectroscopy.

In spontaneously diabetic BB rats, the effect of chronically maintained blood glucose levels on the degree of energy failure and brain pH change during an ischemic insult, and on subsequent recovery after reperfusion, was studied with in vivo 31P magnetic resonance spectroscopy. Short duration forebrain ischemia (10-min carotid occlusion plus hypotension of 50 mmHg) was induced in diabetic and nondiabetic male BB rats whose blood glucose levels were maintained with insulin. Spectra were obtained in 1-min blocks before, during, and for 1 h after ischemia. Before ischemia, hypoglycemic (blood glucose less than 3 mM) diabetic rats had an increased Pi peak intensity, with no significant pH change, compared with other groups. During ischemia, the rate and extent of hydrolysis of high-energy phosphate metabolites (as measured by an increase in Pi) decreased, and the severity of tissue acidosis increased as preischemia blood glucose concentration increased. Among hyperglycemic BB rats, similar ischemia-induced changes were found for subgroups with blood glucose levels of 13.7 +/- 1.2 and 20.3 +/- 0.6 mM, in keeping with the known decrease in hexose binding sites associated with chronic hyperglycemia. Decline in PCr level during ischemia was not significantly different between groups. With reperfusion, both Pi and pH values rapidly returned to preischemia values. PCr levels, however, did not recover in hyperglycemic diabetic animals, with the degree of residual impairment dependent on the preischemia glucose level. Results suggest that optimal management of diabetes may lessen the degree of injury within the ischemic penumbra in diabetic patients who suffer a stroke.     

急性上尿路梗阻性无尿的诊断

目的 提高急性上尿路梗阻性无尿的诊断水平。方法 对58例急性上尿路梗阻患者的临床表现、影像学检查结果和梗阻原因进行总结、分析。结果 临床表现为无尿58例、肾区疼痛41例、肾区叩击痛33例、高血压20例、血尿素氮和肌酐升高57例、高血钾8例。MRU、B超、x线（包括KUB、IVU、逆行肾盂造影）、CT、MRI等影像学检查为主要辅助检查。对上尿路梗阻的检出率，MRU为100％（25／25），B超为88％（50／57），CT／MRI为60％（6／10），X线为49％（19／39）；MRU、B超检出率显著高于X线和CT／MRI（P〈0．05）。对梗阻病因的检出率，MRU为88％（22／25），B超为46％（26／57），X线为46％（18／39），CT／MR为50％（5／10）；MRU检出率显著高于B超、X线和CT／MRI（P〈0．05）。梗阻病因为结石27例、肿瘤18例、输尿管狭窄4例、腹膜后纤维化3例、药物结晶2例、肾结核1例，不明原因3例。结论 影像学检查对急性上尿路梗阻性无尿的诊断具有重要价值，MRU、B超对梗阻的检出率较高，MRU在病因诊断方面具有优势。结石是最常见的上尿路梗阻病因，其次为肿瘤。     

急性梗阻性自发性尿外渗的临床诊治

目的：提高急性梗阻性自发性尿外渗的诊断和治疗水平。方法：回顾性分析9例急性梗阻性自发性尿外渗患者的临床资料,并结合文献探讨其诊断和治疗方法。结果：患者多以肾绞痛发病,逐渐发展成持续或不典型疼痛,并向腹部蔓延,患侧肾区有明显叩击痛。B超、尿路造影及CT检查对诊断有肯定价值。结论：本病为尿路梗阻后继发的临床综合症,早期诊断较为困难,确诊主要依靠影像学检查。尽早解除尿路梗阻是本病治疗的原则。