31P spectroscopy of the human prostate gland in vivo using a transrectal probe.

Using a transrectal probe, good quality 31P magnetic resonance spectroscopy of the human prostate was performed safely, consistently, and in a reasonable amount of time (average of 60 min). Initial results indicate that transrectal 31P MRS has the ability to characterize the phosphorylated metabolites of normal, hyperplastic, and malignant prostates. This study demonstrated that malignant prostates are characterized by significantly decreased levels of phosphocreatine (PCr) and increased levels of phosphomonoesters (PME) as compared to healthy prostates.     

Androgen sensitivity of rat prostate carcinoma studied by 31P NMR spectroscopy, 1H MR imaging, and 23Na MR imaging

31P NMR spectroscopy, 1H magnetic resonance (MR) imaging, and 23Na MR imaging were used to study the biochemical difference between nine hormone-sensitive and six hormone-resistant rat prostate cancers and to follow bioenergetic and morphologic changes subsequent to androgen deprivation in the hormone-sensitive model. Neither 1H nor 23Na MR image characteristics were useful in distinguishing androgen-sensitive from androgen-resistant prostate cancer nor in identifying androgen deprivation. 31P NMR spectroscopy did detect bioenergetic differences between the hormone-sensitive and hormone-resistant tumors. Baseline spectra showed a significantly higher PCr/ATP ratio (mean 0.86 +/- 0.09 SEM) for hormone-sensitive tumors than for hormone-resistant tumors (mean 0.26 +/- 0.07 SEM). By 3 days after androgen deprivation (orchiectomy (castration], PCr/ATP ratios had decreased noticeably; by 1 week, the decrease was statistically significant and remained so for the rest of the study (3 weeks). It appears that 31P NMR spectroscopy is useful in detecting androgen sensitivity of prostatic carcinoma.     

联合应用MR扩散加权成像和MR波谱成像对前列腺癌的诊断价值

 目的 探讨联合应用MR扩散加权成像(DWI)和MR波谱成像(MRS)对前列腺癌的诊断价值.方法 经病理证实的32例前列腺癌患者,进行常规MRI扫描、DWI和3D1HMRS 成像.在前列腺3个连续层面、中央腺体和外周带左右两边选取兴趣区,以T2WI表现为低信号作为肿瘤活检穿刺区.参照穿刺活检取材位置及手术病理结果,分别测量癌区和非癌区的(Cho+Cre)/Cit比值和表观扩散系数(ADC)值,并进行统计学分析.结果 前列腺ADC值:癌区与非癌区比较差异有统计学意义(P<0.05).前列腺MRS:癌区表现为Cit峰降低, (Cho+Cre)峰显著升高,(Cho+Cre) /Cit的均值为(1.94±1.43);非癌区表现为Cit峰高,(Cho+Cre)峰低,(Cho+Cre) /Cit的均值为(0.93±0.28),两者间差异有统计学意义(P<0.05).常规MRI的敏感性为71.9%,MRI结合MRS的敏感性为87.5%,MRI、MRS、DWI联合应用的敏感性为93.7%.结论 联合应用MR扩散加权像和MR波谱成像,较单独应用能提高前列腺癌检出的敏感性.     

1H image-guided localized 31P MR spectroscopy of human brain: quantitative analysis of 31P MR spectra measured on volunteers and on intracranial tumor patients

1H image-guided 31P MR spectra of normal human brain and of intracranial tumors have been analyzed quantitatively. Tumor types examined include prolactinoma, lymphoma, and various grade gliomas. The experimental signals were processed by means of a time-domain least-square fitting procedure, which yields the spectral parameters, as well as a prediction of the standard deviations. Significant spectral variations are observed within both populations of normal brain and of intracranial tumor 31P MR spectra. The metabolic ratios derived from the glioma 31P MR spectra and from corresponding uninfiltrated brain tissue do not differ significantly. Significant differences are, however, observed between the metabolic ratios of prolactinoma and uninfiltrated tissue 31P MR spectra. Alkaline pH values are found for the prolactinoma and the high-grade gliomas. Furthermore, spectral differences are observed between the patient's uninfiltrated tissue 31P MR spectra and those of an unmatched population of volunteers. This underscores the necessity for control measurements on the uninfiltrated tissue of the patient and for controls from a matched population of healthy individuals.     

前列腺中央腺体MR波谱谱线的信噪比研究

目的了解前列腺中央腺体MR波谱（MRS）谱线的信噪比（SNR）与病变性质的关系。方法对18例因良性前列腺增生（BPH）行经尿道前列腺切除（TULIP）术患者的MRS谱线作回顾性分析。根据病理结果分为3组：中央腺体偶发癌（IDPC）组5例、腺体增生为主的BPH（glandular BPH，GBPH）组7例和基质增生为主的BPH（stromal BPH，SBPH）组6例。统计中央腺体感兴趣区内所有SNR≥5、SNR〈5和有脂峰干扰的体素数量及所占比率情况，分析SNR与病变性质的关系。结果18例患者共测量体素3632个，SNRI〉5体素1579个（占总测量体素的43％），SNR〈5的体素1873个。SBPH组SNR〈5的体素所占比率（67．64-21．8）％大于GBPH组（37．1±14．5）％和IDPC组（39．9±18．8）％，差异有统计学意义（P〈0．05）；GBPH组和IDPC组比较，差异无统计学意义（P〉0．05）。结论前列腺中央腺体的MRS谱线中，部分谱线由于SNR低，不能用于代谢物半定量分析，尤以SBPH患者的SNR〈5体素所占比率最大。     

Evaluations of cooling exercised muscle with MR imaging and 31P MR spectroscopy

PURPOSE: To investigate the effects of cooling human skeletal muscle after strenuous exercise using 31P MR spectroscopy and MR imaging. METHODS: 14 male subjects (mean age +/- SD, 23.8 +/- 2.3 yr) were randomly assigned to the normal (N = 7) or the cooling group (N = 7). All subjects performed the ankle plantar flexion exercise (12 repetitions, 5 sets). Localized 31P-spectra were collected from the medial gastrocnemius before and after exercise (immediately, 30, 60 min, 24, 48, 96, and 168 h) to determine the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) and intracellular pH. Transaxial T2-weighted MR images of the medial gastrocnemius were obtained to calculate T2 relaxation time (T2), indicative of intramuscular water level, before and after exercise (24, 48, 96, and 168 h). In addition, the muscle soreness level was assessed at the same time as 31P-spectra measurements. Fifteen-minute cold-water immersion was administered to the cooling group after exercise and initial postexercise measurements. RESULTS: The control group showed significantly increased T2 from rest at 48 h after exercise (P < 0.05), but the cooling group showed no significant change in T2 throughout this study. Both groups showed a significantly decreased intracellular pH immediately after exercise (P < 0.05). After that, the cooling group showed a significantly greater value than the value at rest or the control group at 60 min after exercise (P < 0.05). For the Pi/PCr, no significant change was observed in both groups throughout this study. The muscle soreness level significantly increased immediately and at 24-48 h after exercise in both groups (P < 0.05). CONCLUSION: The findings of this study suggest that cooling causes an increase in intracellular pH and prevents the delayed muscle edema.     

Characterization of tumor hypoxia by 31P MR spectroscopy.

Tumor hypoxia is of considerable importance to the oncologist in selecting and optimizing cancer therapy, because hypoxia can determine the effectiveness of various therapies. The relationship between tumor hypoxia and tumor bioenergetics, assessed by 31P MR spectroscopy, is examined to determine whether 31P MR spectroscopy can be clinically useful to measure or characterize tumor hypoxia. Work with experimental tumors has suggested that several different types of hypoxia may exist and that 31P MR spectroscopy cannot be used to characterize all types. Metabolic hypoxia is the level of hypoxia that results in mitochondrial impairment in cells, and it is associated with declining cellular bioenergetic status, which can be measured by enzymatic assay of adenosine triphosphate (ATP). Because 31P MR spectroscopy is sensitive to levels of ATP, it is potentially sensitive to metabolic hypoxia in vivo and may provide a rapid and noninvasive technique for characterizing metabolic hypoxia in tumors. Radiobiologic hypoxia is the level of hypoxia that results in attenuated cell death due to radiation, because radiotoxicity is directly related to tissue levels of oxygen. Radiobiologic hypoxia of tumors thus has more impact on choice of therapy, yet the relationship between metabolic hypoxia and radiobiologic hypoxia remains to be elucidated. An analysis of published data suggests that 31P MR spectroscopy is directly sensitive to metabolic hypoxia in tumors, but it is only indirectly sensitive to radiobiologic hypoxia in tumors. Therefore, 31P MR spectroscopy may be unable to quantify the cell fraction of a tumor that has radiobiologic hypoxia. However, preliminary data suggest that MR spectroscopy may prove useful for determining the effectiveness of therapeutic interventions designed to manipulate radiobiologic hypoxia in tumors or for monitoring the kinetics of tumor reoxygenation after treatment.     

Comparison of 31P MRS and 1H MRI at 1.5 and 2.0 T

The goals of this study were to compare 31P magnetic resonance spectroscopy (MRS) and 1H magnetic resonance imaging (MRI) of human subjects and phantoms at 1.5 and 2.0 T. The 31P signal-to-noise (S/N) ratios in phantom standards and in localized volumes in human brain and liver were compared at 1.5 and 2.0 T. In addition, T1 values for 31P resonances in human brain, 31P linewidths of metabolites in human brain and liver, 1H S/N in a phantom standard, and MR image quality in human head and body were compared at the two field strengths. The results of our study showed that at the higher strength field, (1) in vivo 31P MRS studies benefited from up to 32% improvement in S/N; (2) in vivo 31P MRS studies also benefited from increased spectral dispersion; (3) the quality of MR head images remained comparable; and (4) body images showed some decrease in image quality due to increased chemical shift, and flow and motion artifacts.     

Simultaneous localized 1H STEAM/31P ISIS spectroscopy in Vivo

A sequence for simultaneous acquisition of ¹H STEAM and ³¹P ISIS spectra is described, and ¹H and ³¹P spectra obtained simultaneously from the same volume of interest in both a phantom and a volunteer are presented. The STEAM and ISIS parts of the sequence use a common gradient scheme that is also used during the localized shimming process, partially compensating for eddy current effects. It is demonstrated that this method of simultaneous multinuclear spectroscopy does not compromise the localization performance of the sequence.     

In vivo 1H and 31P NMR spectroscopy of the developing rat brain.

The biochemical changes associated with brain maturation during the first 28 days postnatal were investigated utilizing proton and phosphorus-31 nuclear magnetic resonance spectroscopy in rat pups in vivo. Phosphocreatine was found to increase linearly during this period of development. Phosphomonoester was high at birth, peaked around the 10th day postnatal, and declined thereafter. N-Acetyl-aspartate was low at birth, increased in an approximately linear fashion, and reached adult levels by about Day 28 postnatal. Choline was high at birth and declined thereafter. Taurine, a sulfur amino acid abundant in fetal brain, was also present in high levels on the first day postnatal.     

离体心肌磁共振波谱的实验研究

目的 连续观察离体心肌高能磷酸盐代谢和寻找其变化的规律;探讨＾３１Ｐ ＭＲ波谱的敏感性;观察离体心肌能量代谢与缺血时间的关系。方法 ８例健康犬离体前后心脏用于＾３１Ｐ ＭＲ波谱的动态观察。结果 心脏离体后,磷酸肌酸（ＰＣｒ）迅速下降。离体２￣３小时后,ＰＣｒ降至零水平。直到离体６小时,三磷酸腺苷（ＡＴＰ）水平逐渐耗竭。结论 在心脏离体后２￣３小时,心肌ＰＣｒ迅速下降到离体６小时,三磷酸腺苷（ＡＴＰ     

Intrauterine fetal brain NMR spectroscopy: 1H and 31P studies in rats

Fetal brain metabolism was investigated in utero noninvasively using multinuclear nuclear magnetic resonance spectroscopy in rats at two representative prenatal stages: early (17-18 days) and late (20-21 days) stages. Phosphorus-31 (31P) spectroscopy revealed that phosphocreatine is significantly lower in the early stage and increases to the level of early neonates by the late prenatal stage. Intracellular pH at the early stage was found to be strikingly high (7.52 +/- 0.21) and decreased to a level similar to that of neonates by the late stage (7.29 +/- 0.07). Phosphomonoester levels at both stages were similar to the values reported for early neonates. Water-suppressed proton (1H) spectroscopy demonstrated a distinctive in vivo fetal brain spectral pattern characterized by low levels of N-acetyl aspartate and high levels of taurine. High-resolution proton spectroscopy and homonuclear chemical-shift correlate spectroscopy of brain perchloric acid extracts confirmed these in vivo findings. In vitro 31P spectroscopy of acidified chloroform methanol extracts showed the characteristic membrane phospholipid profiles of fetal brain. The phosphatidylethanolamine (PE)-to-phosphatidylcholine (PC) ratio (PE/PC) did not show significant changes between the two stages at 0.40 +/- 0.11, a value similar to that of early neonates.     

31P and 1H NMR spectroscopy to study the effects of gallopamil on brain ischemia

Studies were performed on 16 cats to evaluate the potential protective effects of Gallopamil on brain ischemia. Brain energy state was determined by 31P NMR and lactate concentration was determined by 1H NMR. Double-tuned surface coils (tuned to 35.8 and 88.4, respectively) were placed on the head after skin and muscle were removed from the calvarium. A 2.1-T, 25-cm-bore Oxford magnet interfaced to a Phosphoenergetics 250-80 spectrometer was used. The cats were bled to 50 mm Hg for 10 min with subsequent application of bilateral carotid occlusion for 10 min to produce ischemia. In all animals, brain energy state as measured by Pi/PCr and lactate concentrations were determined over 5-min intervals (before, during, and after the onset of ischemia). While Gallopamil did not prevent decreases in brain energy state or attenuate the rise in lactate concentration seen during ischemia, brain from animals treated with Gallopamil had a more rapid return of pHi to baseline during the recovery period. In Gallopamil-treated cats, higher levels of lactate were necessary to cause a similar decrease in pHi when compared to controls. The rate of lactate recovery to baseline levels was similar in both groups (control = -0.38 +/- 0.14 mM/min; Gallopamil = -0.44 +/- 0.32 mM/min). In conclusion, Gallopamil appears to lessen the acidosis caused by cerebral ischemia. In addition, we have demonstrated that multinuclear NMR spectroscopy is a powerful tool to study the effects of drugs on cerebral metabolism.     

A comparison of MR elastography and 31P MR spectroscopy with histological staging of liver fibrosis

Objectives

Conventional imaging techniques are insensitive to liver fibrosis. This study assesses the diagnostic accuracy of MR elastography (MRE) stiffness values and the ratio of phosphomonoesters (PME)/phosphodiesters (PDE) measured using ³¹P spectroscopy against histological fibrosis staging.

Methods

The local research ethics committee approved this prospective, blinded study. A total of 77 consecutive patients (55 male, aged 49 ± 11.5 years) with a clinical suspicion of liver fibrosis underwent an MR examination with a liver biopsy later the same day. Patients underwent MRE and ³¹P spectroscopy on a 1.5 T whole body system. The liver biopsies were staged using an Ishak score for chronic hepatitis or a modified NAS fibrosis score for fatty liver disease.

Results

MRE increased with and was positively associated with fibrosis stage (Spearman’s rank = 0.622, P < 0.001). PME/PDE was not associated with fibrosis stage (Spearman’s rank = −0.041, p = 0.741). Area under receiver operating curves for MRE stiffness values were high (range 0.75–0.97). The diagnostic utility of PME/PDE was no better than chance (range 0.44–0.58).

Conclusions

MRE-estimated liver stiffness increases with fibrosis stage and is able to dichotomise fibrosis stage groupings. We did not find a relationship between ³¹P MR spectroscopy and fibrosis stage.

Key Points

• Magnetic resonance elastography (MRE) and MR spectroscopy can both assess the liver.

• MRE is superior to ³¹ P MR spectroscopy in staging hepatic fibrosis.

• MRE is able to dichotomise liver fibrosis stage groupings.

• Gradient-echo MRE may be problematic in genetic haemochromatosis.

     

1H magnetic resonance spectroscopy of the prostate

PURPOSE: To provide a brief summary of important technical and biochemical aspects and current clinical applications of magnetic resonance spectroscopy (MRS) of the prostate. MATERIAL AND METHODS: Pertinent radiological and biochemical literature was searched and retrieved via electronic media (Medline, PubMed). Basic concepts of MRS of the prostate and its clinical applications were extracted to provide an overview. RESULTS: The prostate lends itself to MRS due to its unique production, storage, and secretion of citrate. While healthy prostate tissue demonstrates high levels of citrate and low levels of choline that marks cell wall turnover, prostate cancer (PCA) utilizes citrate for energy metabolism and shows high levels of choline. The ratio of (choline + creatine)/citrate differentiates healthy prostate tissue and PCA. The combination of magnetic resonance imaging (MRI) and 3-dimensional MRS (3D-MRSI or 3D-CSI) of the prostate localizes PCA to a sextant of the peripheral zone of the prostate with sensitivity/specificity of up to 80/80%. Combined MRI and 3D-MRSI exceed the sensitivity and specificity of sextant biopsy of the prostate. When MRS and MRI agree on PCA presence, the positive predictive value is about 90%. In principle, combined MRI and 3D-MRSI recognize and localize remnant or recurrent cancer after hormone therapy, radiation therapy and cryo-surgery. CONCLUSIONS: Since it is non-invasive and radiation-free, combined MRI and 3D-MRSI lends itself to the planning of prostate biopsy and therapy as well as to post-therapeutic follow-up. For broad clinical application, it will be necessary to facilitate MRS examinations and their evaluation and make MRS available to a wider range of institutions.     

31P and 1H magnetic resonance spectroscopy of acute alcohol cardiac depression in rats

Cardiac depression in the isolated rat heart perfused with 4% ethanol was correlated with intracellular phosphate energetics and tissue water distributions. Energy metabolites were assessed using 31P magnetic resonance spectroscopy (MRS) and correlated to the mitochondrial redox state using epicardial surface fluorometry. Changes in myocardial water compartmentation were measured by using 1H NMR spectroscopy with an extracellular chemical-shift reagent (DyTTHA) and correlated to results of 2D echocardiography (2DE). During alcohol perfusion there was a significant decrease in developed pressure and in coronary flow. No change was seen in ATP, PCr, pHi, Pi, or NADH. After withdrawal of alcohol from the perfusate cardiac function reverted to control values without a depletion of energy levels. During alcohol perfusion 1H MRS showed a marked redistribution of water from the intra- to the extracellular space, corresponding to a 35% left ventricular wall thinning confirmed by 2DE. The results indicate that acute alcohol cardiac depression is related to a dehydration of myocardial cells, but is not associated with intracellular acidosis or energy depletion.