Localized proton spectroscopy using stimulated echoes

Frahm, Jens; Merboldt, Klaus‐Dietmar; Hänicke, W.

doi:10.1016/0022-2364(87)90154-5

Cited by 568 publications

(398 citation statements)

References 2 publications

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“…When spins are not coupled their response to the STEAM sequence is well-represented by a vector model, leading to the well-known 50% yield of the sequence (3,4,12). For spins that are coupled, hard-pulse analytical models that incorporate product operator analyses of STEAM have been undertaken previously (11,(13)(14)(15)(16)(17).…”

Section: Methodsmentioning

confidence: 99%

Response of metabolites with coupled spins to the STEAM sequence

Thompson¹,

Allen²

2001

Magn. Reson. Med.

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This article demonstrates that a numerical solution of the full quantum mechanical equations for all metabolites with coupled spins is an efficient and accurate means, first, of predicting the optimum STEAM sequence design for quantifying any target metabolite in brain, and, second, for providing the basis lineshapes and yields of these metabolites to facilitate their accurate quantification. Using as illustrations the weakly coupled AX 3 system of lactate, the ABX aspartyl group of N-acetylaspartate, which has only two strongly coupled spins, and the much larger strongly coupled AMNPQ glutamyl group of glutamate, the numerical solutions for the response to STEAM highlight the principal source of response variability, namely, the evolution of and transfer between zero quantum terms during the mixing time, TM. These highlights include the rapid oscillations of zero quantum terms due to the chemical shift difference of the coupled spins, the proliferation of oscillating zero order terms due to strong coupling, and the serendipitous smoothing of the response as the number of strongly coupled spins increases. The numerical solutions also demonstrate that the design of the selective 90°pulses is a far less critical factor in determining the response than was the case for the selective 180°pulses Metabolite detection and quantification in vivo with proton spectroscopic methods is most commonly carried out using the spatial localization provided either by the single voxel PRESS (point resolved spectroscopy) (1,2) or STEAM (stimulated echo acquisition mode) (3,4) sequences. When both sequences are available, the sequence of choice is often determined by the metabolite target. For example, the observation of uncoupled singlet resonances in brain, namely, N-acetylaspartate (NAA) at 2.02 ppm, creatine (Cr) at 3.05 ppm, and choline (Cho) at 3.2 ppm, are routinely observed with a long-echo PRESS sequence. This stems from the factor of two advantages in uncoupled-spin signal yield over STEAM and the relatively long T 2 s of these resonances compared with either the macromolecular signals or the J-modulation envelopes of coupled spins. However, when the target metabolites contain coupledspin systems, short-echo STEAM spectroscopy has gained popularity in the clinical setting, due principally to its robustness at echo times from ϳ10 to ϳ50 ms. Nonetheless, the response of certain key, coupled-spin metabolites to the STEAM sequence, not to mention the background metabolite spectrum, exhibit significant variability. The purpose of this article is to demonstrate the efficacy of numerical calculations in the determination of the sources of that variability. The range of echo and mixing times considered (TE and TM, respectively) is that which is typically regarded as falling into the short-echo experimental range, namely, TE and TM less than ϳ50 ms.The short-echo-time limit is regarded as desirable for the observation of coupled spins because the longer echo-time modulations of the metabolite lineshapes lead, more often than not, to...

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Section: Methodsmentioning

confidence: 99%

Response of metabolites with coupled spins to the STEAM sequence

Thompson¹,

Allen²

2001

Magn. Reson. Med.

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“…In-vivo localized MRS was carried out using the STEAM sequence (Frahm et al, 1987). Magnetic field shimming was carried out both globally and over the voxel region prior to MRS. Line-widths (LW) after voxel shimming corresponded typically to 10-25 Hz for the lipid peak in case of normal/control breast and 5-20 Hz for the water peak in patients with breast tumours.…”

Section: Mri/mrs Measurementsmentioning

confidence: 99%

Evaluation of total choline from in-vivo volume localized proton MR spectroscopy and its response to neoadjuvant chemotherapy in locally advanced breast cancer

et al. 2001

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Breast cancer is the commonest cancer among women the world over. In India, the reported age adjusted incidence of breast cancer in women is about 26.7/1 00 000 population (NCRP, 1992). Unlike the West, in India, majority of the patients (about 60%) present with locally advanced breast cancer (LABC) or disseminated disease (Goel et al, 1995). In LABC, the treatment policy followed at most centres, is neoadjuvant chemotherapy (NACT) followed by surgery and local or locoregional radiotherapy. The response to NACT is assessed by clinical evaluation and supplemented by radiological measurement of reduction in tumour volume by mammography and/or ultra sonography. None of the currently available indicators of response (clinical and radiological) correlate well with the actual response as assessed on histopathological examination of the tumour.MR imaging (MRI) is a valuable new tool for diagnostic mammography (Orel et al, 1996;Friedrich, 1998; Harms, 1998;Orel, 1998). Recently, dynamic contrast enhanced MRI techniques have also been developed for differentiation between benign and malignant tumours (Kaiser, 1991;Harms et al, 1993; Haywang-Kobrunner et al, 1997;Piccoli, 1997;Daniel et al, 1998). The above techniques, however, do not provide any metabolic/ biochemical information. On the contrary, magnetic resonance spectroscopy (MRS) permits non-invasive detection of metabolic (biochemical) differences between tumours and normal tissues, and can also be used to monitor response to different treatment regimens. Recently, we have shown that in LABC, the assessment of response to NACT can be made using water-to-fat ratio calculated from volume localized proton MRS (Jagannathan et al, 1998(Jagannathan et al, , 1999. In addition, we also reported the presence of choline in a majority of the breast cancer patients (Jagannathan et al, 1998).In this study, results of evaluation of choline in LABC and its response to NACT using in-vivo proton MRS are presented. The objectives are: (i) to evaluate the potential of proton MRS in the study of breast cancer, and (ii) to investigate further, the recent observation of choline containing compounds in malignant breast tissues and its response to NACT. To the best of our knowledge, this is the first report assessing the response of breast cancer to NACT in a large cohort of patients using in-vivo proton MRS. PATIENTS AND METHODS Patients67 women with cytologically confirmed infiltrating ductal carcinoma (IDC) were recruited. Necessary clearance from the Institute ethical committee and written informed consent were obtained prior to examination from patients and controls. Patients were evaluated clinically and tumour size was measured using Vernier calipers. Metastatic workup included liver function tests, chest

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“…Therefore, we have taken up an earlier suggestion of Zhu et al (1) to phase each acquisition by means of the residual water signal. Their approach required a modification of the stimulated echo acquisition mode (STEAM) sequence (4) to remove the water signal by subtraction. However, perfect water suppression has become obsolete with the advent of automated tools for spectral analysis that include features to cope with residual water.…”

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confidence: 99%