In-vivo proton magnetic resonance spectroscopy in adnexal lesions

Clinical value of N-acetyl mucinous compounds and lipid peaks in differentiating benign and malignant ovarian mucinous tumors by MR spectroscopy

PURPOSE

To retrospectively evaluate the clinical significance of the peaks of N-acetyl mucinous compounds (NAMC) at 2 ppm and lipid at 1.3 ppm in in-vivo proton magnetic resonance (MR) spectroscopy for distinguishing benign and malignant mucinous tumors in patients with ovarian masses.

METHODS

MR spectroscopy was performed in patients with pathologically diagnosed mucinous ovarian tumors at 3 T MRI system. The peaks of NAMC, lipid, and total choline compounds (tCho) were classified into three classes in comparison with the noise level by visual estimation. The NAMC concentration was quantified relative to unsuppressed water by using LCModel analysis.

RESULTS

A total of 27 ovarian mucinous tumors in 27 patients were included in this study. The NAMC peak was observed in all 27 mucinous tumors, and the lipid peak was observed in 14 of 27 tumors: 1 of 9 benign tumors (11%), and 13 of 18 malignant tumors (11 borderline malignancies and 7 carcinomas) (72%). The presence of the lipid peak for the diagnosis of malignant mucinous tumor showed generally better diagnostic ability than MR imaging, with a sensitivity of 72%, specificity of 89%, accuracy of 78%, PPV of 93%, and NPV of 62%. The concentration of the NAMC in malignant mucinous tumors tended to be higher than that in benign mucinous tumors, but there was no statistically significant difference.

CONCLUSIONS

The bimodal peaks of NAMC and lipid are suggestive of malignant mucinous tumors, and the presence of the lipid peak may be useful in distinguishing benign from malignant ovarian mucinous tumors.

Proton MR spectroscopy and the detection of malignancy in ovarian masses

OBJECTIVE

To assess the impact of MR spectroscopy (MRS) on the detection of malignancy in ovarian masses.

METHODS

This prospective work included 230 females that had 245 adnexal/ovarian masses. Tumours were spotted by preliminary pelvic ultrasound. Masses assessed by MRI, multi- or single-voxel spectroscopy. Patients' spectra were assessed for peaks of lactate (Lac, 1.31 ppm), lipid (Lip, 1.33 ppm), N-acetyl aspartate (2.0 ppm), acetone (A, 2.05 ppm), choline (Cho, 3.23 ppm) and creatinine (Cr, 3.4 ppm) and the mean values of the (Cho/Cr) ratios were performed by a semi-quantitative approach. The operative pathology served as the standard of reference.

RESULTS

Cho peak twofold higher than the average noise level was detected in 72% of the malignant and only 5.4% of the benign masses with an accuracy of 83%. Adding lactate to the choline enhanced the accuracy to 93%. The mean Cho/Cr ratios of the malignant ovarian masses (2.8) were significantly higher than that of the benign ones (1.2) . We used a receiver operating characteristic curve to determine the best cut-off value (1.7) for the mean Cho/Cr ratio to discriminate malignancy with sensitivity: 81.2%, specificity: 93.3 %, positive-predictive value: 92.9 %, negative-predictive value: 82.4% and accuracy: 87.1%.

CONCLUSION

The simultaneous presence of choline and lactate peaks in MRS examination of the ovarian masses minimizes the overlap between benign and malignant categories. N-acetyl aspartate and acetone are the metabolites for diagnosing complex cystic masses as benign teratoma, endomterioma and tubo- ovarian abscess.

ADVANCES IN KNOWLEDGE

MRS is a non-contrast based and fast MR sequence that gives an idea about tissue components could be used to improve the sensitivity and the accuracy of detecting malignancy in ovarian masses.

Carcinosarcoma of the uterus: MRI findings including diffusion-weighted imaging and MR spectroscopy

BACKGROUND

Recently carcinosarcoma has become regarded as a subset of endometrial carcinoma. Because the clinical course of carcinosarcoma is aggressive with poor prognosis, it should be differentiated from endometrial carcinomas for the appropriate surgical management and adjuvant therapy.

PURPOSE

To clarify the magnetic resonance imaging (MRI) characteristics of uterine carcinosarcoma including diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) measurement and MR spectroscopy (MRS) with quantitative metabolite evaluation.

MATERIAL AND METHODS

MRI findings of 12 pathologically diagnosed uterine carcinosarcomas obtained on 3T MRI were retrospectively evaluated. The mean and minimum ADCs, and the lipid and choline concentration levels were compared with those of pathologically diagnosed 38 endometrial carcinomas.

RESULTS

The mean and minimum ADCs in carcinosarcomas and endometrial carcinomas were not significantly different. The mean ADC of carcinosarcomas was significantly higher than that of higher grade (G2 and G3) endometrial carcinomas. The choline concentration in carcinosarcomas was significantly lower than that in endometrial carcinomas. High lipid peak was observed in 91% of carcinosarcomas and in 24% of endometrial carcinomas.

CONCLUSION

Large, exophytic heterogeneous endometrial mass containing strongly enhanced areas, which may exhibit "tumor delivery", is a suggestive of carcinosarcoma. Relatively high mean ADC and low choline concentration considering its highly malignant nature due to intra-tumoral heterogeneity with necrosis and epithelial cystic components, and the presence of necrosis-associated high lipid peak may be compatible with carcinosarcoma.

Clinical Imaging of Tumor Metabolism with ¹H Magnetic Resonance Spectroscopy

Magnetic resonance spectroscopy (MRS) is a noninvasive functional technique to evaluate the biochemical behavior of human tissues. This property has been widely used in assessment and therapy monitoring of brain tumors. MRS studies can be implemented outside the brain, with successful and promising results in the evaluation of prostate and breast cancer, although still with limited reproducibility. As a result of technical improvements, malignancies of the musculoskeletal system and abdominopelvic organs can benefit from the molecular information that MRS provides. The technical challenges and main applications in oncology of (1)H MRS in a clinical setting are the focus of this review.

N-acetyl resonances in in vivo and in vitro NMR spectroscopy of cystic ovarian tumors

An unassigned and prominent resonance in the region from delta 2.0-2.1 ppm has frequently been found in the in vivo MR spectra of cancer patients. We demonstrated the presence of this resonance with in vivo MRS in the cyst fluid of a patient with an ovarian tumor. (1)H-NMRS on the aspirated cyst fluid of this patient confirmed the observation. A complex of resonances was observed between 2.0 and 2.1 ppm. It was also present in 11 additional ovarian cyst fluid samples randomly chosen from our biobank. The resonance complex was significantly more prominent in samples from mucinous tumors than in samples from other histological subtypes. A macromolecule (>10 kDa) was found responsible for this complex of resonances. A correlation spectroscopy (COSY) experiment revealed cross peaks of two different types of bound sialic acid suggesting that N-glycans from glycoproteins and/or glycolipids cause this resonance complex. In the literature, plasma alpha-1 acid glycoprotein (AGP), known for its high content of N-linked glycans, has been suggested to contribute to the delta 2.0-2.1 spectral region. The AGP cyst fluid concentration did not correlate significantly with the peak height of the delta 2.0-2.1 resonance complex in our study. AGP may be partly responsible for the resonance complex but other N-acetylated glycoproteins and/or glycolipids also contribute. After deproteinization of the cyst fluid, N-acetyl-L-aspartic acid (NAA) was found to contribute significantly to the signal in this spectral region in three of the 12 samples. GC-MS independently confirmed the presence of NAA in high concentration in the three samples, which all derived from benign serous tumors. We conclude that both NAA and N-acetyl groups from glycoproteins and/or glycolipids may contribute to the delta 2.0-2.1 ppm resonance complex in ovarian cyst fluid. This spectral region seems to contain resonances from biomarkers that provide relevant clinical information on the type of ovarian tumor.

In vivomagnetic resonance spectroscopy by the fast Padé transform

The fast Padé transform (FPT) is thoroughly illustrated on two in vivo time signals encoded at 4 T and 7 T via magnetic resonance spectroscopy (MRS). The exact quantum-mechanical spectrum as the Green function series truncated at any partial sum reduces to the unique quotient of two polynomials, which is the FPT. In this Green function as a Maclaurin series in powers of the harmonic variable, the expansion coefficients are the time signal values as damped complex-exponentials with stationary and non-stationary amplitudes for non-degenerate (Lorentzian) and degenerate (non-Lorentzian) spectra. This is automatically shared by the FPT to represent an enormous advantage over the Hankel-Lanczos singular value decomposition (HLSVD) which works only for Lorentzian spectra. Moreover, the resonance amplitudes in the FPT are obtained analytically, rather than solving a system of linear equations as done in the HLSVD. We use two variants of the FPT, initially defined inside and outside the unit circle, but extended automatically to the whole complex frequency plane by the Cauchy analytical continuation. The converged spectra from these two variants of the FPT are found to give the same results, within the experimental background noise level, and this represents an intrinsic cross-validation of the findings and the error analysis.

Metabolic Changes in Pelvic Lesions: Findings at Proton MR Spectroscopic Imaging

OBJECTIVE

The purpose of this study is to investigate the in vivo magnetic resonance spectroscopic (MRS) features of pelvic lesions using long echo time and to characterize the spectral patterns of various pathological entities.

MATERIALS AND METHODS

17 patients with surgically and histopathologically confirmed pelvic lesions underwent long echo-time MRS, and the results obtained were analyzed. Before laparotomy, choline (Cho), lactate, lipid and creatine (Cr) levels of all lesions were measured by single voxel MRS (point-resolved spectroscopy technique, TE 136 ms). Voxels were placed in the center of the lesions. The MRS results of lesions were compared with the final histopathological diagnoses.

RESULTS

Spectroscopy analysis of serous, mucinous and undifferentiated carcinoma of the ovary revealed Cho, lactate and lipid signals, but granulosa-theca cell tumor showed only a lipid signal. The Cho signal was obtained from only 3 patients with mature cystic teratoma but none of the other benign ovarian tumors and pelvic abscesses. A lipid signal was detected in 3 patients diagnosed with pelvic abscess and all benign ovarian tumors. In addition to the lipid signal, a lactate signal was detected in the spectra of two pelvic abscesses. One case of endometrioma and 1 case of teratoma did not show any signal.

CONCLUSION

MRS demonstrates significant differences in metabolite concentration between benign and malignant ovarian tumors and pelvic abscesses. MRS may therefore be helpful in the differential diagnosis of adnexal lesions.

Magnetic resonance spectroscopy features of uterine leiomyomas

OBJECTIVE

The purpose of this study is to investigate the in vivo magnetic resonance spectroscopy features of uterine leiomyomas using long echo time and to characterize the spectral patterns of these lesions.

METHODS

We calculated metabolites in 15 patients with uterine leiomyomas and myometrium of 20 healthy control subjects using single-voxel proton MR spectroscopy (point resolved spectroscopy technique, TE:136 ms). Voxels were placed at the center of the uterine leiomyomas. The peak areas of creatine, choline, lipid and lactate were determined. The MR spectroscopy results of uterine leiomyomas were compared with the spectroscopy results obtained from the myometrium of healthy control subjects.

RESULTS

The characteristically obtained signal was choline, which was detected not only in 14 of the 15 leiomyomas (93.3%) but also in 18 of the 20 myometrium of control subjects (90%). The lipid signals were determined in 9 of 15 patients with uterine leiomyomas (60%) and 8 of 20 control subjects (40%). The lactate signal was obtained from six of 15 patients with leiomyomas (40%) but only two of myometrium (10%). The creatine signal was obtained from 4 of 15 patients with leiomyomas (26.6%) and 5 of 20 myometrium (25%). Among the tested parameters only lactate peak was statistically significant (p < 0.05).

CONCLUSION

Proton MR spectroscopic imaging may be helpful for the investigation of the underlying pathophysiology of uterine leiomyomas. The presence of lactate and lipid signals in the spectrum may be a useful indicator of metabolic pathway of uterine leiomyomas.

In vivo proton magnetic resonance spectroscopy in the evaluation of the endometrium

BACKGROUND

The purposes of this study were to compare proton magnetic resonance (MR) spectroscopic evaluation of the endometrium with histology obtained by endometrial biopsy in women undergoing diagnostic curettage and to determine whether screening with MR spectroscopy (MRS) might be useful in the evaluation of the endometrium.

METHODS

Twenty-three consecutive women who were scheduled for endometrial biopsy were included in the study. The women were evaluated by MRS, performed immediately before the endometrial biopsy. The MRS results were compared with the histological findings obtained from the endometrial biopsy.

RESULTS

All of the cases were proven by pathological examination, and their diagnoses were secretory endometrium (11 cases), proliferative endometrium (seven cases) and disordered proliferative endometrium (five cases). The characteristically obtained signals of choline (Cho) and lipid were detected in all subjects in the secretory endometrium group. In the same group, eight patients showed lactate signals and six showed creatine (Cr) signals. In the disordered proliferative endometrium group, four patients showed lipid plus Cho signals. Two patients in the same group demonstrated both lactate and Cr signals. All patients in the proliferative endometrium group showed Cho signals, two patients demonstrated lactate plus Cho signals, and none of the patients in this group showed lipid and Cr signals.

CONCLUSION

Proton magnetic resonance spectra can register certain metabolic differences in human endometrium in its different stages.