Usefulness of 1H magnetic resonance spectroscopy in human testes: preliminary study

Diffusion-weighted magnetic resonance imaging and magnetic resonance spectroscopy for non-invasive characterization of azoospermia: A prospective comparative single-center study

BACKGROUND

Azoospermia affects about 15% of childless males. The differential diagnosis between subtypes of azoospermia is the initial step in its management.

OBJECTIVES

To investigate the role of diffusion-weighted magnetic resonance imaging and proton magnetic resonance spectroscopy in distinguishing obstructive azoospermia from non-obstructive azoospermia and predicting sperm retrieval together with histological alterations in men with non-obstructive azoospermia.

MATERIALS AND METHODS

This prospective comparative study involved 60 men with obstructive azoospermia (group A) and 60 men with non-obstructive azoospermia (group B). Scrotal proton magnetic resonance spectroscopy and diffusion-weighted magnetic resonance imaging were conducted for all participants to respectively evaluate testicular metabolites and normalized apparent diffusion coefficient 1 week before sperm retrieval.

RESULTS

Apparent diffusion coefficient was significantly higher in group B as compared to group A (0.47 ± 0.11 vs. 0.29 ± 0.05; and 0.46 ± 0.14 vs. 0.28 ± 0.02) for the right and left testis, respectively. Conversely, testicular choline and lipids were significantly higher in group A as compared to group B. Normalized apparent diffusion coefficient, choline, and lipids at cut-off levels of 0.353, 0.31, and 0.725 could differentiate between obstructive azoospermia and non-obstructive azoospermia (area under the curve = 0.963; confidence interval = 0.939-0.986, area under the curve = 0.985; confidence interval = 0.974-0.997, and area under the curve = 0.970; confidence interval = 0.940-0.999, respectively). Regarding the prediction of sperm retrieval in the non-obstructive azoospermia group, choline levels had the highest area under the curve (0.923), and its cut-off level was 0.195. The normalized apparent diffusion coefficient was significantly lower in men with positive sperm retrieval as compared to men with unsuccessful retrieval. Finally, it was revealed that all magnetic resonance imaging parameters except creatine could independently predict testicular histology in men with non-obstructive azoospermia. The highest prediction was 95% in normal spermatogenesis, and the least prediction was 40% in spermatid arrest. Regression analysis was used to detect final predictors and extrapolate an equation that could be used to predict testicular pathology CONCLUSIONS: Normalized apparent diffusion coefficient and proton magnetic resonance spectroscopy are helpful in differentiating obstructive azoospermia from non-obstructive azoospermia and predicting sperm retrieval and related histological alterations in men with non-obstructive azoospermia.

An Overview of the Role of Multiparametric MRI in the Investigation of Testicular Tumors

Simple Summary

Although conventional ultrasonography remains the primary imaging modality for the assessment of testicular tumors, multiparametric MRI of the scrotum, which combines morphologic and functional data, serves as a powerful adjunct. Based on the recommendations issued by the Scrotal and Penile Imaging Working Group of the European Society of Urogenital Radiology, scrotal MRI is strongly recommended after equivocal US findings. In cases of testicular masses, the main clinical indications are as follows: lesion characterization when sonographic findings are non-diagnostic, discrimination between germ-cell and non-germ-cell testicular tumors, local staging of testicular tumors in patients who are candidates for testis-sparing surgery, and preoperative histological characterization of testicular germ-cell tumors in selected cases. This article aims to provide an overview of the role of multiparametric MRI in the investigation of testicular tumors.

Abstract

Conventional ultrasonography represents the mainstay of testis imaging. In cases in which ultrasonography is inconclusive, scrotal MRI using a multiparametric protocol may be used as a useful problem-solving tool. MRI of the scrotum is primarily recommended for differentiating between benign and malignant testicular masses when sonographic findings are ambiguous. This technique is also accurate in the preoperative local staging of testicular tumors and, therefore, is recommended in patients scheduled for testis-sparing surgery. In addition, MRI may provide valuable information regarding the histological characterization of testicular germ-cell tumors, in selected cases. Scrotal MRI may also help in the differentiation between testicular germ-cell neoplasms and non-germ-cell neoplasms. Axial T1-weighted imaging, axial and coronal T2-weighted imaging, axial diffusion-weighted imaging, and coronal subtracted dynamic contrast-enhanced imaging are the minimum requirements for scrotal MRI. A variety of MRI techniques—including diffusion tensor imaging, magnetization transfer imaging, proton MR spectroscopy, volumetric apparent diffusion coefficient histogram analysis, and MRI-based radiomics—are being investigated for testicular mass characterization, providing valuable supplementary diagnostic information. In the present review, we aim to discuss clinical indications for scrotal MRI in cases of testicular tumors, along with MRI findings of common testicular malignancies.

When to ask for an MRI of the scrotum

Background

Multiparametric MRI (mpMRI) of the scrotum has been established as a useful second‐line diagnostic tool for the investigation of scrotal diseases. Recently, recommendations on clinical indications for scrotal MRI were issued by the Scrotal and Penile Imaging Working Group of the European Society of Urogenital Radiology.

Objective

To update current research on when to ask for an MRI of the scrotum.

Methods

PubMed database was searched for original articles and reviews published during 2010–2021.

Results

Eighty‐three articles fulfilled the search criteria. Scrotal MRI is mainly recommended after inconclusive US findings or inconsistent with the clinical examination and should be asked in the following cases: differentiation between intratesticular and paratesticular lesions (in rare cases of uncertain US findings), characterization of paratesticular and intratesticular lesions (when US findings are indeterminate), discrimination between germ cell and sex cord‐stromal testicular tumors, local staging of testicular malignancies (in patients planned for testis‐sparing surgery), differentiation between seminomas and non‐seminomatous tumors (when immediate chemotherapy is planned and orchiectomy is delayed), assessment of acute scrotum and scrotal trauma (rarely needed, in cases of non‐diagnostic US findings) and detection and localization of undescended testes (in cases of inconlusive US findings). Although preliminary data show promising results in the evaluation of male infertility, no established role for mpMRI still exists.

Conclusion

Multiparametric MRI of the scrotum, by assessing morphologic and functional data represents a valuable problem‐solving tool, helping to improve our understanding on the nature of scrotal pathology and the process of spermatogenesis. The technique may improve patient care and reduce the number of unnecessary surgical procedures.

Proton MR Spectroscopy in Assessing the Biochemical Milieu of Human Testes

Proton magnetic resonance spectroscopy (MRS), considered a connection between metabolism and anatomic and functional information provided by standard MRI, gives information on various tissue metabolites and their pathologic changes. Recently, proton MRS has been added as an adjunct tool to the multiparametric protocol of scrotal MRI, providing a new insight into the extremely complex biochemical milieu of normal and abnormal testes. This article reviews proton MR spectra of normal testes, showing age and bilateralism dependence. Disturbances of various metabolic pathways in testes of infertile men resulting in alterations of metabolite peaks are discussed. Preliminary data on proton MR spectra of testicular mass lesions are presented. LEVEL OF EVIDENCE: 5. TECHNICAL EFFICACY STAGE: 5.

In vivo biochemical investigation of spermatogenic status: 1H-MR spectroscopy of testes with nonobstructive azoospermia

OBJECTIVES

To evaluate the biochemical milieu in testes with nonobstructive azoospermia (NOA) by using proton MR spectroscopy (1H-MRS) in detecting differences in testicular metabolites between histological stages of NOA and in assessing the possible presence of spermatozoa before microdissection testicular sperm extraction (mTESE).

METHODS

Forty-nine NOA men and fifty age-matched controls were included in this prospective study. A single-voxel point-resolved spectroscopy sequence with TR/TE (2000/25 ms) was used. NOA testes were classified using the higher Johnsen score (hJS) (group 1, hJS ≥ 8; and group 2, hJS < 8). Nonparametric statistical tests were used to assess differences in normalized metabolite concentrations, defined as ratios of the metabolite concentrations versus creatine concentration between (a) NOA and controls, (b) NOA groups, and (c) NOA with positive and negative sperm retrieval.

RESULTS

Normalized concentrations of total choline (median 0.396 vs 1.09 mmol/kg, p = 0.002), myo-inositol (median 1.985 vs 3.19 mmol/kg, p = 0.002), and total lipids and macromolecules (TLM) resonating at 0.9 ppm (median 0.962 vs 2.43 mmol/kg, p = 0.024), 1.3 ppm (median 4.88 vs 10.7 mmol/kg, p = 0.043), and 2.0 ppm (median 2.33 vs 5.96 mmol/kg, p = 0.007) were reduced in NOA testes compared with controls. Decreased concentrations of TLM 2.0 (median 3.755 vs 0.436 mmol/kg, p = 0.043) were found in group 2 compared with group 1. Increased normalized concentrations of glutamate were observed in NOA testes with failed sperm retrieval (median 0.321 vs 0.000 mmol/kg, p = 0.028).

CONCLUSIONS

1H-MRS provides metabolic information about the testis in NOA patients and assesses spermatogenic status before mTESE.

KEY POINTS

• NOA testes differed from age-matched controls, in terms of reduced normalized concentrations of tChol, mI, and lipids. • TLM 2.0 peaks were found useful in the identification of NOA testes with the presence of foci of advanced spermatogenesis up to the haploid gamete stage. • Glu proved a reliable metabolic signature of spermatogenesis in NOA population by assessing the possible presence of sperm after mTESE.

Are there differences in the biochemical profile of bilateral normal testes? A 3.0 T 1H-MR spectroscopy study

Bilateral normal testes asymmetry represents an interesting phenomenon. The aim was to assess possible differences in the biochemical profile of bilateral normal testes by 3.0 T proton magnetic resonance spectroscopy (1H-MRS). Twenty-one men were examined with scrotal 3.0 T MRI, including a single-voxel point-resolved spectroscopy sequence. MR spectra were obtained by placing a volume of interest in the middle of each normal testis. Normalised metabolite concentrations, defined as ratios of the calculated metabolite concentrations relative to creatine (Cr) concentration, were compared between bilateral normal testes using Mann-Whitney U test. 1H-MRS allowed the detection of certain testicular metabolites, including total choline, Cr, myo-inositol, Glx, total lipids and macromolecules resonating at 0.9, 1.3 and 2.0 ppm. Normal left testis had higher median normalised concentrations of Glx (p = .002) and lactate (p = .041) compared with the normal right testis. Differences in concentrations of Glx were attributed to differences in glutamate (p = .020). Normal testes asymmetry is confirmed in this study by differences in the biochemical testicular profile, as assessed by 3.0 T 1H-MRS. Increase in levels of glutamate and lactate in normal left testis should be correlated with changes in metabolic pathways, specifically glycometabolism and amino acid metabolism.

Testis spectroscopy may predict sperm retrieval rate in men with non-obstructive azoospermia undergoing micro-TESE: A pilot study

Objective

To investigate whether prior testis magnetic resonance spectroscopy predicts the success or failure of micro-dissection testicular sperm extraction (micro-TESE) in patients with non-obstructive azoospermia (NOA).

Material and Methods

Nine men with NOA who were scheduled for micro-TESE for the first time, 9 NOA men with a history of previous micro-TESE and 5 fertile men were enrolled. All NOA patients and fertile controls underwent testis spectroscopy. A multi-voxel spectroscopy sequence was used. Testicular signals of choline (Cho), creatine (Cr), myo-inositol (MI), lactate, and lipids were analyzed quantitatively and compared with the results of the micro-TESEs.

Results

The most prominent peaks were Cho and Cr in the fertile controls and NOA subjects with positive sperm retrieval in the micro-TESE. A high Cho peak was detected in 87% of the NOA men with positive sperm retrieval. NOA men without sperm at the previous micro-TESE showed a marked decrease in Cho and Cr signals. For positive sperm retrieval in micro-TESE, the cut-off value of Cho was 1.46 ppm, the cut-off value of Cr was 1.43 ppm, and the cut-off value of MI was 0.79 ppm.

Conclusion

Testis spectroscopy can be used as a non-invasive screening method to predict the success or failure of micro-TESE.

MRI of testicular malignancies

Although testicular carcinoma represents approximately only 1% of solid neoplasms in men, it is the most common malignancy between young men. The two main histologic categories are testicular germ cell tumors (TGCTs), including seminomas and nonseminomas, accounting for 90-95% of testicular neoplasms and sex cord-stromal tumors. Scrotal MRI, including a multiparametric protocol, has been proposed as a valuable supplemental imaging technique in the investigation of testicular pathology. Recently, the Scrotal and Penile Imaging Working Group appointed by the board of the European Society of Urogenital Radiology has produced recommendations on when to perform scrotal MRI. Regarding intratesticular masses, MRI of the scrotum may be used for their characterization, when US findings are indeterminate and for local staging of TGCTs, when organ-sparing surgery is planned. Differentiation between seminomas and nonseminomas is possible based on MRI features, when clinically needed. Scrotal MRI may also help in differentiating between TGCTs and nongerm cell tumors. Functional information based on diffusion-weighted imaging and dynamic contrast-enhanced MRI data improve testicular mass lesion characterization. Preliminary observations on diffusion tensor imaging, magnetization transfer imaging, and proton MR spectroscopy bring about new data in the understanding of testicular microstructure and pathophysiology.

Imaging of the scrotum: beyond sonography

The aim of this article is to describe the role of second-level imaging techniques after an initial ultrasonography evaluation in the assessment of scrotal diseases. While ultrasonography remains central as the primary imaging modality for the evaluation of pathologic conditions of the scrotum, the role of magnetic resonance imaging continues to evolve: it can actually be valuable as a problem-solving tool when sonographic findings are equivocal or inconclusive. Magnetic resonance imaging of the scrotum may provide accurate detection and characterization of scrotal diseases, well depicting the precise location of scrotal masses (intratesticular or extratesticular) and reliably characterizing benign conditions simulating neoplastic processes, thus preventing unnecessary radical surgery. Advanced magnetic resonance techniques, most of all diffusion weighted imaging and magnetic resonance spectroscopy, play in the meanwhile a more significant role in evaluating scrotal diseases.

TEACHING POINTS

• Multiparametric ultrasonography usually represents the initial imaging modality for approaching scrotal diseases. • MRI is well established as a problem-solving tool for inconclusive sonographic findings. • Advanced MRI techniques can be successfully applied in scrotal pathology assessment. • MRI is valuable in differentiating benign conditions from neoplastic processes. • CT plays a role in trauma assessment and cancer staging alongside PET/CT.

Normal testes asymmetry evaluated by apparent diffusion coefficient and magnetization transfer ratio

Background In humans, the left testis generally hangs lower than the right and the right is larger than the left. Magnetic resonance imaging (MRI) represents an important adjuvant modality in the investigation of testicular diseases. Purpose To assess if normal testes asymmetry is related to apparent diffusion coefficient (ADC) and magnetization transfer ratio (MTR). Material and Methods The normal testes from 106 men were included. Testicular volume (TV) was calculated by using the ellipsoid formula: length × width × height × 0.52. Diffusion-weighted imaging was performed using a SS EPI diffusion pulse sequence and b-values of 0 and 900 s/mm^-2. Magnetization transfer imaging was obtained using a 3D GRE sequence both with and without an off-resonance radiofrequency pulse. MTR maps were obtained by the following formula: (SIo-SIm) / (SIo) × 100%, where SIo and SIm represent the signal intensity in the baseline image and that in the corresponding image acquired with an off-resonance MT pulse, respectively. The mean and standard deviation of testicular volume (TV), ADC, and MTR of both testes was calculated and compared using a paired sample t-test. Results The mean TV (mL) was greater ( P = 0.006) for the right testis (16.77 ± 4.84) compared to the left (15.97 ± 4.45). ADC of the right testis (1.09 ± 0.12 × 10 ^- 3mm²s^-1) was not different ( P = 0.064) from that of the left testis (1.07 ± 0.12 × 10^-3mm²s^-1). Differences ( P = 0.032) were observed between MTR of the right (46.6 ± 2.1%) and left testis (46.0 ± 2.2%). Conclusion The reported differences in paired testes size was confirmed, introducing a possible relationship with structural and functional asymmetry of normal testes, based on MTR.

Laminoplasty versus laminectomy and fusion for multilevel cervical compressive myelopathy: A meta-analysis

This is a meta-analysis to compare the results between laminoplasty and laminectomy followed by fusion for the patients with multilevel cervical compressive myelopathy. An extensive search of literature was performed in MEDLINE, Embase, the Cochrane library, CNKI, and WANFANG. The following outcome measures were extracted: the Japanese Orthopaedic Association (JOA) scores, cervical curvature index (CCI), visual analog scale (VAS), cervical lordosis (C2-7), complications, blood loss, and operation time. Data analysis was conducted with RevMan 5.3 and STATA 12.0. A total of 23 studies comprising 774 and 743 patients treated with laminoplasty and laminectomy followed by fusion, respectively, were included in the final analysis. The pooled analysis showed that there was no significant difference in preoperative JOA scores [P = 0.89], postoperative JOA scores [P = 0.13], JOA scores improvement rate [P = 0.27], preoperative CCI [P = 0.15], postoperative CCI [P = 0.14], preoperative VAS [P = 0.41], postoperative VAS [P = 0.52], preoperative cervical lordosis (C2-7) [P = 0.46], postoperative cervical lordosis (C2-7) [P = 0.67], total complications [P = 0.07], axial pain [P = 0.94], and blood loss [P = 0.51]. However, there were significant difference in operation time (WMD = -19.57 [-32.11, -7.02], P = 0.002) and C5 palsy (OR = 0.26 [0.15, 0.44], P < 0.001). As compared with laminectomy followed by fusion, expansive laminoplasty showed no significant differences in JOA scores, CCI, ROM, VAS, cervical lordosis (C2-7), axial pain, total complications, and blood loss, but shorter operation time and fewer C5 palsy.