Quantification of spinal cord compression using T1 mapping in patients with cervical spinal canal stenosis - Preliminary experience

T1 mapping in patients with cervical spinal canal stenosis with and without decompressive surgery: A longitudinal study

BACKGROUND AND PURPOSE

Cervical spinal canal stenosis (cSCS) is a common cause of spinal impairment in the elderly. With conventional magnetic resonance imaging (MRI) suffering from various limitations, high-resolution single-shot T1 mapping has been proposed as a novel MRI technique in cSCS diagnosis. In this study, we investigated the effect of conservative and surgical treatment on spinal cord T1 relaxation times in cSCS.

METHODS

T1-mapping was performed in 54 patients with cSCS at 3 Tesla MRI at the maximum-, above and below the stenosis. Subsequently, intraindividual T1-differences (ΔT1) intrastenosis were calculated. Twenty-four patients received follow-up scans after 6 months.

RESULTS

Surgically treated patients showed higher ΔT1 at baseline (154.9 ± 81.6 vs. 95.3 ± 60.7), while absolute T1-values within the stenosis were comparable between groups (863.7 ± 89.3 milliseconds vs. 855.1 ± 62.2 milliseconds). In surgically treated patients, ΔT1 decreased inverse to stenosis severity. After 6 months, ΔT1 significantly decreased in the surgical group (154.9 ± 81.6 milliseconds to 85.7 ± 108.9 milliseconds, p = .021) and remained unchanged in conservatively treated patients. Both groups showed clinical improvement at the 6-month follow-up.

CONCLUSIONS

Baseline difference of T1 relaxation time (ΔT1) might serve as a supporting marker for treatment decision and change of T1 relaxation time might reflect relief of spinal cord narrowing indicating regenerative processes. Quantitative T1-mapping represents a promising additional imaging method to indicate a surgical treatment plan and to validate treatment success.

Quantitative evaluation of the spinal cord compression in patients with cervical spondylotic myelopathy using synthetic MRI

Objectives: This work aimed to investigate the feasibility and diagnostic value of synthetic MRI, including T1, T2 and PD values in determining the severity of cervical spondylotic myelopathy (CSM). Methods: All subjects (51 CSM patients and 9 healthy controls) underwent synthetic MRI scan on a 3.0T GE MR scanner. The cervical canal stenosis degree of subjects was graded 0-III based on the method of a MRI grading system. Regions of interest (ROIs) were manually drawn at the maximal compression level (MCL) by covering the whole spinal cord to generate T1_MCL, T2_MCL, and PD_MCL values in grade I-III groups. Besides, anteroposterior (AP) and transverse (Trans) diameters of the spinal cord at MCL were measured in grade II and grade III groups, and relative values were calculated as follows: rAP = AP_MCL/AP_normal, rTrans = Trans_MCL/Trans_normal. rMIN = rAP/rTrans. Results: T1_MCL value showed a decreasing trend with severity of grades (from grade 0 to grade II, p < 0.05), while it increased dramatically at grade III. T2_MCL value showed no significant difference among grade groups (from grade 0 to grade II), while it increased dramatically at grade III compared to grade II (p < 0.05). PD_MCL value showed no statistical difference among all grade groups. rMIN of grade III was significantly lower than that of grade II (p < 0.05). T2_MCL value was negatively correlated with rMIN, whereas positively correlated with rTrans. Conclusion: Synthetic MRI can provide not only multiple contrast images but also quantitative mapping, which is showed promisingly to be a reliable and efficient method in the quantitative diagnosis of CSM.

High Periventricular T1 Relaxation Times Predict Gait Improvement After Spinal Tap in Patients with Idiopathic Normal Pressure Hydrocephalus

PURPOSE

The diagnosis of idiopathic normal pressure hydrocephalus (iNPH) can be challenging. Aim of this study was to use a novel T1 mapping method to enrich the diagnostic work-up of patients with suspected iNPH.

METHODS

Using 3T magnetic resonance imaging (MRI) we prospectively evaluated rapid high-resolution T1 mapping at 0.5 mm resolution and 4 s acquisition time in 15 patients with suspected iNPH and 8 age-matched, healthy controls. T1 mapping in axial sections of the cerebrum, clinical and neuropsychological testing were performed prior to and after cerebrospinal fluid tap test (CSF-TT). T1 relaxation times were measured in 5 predefined periventricular regions.

RESULTS

All 15 patients with suspected iNPH showed gait impairment, 13 (86.6%) showed signs of cognitive impairment and 8 (53.3%) patients had urinary incontinence. Gait improvement was noted in 12 patients (80%) after CSF-TT. T1 relaxation times in all periventricular regions were elevated in patients with iNPH compared to controls with the most pronounced differences in the anterior (1006 ± 93 ms vs. 911 ± 77 ms; p = 0.023) and posterior horns (983 ± 103 ms vs. 893 ± 68 ms; p = 0.037) of the lateral ventricles. Montreal cognitive assessment (MoCA) scores at baseline were negatively correlated with T1 relaxation times (r < -0.5, p < 0.02). Higher T1 relaxation times were significantly correlated with an improvement of the 3‑m timed up and go test (r > 0.6 and p < 0.03) after CSF-TT.

CONCLUSION

In iNPH-patients, periventricular T1 relaxation times are increased compared to age-matched controls and predict gait improvement after CSF-TT. T1 mapping might enrich iNPH work-up and might be useful to indicate permanent shunting.

Correlations between preoperative diffusion tensor imaging and surgical outcome in patients with cervical spondylotic myelopathy

OBJECTIVE

To investigate the correlations between preoperative diffusion tensor imaging (DTI), a Magnetic Resonance Imaging (MRI)-based technique and surgical outcome in patients with cervical spondylotic myelopathy (CSM).

METHODS

A retrospective study of 95 patients with CSM who received diagnosis and surgical treatment in our hospital was carried out. According to the recovery rate of the Japanese Orthopaedic Association (JOA) scale at the 1-year postoperative follow-up, the patients were divided into a good recovery group (JOA recovery rate ≥60%, n = 47) and a poor recovery group (JOA recovery rate <60%, n = 48). Patients in both groups underwent diffusion tensor imaging examination before surgery. The preoperative fractional anisotropy (FA) value, apparent diffusion coefficient (ADC) value, longitudinal dispersion (AD) rate, and lateral dispersion (VD) rate were compared between the two groups. Pearson correlation coefficient was used to analyze the correlation between the preoperative DTI quantization parameters (FA, ADC, AD, VD) and the postoperative JOA recovery rate. In addition, we compared the preoperative spinal cord compression ratio (CR), spinal cord cross-sectional area (TA), maximum spinal cord compression (MSCC), and maximum canal compromise (MCC) between the above two groups. The correlations between the four measurements and the postoperative JOA recovery rate were analyzed using Pearson correlation coefficient.

RESULTS

The preoperative FA value in the good recovery group was significantly higher than that in the poor recovery group, while the ADC value was significantly lower (both P<0.001). The good recovery group had lower preoperative AD and VD, but there was no statistical significance (both P>0.05). Pearson correlation analysis showed that the preoperative FA value was positively correlated with the JOA recovery rate (P<0.05), while the VD value had significantly negative correlation with the JOA recovery rate (P<0.05). The preoperative ADC and AD values were negatively correlated with JOA recovery rate, whereas there was no statistical significance (both P>0.05). The CR, TA, MSCC and MCC values measured before surgery in the good recovery group were significantly lower than those in the poor recovery group (all P<0.001); were negatively correlated with the JOA recovery rate (all P<0.05), while the correlation with TA was not statistically significant (P>0.05).

CONCLUSION

DTI can evaluate the severity of the patient's condition before surgery by analyzing the subtle structural changes in patients with CSM. At the same time, the preoperative FA, VD, CR, MSCC, and MCC values are all associated with the surgery efficacy, which paves the way for the next step of clinical treatment.

T1 Mapping for Microstructural Assessment of the Cervical Spinal Cord in the Evaluation of Patients with Degenerative Cervical Myelopathy

BACKGROUND AND PURPOSE

Although current radiologic evaluation of degenerative cervical myelopathy by conventional MR imaging accurately demonstrates spondylosis or degenerative disc disease causing spinal cord dysfunction, conventional MR imaging still fails to provide satisfactory anatomic and clinical correlations. In this context, we assessed the potential value of quantitative cervical spinal cord T1 mapping regarding the evaluation of patients with degenerative cervical myelopathy.

MATERIALS AND METHODS

Twenty patients diagnosed with mild and moderate-to-severe degenerative cervical myelopathy and 10 healthy subjects were enrolled in a multiparametric MR imaging protocol. Cervical spinal cord T1 mapping was performed with the MP2RAGE sequence procedure. Retrieved data were processed and analyzed regarding the global spinal cord and white and anterior gray matter on the basis of the clinical severity and the spinal canal stenosis grading.

RESULTS

Noncompressed levels in healthy controls demonstrated significantly lower T1 values than noncompressed, mild, moderate, and severe stenotic levels in patients. Concerning the entire spinal cord T1 mapping, patients with moderate-to-severe degenerative cervical myelopathy had higher T1 values compared with healthy controls. Regarding the specific levels, patients with moderate-to-severe degenerative cervical myelopathy demonstrated a T1 value increase at C1, C7, and the level of maximal compression compared with healthy controls. Patients with mild degenerative cervical myelopathy had lower T1 values than those with moderate-to-severe degenerative cervical myelopathy at the level of maximal compression. Analyses of white and anterior gray matter confirmed similar results. Strong negative correlations between individual modified Japanese Orthopaedic Association scores and T1 values were also observed.

CONCLUSIONS

In this preliminary study, 3D-MP2RAGE T1 mapping demonstrated increased T1 values in the pathology tissue samples, with diffuse medullary alterations in all patients with degenerative cervical myelopathy, especially relevant at C1 (nonstenotic level) and at the maximal compression level. Encouraging correlations observed with the modified Japanese Orthopaedic Association score make this novel approach a potential quantitative biomarker related to clinical severity in degenerative cervical myelopathy. Nevertheless, patients with mild degenerative cervical myelopathy demonstrated nonsignificant results compared with healthy controls and should now be studied in multicenter studies with larger patient populations.

T1 Mapping Quantifies Spinal Cord Compression in Patients With Various Degrees of Cervical Spinal Canal Stenosis

Age-related degeneration of the cervical spinal column is the most common cause of spinal cord lesions. T1 mapping has been shown to indicate the grade and site of spinal cord compression in low grade spinal canal stenosis (SCS). Aim of our study was to further investigate the diagnostic potential of a novel T1 mapping method at 0.75 mm resolution and 4 s acquisition time in 31 patients with various grades of degenerative cervical SCS. T1 mapping was performed in axial sections of the stenosis as well as above and below. Included subjects received standard T2-weighted MRI of the cervical spine (including SCS-grading 0-III), electrophysiological, and clinical examination. We found that patients with cervical SCS showed a significant difference in T1 relaxation times within the stenosis (727 ± 66 ms, mean ± standard deviation) in comparison to non-stenotic segments above (854 ± 104 ms, p < 0.001) and below (893 ± 137 ms, p < 0.001). There was no difference in mean T1 in non-stenotic segments in patients (p = 0.232) or between segments in controls (p = 0.272). Mean difference of the T1 relaxation times was significantly higher in grade III stenosis (234 ± 45) vs. in grade II stenosis (176 ± 45, p = 0.037) vs. in grade I stenosis (90 ± 87 ms, p = 0.010). A higher difference in T1 relaxation time was associated with a central efferent conduction deficit. In conclusion, T1 mapping may be useful as a tool for SCS quantification in all grades of SCS, including high-grade stenosis with myelopathy signal in conventional T2-weighted imaging.

Real-Time Magnetic Resonance Imaging: Radial Gradient-Echo Sequences With Nonlinear Inverse Reconstruction

OBJECTIVE

The aim of this study is to evaluate a real-time magnetic resonance imaging (MRI) method that not only promises high spatiotemporal resolution but also practical robustness in a wide range of scientific and clinical applications.

MATERIALS AND METHODS

The proposed method relies on highly undersampled gradient-echo sequences with radial encoding schemes. The serial image reconstruction process solves the true mathematical task that emerges as a nonlinear inverse problem with the complex image and all coil sensitivity maps as unknowns. Extensions to model-based reconstructions for quantitative parametric mapping further increase the number of unknowns, for example, by adding parameters for phase-contrast flow or T1 relaxation. In all cases, an iterative numerical solution that minimizes a respective cost function is achieved with use of the iteratively regularized Gauss-Newton method. Convergence is supported by regularization, for example, to the preceding frame, whereas temporal fidelity is ensured by downsizing the regularization strength in comparison to the data consistency term in each iterative step. Practical implementations of highly parallelized algorithms are realized on a computer with multiple graphical processing units. It is "invisibly" integrated into a commercial 3-T MRI system to allow for conventional usage and to provide online reconstruction, display, and storage of regular DICOM image series.

RESULTS

Depending on the application, the proposed method offers serial imaging, that is, the recording of MRI movies, with variable spatial resolution and up to 100 frames per second (fps)-corresponding to 10 milliseconds image acquisition times. For example, movements of the temporomandibular joint during opening and closing of the mouth are visualized with use of simultaneous dual-slice movies of both joints at 2 × 10 fps (50 milliseconds per frame). Cardiac function may be studied at 30 to 50 fps (33.3 to 20 milliseconds), whereas articulation processes typically require 50 fps (20 milliseconds) or orthogonal dual-slice acquisitions at 2 × 25 fps (20 milliseconds). Methodological extensions to model-based reconstructions achieve improved quantitative mapping of flow velocities and T1 relaxation times in a variety of clinical scenarios.

CONCLUSIONS

Real-time gradient-echo MRI with extreme radial undersampling and nonlinear inverse reconstruction allows for direct monitoring of arbitrary physiological processes and body functions. In many cases, pertinent applications offer hitherto impossible clinical studies (eg, of high-resolution swallowing dynamics) or bear the potential to replace existing MRI procedures (eg, electrocardiogram-gated cardiac examinations). As a consequence, many novel opportunities will require a change of paradigm in MRI-based radiology. At this stage, extended clinical trials are needed.