Effects of MR Parameter Changes on the Quantification of Diffusion Anisotropy and Apparent Diffusion Coefficient in Diffusion Tensor Imaging: Evaluation Using a Diffusional Anisotropic Phantom

Objective

To validate the usefulness of a diffusional anisotropic capillary array phantom and to investigate the effects of diffusion tensor imaging (DTI) parameter changes on diffusion fractional anisotropy (FA) and apparent diffusion coefficient (ADC) using the phantom.

Materials and Methods

Diffusion tensor imaging of a capillary array phantom was performed with imaging parameter changes, including voxel size, number of sensitivity encoding (SENSE) factor, echo time (TE), number of signal acquisitions, b-value, and number of diffusion gradient directions (NDGD), one-at-a-time in a stepwise-incremental fashion. We repeated the entire series of DTI scans thrice. The coefficients of variation (CoV) were evaluated for FA and ADC, and the correlation between each MR imaging parameter and the corresponding FA and ADC was evaluated using Spearman''s correlation analysis.

Results

The capillary array phantom CoVs of FA and ADC were 7.1% and 2.4%, respectively. There were significant correlations between FA and SENSE factor, TE, b-value, and NDGD, as well as significant correlations between ADC and SENSE factor, TE, and b-value.

Conclusion

A capillary array phantom enables repeated measurements of FA and ADC. Both FA and ADC can vary when certain parameters are changed during diffusion experiments. We suggest that the capillary array phantom can be used for quality control in longitudinal or multicenter clinical studies.     

Suicidal Callers to a National Helpline in the UK: A Comparison of Depressive and Psychotic Sufferers

Little information is available on the profile of suicidal mentally ill sufferers seeking help from helplines. In this article we describe the profile and experience with services of suicidal people calling SANELINE, a national mental health helpline in the UK. Analyses were conducted on 1,331 calls made during 1996-1997 by callers who resided in London. Sixty-one percent of all callers were female. Half of all callers were suffering from depression and 32% from psychosis. Psychotic sufferers were significantly more likely not to have been complying with treatment, to have wanted information about medication, and to have been dissatisfied with the local services. Suicidal psychotic sufferers were more likely than non-suicidal ones to have inquired about mental health laws or about state benefits. On the other hand, depressive sufferers were more likely to have wanted information about social support groups, and to have complained about the lack of services in their area of residence. The findings suggested the need to target male sufferers, to meet the information needs of suicidal people with psychosis or depression, and to increase awareness about available sources of help.     

Cervical Compressive Myelopathy due to Anomalous Bilateral Vertebral Artery

We report a very rare case of cervical compressive myelopathy by an anomalous bilateral vertebral artery (VA) entering the spinal canal at the C1 level and compressing the spinal cord. A 70-year-old woman had been suffering from progressive gait disturbance. Magnetic resonance imaging revealed that a bilateral VA at the V4 segment had abnormal courses and caused compression to the high cervical cord. VA repositioning was performed by anchoring a suture between the artery and around the arachnoid membrane and dentate ligament, and then, microvascular decompression using a Teflon sponge was done between the VA and the spinal cord. The weakness in the patient improved in the lower extremity after the operation. Anomalous VA could be one of the rare causes of cervical compressive myelopathy. Additionally, an anchoring suture and microvascular decompression around the VA could be a sufficient and safe method to indirectly decompress the spinal canal.     

Effects of rod stiffness and fusion mass on the adjacent segments after floating mono-segmental fusion: a study using finite element analysis

Purpose

The aims of the present study were to compare the biomechanical effects on the adjacent segments after mono-segmental floating fusion with posterior semi-rigid or rigid stabilization, and to evaluate the effect of the amount of fusion mass on the biomechanical differences.

Methods

A detailed, nonlinear L1–S1 finite element model had been developed and validated. Then five models were reconstructed by different fixation techniques on the L3–L4 level: rigid fixation with an interbody spacer (Ti + IS), rigid fixation with a large interbody spacer (Ti + IS_all), semi-rigid fixation with an interbody spacer (PEEK + IS), semi-rigid fixation with a large interbody spacer (PEEK + IS_all), and semi-rigid fixation only (PEEK). Analyses were conducted for the case of erect standing position, flexion, and extension motion.

Results

At L1–L2 and L2–L3, PEEK + IS demonstrated less inter-segmental rotation and nucleus pressure increments from the intact model compared with Ti + IS. The L4–L5 and L5–S1 levels showed slightly higher values with PEEK + IS, but these differences among the instrumented models were not significant. The motion difference based on the fusion mass at the adjacent levels was at most 3 %. All instrumentation cases generated a 55 % higher facet contact force at the lower adjacent level (L4–L5) compared to that of the intact model during 26° extension and the largest increment was detected at the upper adjacent level (L2–L3) in the Ti + IS. Instrumentation with Ti + IS markedly increased the stress in the intervertebral disk at the upper adjacent level, while the stress with PEEK + IS appeared largest at the lower adjacent level.

Conclusions

Posterior instrumentation with semi-rigid rods may lower the incidence of disk and facet degeneration in the upper adjacent segment compared to rigid rods. On the other hand, the possibility of facet degeneration will be similar for all instrumentation devices in the lower adjacent segment in the long-term. The stiffness difference between rigid and semi-rigid rods on the changes in the adjacent motion segments was more crucial than amount of fusion mass.     

Long-term recurrence rates after the removal of spinal meningiomas in relation to Simpson grades

Purpose

Simpson grade II removal (coagulation of the dural attachment after gross total removal) of spinal meningioma is considered an acceptable alternative, but increased recurrence after more than 10 years has been reported. More attention must be paid to the long-term surgical outcomes after Simpson grade II removal.

Methods

A retrospective review was performed for 20 patients (M:F = 5:15; age, 59 ± 9 years) with Simpson grade II removal (mean follow-up period, 12.9 years; range 10.0–17.5). Magnetic resonance (MR) imaging was conducted in 17 patients at 88 ± 52 months (range 12–157). During the same period, Simpson grade I removal (removal of the dural origin) was performed in 21 patients (follow-up, 89 ± 87 months; range 9–316). Radiological recurrence was defined as a visible tumor on a follow-up MR image, and clinical tumor recurrence was defined as the recurrence of symptoms.

Results

At the final follow-up, neurological symptoms had improved in 16/20 patients and remained stable in 4/20. A recurrent tumor was detected in one patient due to increased back pain at 92 months postoperative, but the symptom was stable without surgery until the last follow-up (124 months). The radiological and clinical recurrence-free survival periods were 150 ± 7 months (95 % CI 136–163) and 204 ± 6 months (95 % CI 193–215), respectively. There was no recurrence after Simpson grade I removal, whereas neurological deterioration occurred in two patients after surgery.

Conclusions

Simpson grade II removal may be an alternative option if the risk of complications with Simpson grade I removal is expected to be high.