Evaluation of spatial precision and accuracy of cone-beam CT using an in vitro phantom model

OBJECTIVE

High accuracy and precision are essential in stereotactic neurosurgery, as targeting errors can significantly affect clinical outcomes. Image registration is a vital step in stereotaxis, and understanding the error associated with different image registration methods is important to inform the choice of equipment and techniques in stereotactic neurosurgery. The authors aimed to quantify the test-retest reliability and stereotactic accuracy of cone-beam CT (CBCT) compared with the current clinical gold-standard technique (i.e., CT).

METHODS

Two anthropomorphic phantom models with 40 independent unique steel spheres were developed to compare CBCT frame and stereotactic space registration with the clinical gold standard (CT). The cartesian coordinates of each sphere were compared between the imaging modalities for test-retest reliability and overall accuracy.

RESULTS

Both imaging modalities showed similar levels of fiducial deviation from the expected geometry. The equivalence test demonstrated mean differences between CT and CBCT registration of -0.082 mm (90% CI -0.27 to 0.11), -0.045 mm (90% CI -0.43 to 0.34), and -0.041 mm (90% CI -0.064 to 0.018) for coordinates in the x-, y-, and z-axes, respectively. The mean euclidean distance difference between the two modalities was 0.28 mm (90% CI 0.27-0.29).

CONCLUSIONS

Accuracy and precision were comparable between CBCT and CT image registrations. These findings suggest that CBCT registration can be used as a clinically equivalent substitute to gold-standard CT acquisition.

Preliminary experience with a transcranial magnetic resonance-guided focused ultrasound surgery system integrated with a 1.5-T MRI unit in a series of patients with essential tremor and Parkinson's disease

OBJECTIVE Transcranial magnetic resonance-guided focused ultrasound surgery (tcMRgFUS) is one of the emerging noninvasive technologies for the treatment of neurological disorders such as essential tremor (ET), idiopathic asymmetrical tremor-dominant Parkinson's disease (PD), and neuropathic pain. In this clinical series the authors present the preliminary results achieved with the world's first tcMRgFUS system integrated with a 1.5-T MRI unit. METHODS The authors describe the results of tcMRgFUS in a sample of patients with ET and with PD who underwent the procedure during the period from January 2015 to September 2017. A monolateral ventralis intermedius nucleus (VIM) thalamic ablation was performed in both ET and PD patients. In all the tcMRgFUS treatments, a 1.5-T MRI scanner was used for both planning and monitoring the procedure. RESULTS During the study period, a total of 26 patients underwent tcMRgFUS thalamic ablation for different movement disorders. Among these patients, 18 were diagnosed with ET and 4 were affected by PD. All patients with PD were treated using tcMRgFUS thalamic ablation and all completed the procedure. Among the 18 patients with ET, 13 successfully underwent tcMRgFUS, 4 aborted the procedure during ultrasound delivery, and 1 did not undergo the tcMRgFUS procedure after stereotactic frame placement. Two patients with ET were not included in the results because of the short follow-up duration at the time of this study. A monolateral VIM thalamic ablation in both ET and PD patients was performed. All the enrolled patients were evaluated before the treatment and 2 days after, with a clinical control of the treatment effectiveness using the graphic items of the Fahn-Tolosa-Marin tremor rating scale. A global reevaluation was performed 3 months (17/22 patients) and 6 months (11/22 patients) after the treatment; the reevaluation consisted of clinical questionnaires, neurological tests, and video recordings of the tests. All the ET and PD treated patients who completed the procedure showed an immediate amelioration of tremor severity, with no intra- or posttreatment severe permanent side effects. CONCLUSIONS Although this study reports on a small number of patients with a short follow-up duration, the tcMRgFUS procedure using a 1.5-T MRI unit resulted in a safe and effective treatment option for motor symptoms in patients with ET and PD. To the best of the authors' knowledge, this is the first clinical series in which thalamotomy was performed using tcMRgFUS integrated with a 1.5-T magnet.

Benefits of a frame-based stereotactic surgical planning system for the treatment of spontaneous intracerebral haematomas

OBJECTIVE

Frame-based stereotactic surgical planning systems (SSPSs) have been used for deep brain stimulation and radioneurosurgery. Here, we evaluated the feasibility, safety and efficacy of using a SSPS to aid spontaneous intracerebral haematoma (ICH) treatment.

METHODS

Patients with moderate spontaneous putamen haematomas were randomized into two groups: treatment (group A) and control (group B). In group B, the catheter for evacuating haematomas was inserted into a target point, located at the centre of the haematoma, using conventional frame-based stereotactics; urokinase thrombolysis was subsequently delivered through the catheter. In group A, this procedure was assisted by a SSPS, which designed both the target point and trajectory in the haematoma through virtual reality. Duration of evacuating haematomas and number of urokinase injections was compared between groups.

RESULTS

In total, 65 patients were recruited: in group A (n = 30), the duration of evacuating haematomas (35.27 ± 9.17 h) was shorter than in group B (n = 35; 67.77 ± 13.82 h). There were fewer urokinase injections in group A (3.63 ± 1.16) than in group B (6.40 ± 1.29).

CONCLUSIONS

The feasibility, efficacy and safety of spontaneous ICH treatment were optimized by the use of a frame-based SSPS.