Novel MRI and CT compatible stereotactic brain biopsy system in dogs using patient-specific facemasks

Masticatory muscle changes on magnetic resonance imaging of dogs with Neospora caninum compared to meningoencephalitis of unknown origin

Infectious meningoencephalitides represent an important differential diagnosis for meningoencephalitis of unknown origin (MUO) in dogs. Treatment of the latter requires immunosuppression, but laboratory test results for infectious agents may take several days to return. This study investigated whether the presence of masticatory muscle changes on magnetic resonance imaging (MRI) of the head can be used to distinguish dogs with neosporosis from those with MUO at the time of diagnosis. Cases diagnosed with neosporosis or MUO at two referral centers in the United Kingdom (UK) were retrospectively collected. Clinical data were reviewed, and each MRI study was blindly assessed by a radiologist, a neurologist, and a neurology resident for the presence of masticatory muscle changes by consensus opinion. Statistical analysis was performed on obtained data. Twenty-two neosporosis cases and 23 MUO cases were enrolled. In the neosporosis group, six dogs (27%) had masticatory muscle changes, compared to one dog (4%) in the MUO group (p = 0.047). All six neosporosis cases had bilateral, multifocal, T2W and FLAIR hyperintense, contrast enhancing muscular changes, with three having concurrent masticatory muscle atrophy. The only MUO case with muscle changes had a mild, focal, unilateral temporal muscle lesion which was only visible in the T1W post-contrast images. Within the neosporosis group, dogs with masticatory muscle lesions had significantly higher cerebrospinal fluid WBC counts (p = 0.017) and protein concentrations (p = 0.025) compared to those without muscle changes. In conclusion, characteristic bilateral, multifocal masticatory muscle changes should raise the index of suspicion for neosporosis in dogs with an imaging diagnosis of meningoencephalitis and starting early antimicrobial treatment is recommended. However, the absence of masticatory muscle abnormalities does not exclude active Neospora caninum infection. In these cases, whether immunosuppressive or antimicrobial treatments are started prior to receiving further test results should still be based on the clinical status of the animal and index of suspicion using a combination of all available clinical information at that time.

Biopsy of Brain Lesions

Brain biopsy is essential for accurate diagnosis but is frequently avoided in veterinary medicine because of doubts about its safety, reliability, and clinical value. Data available from human and veterinary investigations suggest that such doubts are largely unwarranted. Many devices are available to guide minimally invasive biopsy but some can be costly to purchase and use, which can be problematic in veterinary medicine. Nowadays, costs can be substantially reduced by using 3-dimensional-printed guides.

Evaluation of the Accuracy of 3D Printed Patient-Specific Brain Biopsy Guide Using 3D Volume Rendering Technique in Canine Cadavers

The objective of this study was to evaluate the accuracy of a CT-based, 3D-printed, patient-specific brain biopsy guide (3D-psBBG) through the application of a transfrontal approach in canine cadavers. A total of ten canine cadavers, with weights ranging from 4.36 to 14.4 kg, were subjected to preoperative CT scans to generate 3D skull models. Customized biopsy guides were created based on these models and manufactured using 3D printing technology. Twenty spinal needle insertions were performed, and the accuracy of needle placement was evaluated through both CT and 3D volume-rendering techniques. The mean needle placement error was 2.1 mm, with no significant differences observed between insertions targeting the fronto-olfactory and piriform lobes. The 3D volume-rendering method demonstrated superior accuracy compared to the CT method, with statistically significant differences in placement errors for both targets. The average time required for the design and manufacture of the guides was 249 min. These findings indicate the high accuracy and potential clinical application of CT-based 3D-psBBG for improving diagnostic outcomes in veterinary neurology.

Comparison of stereotactic brain biopsy techniques in dogs: neuronavigation, 3D-printed guides, and neuronavigation with 3D-printed guides

The objective of this research was to compare two previously described stereotactic brain biopsy (SBB) techniques, three-dimensional skull contoured guides (3D-SCGs) and neuronavigation with Brainsight, to a novel SBB technique using Brainsight combined with a 3D-printed headframe (BS3D-HF) to improve the workflow of SBB in dogs. This was a prospective methods comparison with five canine cadavers of different breeds and size. Initial helical CT was performed on cadavers with fiducial markers in place. Ten different target points were randomly selected for each method. The headframe for the BS3D-HF was designed and printed. Trajectories were planned for each method. Steinmann pins (SPs) were placed into the target points using the planned trajectories for each method, and CT was repeated (post CT). Accuracy was assessed by overlaying the initial CT onto the post CT and measuring the difference of the planned target point to the SP placement. For 3D-SCG, the median deviation was 2.48 mm (0.64-4.04). With neuronavigation, the median deviation was 3.28 mm (1.04-4.64). For BS3D-HF, the median deviation was 14.8 mm (8.87-22.1). There was no significant difference between 3D-SCG and neuronavigation for the median deviation (p = 0.42). When comparing BS3D-HF to 3D-SCG, there was a significant difference in the median deviation (p < 0.0001). Additionally, when comparing BS3D-HF to neuronavigation, there was a significant difference for the median deviation (p < 0.0001). Our findings concluded that both 3D-SCGs and neuronavigation were accurate for SBB, however BS3D-HF was not. Although feasible, the current BS3D-HF technique requires further refinement before it can be recommended for use for SBB in dogs.

Diagnostic Yield of Stereotactic Brain Biopsy in a Sub-Saharan Tertiary Center: A Comprehensive 10-Year Retrospective Analysis

BACKGROUND

Stereotactic brain biopsy is a crucial minimally invasive surgical technique leveraged to obtain tissue specimens from deep-seated intracranial lesions, offering a safer alternative to open craniotomy for patients who cannot tolerate the latter. Despite its effectiveness, the diagnostic yield varies across different centers and has not been widely studied in Sub-Saharan Africa.

METHODS

A single-center retrospective analysis was conducted on 67 consecutive stereotactic brain biopsy procedures carried out by experienced neurosurgeons between January 2012 and December 2022 at a tertiary center in Sub-Saharan Africa. Preoperative clinical status, biopsy type, postoperative complication rate, and histological diagnosis were meticulously analyzed. Factors associated with negative biopsy results were identified using IBM Statistical Package for the Social Sciences SPSS version for Mac, with Fisher exact test employed to detect differences in patient characteristics. Statistical significance was pegged at P < 0.05.

RESULTS

The overall diagnostic yield rate was 67%. Major contributors to negative biopsy outcomes were superficial location of the lesion, lesion size less than 10 cc, and the use of the Cape Town Stereotactic System. Enhanced yield rates of up to 93% were realized through the application of magnetic resonance imaging-based images, Stealth Station 7, and frozen section analysis. No correlation was observed between the number of cores obtained and the yield rate. Procedure complications were negligible, and no procedure-related mortality was recorded.

CONCLUSIONS

The diagnostic yield rate from our study was somewhat lower than previously reported in contemporary literature, primarily attributed to the differing definitions of diagnostic yield, the dominant use of the older framed Cape Town Stereotactic System, computed tomography-based imaging, and the absence of intraoperative frozen section. Nevertheless, biopsies conducted using the frameless system were comparable with studies from other global regions. Our findings reaffirm that stereotactic brain biopsy when complemented with magnetic resonance imaging-based imaging, frameless stereotactic systems and intraoperative frozen section is a safe, effective, and reliable method for obtaining histological diagnosis.

Application accuracy of a frameless optical neuronavigation system as a guide for craniotomies in dogs

BACKGROUND

Optical neuronavigation systems using infrared light to create a virtual reality image of the brain allow the surgeon to track instruments in real time. Due to the high vulnerability of the brain, neurosurgical interventions must be performed with a high precision. The aim of the experimental cadaveric study was to determine the application accuracy of a frameless optical neuronavigation system as guide for craniotomies by determining the target point deviation of predefined target points at the skull surface in the area of access to the cerebrum, cerebellum and the pituitary fossa. On each of the five canine cadaver heads ten target points were marked in a preoperative computed tomography (CT) scan. These target points were found on the cadaver skulls using the optical neuronavigation system. Then a small drill hole (1.5 mm) was drilled at these points. Subsequently, another CT scan was made. Both CT data sets were fused into the neuronavigation software, and the actual target point coordinates were identified. The target point deviation was determined as the difference between the planned and drilled target point coordinates. The calculated deviation was compared between two observers.

RESULTS

The analysis of the target point accuracies of all dogs in both observers taken together showed a median target point deviation of 1.57 mm (range: 0.42 to 5.14 mm). No significant differences were found between the observers or the different areas of target regions.

CONCLUSION

The application accuracy of the described system is similar to the accuracy of other optical neuronavigation systems previously described in veterinary medicine, in which mean values of 1.79 to 4.3 mm and median target point deviations of 0.79 to 3.53 mm were determined.

Case Report: Clinical Use of a Patient-Individual Magnetic Resonance Imaging-Based Stereotactic Navigation Device for Brain Biopsies in Three Dogs

Three-dimensional (3D) printing techniques for patient-individual medicine has found its way into veterinary neurosurgery. Because of the high accuracy of 3D printed specific neurosurgical navigation devices, it seems to be a safe and reliable option to use patient-individual constructions for sampling brain tissue. Due to the complexity and vulnerability of the brain a particularly precise and safe procedure is required. In a recent cadaver study a better accuracy for the 3D printed MRI-based patient individual stereotactic brain biopsy device for dogs is determined compared to the accuracies of other biopsy systems which are currently used in veterinary medicine. This case report describes the clinical use of this 3D printed MRI-based patient individual brain biopsy device for brain sampling in three dogs. The system was characterized by a simple handling. Furthermore, it was an effective and reliable tool to gain diagnostic brain biopsy samples in dogs with no significant side effects.

Clinical use of a new frameless optical neuronavigation system for brain biopsies: 10 cases (2013-2020)

OBJECTIVES

The aim of the retrospective study was to describe the brain biopsy procedure using a new frameless optical neuronavigation system and to report diagnostic yield and complications associated with the procedure.

MATERIALS AND METHODS

The medical records for all dogs with forebrain lesions that underwent brain biopsy with a frameless optical neuronavigation system in a single referral hospital between 2013 and 2020 were retrospectively analysed. Following data were collected: signalment, neurological signs, diagnostic findings, number of brain biopsy samples, sampled region, complications, duration of hospitalisation, whether the samples were diagnostic and histopathological diagnoses. The device consists of a computer workstation with navigation software, an infrared camera, patient tracker and reflective instruments. The biopsy needle was equipped with reflective spheres, so the surgeon could see the position of the needle during sampling the intracranial lesion free handed through a mini-burr hole.

RESULTS

Ten dogs were included. Absolute diagnostic yield based on specific histopathological diagnosis was 73.9%. Three dogs had immune-mediated necrotizing encephalitis, two dogs showed a necrotizing leukoencephalitis and two dogs a meningoencephalitis of unknown origin. In two dogs, the brain specimen showed unspecific changes. In one dog, the samples were non-diagnostic. Seven dogs showed no neurological deterioration, one dog mild temporary ataxia and two dogs died within 36 hours post brain biopsy.

CLINICAL SIGNIFICANCE

In these 10 dogs, the frameless optical neuronavigation system employed was useful to gain diagnostic brain biopsy samples. Considering the mortality rate observed, further studies are needed to confirm the safety of this procedure and prove its actual clinical effectiveness.

Feasibility and accuracy of 3D printed patient-specific skull contoured brain biopsy guides

Objective

Design 3D printed skull contoured brain biopsy guides (3D‐SCGs) from computed tomography (CT) or T1‐weighted magnetic resonance imaging (T1W MRI).

Study Design

Feasibility study.

Sample Population

Five beagle dog cadavers and two client‐owned dogs with brain tumors.

Methods

Helical CT and T1W MRI were performed on cadavers. Planned target point was the head of the caudate nucleus. Three‐dimensional‐SCGs were created from CT and MRI using commercially available open‐source software. Using 3D‐SCGs, biopsy needles were placed into the caudate nucleus in cadavers, and CT was performed to assess needle placement accuracy, followed by histopathology. Three‐dimensional‐SCGs were then created and used to perform in vivo brain tumor biopsies.

Results

No statistical difference was found between the planned target point and needle placement. Median needle placement error for all planned target points was 2.7 mm (range: 0.86–4.5 mm). No difference in accuracy was detected between MRI and CT‐designed 3D‐SCGs. Median needle placement error for the CT was 2.8 mm (range: 0.86–4.5 mm), and 2.2 mm (range: 1.7–2.7 mm) for MRI. Biopsy needles were successfully placed into the target in the two dogs with brain tumors and biopsy was successfully acquired in one dog.

Conclusion

Three‐dimensional‐SCGs designed from CT or T1W MRI allowed needle placement within 4.5 mm of the intended target in all procedures, resulting in successful biopsy in one of two live dogs.

Clinical Significance

This feasibility study justifies further evaluation of 3D‐SCGs as alternatives in facilities that do not have access to stereotactic brain biopsy.

Accuracy of a magnetic resonance imaging-based 3D printed stereotactic brain biopsy device in dogs

BACKGROUND

Brain biopsy of intracranial lesions is often necessary to determine specific therapy. The cost of the currently used stereotactic rigid frame and optical tracking systems for brain biopsy in dogs is often prohibitive or accuracy is not sufficient for all types of lesion.

OBJECTIVES

To evaluate the application accuracy of an inexpensive magnetic resonance imaging-based personalized, 3D printed brain biopsy device.

ANIMALS

Twenty-two dog heads from cadavers were separated into 2 groups according to body weight (<15 kg, >20 kg).

METHODS

Experimental study. Two target points in each cadaver head were used (target point 1: caudate nucleus, target point 2: piriform lobe). Comparison between groups was performed using the independent Student's t test or the nonparametric Mann-Whitney U Test.

RESULTS

The total median target point deviation was 0.83 mm (range 0.09-2.76 mm). The separate median target point deviations for target points 1 and 2 in all dogs were 0.57 mm (range: 0.09-1.25 mm) and 0.85 mm (range: 0.14-2.76 mm), respectively.

CONCLUSION AND CLINICAL IMPORTANCE

This magnetic resonance imaging-based 3D printed stereotactic brain biopsy device achieved an application accuracy that was better than the accuracy of most brain biopsy systems that are currently used in veterinary medicine. The device can be applied to every size and shape of skull and allows precise positioning of brain biopsy needles in dogs.

A concept for a 3D-printed patient-specific stereotaxy platform for brain biopsy -a canine cadaver study

The treatment of intracranial lesions requires a precise diagnosis with subsequent identification of an adequate therapeutic approach. Stereotactic tumor biopsy may be considered the safest neurosurgical procedure in terms of anticipated results and potential surgical complications. The aim of the present paper was to demonstrate a new method of stereotactic biopsy, based on a patient-specific 3D printed platform in dogs. The system was tested on two canine cadavers, a small (Shih Tzu) and a large (Labrador) breed. Imaginary biopsy targets were defined in a superficial (caudate nucleus) and a deep (piriform lobe) position. Based on 3 Tesla MRI, individualized stereotactic platforms were designed using a semi-automatic approach, and manufactured additively using ABS M30. A pre- and intra-operative CT was performed to compare the planned vs. the realized needle position for precision analyses of the procedure. The target points varied with a precision between 0.09 mm and 0.48 mm. Manufacturing time required 480 to 700 min per platform. The presented patient-specific stereotactic system seems a suitable instrument for application in small animal neurosurgery. In particular, the implementation of relevant stereotactic data may help performing the procedure in rapid sequence and with higher precision than currently-used systems. Required adjustments and adaptions to the respective anatomical conditions are omitted and make the procedure reliable and safe.