Frameless Stereotaxy in Children
Bibliographic record
Abstract
Frameless stereotaxy provides stereotactic localization without a standard stereotactic frame. Other reference points on the patient are linked to radio-graphic images by means of a three-dimensional (3D) digitizer. We report the use of a frameless stereotactic system to assist in 53 procedures in 52 children using the ISG Viewing Wand system (ISG Technologies, Missasauga, Ont.). This device uses surface landmarks as well as random surface points as the reference system. The three-dimensional digitizer consists of a six-jointed articulated arm to which pointers, a rigid ventriculoscope, or stereotactic biopsy probe guide can be attached. Image reconstruction is performed on standard CT or MRI (3D volume acquisition) images, with typically 3-mm slice thickness. The tip of the probe can be displayed on 3D surfaced objects which can be cut away to reveal reformatted gray scale displayed on the cut surfaces, or in a triorthogonal view where simultaneous reformatted coronal and sagital views at the level of the tip of the probe are displayed. Cases for which the viewing wand was used included craniotomies for tumor (30), vascular malformation (6), epilepsy surgery (5), other lesions (3), rigid ventriculoscopy (9), and stereotactic biopsy (2). The accuracy of the system was measured by placing 20 fiducial markers on a plastic head of which 3-mm thickness CT images had been made. The average error using 4 fiducials as reference points was 1.5 mm when the fiducials were distributed around the circumference of the head. Using random surface points of 10, 20 and 40 in number gave average errors of 2.3, 1.6, 1.5 mm, respectively. Twenty targets were implanted in a cadaver head to which a BRW stereotactic frame (Radionics, Burlington, Mass.) was attached and imaged in the same fashion. The average error of the Viewing Wand, using 20-random surface point registration, was 2.3 mm, compared to 1.8 mm with the BRW frame using the arc system. Frameless stereotaxy is a valuable aid for a variety of neurosurgical procedures in children providing rapid and relatively accurate stereotactic guidance without the hindrance of a stereotactic frame.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".