We present a new algorithm, called marching cubes, that creates triangle models of constant density surfaces from 3D medical data. Using a divide-and-conquer approach to generate inter-slice connectivity, we create a case table that defines triangle topology. The algorithm processes the 3D medical data in scan-line order and calculates triangle vertices using linear interpolation. We find the gradient of the original data, normalize it, and use it as a basis for shading the models. The detail in images produced from the generated surface models is the result of maintaining the inter-slice connectivity, surface data, and gradient information present in the original 3D data. Results from computed tomography (CT), magnetic resonance (MR), and single-photon emission computed tomography (SPECT) illustrate the quality and functionality of marching cubes. We also discuss improvements that decrease processing time and add solid modeling capabilities.

/pdf/marching-cubes-a-high-resolution-3d-surface-construction-3ealswkmtb.pdf

Marching cubes: A high resolution 3D surface construction algorithm

Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

https://users.fmrib.ox.ac.uk/~jesper/papers/readgroup_071009/Ashburner07.pdf

A fast diffeomorphic image registration algorithm

http://midag.cs.unc.edu/pubs/papers/Neuroimage06_Yushkevich.pdf

User-guided 3D active contour segmentation of anatomical structures: Significantly improved efficiency and reliability

A novel approach to correcting for intensity nonuniformity in magnetic resonance (MR) data is described that achieves high performance without requiring a model of the tissue classes present. The method has the advantage that it can be applied at an early stage in an automated data analysis, before a tissue model is available. Described as nonparametric nonuniform intensity normalization (N3), the method is independent of pulse sequence and insensitive to pathological data that might otherwise violate model assumptions. To eliminate the dependence of the field estimate on anatomy, an iterative approach is employed to estimate both the multiplicative bias field and the distribution of the true tissue intensities. The performance of this method is evaluated using both real and simulated MR data.

/pdf/a-nonparametric-method-for-automatic-correction-of-intensity-4smqm7oz20.pdf

A nonparametric method for automatic correction of intensity nonuniformity in MRI data

Image-Guided Therapy

Chemodenervation by injection of botulinum toxin type A into the vocal fold(s) has become the preferred treatment for patients with adductor spasmodic dysphonia. Injection may be done either perorally or transcutaneously; each method has its advocates and advantages. The authors have used the transcutaneous transcricothyroid membrane route exclusively with satisfactory results in more than 50 patients. Temporary breathiness and aspiration are common. The preferred injection site should be as close as possible to the motor end plates of the affected muscle

Anatomic considerations in botulinum toxin type A therapy for spasmodic dysphonia

The nature of Taung dental maturation continued.

This paper describes a device that allows the imaging of prosthetic legs under load conditions using spiral computerized tomography (CT). The device consists of a chair and a vertical footplate mounted on a 17.8 x 1.9 cm oak board that is 197 cm long. The load device can be easily positioned onto the CT bed. A subject sits in the chair and applies force by pushing the foot portion of the prosthesis against the footplate. The magnitude of the force is monitored by a digital force gauge coupled to the footplate. Because the load is borne by the hips and lower back of the subject against the chair, substantial forces can be generated and steadily maintained for the 20-45 s duration of the CT study. This device has been used successfully with 19 transtibial amputees, allowing the acquisition of spiral CT studies with half and full body weight loads.

A device for applying static loads to prosthetic limbs of transtibial amputees during spiral CT examination.

Lower-limb prosthesis quality-of-fit assessment is purely subjective in routine clinical practice, relying on patient reports of discomfort, erythema (localized pain), and palpation. Wide variations in residual limb physical characteristics and conditions preclude a rigid approach to prosthesis prescription. With relatively long life expectancy for many lower-limb amputees, clinicians measure outcome in terms of return to work and quality of life, which have important social and economic consequences. An objective quantitative metric of fit that predicts functional outcome has not been described to date. Volumetric CT scanning provides in situ static 3D determination of residual limb soft tissue changes caused by the prosthesis socket. This mapping aids in prosthesis design and evaluation.

Michael W. Vannier

Papers

Image-Guided Therapy

Anatomic considerations in botulinum toxin type A therapy for spasmodic dysphonia

The nature of Taung dental maturation continued.

A device for applying static loads to prosthetic limbs of transtibial amputees during spiral CT examination.

Visualization of prosthesis fit in lower-limb amputees