mri_slicer.cpp

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//=============================================================================================================
 
//=============================================================================================================
// INCLUDES
//=============================================================================================================
 
#include "mri_slicer.h"
#include "mri_vol_data.h"
 
#include <Eigen/LU>
 
#include <algorithm>
#include <array>
#include <cmath>
 
//=============================================================================================================
// USED NAMESPACES
//=============================================================================================================
 
using namespace MRILIB;
using namespace Eigen;
 
namespace
{
 
struct PlaneSpec
{
    int columnAxis;
    int rowAxis;
    int fixedAxis;
};
 
Vector3f anatomicalNormal(SliceOrientation orientation)
{
    switch (orientation) {
        case SliceOrientation::Axial:
            return Vector3f::UnitZ();
        case SliceOrientation::Coronal:
            return Vector3f::UnitY();
        case SliceOrientation::Sagittal:
            return Vector3f::UnitX();
    }
    return Vector3f::UnitZ();
}
 
Vector3f anatomicalColumnDirection(SliceOrientation orientation)
{
    switch (orientation) {
        case SliceOrientation::Axial:
            return Vector3f::UnitX();
        case SliceOrientation::Coronal:
            return Vector3f::UnitX();
        case SliceOrientation::Sagittal:
            return Vector3f::UnitY();
    }
    return Vector3f::UnitX();
}
 
Vector3f anatomicalRowDirection(SliceOrientation orientation)
{
    switch (orientation) {
        case SliceOrientation::Axial:
            return Vector3f::UnitY();
        case SliceOrientation::Coronal:
            return Vector3f::UnitZ();
        case SliceOrientation::Sagittal:
            return Vector3f::UnitZ();
    }
    return Vector3f::UnitY();
}
 
int bestVoxelAxisForDirection(const Matrix4f& vox2ras,
                              const Vector3f& target,
                              const std::array<bool, 3>& used)
{
    int bestAxis = 0;
    float bestScore = -1.0f;
 
    for (int axis = 0; axis < 3; ++axis) {
        if (used[axis]) {
            continue;
        }
        Vector3f axisDirection = vox2ras.block<3, 1>(0, axis);
        const float norm = axisDirection.norm();
        if (norm > 0.0f) {
            axisDirection /= norm;
        }
        const float score = std::abs(axisDirection.dot(target));
        if (score > bestScore) {
            bestScore = score;
            bestAxis = axis;
        }
    }
 
    return bestAxis;
}
 
PlaneSpec planeSpecForOrientation(const Matrix4f& vox2ras,
                                  SliceOrientation orientation)
{
    std::array<bool, 3> used = {false, false, false};
    const int fixedAxis = bestVoxelAxisForDirection(vox2ras,
                                                    anatomicalNormal(orientation),
                                                    used);
    used[fixedAxis] = true;
 
    const int columnAxis = bestVoxelAxisForDirection(vox2ras,
                                                     anatomicalColumnDirection(orientation),
                                                     used);
    used[columnAxis] = true;
 
    const int rowAxis = bestVoxelAxisForDirection(vox2ras,
                                                  anatomicalRowDirection(orientation),
                                                  used);
 
    return {columnAxis, rowAxis, fixedAxis};
}
 
int axisDimension(const QVector<int>& dims, int axis)
{
    return dims[axis];
}
 
int flatIndex(int x, int y, int z, int dimX, int dimY)
{
    return x + dimX * (y + dimY * z);
}
 
} // anonymous namespace
 
//=============================================================================================================
// STATIC METHODS
//=============================================================================================================
 
MriSliceImage MriSlicer::extractSlice(
    const QVector<float>& volData,
    const QVector<int>& dims,
    const Matrix4f& vox2ras,
    SliceOrientation orientation,
    int sliceIndex)
{
    const int dimX = dims[0];
    const int dimY = dims[1];
    const PlaneSpec spec = planeSpecForOrientation(vox2ras, orientation);
    const int width = axisDimension(dims, spec.columnAxis);
    const int height = axisDimension(dims, spec.rowAxis);
    const int fixedDim = axisDimension(dims, spec.fixedAxis);
 
    sliceIndex = std::clamp(sliceIndex, 0, fixedDim - 1);
 
    MriSliceImage result;
    result.orientation = orientation;
    result.width = width;
    result.height = height;
    result.sliceIndex = sliceIndex;
    result.pixels.resize(width, height);
 
    for (int row = 0; row < height; ++row) {
        for (int col = 0; col < width; ++col) {
            std::array<int, 3> voxel = {0, 0, 0};
            voxel[spec.columnAxis] = col;
            voxel[spec.rowAxis] = row;
            voxel[spec.fixedAxis] = sliceIndex;
            result.pixels(col, row) = volData[flatIndex(voxel[0], voxel[1], voxel[2], dimX, dimY)];
        }
    }
 
    result.sliceToRas = Matrix4f::Zero();
    result.sliceToRas.col(0) = vox2ras.col(spec.columnAxis);
    result.sliceToRas.col(1) = vox2ras.col(spec.rowAxis);
    result.sliceToRas.col(2) = vox2ras.col(spec.fixedAxis);
    Vector4f origin = Vector4f::Zero();
    origin(spec.fixedAxis) = static_cast<float>(sliceIndex);
    origin.w() = 1.0f;
    result.sliceToRas.col(3) = vox2ras * origin;
 
    // Normalize pixels to [0, 1]
    float minVal = result.pixels.minCoeff();
    float maxVal = result.pixels.maxCoeff();
    if (maxVal > minVal) {
        result.pixels = (result.pixels.array() - minVal) / (maxVal - minVal);
    } else {
        result.pixels.setZero();
    }
 
    return result;
}
 
//=============================================================================================================
 
int MriSlicer::voxelAxisForOrientation(const Matrix4f& vox2ras,
                                       SliceOrientation orientation)
{
    return planeSpecForOrientation(vox2ras, orientation).fixedAxis;
}
 
//=============================================================================================================
 
int MriSlicer::dimensionForOrientation(const QVector<int>& dims,
                                       const Matrix4f& vox2ras,
                                       SliceOrientation orientation)
{
    return axisDimension(dims, voxelAxisForOrientation(vox2ras, orientation));
}
 
//=============================================================================================================
 
int MriSlicer::sliceIndexForOrientation(const Matrix4f& vox2ras,
                                        SliceOrientation orientation,
                                        const Vector3i& voxel)
{
    return voxel(voxelAxisForOrientation(vox2ras, orientation));
}
 
//=============================================================================================================
 
QVector<MriSliceImage> MriSlicer::extractOrthogonal(
    const QVector<float>& volData,
    const QVector<int>& dims,
    const Matrix4f& vox2ras,
    const Vector3f& rasPoint)
{
    Vector3i voxel = rasToVoxel(vox2ras, rasPoint);
 
    QVector<MriSliceImage> slices;
    slices.reserve(3);
    slices.append(extractSlice(volData, dims, vox2ras, SliceOrientation::Axial,
                               sliceIndexForOrientation(vox2ras, SliceOrientation::Axial, voxel)));
    slices.append(extractSlice(volData, dims, vox2ras, SliceOrientation::Coronal,
                               sliceIndexForOrientation(vox2ras, SliceOrientation::Coronal, voxel)));
    slices.append(extractSlice(volData, dims, vox2ras, SliceOrientation::Sagittal,
                               sliceIndexForOrientation(vox2ras, SliceOrientation::Sagittal, voxel)));
 
    return slices;
}
 
//=============================================================================================================
 
Vector3i MriSlicer::rasToVoxel(const Matrix4f& vox2ras,
                               const Vector3f& rasPoint)
{
    Matrix4f ras2vox = vox2ras.inverse();
    Vector4f rasH;
    rasH << rasPoint, 1.0f;
    Vector4f voxH = ras2vox * rasH;
 
    return Vector3i(
        static_cast<int>(std::round(voxH.x())),
        static_cast<int>(std::round(voxH.y())),
        static_cast<int>(std::round(voxH.z())));
}
 
//=============================================================================================================
 
Vector3f MriSlicer::voxelToRas(const Matrix4f& vox2ras,
                               const Vector3i& voxel)
{
    Vector4f voxH;
    voxH << static_cast<float>(voxel.x()),
        static_cast<float>(voxel.y()),
        static_cast<float>(voxel.z()),
        1.0f;
    Vector4f rasH = vox2ras * voxH;
 
    return rasH.head<3>();
}
 
//=============================================================================================================
// MriVolData convenience overloads
//=============================================================================================================
 
MriSliceImage MriSlicer::extractSlice(const MriVolData& vol,
                                      SliceOrientation orientation,
                                      int sliceIndex)
{
    return extractSlice(vol.voxelDataAsFloat(), vol.dims(),
                        vol.computeVox2RasTkr(), orientation, sliceIndex);
}
 
//=============================================================================================================
 
int MriSlicer::voxelAxisForOrientation(const MriVolData& vol,
                                       SliceOrientation orientation)
{
    return voxelAxisForOrientation(vol.computeVox2RasTkr(), orientation);
}
 
//=============================================================================================================
 
int MriSlicer::dimensionForOrientation(const MriVolData& vol,
                                       SliceOrientation orientation)
{
    return dimensionForOrientation(vol.dims(), vol.computeVox2RasTkr(), orientation);
}
 
//=============================================================================================================
 
int MriSlicer::sliceIndexForOrientation(const MriVolData& vol,
                                        SliceOrientation orientation,
                                        const Vector3i& voxel)
{
    return sliceIndexForOrientation(vol.computeVox2RasTkr(), orientation, voxel);
}
 
//=============================================================================================================
 
QVector<MriSliceImage> MriSlicer::extractOrthogonal(const MriVolData& vol,
                                                    const Vector3f& rasPoint)
{
    return extractOrthogonal(vol.voxelDataAsFloat(), vol.dims(),
                             vol.computeVox2RasTkr(), rasPoint);
}
 
//=============================================================================================================
 
Vector3i MriSlicer::rasToVoxel(const MriVolData& vol,
                               const Vector3f& rasPoint)
{
    return rasToVoxel(vol.computeVox2RasTkr(), rasPoint);
}
 
//=============================================================================================================
 
Vector3f MriSlicer::voxelToRas(const MriVolData& vol,
                               const Vector3i& voxel)
{
    return voxelToRas(vol.computeVox2RasTkr(), voxel);
}