alexandria-project 0.1.3

Unified CatPhan phantom analysis library - combining best features from multiple implementations

Alexandria - Unified CatPhan Phantom Analysis Library

Alexandria is a comprehensive, unified library for analyzing CatPhan CT phantom DICOM images. It combines the best features from multiple CatPhan analysis implementations into a single, well-tested, and maintainable codebase.

Features

Comprehensive Analysis Modules

• UniformityAnalyzer (CTP486) - Measures image uniformity across 5 ROIs
• DetailedUniformityAnalyzer - Concentric profile sampling for detailed uniformity inspection
• HighContrastAnalyzer (CTP528) - Line pair resolution and MTF analysis
• CTP401Analyzer (CTP401) - Material contrast, HU accuracy, rotation detection
• CTP404Analyzer (CTP404) - 9-ROI sensitometry / material measurement
• CTP515Analyzer (CTP515) - Low-contrast detectability and CNR measurements

Dual Operation Modes

Each analyzer supports two modes:

1. Single-image mode: Direct analysis of individual CT slices
2. DICOM-series mode: Automatic 3-slice averaging for improved SNR

Advanced Features

• Automatic rotation detection using air ROI positions
• Intelligent slice selection for optimal image quality
• Rotation propagation across analysis modules
• Flexible initialization for different workflow patterns
• JSON-compatible results for easy integration

Installation

# Install from source (recommended: run from the repository root)
pip install -e .[docs]

# Alternatively, if you have a separate clone of the package folder:
# cd alexandria
# pip install -e .[docs]

# Or install from PyPI (when published)
pip install alexandria-project

Quick Start

Single-Image Mode

from alexandria import UniformityAnalyzer, HighContrastAnalyzer
import numpy as np

# Load your CT image
image = ...  # 2D numpy array
center = (256, 256)  # (x, y) phantom center
pixel_spacing = 0.488  # mm

# Analyze uniformity
uniformity = UniformityAnalyzer(
    image=image,
    center=center,
    pixel_spacing=pixel_spacing
)
results = uniformity.analyze()
print(f"Uniformity: {results['uniformity']:.2f}%")

# Analyze resolution
high_contrast = HighContrastAnalyzer(
    image=image,
    center=center,
    pixel_spacing=pixel_spacing,
    t_offset_deg=2.5  # rotation offset
)
mtf_results = high_contrast.analyze()
print(f"MTF50: {mtf_results['mtf_50']:.3f} lp/mm")

DICOM-Series Mode

from alexandria import CTP401Analyzer
import pydicom

# Load DICOM series
dicom_files = [...]  # list of DICOM datasets
center = (256, 256)

# Analyze with automatic rotation detection
analyzer = CTP401Analyzer(
    dicom_set=dicom_files,
    slice_index=10,
    center=center,
    use_all_rois=True
)
results = analyzer.analyze(detect_rotation=True)
print(f"Rotation: {results['rotation_angle']:.2f}°")
print(f"LCV: {results['LCV_percent']:.2f}%")
    # Note on angle convention: rotation angles follow image coordinates —
    # 90° corresponds to south (bottom of the image) and 270° corresponds to
    # north (top of the image).

    # Clarification:
    # - The note above describes image coordinates: origin at the top-left
    #   and the y-axis increasing downward (image/screen convention). In
    #   that system positive angles are clockwise (90° → south).
    # - `alexandria.utils.find_rotation` returns a mathematical (Cartesian)
    #   angle in degrees where positive is counter-clockwise (CCW). Callers
    #   that need an image-oriented, clockwise-positive angle for placing
    #   ROIs should convert the returned value (for example by negating it)
    #   before use.

Custom Center-Finding Algorithms

If you want to use your own center-finding method, pass a callable via center_finder when creating an analyzer. This is a simple hook: a function you provide that Alexandria calls to compute the phantom center instead of the default edge-based method.

The callable should return either:

• (row, col)
• (row, col, diameter_y_px, diameter_x_px) if you also want the boundary drawn from measured diameters.

from alexandria import CTP401Analyzer

def my_center_finder(image, *, min_hu=-850):
    # Replace with your own logic
    row, col = 250, 260
    return row, col

analyzer = CTP401Analyzer(
    image=ct_image,
    pixel_spacing=0.488,
    center_finder=my_center_finder,
    center_finder_kwargs={"min_hu": -850}
)
results = analyzer.analyze()

You can also keep the default finder and adjust its primary and fallback thresholds:

analyzer = CTP401Analyzer(
    image=ct_image,
    pixel_spacing=0.488,
    center_threshold=-980,
    center_threshold_fallback=-900
)

Architecture

With the src/ layout the package source lives under src/alexandria:

src/
└── alexandria/
    ├── analyzers/          # Core analysis modules
    │   ├── uniformity.py   # CTP486 uniformity
    │   ├── high_contrast.py # CTP528 resolution/MTF
    │   ├── ctp401.py       # CTP401/404 contrast
    │   └── ctp515.py       # CTP515 low-contrast
    ├── plotters/           # Visualization modules
    ├── wrappers/           # Convenience reporters (analyzer + plotter)
    └── utils/              # Shared utilities

Wrappers in `alexandria.wrappers` provide small, consistent entrypoints that orchestrate an analyzer and its plotter for simple scripting and reporting workflows.

Documentation source now lives at docs/source and built HTML appears in docs/_build/html.

Plotters

Each analyzer has a corresponding plotter in alexandria.plotters that renders figures from an analyzer instance. Plotters read both the analyzer results and key parameters (ROI coordinates, pixel_spacing, center, boundary, etc.) so their output matches the analysis configuration. Available plotters include:

• UniformityPlotter — visualizes image, ROI overlays, histograms and uniformity panels
• DetailedUniformityPlotter — concentric profile traces and polar/linear views
• HighContrastPlotter — per-pair profiles and combined MTF curve with annotated benchmarks
• CTP401Plotter, CTP404Plotter, CTP515Plotter — plot ROI overlays and labeled statistics for each module

Use plotters by passing an analyzer instance, e.g.:

from alexandria.plotters.uniformity_plotter import UniformityPlotter
plotter = UniformityPlotter(uniformity_analyzer)
fig = plotter.plot()

Integration with Existing Projects

Alexandria is designed to be a drop-in replacement for existing CatPhan analysis code:

catphan404 project:

# Old
from catphan404.uniformity import UniformityAnalyzer

# New
from alexandria import UniformityAnalyzer  # Same API!

XVI-CatPhan project:

# Old  
from catphan_analysis.modules.ctp486 import CTP486Module

# New
from alexandria import UniformityAnalyzer  # Unified interface

Future Scope

Alexandria is intentionally starting with CatPhan analysis, but the long-term goal is a broader medical-physics toolkit for phantom-based QA and research. Planned expansions include:

• Support for additional phantom types and modules (beyond CatPhan), with consistent analyzer and reporter APIs.
• Common utilities for phantom I/O, simulated phantoms, standardized ROI definitions, and QA metrics that apply across phantom families.
• Reusable plotting, reporting, and JSON results schemas to make outputs easy to integrate into CI or clinical QA dashboards.
• Example notebooks, dataset loaders, and validation tests to help users adapt Alexandria to new phantom designs and workflows.

Contributions that add new phantom modules, helpers, or integration examples are encouraged — the project aims to be a shared foundation for medical-physics phantom analysis.

Design Principles

1. Union of Functionalities: Each unified analyzer contains the superset of features from both source projects
2. Backward Compatibility: Maintains API compatibility with existing code where possible
3. Mode Flexibility: Supports both single-image and DICOM-series workflows
4. Clean Separation: Analysis logic separated from I/O and visualization
5. Extensive Documentation: Clear docstrings and examples

Contributing

Contributions are welcome! Please ensure:

• Code follows PEP 8 style guidelines
• All tests pass
• Documentation is updated
• Backwards compatibility is maintained

License

MIT License - See LICENSE file for details

Credits

Alexandria unifies and extends CatPhan analysis implementations from:

• catphan404 project - Modern modular toolkit
• XVI-CatPhan project - Production-validated workflows

Version History

1.0.0 (2026-01-26)

• Initial release
• Unified analyzers from catphan404 and XVI-CatPhan
• Support for both single-image and DICOM-series modes
• Comprehensive documentation and examples