Medical Radiation Physics, Clinical Sciences Lund, Lund University

Michael Ljungberg

Evaluation of renography by Monte Carlo simulations

Användarmöte Nuklearmedicin 15 nov, 2011

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Quality Control of procedures

Physical Phantoms

Commonly used in general SPECT research.

Cylindrcal and elliptical and more realistic antropomorphic phantoms available.

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Kidney phantoms

Static phantom with kidneys available

Not possible to simulate dynamic processes

Limited number of organs

•Liver •Kidney •Tumors in the liver

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Computer Phantoms

Mathematically described geometries

Useful in simulation studies to • Evaluate image reconstruction methods • Effects such as photon attenuation, scatter and partial volume effect • Detector characteristics and optimisation studies • ROC studies

Often used in Monte Carlo programs that simulate the radiation transport

from a decay to a registered event in the image.

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Pixar’s Transformable Model

The 4D XCAT Phantoms

Based on state-of-the-art computer graphics techniques

• Organs modeled using NURBS and subdivision surfaces, tools widely used in current games and movies

Utilize Pixar’s Universal Man and Woman Idea

• Transformable base anatomies upon which to model different types of people (inside and out)

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

NURBS and Subdivision Surfaces

Shape can be modified through the set of control points that define them

• Can be deformed by transforming the control points

NURBS surface Modified NURBS surface

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Visible Female Anatomical Images Male Anatomy Female Anatomy

Segmented Organs From Imaging Data

Visible Male Anatomical Images

Fit 3D NURBS and Subdivision Surfaces to Segmented Organs

Development of the XCAT Male and Female Base Anatomies

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Male Abdomen Respiratory Motion

Chest

Female Abdomen Right Left

Head

Phantom Anatomy

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

4D Beating Heart Model

RCA LCX

RV

RA

LA

LV

Aorta

LAD

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Segmented Branches Extended Branches

Mathematical Extension of the Segmented Coronary Artery Tree

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Plaques and Perfusion Defects

Myocardial SPECT

Plaque Imaging

Ant. Projection

SA LA

plaque defect

• Plaques modeled as NURBS surfaces on the interior of the arteries

• Perfusion defects modeled as wedges in the LV myocardium

Beating Heart Model Coronary Artery Disease (CAD)

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Interactive IDL Program

Motion vectors for the lung

* *

4D Respiratory Model

• Based on respiratory-gated CT data

• IDL program to mark and track points on the respiratory structures

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Gated Chest CT

Lung with Spherical Tumor

w/o resp. motion w/ resp. motion

Contrast ~0.5

Effect of Motion on the Lung Tumor Imaging (SPECT)

Modeling of Tumors

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Effect of Anatomy on Imaging

Nuclear Medicine procedures are made on a population with large variations Methods can be studied on a population of computer phantoms in a controlled way May catch problems that a measurement or a simulations using a single phantom can not find

Male Female

Courtesy Paul Segars, Duke University, NC, USA

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Monte Carlo Calculation

A method to simulate the radiation transport Main applications are in Dosimetry and Medical Imaging

Medical Radiation Physics, Clinical Sciences Lund, Lund University

SIMIND Monte Carlo program

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Scintillation Camera Simulation

SIMIND is a Monte Carlo program that simulates a scintillation camera system.

Useful to evaluate imaging parameters. A. No patient motion and perfect camera resolution. B. Patient respiration and heart beating. C. Normal system resolution and patient movements D. Photon attenuation added E. Photon attenuation and scatter F. Realistic noise level added.

A B C D E F

Medical Radiation Physics, Clinical Sciences Lund, Lund University

EQUALIS Project

Modified to simulate Dynamic Scintigraphy

Activity in the lidney compartment and in other organs in the XCAT phantom can be described by a time-activity curve

Hospital-specific parameters • Time sequences, typical for clinical acquisitions • Camera type • Collimator • Activity • Acquisition time

Medical Radiation Physics, Clinical Sciences Lund, Lund University

XCAT Kidney

Separated into cortex, medulla and pelvis

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Kidney kinetics – version 0.0

Kinetics is defined for • Left cortex, medulla and pelvis • Left cortex, medulla and pelvis • Ureter and bladder • Liver, spleen,……

Normal and abnormal kinetic

Possible to include anatomical patient variations

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Kidney kinetics

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

0 100 200 300 400 500 600 700 800 900

Cortex-L

Medulla-L

Pelvis-L

Cortex-R

Medulla-R

Pelvis-R

Bladder

ureter

liver

spleen

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Example of a Monte Carlo simulated renography study

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Import to Xeleris possible

Medical Radiation Physics, Clinical Sciences Lund, Lund University

Image Transfer

Image data from simulations converted to Interfile or DICOM Download data from a web page and import into the clinical system Evaluated on site using daily clinical routine procedure Results are compared to truth

Future developments • More cases • More patients • Perhaps a better kidney model • ……..