1. 3D Viewer
  2. Accute Pain Research
  3. Eclipse Systems Uses IDL to Commercialize a Nuclear Cardiology Imaging System
  4. IDL Aids in Noninvasive Brain Research
  5. IDL Speeds Assessment of Myocardial Perfusion
  6. MIMVista Selects IDL as Development Platform for Advanced Medical Imaging System
  7. MIStar Puts Powerful Medical Imaging Software in the Right Hands
  8. NeuroQ Uses IDL to Provide Objective Methods for Quantying Brain PET Images 25
  9. The "LundADose" Project: Software Development for Dosimetry in Nuclear Medicine 26
  1. Customer Challenge

    The Queens Medical Centre needed a way to dynamically visualize data fromthree-dimensional, dynamic contrast-enhanced MRI (DCE-MRI), and to visually discern between arteries and veins.

  2. Solution Achieved

    Deep venous thrombosis (DVT) occurs in approximately two out of every 1,000 people, predominately in those over 60 years of age, and present diagnostic techniqes are both invasive and painful. In DVT, a blood clot developes in the deep veins in the leg. The clot, which is called a thrombus, blocks the blood flow through the vein. In addition, portions of the clot may break away from the vein wall and travel through the veins into the lung, where it can lodge in a pulmonary artery causing a life threatening embolism.

    At present, x-ray venography is one of the standard techniques used to image the deep veins of the leg and pelvis. Venography, however, has it's drawbacks. It is invasive as it involves injecting contrast media directly into the veins of the foot. It can be painful and difficult to perform if the patient's legs are swollen.

    Three-dimensional, dynamic contrast-enhanced MRI (DCE-MRI) is an alternative technique which is less invasive because the contrast media can be injected into a vein in the arm. Using DCE-MRI is difficult, because when it is used on veins, the contribution of the arteries ans well as the veins are both enhanced by the contrast agent, making it difficult to decern between the two. The images need additional post-processing to separate those contributions.

    Dr. Anne Martel of Queens Medical Centre in the UK developed an MRI-based, non-invasive alternative to the commonly-performed venography. Medical Physicist Anne Martel and her colleagues have built an IDL application which enables hospital clinicians to more accurately analyze contrast-enhanced MRI images to gain new insight into the causes and treatment options of DVT. Dr. Martel uses several IDL routines to perform specific functions in her custom application. A GUI allows hospital clinicians to select representative arterial and venous pixels from a dynamic sequence of 3D images to separate the arterial and venous information. The team then wrote another IDL procedure that uses this information to carry out factor analysis and generate 3D arterial and venous images, and developed another GUI to read the 3D data sets and display the data in the form of a 3D surface rendered object. This second GUI allows the user to control all aspects of the 3D display, including the orientation of both the image objects and the light sources used to illuminate the object.

    The users of this application are hospital personnel, such as radiographers, clinicians, and radiologists who typically have limited computer experience. The clinician can can carry out all of the steps necessary to separate the arterial and venous images and to display them as 3D objects with this custom-built application.

  3. Key Benefits

    • Using IDL routines to generate 3D arterial and venous images, clinicians can use non-invasive DCE-MRI images to diagnose deep venous thrombosis.
    • IDL's object graphics routines have been essential for doing the 3D viewer. IDL's matrix routines allow doctors to manipulate images quickly. IDL also allows them to create custom interfaces and port their applications across different platforms very efficiently.
    • IDL saved both time and money compared to building an application from scratch. There was no competitor.

    IDL-rendered image showing the arteries and veins of the pelvis. Thrombosis is demonstrated using a 3-D overlay of magnetic resonance direct clot imaging (yellow) onto combined magnetic resonance venography and arteriography (red and blue). The subtraction technique isolates venous and arterial phases using timing information after a contrast bolus is given into a periheral vein. Direct clot imaging isolates fresh clot as high signal on a background of suppressed blood and fat signal. 3-D overlay is then possible so that the relative positions of the vessels and thrombus can be appreciated.
    Images credit Queens Medical Centre.
    Image shows 3D viewer, developed using IDL's object graphics routines. The 3D viewer is used by hospital clinicians to display and analyze contrast-enhanced MRI images.
    Images Credit Queens Medical Centre
  1. Customer Challenge

    Robert Coghill of Wake Forest University in Winston-Salem needed to develop a map of the brain regions which are activated by acute and cronic pain.

  2. Solution Achieved

    Coghill collects data from 10 to 20 human sujects, scanned eight times. Each person is subjected to PET scanning duriing the testing, first when not in pain and then after being injected with capsaisin into the skin in the upper arm. Consequently, a substantially large amount of data builds up. Using IDL to process the data, he creates images of different condition (pain vs. no pain) and images of the variance used in generating the statistics.

  3. Key Benefits

    • IDL's data manipulation and display are straightforward. Coghill developed a set of routines that made his life considerably easier. He is not a programmer, he is a psychologist and found IDL easy to use.
    • IDL saved time and allowed the customer to have a far better feel for his data than ever before.
    • Before using IDL, data analysis and display were handled by a series of C program and Matlab routines. Coghill found it difficult to get the answers he was looking for. Also, the display capabilities wer inflexible and highly limited.

  1. Customer Challenge

    The Cardiac Nuclear Medicine department at Yale University needed to convert a legacy application written in several older languages so it would be compatible with new medical imaging modalities.

  2. Solution Achieved

    Eclipse Systems Inc., located in Branford, CT, contracted with Yale to commercialize a quantification package (Wackers-Liu CQ and Wackers-Liu CQ "On the Web") developed under the direction of Dr. Frans Wackers, one of the pioneers in Nuclear Cardiology. Although Dr. Wackers quantification technique was the "gold standard" for non SPECT imaging, when the application was extended to SPECT (and now PET), it was never commercialized. At that time, nuclear medicine computers were using UNIX, Mac and PC based operating systems and an environment that was easily adaptable to all was required. IDL clearly filled the bill. It allowed the programmers at Yale to work on one system while the programmers at Eclipse worked on another. Ultimately it allowed Eclipse Systems Inc. to distribute a package that was compatible with all of the systems used in Nuclear Cardiology. The quantification suite is now available for all Nuclear Cardiology systems, either directly from Eclipse or through an OEM like General Electric Medical Systems.

    The flexibility and portability of IDL still makes it the choice for today. As medical imaging in general, and Nuclear Medicine and Nuclear Cardiology specifically, move in the direction of standardization, the continual development of IDL becomes more and more of a factor. The adoption of DICOM standards by the Society of Nuclear Medicine (SNM) and the American Society of Nuclear Cardiology (ASNC) place a large burden on any software development group. As these standards extend to the PACS and RIS/HIS environments, data and image transmission become a more and more important criteria for any of the distributed quantification packages within Nuclear Cardiology.

    Unlike some other groups within the field, Eclipse Systems Inc. is not a large company with a staff of multiple programmers. Meeting these standards and staying current as the clinical field changes and its needs and requirements change as well, places an incredibly large burden of time and resources on the group. Again, the choice of IDL is proven correct. It allows a small company, like Eclipse Systems Inc., to meet the challenge of competing on an industry standard level with groups that have staff and resources far exceeding our own.

  3. Key Benefits

    • IDL allowed Eclipse Systems Inc. to distribute a package that was compatible with all of the systems used in Nuclear Cardiology.
    • IDL is compatible with older and new equipment, and is easily integrated with legacy code, saving time and money in converting systems from an old language to another newer language.
    • The flexibility and portability of IDL still makes it the choice for today. As medical imaging in general, and Nuclear Medicine and Nuclear Cardiology specifically, move in the direction of standardization, the continual development of IDL becomes more and more of a factor.
    IDL allowed Eclipse Systems to distribute a package that is compatible with all the systems used in nuclear cardiology
    Image courtesy Eclipse Systems, Inc.

  1. Customer Challenge

    Los Alamos Biophysics Group needed a way to visualize and analyze large datasets from multiple imaging modalities used to image the human brain. These data sets range in size from tens of megabytes to more than a gigabyte. Working with extraordinarily large data sets in a variety of formats presents a unique challenge.

  2. Solution Achieved

    Noninvasive Brain Imaging

    Prior to the advent of modern brain imaging methods, patients had to accept the risk of exposure to ionizing radiation from x-rays. Today, neuroimaging researchers use noninvasive methods to view both brain anatomy and brain function, taking advantage of advanced software tools like ExelisVIS's IDL to study the brain while protecting patients from ill side effects.

    The Human Brain Project, spearheaded by Los Alamos National Lab's (LANL) Biophysics Group, is dedicated to noninvasive neuroimaging research to understand general brain function as well as aid in clinical applications such as neurosurgery planning, epilepsy and stroke recovery. To further advance the project's research, the Biophysics Group created custom software using IDL to combine gigabyte-sized data files from multiple imaging systems?including magnetic resonance imaging (MRI), electroencephalography (EEG) and magnetoencephalography (MEG)?and then display and visualize the data intuitively.

    Mapping Brain Activity: The Challenge of Medical Image Data

    A number of medical imaging systems are required to obtain brain data, including anatomical and functional MRI, and MEG and EEG time-series data. These data sets range in size from tens of megabytes to more than a gigabyte. Because working with extraordinarily large data sets in a variety of formats presents a unique challenge, the Biophysics Group needed a software solution that would be up to the task.

    The Magic of MRIVIEW and IDL

    Equipped with IDL's programming power, the Biophysics Group developed a software tool called MRIVIEW for viewing and manipulating volumetric MRI head data. MRIVIEW supplies methods for reading in raw MRI data, viewing this data in two and three dimensions, segmenting structures in the data, reconciling coordinate systems between the MRI data volume and data obtained from brain functional modalities, and viewing combinations of anatomical and functional information.

    MRIVIEW includes a MEG inverse solver called Cortical Start Spatial-Temporal (CSST). CSST uses Message Passing Interface to start multiple IDL analyses on a Linux cluster, then gather and save the results. Where multiprocessor machines are present, CSST will also use IDL's multi-threading capabilities to further speed up computations. Used on a single processor, this type of analysis might require several days, so "this parallel processing capability using IDL has been very useful," according to Ranken.

    Ranken also prizes IDL for the flexibility it allows when working with other commercial programming packages and languages. "With IDL, I can quickly integrate MRIVIEW with other software developed here and elsewhere because IDL allows simple links to other packages written in IDL, C, Fortran, and MATLAB."

  3. Key Benefits

    • MRIVIEW allows researchers to visualize large data sets from multiple formats.
    • IDL's flexibility allows programmers to quickly integrate MRIVIEW with other software.
    • IDL allows simple links to other packages written in IDL, C, Fortran, and MATLAB. IDL is the only software with the power to handle the large, multi-format images.
    • neuro MRIVIEW MRI medical imaging

    This view shows the 3D Model Viewer being used to combine 2 volumes with 2 sets of geometric data. Model 1 contains the MRI head data, model 2 contains the MRI brain data, Model 3 contains the arrows, and Model 4 contains the contoured MEG data on the hel
    Los Alamos National Lab's Biophysics Group.
    A magnetic field resulting from the brain's response to a visual stimulus is shown as a color contour map on a head surface reconstructed from MRI data. The disks represent sensor locations in a full-head MEG system. The fields shown are an averaged respo
    Los Alamos National Lab's Biophysics Group.
    CSST results from an MEG visual study, showing the range of visualizations options of the Source Plotting interface. All text, plot, 2D images and 3D renderings are modifiable. They can be moved, resized, re-colored, added or deleted from the viewing wind
    Los Alamos National Lab's Biophysics Group.
  1. Customer Challenge

    Researchers at Emory School of Medicine in Atlanta Georgia needed a single, effective software system to evaluate cardiac perfusion and function.

  2. Solution Achieved

    Medical interns, practicing physicians and patients at the Emory School of Medicine in Atlanta, Georgia are benefitting from faster, more informed diagnoses using an IDL application that provides accurate, quantified measurement of cardiac perfusion and function. This non-invasive diagnostic technique lets doctors, whose patients have experienced signs of heart attack, rapidly assess the relative blood flow through the cardiac arteries.

    Developed by a team of researchers at Emory (Ernest Garcia, Ph.D., David Cooke, M.S.E.E., Tracy Faber, Ph.D., and Russ Folks, B.S.), the Emory Cardiac Toolbox™ has streamlined a physician's reading of cardiac PET (positron emission tomography) and SPECT (single photon emission computed tomography) studies, into a single, effective software system. "Prior to the application we developed, physicians had to employ several different analysis tools to evaluate cardiac perfusion and function. Now, through a point and click GUI, they can analyze the data and process the images more quickly than ever?all in one computer environment," says Cooke.

    Speed and Accuracy Are Critical

    "Accurate processing and the ability to move from screen to screen quickly is critical," Cooke says. The application helps physicians estimate a heart's efficiency. Some of the telltale parameters assessed are the heart's blood flow, ejection fraction, endocardial chamber volume and estimated wall-thickening.

    Ejection fraction represents the percentage of blood pumped with each contraction and is directly related to the chamber volume; the lower the ejection fraction, the lower the amount of blood pumped. Since the heart is a muscle, it gets bigger as it works harder to pump blood, just as one's bicep increases in size with exercise. When a heart gets too large, or its walls get too thick, it is less able to pump properly and it is more difficult for blood to diffuse into the heart muscle.
    With the Emory Cardiac Toolbox, physicians can ascertain the probable source of chest pain or other signs of abnormal heart activity. Easily getting to the correct answer fast is important; lives are at stake.

    The raw results from the nuclear medicine tests are accessed by querying the patient's file in the database. "All the physician or technician has to do is enter the patient's name and select 'Go.' The data is processed automatically. After that, it's so easy to work through the GUI and review the results that the doctor can just use the program straight out," says Cooke.

    3D Display Gives Best Insight

    Using three dimensional displays of the patient's heart, physicians can determine whether blood is flowing to all aspects of the myocardium. "IDL's shading, 3D graphics and support for OpenGL are some features that are very effective for our imaging," Cooke says. Emory's application also provides three "generic" sets of coronary arteries which can be overlaid on the 3D images to help the physician infer which coronary arteries may be diseased. "Physicians are able to view the fused data as never before," Cooke says.

    Program Linking Tools, Cross-Platform Development

    "All this began about five years ago when Emory bought a PET scanner. We needed a good cardiac package and the scanner included IDL-based applications. To prepare for the future, we began using IDL," Cooke says.

    A lot of programming had been completed prior to when Emory started developing with IDL. They needed to be able to use the previously developed code (CEqual®), written in C, in addition to the new IDL programs. IDL's ability to link to existing code proved to be a big, labor-saving benefit. "Not having to rewrite the C code was great," says Cooke. "Currently, we have about fifteen thousand lines of IDL code and fifteen thousand lines of C code. The C code is called and executed when necessary, as the physician reviews and reads the study."

    Emory developed the application on Sun® and Power Macintosh® platforms. Because IDL is a "platform-neutral" language, they have been able to distribute the application without rewriting the code. Because the majority of people who use the application are non-programmers, it's important that they can get good performance in a very user-friendly computer environment. "Performance on the Macintosh has been quite good. One of our external sites, with an older Power Macintosh, tells us they are impressed with the speed," Cooke remarks.

    The Emory Cardiac Toolbox is distributed commercially by Syntermed, Inc. Visit their website at www.syntermed.com

  3. Benefits

    • Using IDL, the researchers were able to engineer a cross-platform solution for visualizing cardiac images.
    • IDL allowed the team to create a single solution for many tasks, where medical imaging professionals in the past had to use multiple software packages.
    • IDL easily integrated with existing code, so the team did not have to re-develop solutions.

    A PET image shows blood flow from the heart, visualized using the Emory Cardiac Toolbox.
    Images credit Emory University

    Multiple views of a patient-derived three-dimensional models of Stress Tc-99m and Rest TI-201 myocardial perfusion for an abnormal patient. Brighter colors show better blood flow and darker colors show poorer blood flow. An extensive stress-induced defect can be seen in the anterior, lateral, septal and apical portions of the myocardium that partially returns to normal at rest.
    Images credit Emory University

  1. Customer Challenge

    MIMvista, the leading third party software provider for PET and PET/CT display, needed a way to reduce the complexity of analyzing visual data from multiple modalities such as PET, MRI, SPECT and CT.

  2. Solution Achieved

    Reducing the complexity of analyzing visual data from multiple modalities such as PET, MRI, SPECT and CT was a research problem that attracted the attention of Dr. A. Dennis Nelson, founder of MIMvista and physician at the University Hospitals of Cleveland.One of today's most challenging medical diagnostic tasks for doctors is to synthesize information from the numerous types of available imagery and perform faster, more accurate patient diagnoses. IDL plays a critical role in addressing this challenge through work being done by MIMvista.

    A pioneer in the medical imaging field with more than 25 years of experience in the areas of clinical and research oriented medical image processing, Dr. Nelson developed a solution to this medical imaging problem with the help of IDL. His groundbreaking image analysis application, called MIM™ image display system, is widely recognized as a significant advancement for the registration, fusion, and display of medical images from multiple modalities. Once he realized the widespread need for the image display system, Dr. Nelson founded MIMvista, Corp. to distribute MIM and continue to enhance its capabilities.

    The MIM Image Display System

    "Our goals were to develop a more powerful processing and analysis system for the viewing and fusion of medical images, and to combine those capabilities with a user interface that was easy for doctors to use," said Pete Simmelink, operations manager at MIMvista. "IDL software gave Dr. Nelson and the MIMvista team the tools we needed to achieve both of these difficult goals in a very cost-effective way and with a very aggressive development timeline."

    Using IDL, Dr. Nelson and the MIMvista team designed a Windows-based image display system that enables radiologists, medical researchers and other doctors to easily display and manually overlay tomographic images. MIM allows the operator to rotate, translate and align images anatomically, and match the geometric position of the images relative to one another. This allows doctors to more easily combine visual data from multiple modalities, thereby significantly increasing the speed and accuracy of diagnoses.

    MIM is used for the general viewing of DICOM PET, DICOM NM, DICOM MR, DICOM CT, DICOM US, ECAT PET, Interfile and ICON imagery - large imagery files that can range in size from 5MB to 200MB. MIM maintains original scan volume accuracy while avoiding the time required for pre-calculation of resized image volumes. It is also significantly faster than methods that require translation and rotation of the entire image volume. MIM allows the operator to control three orthogonal slice display view ports of each volume and align image volumes by translation and rotation of these view ports with respect to the original image volume orientation.

    Choosing IDL

    "IDL was the clear choice as our development platform for MIM because it works so well with arrays and medical images," said Simmelink. "IDL's Object Graphics, high level array procedures and math functions saved the development team a tremendous amount of time and helped us achieve a significant advancement in medical imaging."

    "We handle all development related to MIM with a tight team of just five programmers, which is possible because IDL's development tools take care of so many of the complex elements we would otherwise have to build from scratch," said Simmelink. "IDL's Object Graphics have been particularly useful for our recent work developing the latest version - MIM 3.0. I would estimate that IDL saved us about six months of development time on that latest development project alone. That probably saved us at least two hundred thousand dollars."

    "Technical support from ExelisVIS has been very helpful during our development efforts," said Simmelink. "We use the Internet news groups extensively, and that has been a great resource for our team. ExelisVIS is very active in the news groups, gets answers to the user community very quickly and demonstrates a strong commitment to supporting its customers."

    Helping Doctors and Their Patients

    MIMvista's development efforts have been a tremendous success, with a MIM user base that has grown from 30 original sites in 2002 to more than 250 users at 120 sites today.

    Simmelink added, "The feedback from doctors who use our image display system has been very positive. With MIM, doctors are able to do previously complex image fusion with ease and speed, which is a tremendous asset when analyzing complex visual data about cancerous tumor growth and other serious medical conditions. MIM is an advancement that is having a significant positive impact on patient care and outcomes, and IDL has played an important role in making it possible."

    Image courtesy MIMVista Corporation

  3. Key Benefits

    • With MIM, doctors are able to do previously complex image fusion with ease and speed, which is a tremendous asset when analyzing complex visual data about cancerous tumor growth and other serious medical conditions.
    • IDL's Object Graphics, high level array procedures and math functions saved the development team a tremendous amount of time and helped them achieve a significant advancement in medical imaging.
    • MIMVista developed the MIM Image Display System with a team of just five programmers, which was possible because IDL's development tools took care of so many of the complex elements they would otherwise have to build from scratch.

    Image courtesy MIMVista Corporation

    Image courtesy MIMVista Corporation

    Image courtesy MIMVista Corporation

    Image courtesy MIMVista Corporation

    Image courtesy MIMVista Corporation

    Image courtesy MIMVista Corporation
  1. Customer Challenge

    Apollo needed to create a commercial application that allowed users of CT MR and NM to perform postprocessing on images acquired during and after the injection of a compact bolus of contrast media. They also wanted to have the ability to support various manufacturer-dependent protocols and deliver a product that was fast, easy-to-use, portable and affordable.

  2. Solution Achieved

    MIStar provides easy-to-use, portable and affordable analysis software that supports various manufacturer-dependent protocols, and the DICOM medical standard file format. MIStar users can interact with multiple imaging modalities, including X-Ray, CT, MR and NM while benefiting from an environment for fast and easy post-processing routines. Ease-of-use and flexibility make it an ideal tool in clinical and research applications and radiologists, scientists, physicians and surgeons in hospitals, medical centers and universities can easily operate it. And, because of IDL's built-in, multiple platform support, MIStar operates in many environments, including portable laptop and desktop models. Its flexibility also extends to the hardware realm, being easily integrated with workstations manufactured by most OEMs and PACS vendors.

  3. Key Benefits

    • Physicians, researchers, radiologists and other medical professionals can now easily perform post-processing routines on multiple types of medical images.
    • IDL allowed Apollo to rapidly create a reliable, off the shelf solution for multi-modality image analysis.
    • IDL's rich library of routines makes it very easy to creat GUI widgets, graphics, math calculations, array manipulation, and many complex tasks in just a few lines.

    NM perfusion color overlays of renal blood volume and filtration rate in a patient with one kidney.
    Data courtesy Prof. Isky Gordon, Great Ormond Street Hospital for Children, London, UK. Image courtesy Apollo Medical Imaging Technology.

  1. Customer Challenge

    Researchers, physicians, and other interpreters of PET images needed a quantified, objective method to analyze brain PET imaging.

  2. Solution Achieved

    Syntermed, in affiliation with Daniel Silverman M.D., Ph D, head of the neuronuclear imaging section at UCLA Medical Center, has used IDL to develop NeuroQ™ ? an automated software platform that generates quantified analyses of regional cerebral activity from PET 18F-FDG images. NeuroQ's PET DP program has a validated capability to:

    • generate comprehensive image presentations and objective diagnostic indices
    • accurately quantify the relative activity in multiple brain regions
    • quantitatively detect clinically meaningful abnormalities of regional brain metabolism

  3. Key Benefits

    • With NeuroQ™, the Nuclear Medicine physician and other professional interpreters of PET images now have a quantified, objective method to analyze brain PET imaging.
    • IDL provided all the tools they needed in one package.
    • IDL had the medical image processing and analysis routines built-in to allow them to create a distributed product that met their requirements.

Image courtesy Syntermed

Written and submitted by: Michael Ljungberg, professor and Katarina Sjogreen Gleisner, assistant professor Medical Radiation Physics, Dept. Clincial Sciences, Lund, Lund University, Sweden.

  1. Customer Challenge

    Scientists at the Radiation Physics Department, part of the Clincial Sciences branch of Lund University in Sweden needed a data visualization and analysis solution that could support their data type, and could produce intuitive visualizations of raditation therapy treatment courses.

  2. Solution Achieved

    Medical Radiation Physics is a subject field dealing with the use of ionizing and non- ionizing radiation, both for diagnosis and treatment of different diseases, and for radiation protection. Radiation, in general, is harmful to normal tissues but is used with success in therapy applications to eradicate malignant cells. In therapy situations it is of great importance to determine the energy absorbed in various tissue due to a radiation exposure, in terms of the general quantity "the absorbed dose" (J/kg). Radiation therapy can also be performed using internally administrered radioactive pharmaceuticals.

    When determining the absorbed dose from an administrered radiopharmaceutical, its distribution path within the body and its redistribution over time must be determined. This is required to determine the total number of nuclear disintegrations occuring in a tissue, which in principle determines the absorbed energy. Practically, this information is obtained by performing sequential measurements using a scintillation camera. This device images gamma radiation and can produce either planar 2D images or tomographic 3D SPECT images (Single-Photon Emission Computer Tomography).

    To obtain quantitatively correct information from the scintillation camera images, corrections for various physical phenomena are required; photon attenuation within the patient's body, scattering of photons, and the relatively poor spatial resolution of the system. The total number of nuclear disintegrations is determined from the multiple measurements using curve-fitting and subsequent integration over time. At the Medical Radiation Physics in Lund, we are developing a dosimetry package, named LundADose, as part of a long-term research project, which performs accurate dosimetry based on both 2D and 3D images. The software has a user-friendly graphical interface and can be run on different computer platforms.

    2D based dosimetry calculations: The most common method of determining the absorbed dose in nuclear medicine is based on planar scintillation camera imaging where the average activity in organs and tissue is determined in selected regions-of-interest. The absorbed dose is calculated from the activity measurements using pre-calculated dose-conversion factors for standardized phantom geometries. As a basic tool for patient dose calculations, we have developed a quantification method and a dose calculation program in IDL. Although being widely used, the 2D based dosimetry method has inherent limitations which are of importance when performing individual based patient dosimetry for therapy applications. It is therefore of interest to compare the results when using 2D and 3D methods to determine the absorbed dose.

    3D based dosimetry calculations: In our 3D based dosimetry approach, the voxel-distribution of absorbed dose is calculated. Each patient's geometry is constructed from registered CT images and quantitative SPECT images. This information is used as input to a Monte Carlo program, developed by us, for the simulation of the coupled transport of electrons and photons. The physical characteristics of the radiation are sampled according to the activity distribution from the SPECT images, and the energy spectrum of the radionuclide. The absorbed energy from all interactions is scored within the patient-specific geometry and 3D images of the absorbed dose are thus calculated. By this methodology each patient is individually modeled in the computation of the absorbed dose.

    Conclusions: The IDL programming environment has been very useful for this project thanks to its comprehensive library of functions and procedures that have made development of the various programs efficient. We have not fully adopted the structures, in which GUI programming is recommended by IDL, and have not yet implemented objects. We have a need to run most of our programs in 'batch' mode because of long calculation times. Our programs have therefore been written so as to allow for an alternative input from a command line in addition to using user-driven events, and therefore most programs include its own event loop. We feel that the continuous development of the IDL programming language and the library of functions, concurrent to our own program development, have been valuable with new useful tools in every new version.

    The SPECT system: The program has been interfaced to image files acquired by our hybrid SPECT/CT HawkEye System (GE Medical Systems). This SPECT system has two scintillation cameras with a one-inch NaI(Tl) crystal. It also has a Computed Tomography X-ray unit for the measurement of morphological information, which is useful for both image fusion, correction for photon attenuation and for 3D absorbed dose calculations. The acquired camera studies are exported as Dicom files and are transfered to external computers for post-processing in the LundADose program. This figure shows the camera system.
    Images Credit Medical Radiation Physics Center.

    Image registration: For analysis of a time series of images it is important that images are spatially aligned to each other, so that the information contained in each of the pixels of the two images inhere from the same anatomical position in the patient. We have developed a method for image registration in IDL which is based on optimization of a polynomial warping transformation with regards to the mutual information between the images. The method has been developed for the registration of both planar whole-body images and for 3D CT and SPECT images. Within the context of LundADose, the registered anatomical information is used to correct for scatter, photon attenuation and collimator blur and serves as a patient-specific model when calculating the absorbed dose distribution in 3D. It is also used to improve the localization of tumours by use of overlay of SPECT and CT images.

    SPECT reconstruction: An accurate image SPECT reconstruction is required for an accurate 3D activity determination, and 3D absorbed dose calculation. We have in this field an ongoing collaboration with Johns Hopkins Medical Centre, Baltimore, USA regarding the implementation of state-of-the-art iterative reconstruction methods (ML-EM,OSEM) that include non-homogeneous scatter and attenuation correction and correction for both collimator response and collimator septal penetration caused by high-energy photons. This figure shows the user interface.
    Images Credit Medical Radiation Physics Center.

    Biokinetics: To determine the absorbed dose from the radiopharmaceutical, several scintillation camera measurements need to be performed. Curve-fitting of the activity-versus-time data of each volume-of-interest is required to model the uptake and excretion of the radiopharmaceutical over time. By integration the area under the curve is determined. For SPECT, the absorbed dose is determined on a voxel-by-voxel level. This figure shows the user interface of the program for curve fitting and analysis of the absorbed dose images.
    Images Credit Medical Radiation Physics Center