Registration and display of brain SPECT and MRI using external markers

Cerebral blood flow alterations in pain-processing regions of patients with fibromyalgia using perfusion MR imaging

BACKGROUND AND PURPOSE

Widespread pain sensitivity in patients with FM suggests a CNS processing problem. The purpose of this study was to assess alterations in perfusion as measured by DSC in a number of brain regions implicated in pain processing between patients with FM and healthy controls.

MATERIALS AND METHODS

Twenty-one patients with FM and 27 healthy controls underwent conventional MR imaging and DSC. For DSC, 12 regions of interest were placed in brain regions previously implicated in pain processing. rCBF values were calculated for each region of interest. Subjects answered mood/pain coping questionnaires and underwent clinical/experimental pain assessment.

RESULTS

There were significant correlations between the thalamic rCBF values and the pain-control beliefs of FM subjects. The strength of the relationship between clinical pain measures and thalamic rCBF values increased after adjusting for pain-control beliefs. There was a significantly different distribution pattern of rCBF values across various brain regions between the FM group and the healthy controls. There was a lower degree of correlation in the FM group between the thalamic rCBF values and the other brain regions relative to the healthy controls.

CONCLUSIONS

Significant correlations were found between thalamic rCBF values and pain belief values. These data suggest that there are baseline alterations of brain perfusion in patients with FM. rCBF values of the thalami exhibited lower correlations with respect to other brain regions thought to be involved in pain processing compared with those in healthy controls.

Construction of patient-specific surface models from MR images: application to bioelectromagnetism

Patient-specific geometric models are needed in many engineering problems. This work reports a novel software tool developed to construct individualized triangulated surface models from MR images. The program consists of three main parts: segmentation, triangulation and registration. The software tool was developed under the UNIX operating system. The application area demonstrated in this work is bioelectromagnetism but the program can be used as well in other engineering problems. The tool has been successfully applied in numerous cases, both for the thorax and the head.

Spatial normalization of lesioned HMPAO-SPECT images

We investigated the effect of nonlinear alignment on SPECT images with lesions. Linear alignment produces reliable results but the introduction of nonlinear methods can improve matching by accounting for global brain shape. We examined the hypothesis that nonlinear alignment can introduce unwanted image distortions when lesions are present. We set out to quantify possible distortions by constructing artificial lesions in order to obtain images with controllable characteristics. We examined the use of basis functions (in SPM96 and SPM99) and other nonlinear models (in AIR3.08) designed to achieve optimum alignment between image and template. We found that the use of models with high degrees of nonlinearity will result in unwanted deformations and that the safest way to align images with lesions is to use 12-point linear affine transformations. Masking was examined as a remedy to distortions caused by nonlinear methodologies and produced significantly improved results.

Image fusion in open-architecture PACS-environment

Multimodal digital imaging is common in many fields of diagnosis and therapy planning - there is great interest in matching globally, fusing or registering data from the same part of the body. In practice, there are still difficulties in customizing image fusion in hospitals. Efficient routine use of image fusion requires, among others, an image management infrastructure - a picture archiving and communication system (PACS) - to provide storage of image data in a standard digital format, intelligent image management and fault-tolerant high-speed image networking. In order to customize image fusion, advances in both fusion software and hardware are also needed. The algorithms should be automatic, fast and accurate enough. Registration of multimodal data also creates a need for different display techniques and user-friendly interfaces. Image fusion has been impractical and too tedious to be performed in routine work, but in the future, fused images will be used in clinical practice - even in teleradiological consultation.

Calculating internal dose by convolution from SPECT/MR fusion images

A new computer program was developed to calculate the absorbed dose. The program is based on the use of the convolution method and abdominal SPECT/MR fusion images. The applicability of the method was demonstrated by using data from (111)In-labeled thrombocyte and 99mTc-labeled colloid studies of three healthy volunteers. Dose distributions in the volunteers and the average absorbed doses in liver and spleen were calculated. The average doses for 99mTc-labeled colloid study were 0.07 +/- 0.02 (liver) and 0.046 +/- 0.005 mGy/MBq (spleen). The results are in good agreement with a Monte Carlo (MC) based method (0.074 for liver and 0.077 mGy/MBq for spleen) used by the International Commission on Radiological Protection (ICRP). For (111)In-labeled thrombocyte study the doses were 0.33 +/- 0.05 (liver) and 8.9 +/- 1.2 mGy/MBq (spleen) versus 0.730 and 7.50, respectively. The differences in dose estimates in the (111)In-labeled thrombocyte study are mainly due to the approximation used in activity quantitation. Convolution of the activity distribution with a point dose kernel is an effective method for calculating absorbed dose distribution in a homogeneous media. Activity distribution must be aligned to anatomical data in order to utilize the calculated dose distribution. The program developed is applicable to and practical for clinical use provided that the input data needed are available.

Abdominal SPECT/MRI fusion applied to the study of splenic and hepatic uptake of radiolabeled thrombocytes and colloids

The importance of applying MRI (CT)/SPECT fusion in the abdominal and thoracic areas has been recognized in recent studies aiming at radionuclide therapy of cancer. According to our earlier results spleen and liver volume determination with different segmentation methods is inaccurate with SPECT alone. We therefore applied a SPECT/MRI registration procedure to the estimation of spleen and liver volumes and spleen/liver activity ratios in three male volunteers administered 111In-labeled thrombocytes and 99mTc-labeled colloids. The objectives of the study were to investigate if the uptake of thrombocytes in the spleen and liver can be measured more accurately when the anatomical borders of these organs are transferred from MRI to SPECT, and to test a SPECT/MRI registration method for improving three-dimensional dosimetry for radiotherapy treatment planning. A good correlation was found between spleen/liver activity ratios calculated from volumetric average activity per pixel values and from total volumetric counts derived from registered data but not from projection data. The average registration residual with this SPECT/MRI fusion method is approximately 1-2 cm in the abdominal area. Combining anatomical images with SPECT is therefore important for improving quantitative SPECT also in the abdomen.

Imaging and staging of head and neck cancer using a low pH In-111-bleomycin complex

Bleomycin (BLM), a natural antibiotic toxic to dividing cells has been used for treatment of several forms of cancer. BLM has been labelled with various cations but most have turned out to be unstable in vivo. In-BLM has demonstrated high bone marrow uptake, but by using an In-111-bleomycin complex (BLMC) formed at low pH, the low in vivo stability and high bone marrow uptake can be avoided. Our premise is to combine radiotherapy and chemotherapy by using radionuclide-BLMC. In this study we used In-111-A'2a-c-BLMC in 28 head and neck cancer patients. Scintigraphic findings were compared to those of surgery, pre-operative radiology and proliferation markers. The injected patient activity was approximately 85 MBq, 100 MBq/mg. The half-life of In-111 activity in serum varied from 1.5 to 3.1 h, and in urine from 1.4 to 3.7 h. More than 95% of the urine activity was excreted within 24 h. From biopsies obtained from surgical specimens of 22 patients the absolute uptakes in tumour tissues varied between 0.10 and 0.95 x 10(-3)% ID/g. Uptakes in normal tissues varied from 0.01 to 0.32 x 10(-3)% ID/g, and were always lower than in malignant tissues of the same patients. All patients were examined on the injection day with ultrasonography of the neck. Using In-111-BLMC we missed small metastatic lymph nodes (< 1 cm) in 2 patients, but there were no false positive findings. The critical organ from the dosimetric point of view was the kidney. The absorbed radiation doses with these injected activities were 19 mGy in liver, 75 mGy in kidney and 1.0 mGy in whole body (5 h mean residence time). Our results indicate that In-111-BLMC targets head and neck cancer, and identifies metastatic spread. It could possibly be applied with higher activities for adjuvant Auger-electron therapy of head and neck cancer.