SPECT-guided CT for evaluating foci of increased bone metabolism classified as indeterminate on SPECT in cancer patients.

UNLABELLED: Hybrid cameras combining SPECT and spiral CT offer the opportunity to obtain a diagnostic-quality CT image of scintigraphically suggestive lesions that directly correlates with the SPECT image. The field of view of the CT scan can be adapted on the basis of the SPECT findings ("SPECT-guided CT"). The aim of the present study was to investigate the value of SPECT-guided CT in the assessment of foci of increased bone metabolism classified as indeterminate on SPECT. METHODS: Of 272 consecutively examined patients with histologically confirmed malignancy who underwent bone scintigraphy, 112 (41%) required further workup by SPECT because a definite diagnosis could not be established using whole-body planar scintigraphy alone. In 57 of these patients, SPECT was accompanied by inline CT over the body region of interest; the remaining 55 subjects underwent only stand-alone SPECT for logistic reasons. The 57 SPECT/CT studies were retrospectively evaluated by readers who were unaware of the clinical pretest probability and the findings on the planar scans. In total, 52 lesions in 44 patients were rated as indeterminate on the SPECT images. Afterwards, the corresponding SPECT/CT images were analyzed and the findings previously rated as indeterminate were classified either as definitely benign, indeterminate, or definitely malignant. RESULTS: Of the 52 indeterminate findings on SPECT, 33 (63%) could be correlated with benign findings on CT. These findings involved mostly osteochondrosis, spondylosis, and spondylarthrosis of the spine. Fifteen lesions (29%) could be correlated with osteolysis or sclerotic metastases on CT. Even after analysis of the SPECT/CT images, 4 lesions (8%) remained indeterminate. These lesions were in the ribs and the scapula. CONCLUSION: SPECT-guided CT was able to clarify more than 90% of SPECT findings classified as indeterminate in an analysis that was masked as to clinical pretest probability and the planar scan findings. Further studies carefully addressing the cost efficiency of this new technology and its actual clinical value are encouraged by this observation.

Anatomical accuracy of hybrid SPECT/spiral CT in the lower spine.

AIM: The anatomical accuracy of hardware-based registration of skeletal single photon emission computed tomography (SPECT) and X-ray computerized tomography (CT) has as yet not been studied. The aim of this study was to evaluate this variable in the lower spine for a newly introduced hybrid SPECT/spiral-CT camera. METHODS: In 22 patients referred for degenerative joint disease or tumours, whole-body bone scintigraphy including hybrid SPECT/spiral CT of the lower spine was performed. Subsequent analyses were performed on these pairs of images as well as on data sets obtained after using a rigid automated fusion procedure in addition. Two observers independently measured the distances between the visually determined centres of gravity of the CT and SPECT representation of the fourth and fifth lumbar vertebral body in the X-, Y- and Z-directions (X-, Y- and Z-distances). RESULTS: The distances determined by the two observers for the two vertebral bodies correlated significantly and were averaged for further analysis. For hybrid SPECT/spiral CT without consecutive automated registration, the mean X-, Y- and Z-distances were 1.6+/-1.9 mm, 1.7+/-1.3 mm and 0.9+/-0.5 mm, respectively. Additional automated registration lowered these values to 1.2+/-0.9 mm, 1.1+/-0.7 mm and 0.8+/-0.4 mm, respectively. The difference for the Y-distance proved statistically significant (P<0.05). Additional automated registration significantly reduced the number of subjects in whom at least one of the distances determined was greater than the SPECT pixel size of 4.6 mm from 14% (n=3) to 0% (P<0.05). CONCLUSION: Hardware-based fusion between skeletal SPECT and CT offers a nearly perfect data match in the lower spine. The additional use of a tool for automated rigid registration has the potential to reduce the error of alignment even further and may be useful in patients with reduced compliance leading to movements between the two examinations.

COMPARE/Radiology, an interactive Web-based radiology teaching program evaluation of user response.

RATIONALE AND OBJECTIVES: The aim of this study is to assess user benefits of COMPARE/Radiology, a highly interactive World Wide Web-based training program for radiology, as perceived by its users. MATERIALS AND METHODS: COMPARE/Radiology (http://www.idr.med.uni-erlangen.de/compare.htm), an interactive training program based on 244 teaching cases, was created by the authors and made publicly available on the Internet. An anonymous survey was conducted among users to investigate the composition of the program's user base and assess the acceptance of the training program. In parallel, Web access data were collected and analyzed using descriptive statistics. RESULTS: The group of responding users (n = 1370) consisted of 201 preclinical medical students (14.7%), 314 clinical medical students (22.9%), 359 residents in radiology (26.2%), and 205 users of other professions (14.9%). A majority of respondents (1230; 89%) rated the interactivity of COMPARE/Radiology as good or excellent. Many respondents use COMPARE/Radiology for self-study (971; 70%) and for teaching others (600; 43%). Web access statistics show an increase in number of site visits from 1248 in December 2002 to 4651 in April 2004. CONCLUSION: Users appreciate the benefits of COMPARE/Radiology. The interactive instructional design was rated positively by responding users. The popularity of the site is growing, evidenced by the number of network accesses during the observation period.

Dose reduction in CT examination of children by an attenuation-based on-line modulation of tube current (CARE Dose).

In a controlled patient study we investigated the potential of attenuation-based on-line modulation of the tube current to reduce milliampere values (mAs) in CT examinations of children without loss of image quality. mAs can be reduced for non-circular patient cross sections without an increase in noise if tube current is reduced at those angular positions where the patient diameter and, consequently, attenuation are small. We investigated a technical approach with an attenuation-based on-line control for the tube current realised as a work-in-progress implementation. The CT projection data are analysed in real time to determine optimal mAs values for each projection angle. We evaluated mAs reduction for 100 spiral CT examinations with attenuation-based on-line modulation of the tube current in a group of children. Two radiologists evaluated image quality by visual interpretation in consensus. We compared the mAs values read from the CT scanner with preset mAs of a standard protocol. Four different scan regions were examined in spiral technique (neck, thorax, abdomen, thorax and abdomen). We found the mAs product to be reduced typically by 10-60% depending on patient geometry and anatomical regions. The mean reduction was 22.3% (neck 20%, thorax 23%, abdomen 23%, thorax and abdomen 22%). In general, no deterioration of image quality was observed. There was no correlation between the age and the mean mAs reduction in the different anatomical regions. By classifying the children respectively to their weight, there is a positive trend between increasing weight and mAs reduction. We conclude that mAs in spiral CT examinations of children can be reduced substantially by attenuation-based on-line modulation of the tube current without deterioration of image quality. Attenuation-based on-line modulation of tube current is efficient and practical for reducing dose exposure to children.