Overview of two years of clinical experience of chest tomosynthesis at Sahlgrenska University Hospital.

Since December 2006, approximately 3800 clinical chest tomosynthesis examinations have been performed at our department at Sahlgrenska University Hospital. A subset of the examinations has been included in studies of the detectability of pulmonary nodules, using computed tomography (CT) as the gold standard. Visibility studies, in which chest tomosynthesis and CT have been compared side-by side, have been used to determine the depiction potential of chest tomosynthesis. Comparisons with conventional chest radiography have been made. In the clinical setting, chest tomosynthesis has mostly been used as an additional examination. The most frequent indication for chest tomosynthesis has been suspicion of a nodule or tumour. In visibility studies, tomosynthesis has depicted over 90 % of the nodules seen on the CT scan. The corresponding figure for chest radiography has been <30 %. In the detection studies, the lesion-level sensitivity has been approximately 60 % for tomosynthesis and 20 % for chest radiography. In one of the detection studies, an analysis of all false-positive nodules was performed. This analysis showed that all findings had morphological correlates on the CT examinations. The majority of the false-positive nodules were localised in the immediate subpleural region. In conclusion, chest tomosynthesis is an improved chest radiography method, which can be used to optimise the use of CT resources, thereby reducing the radiation dose to the patient population. However, there are some limitations with chest tomosynthesis. For example, patients undergoing tomosynthesis have to be able to stand still and hold their breath firmly for 10 s. Also, chest tomosynthesis has a limited depth resolution, which may explain why pathology in the subpleural region is more difficult to interpret and artefacts from medical devices may occur.

Effect of clinical experience of chest tomosynthesis on detection of pulmonary nodules.

BACKGROUND: The new technique chest tomosynthesis refers to the principle of collecting low-dose projections of the chest at different angles and using these projections to reconstruct section images of the chest at a radiation dose comparable to that of chest radiography. PURPOSE: To investigate if, for experienced thoracic radiologists, the detectability of pulmonary nodules obtained after only a short initial learning period of chest tomosynthesis improves with additional clinical experience of the new technique. MATERIAL AND METHODS: Two readings of the same clinical chest tomosynthesis cases, the first performed after 6 months of clinical experience and the second after an additional period of 1 year, were conducted. Three senior thoracic radiologists, with more than 20 years of experience of chest radiography, acted as observers, with the task of detecting pulmonary nodules in a jackknife free-response receiver operating characteristics (JAFROC1) study. The image material consisted of 42 patients with and 47 patients without pulmonary nodules examined with chest tomosynthesis. Multidetector computed tomography (MDCT) was used as a reference. The total number of nodules was 131. The JAFROC1 figure of merit (FOM) was used as the principal measure of detectability. RESULTS: The difference in the observer-averaged JAFROC1 FOM of the two readings was 0.004 (95% confidence interval: -0.11, 0.12; F-statistic: 0.01 on 1 and 2.65 df; P=0.91). Thus, no significant improvement in detectability was found after the additional clinical experience of tomosynthesis. CONCLUSION: The study indicates that experienced thoracic radiologists already within the first months of clinical use of chest tomosynthesis are able to take advantage of the new technique in the task of detecting pulmonary nodules.

Abnormalities of small intestinal endocrine cells in non-obese diabetic mice.

The endocrine cells in the duodenum of pre-diabetic and diabetic female non-obese diabetic (NOD) mice aged 22-24 weeks were studied by means of immunohistochemistry and computed image analysis as well as by radioimmunoassays of tissue extracts. As controls, 12 female BALB/cJ mice of the same age as NOD mice were used. The number of secretin-immunoreactive cells increased in diabetic but not in pre-diabetic NOD mice. The level of extractable secretin was higher in both pre-diabetic and diabetic NOD mice. The number of GIP-, CCK/gastrin-, and serotonin-immunoreactive cells was significantly reduced in both pre-diabetic and diabetic NOD mice. There was no statistical difference in the number of somatostatin-immunoreactive cells between the NOD mice and controls. The level of GIP was higher and gastrin was lower in NOD mice compared to controls. There was no statistical difference in the somatostatin level between the NOD mice and controls. The cell secretory index was elevated in all the endocrine cell types except CCK/gastrin cells. It has been suggested that some of the changes in the duodenal endocrine cells could be attributed to the diabetes state, but most of the changes seem to take place before the onset of diabetes. The abnormalities in the duodenal endocrine cells observed here in an animal model for diabetes type I might have relevance for the gastrointestinal dysfunction displayed in human diabetes.

Application of computer image analysis in endocrine cell quantification.

Computer image analysis was applied for quantifying endocrine cells by using an automatic standard sequence analysis operation. Two parameters were used, namely the number of cells per mm3 of epithelial cells and the cell secretory index (the volume of the immunoreactive secretory granules per cell). The first indicates the variation in the anatomical peptide-producing unit and the second the synthesis and secretion activity of the cell. The endocrine cells chosen in this study were chromogranin-immunoreactive cells and secretin-immunoreactive cells in the human duodenum. The measurements were made by five different investigators with different backgrounds in order to evaluate the effect of the intra- and inter-individual variation. This study showed that the intra- and inter-individual variation had no impact on the results. Comparisons with the classical point-counting method considered to be easy and most efficient in volumetry showed that the present approach is between two and three times faster and less strenuous for the performer. It is concluded that this approach seems to be suitable for adaptation in morphometric studies when information is required about the changes in the number of endocrine cells and about changes in secretory activities.