Tomosynthesis in pulmonary cystic fibrosis

The aims of this thesis were to investigate whether chest tomosynthesis might be used in pulmonary cystic fibrosis, to design and validate a tomosynthesis scoring system, and to determine the effective dose from chest tomosynthesis in children. In a prospective study starting in 2008 clinical chest radiography or computed tomography (CT) were supplemented with a tomosynthesis examination of the lungs. Tomosynthesis findings were characterized in comparison with radiography and CT findings, and used to design a scoring system for tomosynthesis. Conversion factors for paediatric chest tomosynthesis were determined by Monte Carlo simulations and used to estimate the effective dose from the registered dose-area-product from the patient examinations included in the study. The typical imaging findings of pulmonary cystic fibrosis were much better depicted with tomosynthesis compared with radiography. Most pulmonary changes visualised with computed tomography could also be evaluated well with tomosynthesis. A dedicated tomosynthesis scoring system was designed and validated, and proved to be robust. Bronchiectasis and mucus plugging are the most specific pulmonary changes of cystic fibrosis, and were in a review of commonly used radiological scoring systems generally considered the most important scoring components. For chest tomosynthesis in children the conversion factor was considerably higher for young children than previously reported for adults. The conversion factor increased with increasing tube energy and filtration. The mean paediatric effective dose from posteroanterior chest tomosynthesis was 0.17 mSv, which is about 40 times less than recently reported effective doses from paediatric chest CT. Using the previously reported conversion factor for adults the paediatric effective dose was estimated to 0.11 mSv. Consequently, when using conversion factors not adapted to children for paediatric examinations, the radiation dose may be underestimated. Anteroposterior exposures should be avoided, as the effective dose is approximately three times higher than for posteroanterior exposures. In these studies tomosynthesis has been shown to be a valuable tool for monitoring pulmonary cystic fibrosis, as typical imaging findings of this lung disease are well depicted and the radiation dose is low. The dedicated scoring system may improve diagnostic precision. At our radiology department, tomosynthesis now has to a great extent replaced radiography in the follow-up of these patients. CT is only performed in selected cases. Further studies are planned to determine the roles of tomosynthesis and CT in the evaluation of cystic fibrosis lung disease

Radiography, tomosynthesis, CT and MRI in the evaluation of pulmonary cystic fibrosis: an untangling review of the multitude of scoring systems.

The first radiographic scoring system for pulmonary cystic fibrosis was presented in 1958. Since then a multitude of scoring systems for radiography and computed tomography (CT) have been presented, recently also for tomosynthesis and magnetic resonance imaging (MRI). The aim of the current review was to analyse and compare the plethora of scoring systems for cystic fibrosis, especially regarding which scoring components are considered most important

Does implantoplasty affect the failure strength of narrow and regular diameter implants? : A laboratory study

Objective To assess whether the impact of implantoplasty (IP) on the maximum implant failure strength depends on implant type/design, diameter, or material. Methods Fourteen implants each of different type/design [bone (BL) and tissue level (TL)], diameter [narrow (3.3 mm) and regular (4.1 mm)], and material [titanium grade IV (Ti) and titanium-zirconium alloy (TiZr)] of one company were used. Half of the implants were subjected to IP in a computerized torn. All implants were subjected to dynamic loading prior to loading until failure to simulate regular mastication. Multiple linear regression analyses were performed with maximum implant failure strength as dependent variable and IP, implant type/design, diameter, and material as predictors. Results Implants subjected to IP and TL implants showed statistically significant reduced implant failure strength irrespective of the diameter compared with implants without IP and BL implants, respectively. Implant material had a significant impact for TL implants and for regular diameter implants, with TiZr being stronger than Ti. During dynamic loading, 1 narrow Ti TL implant without IP, 4 narrow Ti TL implants subjected to IP, and 1 narrow TiZr TL implant subjected to IP were fractured. Conclusion IP significantly reduced the maximum implant failure strength, irrespective implant type/design, diameter, or mate- rial, but the maximum implant failure strength of regular diameter implants and of narrow BL implants remained high. Clinical Relevance IP seems to have no clinically relevant impact on the majority of cases, except from those of single narrow Ti TL implants, which may have an increased risk for mechanical complications. This should be considered for peri-implantitis treatment planning (e.g., communication of potential complications to the patient), but also in the planning of implant installation (e.g., choosing TiZr instead of Ti for narrow implants)

Implantoplasty and the risk of fracture of narrow implants with advanced bone loss : A laboratory study

Objectives: To assess the impact of implantoplasty (IP) on maximum implant failure strength of narrow diameter implants of different type/design and material, with simulated advanced bone loss. Materials and Methods: Narrow, parallel-walled implants (3.3 mm in diameter x 10 mm long) with an internal connection of different type/design [bone level (BL), tissue level (TL)] and material [Titanium grade IV (Ti), Titanium-Zirconium alloy (TiZr)] from one specific manufacturer were used. Half of the implants were subjected to IP in their coronal 5 mm; the remaining were used as controls (seven implants per group). Dynamic loading prior to maximum load strength testing was included. Results: During dynamic loading, the fracture rate of BL implants was low and independent of IP, while that of TL implants increased significantly with IP compared with controls (p = .001). Maximum implant failure strength reduction (in %) due to IP, was 1.3%-25.4%; TiZr BL implants were least affected. Implants subjected to IP compared to those without IP as well as TL implants compared to BL implants showed a significantly lower maximum implant failure strength (p < .002); implant material was not significant (p = .845). Conclusions: Based on data from implants of one specific manufacturer, IP has a significant negative impact on the fracture strength of narrow implants suffering from advanced peri-implantitis. TL implants have been more severely affected compared to BL implants and presented an increased risk for failure during normal chewing forces. In addition, this negative impact of IP on TL implants was independent of the implant material (i.e., Ti or TiZr). Clinical Relevance: Narrow single TL implants with advanced horizontal bone loss (e.g., 5 mm), when subjected to IP, appear to have an increased fracture risk during normal function

CONVERSION FACTORS FOR ESTIMATION OF EFFECTIVE DOSE IN PAEDIATRIC CHEST TOMOSYNTHESIS.

For chest tomosynthesis in adults, a conversion factor of 0.26 mSv/Gy cm(2) has been reported for calculating the effective dose from the registered dose-area-product. The aim of this study was to determine conversion factors for chest tomosynthesis in children. Using the Monte Carlo-based computer software PCXMC 2.0, simulations were performed on modified phantoms for males and females aged 8-19 y, in the posteroanterior and anteroposterior projection, with energies 80-140 kV and copper filtration 0.1-0.3 mm. Resulting conversion factors ranged between 0.23 and 1.09 mSv/Gy cm(2), decreased with patient age, were significantly higher in the anteroposterior projection and increased with increased energy or copper filtration. To avoid an underestimation of effective dose in children, it is recommended to use age-dependent conversion factors. As a simplified approach, three conversion factors might be used for posteroanterior chest tomosynthesis and radiography in children, namely 0.6 (8-10 y), 0.4 (11-14 y) and 0.3 mSv/Gy cm(2) (15-19 y)

Visualisation of the rectoanal inhibitory reflex with a modified contrast enema in children with suspected Hirschsprung disease.

BACKGROUND: Patients with Hirschsprung disease lack the normal rectoanal inhibitory reflex, which can be studied with anorectal manometry or US. OBJECTIVE: To see whether the rectoanal inhibitory reflex could be visualised with a modified contrast enema, thereby increasing the diagnostic accuracy of the contrast enema and reducing the number of rectal biopsies. MATERIALS AND METHODS: Fifty-nine boys and 42 girls (median age, 12 months) with suspected Hirschsprung disease were examined with a modified contrast enema, supplemented with two injections of cold, water-soluble contrast medium, to induce the reflex. Two paediatric radiologists evaluated the anonymised examinations in consensus. The contrast enema findings were correlated with the results of rectal biopsy or clinical follow-up. RESULTS: Five boys and one girl (median age, 7.5 days) were diagnosed with Hirschsprung disease. The negative predictive value of the rectoanal inhibitory reflex was 100%. A contrast enema with signs of Hirschsprung disease in combination with an absent rectoanal inhibitory reflex had the specificity of 98% and sensitivity of 100% for Hirschsprung disease. CONCLUSION: The modified contrast enema improves the radiological diagnosis of Hirschsprung disease. By demonstrating the rectoanal inhibitory reflex in children without Hirschsprung disease, we can reduce the proportion of unnecessary rectal biopsies

Evaluation of an iterative model-based reconstruction of pediatric abdominal CT with regard to image quality and radiation dose

BackgroundIn pediatric patients, computed tomography (CT) is important in the medical chain of diagnosing and monitoring various diseases. Because children are more radiosensitive than adults, they require minimal radiation exposure. One way to achieve this goal is to implement new technical solutions, like iterative reconstruction.PurposeTo evaluate the potential of a new, iterative, model-based method for reconstructing (IMR) pediatric abdominal CT at a low radiation dose and determine whether it maintains or improves image quality, compared to the current reconstruction method.Material and MethodsForty pediatric patients underwent abdominal CT. Twenty patients were examined with the standard dose settings and 20 patients were examined with a 32% lower radiation dose. Images from the standard examination were reconstructed with a hybrid iterative reconstruction method (iDose4), and images from the low-dose examinations were reconstructed with both iDose4 and IMR. Image quality was evaluated subjectively by three observers, according to modified EU image quality criteria, and evaluated objectively based on the noise observed in liver images.ResultsVisual grading characteristics analyses showed no difference in image quality between the standard dose examination reconstructed with iDose4 and the low dose examination reconstructed with IMR. IMR showed lower image noise in the liver compared to iDose4 images. Inter- and intra-observer variance was low: the intraclass coefficient was 0.66 (95% confidence interval = 0.60–0.71) for the three observers.ConclusionIMR provided image quality equivalent or superior to the standard iDose4 method for evaluating pediatric abdominal CT, even with a 32% dose reduction