ASSESSMENT OF OVERRANGING AS A FUNCTION OF PITCH, COLLIMATION AND ROTATION TIME FOR THREE OF THE MOST RECENT AND WIDESPREAD CT SCANS IN FRANCE.

PURPOSE: to assess overranging (OR) as a function of pitch, collimation and rotation time for three commonly used CT models in France. METHODS: OR was measured using XR-SP2 Gafchromic films (Ashland, USA) and computed from exposure data for three widely used CT models in France. The impact of collimation, pitch and rotation time on OR was analyzed while comparing the three CT models. RESULTS: for a typical head protocol, measured OR was found to be equal to 1.64 cm for CT scan A, 0.5 cm for CT scan B and 3.44 cm for CT scan C. OR values were respectively of 4.47, 3.24 and 7.81 cm for the typical chest protocol and the 3 CT models. OR was lowest at pitch values <1 for CT scan A, while it linearly increased with pitch for CT scan B and was lowest for high pitch values for CT scan C. Additionally, OR increase with collimation (24 mm to 38.4 mm) was most pronounced for CT scan B (factor of 2.2 for low pitch (0.5) and 2.8 for high pitch (1.2)) while it increased linearly regardless of the pitch for CT scans A and C. Rotation time also proved to slightly affect OR mainly for CT scan B (up to 2.2 mm). CONCLUSION: the present study shows that overranging remains an issue in modern CT scanners with large disparities across the vendors.

Mutations in the autoinflammatory cryopyrin-associated periodic syndrome gene: epidemiological study and lessons from eight years of genetic analysis in France.

BACKGROUND: Cryopyrin-associated periodic syndromes (CAPS) consist of a continuum of autoinflammatory diseases caused by a defect in interleukin 1ß regulation. Although symptoms may vary widely, the discovery, in 2001, of the gene involved (NLRP3) has dramatically helped diagnosis. OBJECTIVES: To define the spectrum and prevalence of NLRP3 mutations in France and to delineate initial criteria before molecular analysis. METHODS: Retrospective review (2001-9) of genetic analysis data and request forms of patients living in France with an NLRP3 mutation since the set up of CAPS molecular diagnosis by the three French laboratories providing this test (GenMAI network). RESULTS: Over 800 analyses of this gene have been conducted, identifying 135 cases with an NLRP3 mutation (55 probands; 33 multiplex families); the estimated prevalence in France was equal to 1/360 000. A total of 21 different sequence variants were detected, among which four are common and nine are new mutations. CONCLUSIONS: Although the number of NLRP3 test requests has doubled over the past 5 years, genetic screening has not contributed to enhanced detection of new index cases each year. There are two possible reasons for this: (i) no clinical prerequisite for genetic diagnosis and (ii) few new large families are now identified (unlike the initial study based on a selection by linkage). A set of initial clinical criteria have been drawn up which it is recommended should be fulfilled before a patient is tested: at least three recurrent bouts, age at disease onset < 20 years and elevated levels of C-reactive protein, especially in individuals with urticaria and moderate fever.

First-trimester enzymatic and molecular prenatal diagnosis of mevalonic aciduria.

Prenatal diagnosis was offered to a family at risk of mevalonic aciduria. A chorionic villus sample was obtained and both mevalonate kinase activity and mutation analysis were done. An affected fetus was diagnosed.