MACACO II test-beam with high energy photons.

The IRIS group at IFIC Valencia is developing a three-layer Compton camera for treatment monitoring in proton therapy. The system is composed of three detector planes, each made of a [Formula: see text] monolithic crystal coupled to a SiPM array. Having obtained successful results with the first prototype (MACACO) that demonstrated the feasibility of the proposed technology, a second prototype (MACACO II) with improved performance has been developed, and is the subject of this work. The new system has an enhanced detector energy resolution which translates into a higher spatial resolution of the telescope. The image reconstruction method has also been improved with an accurate model of the sensitivity matrix. The device has been tested with high energy photons at the National Accelerator Centre (CNA, Seville). The tests involved a proton beam of 18 MeV impinging on a graphite target, to produce 4.4 MeV photons. Data were taken at different system positions of the telescope with the first detector at 65 and 160 mm from the target, and at different beam intensities. The measurements allowed successful reconstruction of the photon emission distribution at two target positions separated by 5 mm in different telescope configurations. This result was obtained both with data recorded in the first and second telescope planes (two interaction events) and, for the first time in beam experiments, with data recorded in the three planes (three interaction events).

[Validity of semiquantitative methods of microalbuminuria screening in diabetes mellitus]. / Validez de los métodos semicuantitativos de cribado de la microalbuminuria en la diabetes mellitus.

OBJECTIVE: To analyse the validity of the Micraltest and Microbumintest semi-quantitative methods for microalbuminuria screening in type 2 diabetes mellitus in primary care clinics. DESIGN: Crossover study to validate diagnostic tests. SETTING: Three general practices at an urban health centre. PATIENTS: Consecutive sample of 64 diabetics not dependent on insulin. MEASUREMENTS AND MAIN RESULTS: Each patient's own doctor performed in the consultation the semi-quantitative determinations in a simple sample of the morning's first urine. As standard, a rate of albumin excretion above 20 micrograms/min, determined by immunonephelometry in a 2-hour controlled time sample, was used. The prevalence of Microalbuminuria was 25% (C.I. 95%, 14.4-35.6). The sensitivity of Micraltest was 69% (CI, 42-88), and its specificity 52% (CI, 37-67), corresponding to the cut-off point of 10 mg/L. The sensitivity of Microbumintest was 63% (CI, 36-84), and its specificity 67% (CI, 52-79). The combination of both tests in one sample had 75% sensitivity (CI, 47-92) and 44% specificity (CI, 30-59). Negative predictive values ranged between 84 and 85%. CONCLUSIONS: The semi-quantitative microalbuminuria detection tests are of limited use in the primary care clinic. Their sensitivity and the negative predictive value obtained in an isolated sample do not seem acceptable for a screening method.