Scatter correction in scintigraphy: the state of the art

In scintigraphy, the detection of scattered photons degrades both visual image analysis and quantitative accuracy. Many methods have been proposed and are still under investigation to cope with scattered photons. The main features of the problem of scattering in radionuclide imaging are presented first, to provide a sound foundation for a critical review of the existing scatter correction techniques. These are described using a classification relating to their aims and principles. Their theoretical potentials are analysed, as well as the difficulties of their practical implementation. Finally, the problems of their evaluation and comparison are discussed. Correspondence to: I. Buvat     

Magnetic resonance and arthroscopy of the knee. A double-blind study in 40 patients]

To evaluate the capabilities of ultra-low-field MR for the high-resolution imaging of the knee with a short acquisition time, a prospective double-blind study was carried out on 40 consecutive patients with acute or chronic articular conditions who were examined with both MR imaging and arthroscopy. Three-dimensional gradient-echo MR sequences were employed which allow many thin high-resolution slices to be obtained in a relatively short time. To evaluate the results arthroscopy, performed the day after MR imaging, was considered the gold standard. MR imaging and arthroscopy were in agreement in 84.6% of meniscal tears with 91.6% sensitivity and 80% specificity, in 82% of anterior cruciate ligament lesions with 100% sensitivity and 80% specificity and in 81% of cartilage lesions with 100% sensitivity and 61% specificity. On the whole, MR imaging and arthroscopy were in agreement in 82.5% of cases with 97.2% sensitivity and 75.3% specificity. MR imaging gave more information about collateral ligament, muscle and bone involvement. These results confirm the capabilities of ultra-low-field MR imaging in the study of the knee: the technique allows diagnostic studies to be performed in a short time, at a low cost, and with similar results to those obtained with higher field strengths.     

C-fos immunoreactivity in the brain following unilateral electrical stimulation of the dorsal periaqueductal gray in freely moving rats.

C-fos immunoreactivity was used to reveal brain areas in which neurons were influenced by electrical stimulations applied to the dorsal periaqueductal gray. These stimulations were applied in freely moving rats so that the resulting behaviors could be observed. Shortly afterwards, the brains of the rats were processed for C-fos immunoreactivity. In order to determine the specificity of the brain areas thus labeled, control stimulations were applied to the ventral tegmental area of other rats. Immunoreactive cells were found surrounding the tip of the stimulation electrode within a radius of 0.5 mm. This labeled area extended further along the rostro-caudal axis than along the medio-lateral or dorso-ventral axis in the periaqueductal gray. Distally, clusters of labeled cells were found ipsilaterally in the caudal periaqueductal gray extending to the nucleus cuneiformis, and bilaterally in the locus coeruleus and supramamillary decussation. More widespread labeling was found in most hypothalamic subareas and in the lateral habenula. The labeled brain areas following ventral tegmental area stimulations were totally distinct, and comprised the medial forebrain bundle, the nucleus accumbens, the vertical limb of the diagonal band and the medial septum. The pattern of labeling produced by periaqueductal gray stimulations was therefore specific, and provided information about brain structures involved in the motivational and behavioral effects of such stimulations.     

Aortic root substitution after aortic valve replacement: a prosthesis-sparing operation.

Patients who underwent isolated aortic valve replacement could come to attention for new onset aortic disease or progression of borderline alterations not corrected at the first operation, especially in the subset of bicuspid valve disease. We describe our technique in redo operations for aortic root disease, using only a vascular graft and sparing the previously implanted valve prosthesis. In case of normally functioning mechanical prosthesis, we always left the valve in situ and substituted the aortic root with a Dacron conduit, extending the replacement if necessary to the other diseased portions of the thoracic aorta.     

微创穿刺术治疗基底节区脑出血临床随机对照研究

目的评价比较微创穿刺血肿粉碎清除术与内科保守治疗两种方法治疗基底节区脑出血(25～40m l)的疗效异同。方法采用多中心、随机对照试验的方法,42个参研医院共随机入选465例基底节区脑出血患者,根据纳入与排除标准共排除88例,其中资料不全者16例;不符合入选标准者72例,分别为Glasgow评分≤8分(64例)、术前出血量>40m l(7例)、从发病到达急诊室时间>72h(1例)。评价治疗14d时两组患者神经功能缺损程度和日常生活活动能力、治疗3个月时的日常生活活动能力以及3个月和住院期间病死率。结果最终符合入组标准的病例数为377例,其中微创治疗组195例,对照组182例。微创治疗组患者于治疗14d时,神经功能改善明显优于对照组(χ2=7.931,P=0.02);治疗3个月时达良好功能状态的患者比例明显多于对照组(35.91%vs21.82%;χ2=8.294P=0.004)。微创治疗组病,残率明显低于对照组(40.88%vs63.03%,χ2=16.948,P<0.01);两组病死率间差异无显著性意义(6.67%vs8.79%)。结论与单纯内科保守治疗相比,应用微创穿刺血肿粉碎清除术治疗基底节区小血肿不增加病死率,并可明显提高脑出血患者的日常生活活动能力,降低病残率。     

Effects of atorvastatin on arterial endothelial function in coronary bypass surgery

Objective: Endothelial dysfunction represents a critical early component of organ injury following cardiopulmonary bypass. Recent studies demonstrate that the treatment with atorvastatin is associated with a significant improvement of endothelial function independently of its efficacy on cholesterol levels. Therefore, we investigated the effects of preoperative atorvastatin treatment on endothelium function after coronary surgery. Methods: Forty patients undergoing coronary surgery were randomized to treatment with atorvastatin (20 mg/die; N = 20) or placebo (N = 20) 3 weeks before surgery. Twenty normal patients served as control group. The flow-mediated dilations (FMD) of the brachial artery after both reactive hyperemia (endothelium dependent) and nitroglycerin administration (endothelium independent) were evaluated at baseline, at 48 h, and 5 days postoperatively. Results: At baseline, the endothelium-dependent FMD was significantly attenuated in coronary versus normal patients (normal 10.3 ± 1.8% vs coronary 4.1 ± 1.6%, p < 0.01). At 48 h postoperatively all patients exhibited a reduced FMD compared with baseline values: the endothelium-dependent dilatation showed a drop of 60.1 + 15% in the patients of the placebo group compared with 45.8 + 16.6% (p < 0.05) those in the atorvastatin group. At the univariate analysis, no significant correlation was found between serum levels of either total cholesterol or HDL cholesterol and FMD. The nitroglycerin-induced dilation was not significantly influenced by extracorporeal circulation as well as by atorvastatin treatment. Conclusions: The endothelial dysfunction following cardiopulmonary bypass is improved by the treatment with atorvastatin, by a mechanism unrelated to the drug efficacy of controlling serum cholesterol levels.