[Determination of the best diagnostic criteria of sacroiliitis with MRI]

AIM

To determine which signs are the most accurate in the diagnosis of sacroiliitis with MRI.

MATERIAL AND METHODS

40 consecutive patients with inflammatory low back pain underwent MRI at 1.5 T with FSE T2 and SE T1 weighted-images before and after Gadolinium-DOTA injection. 22 patients were suffering from spondylarthropathy while the other 18 patients constituted the control group. Each examination was interpreted by two independent observers who analysed 11 different signs.

RESULTS

Intra and inter observer reproducibility were high (respectively 76% and 70%). Inter observer reproducibility was excellent for bone marrow edema (89%) but low for bone productions (38%). Three lesions displayed a high positive predictive value: ligamentous contrast enhancement (86%), bone marrow edema (80%) and bone erosions (70%). Intra articular enhancement of the sacro-iliac joint was a less sensitive sign than bone marrow edema.

CONCLUSION

This study confirms the excellent positive predictive value of MRI for an early diagnosis of active sacroiliitis. Bone marrow edema seems to be a more pertinent sign than intra articular enhancement.

Utility of CT scan for the diagnosis of chest wall tuberculosis

The objective of this study was to determine the utility of CT scan findings for the diagnosis of chest wall tuberculosis, excluding the spine. We reviewed 15 patients (13 Africans and 2 Indians) with chest wall tuberculosis, retrospectively. The radiologic examination consisted of a plain X-ray and a CT scan of the chest for each patient. The site of disease was the rib in 13 patients or the body of the sternum in 2 patients. One rib was involved in 11 patients, 2 contiguous ribs (one site) in 2 patients, and bilateral disease (two sites) was observed in the remaining patient. The 14 rib sites involved the posterior arc or costovertebral joint in 11 cases, the anterior arc in 2 cases, and the anterior and middle arc in 1 case. The CT scan findings were an abscess (n = 14) or a soft tissue mass (n = 2), osteolytic lesions (n = 13), periosteal reaction (n = 10), and sequestrum (n = 14). Bone sclerosis was observed only in 3 cases of rib involvement. The association of a soft tissue abscess, an osteolytic lesion, and sequestrum, especially in immigrants to France, suggests chest wall tuberculosis on CT scan.

Effects of low temperature on nitrate uptake, and xylem and phloem flows of nitrogen, in Secale cereale L. and Brassica napus L

The effect of low temperature on nitrate uptake and subsequent N translocation and cycling was investigated in Secale cereale L. and Brassica napus L. transferred to 7 °C for 9 d or kept at a warm temperature (20 °C). Some plants were grown with a split root system and ¹⁵ NO₃ ^- , labelled to measure NO₃ ^- uptake, root-to-shoot and shoot-to-root translocation of N from NO₃ ^- , taken up. Other plants with single-root system were subjected to ¹⁵ N pulse-chase labelling to quantify endogenous N remobilization. Lowering growth temperature from 20 to 7 °C reduced nitrate uptake more strongly in rye (-59%) than in winter rape (-28%). A very large proportion of the nitrate taken up was further translocated to shoots in both species. However, lowering the temperature decreased, xylem N translocation by about 60 and 30% in S. cereale and B. napus, respectively. Most root N in the latter species came directly from root absorption, while in rye roots the proportions ascribe able to direct root allocation and phloem flow were well balanced. Cold treatment did not significantly modify the imbalance between the two origins. Mobilization of endogenous N from roots to shoot, estimated by pulse-chase labelling, was limited in B. napus and significant in S. cereale despite a depressive effect of low temperature. In general, low temperature led to an increase in root N concentration in both species. It is Suggested that low temperature may directly affect the nitrate uptake system, and also that N accumulation in the roots (resulting from greater inhibition of N xylem flow than of NO₃ ^- uptake) might increase the inhibition of uptake by higher cellular NO₃ , and/or amino acid content. The usefulness (for spring growth) of root N accumulation triggered by low temperature is discussed.