MR imaging of the wrist in rheumatoid arthritis using gadobenate dimeglumine

Objective. To determine the dosage of gadobenate dimeglumine (Gd-BOPTA) necessary for MRI of rheumatoid arthritis of the wrist. Design and patients. Seven wrists inflamed with rheumatoid arthritis were imaged using a dedicated 0.2-T MR unit. Four cumulative dosages of 0.0125, 0.025, 0.05 and 0.1 mmol/kg body weight (BW) Gd-BOPTA were tested. Three-dimensional T1-weighted gradient-recalled echo sequences (GRE; TR: 100 ms, TE: 18 ms, flip angle 90°, 4:55 min) were acquired prior to an intravenous injection and after each additional dosage of Gd-BOPTA. Relative enhancement, signal-difference-to-noise ratios (SDNRs) and the size of the inflamed tissue were quantified. Three radiologists independently evaluated the image quality, the size and the contrast of the enhancing tissue. Results. The readers agreed on a dose of 0.05 mmol/kg BW as satisfactory for the evaluation of the size of the inflammatory tissue and for determination of bone involvement (κ=0.9, P<0.001). Highly inflammatory pannus was depicted with adequate image contrast using 0.025 mmol/kg BW Gd-BOPTA. According to the SDNR and relative enhancement findings, a dose of 0.05 mmol/kg BW suffices for both off-center and centered regions of tissue inflammation (t-test, P<0.05). Conclusion. Gadolinium-BOPTA is an alternative contrast agent for MRI of rheumatoid disease. This study shows that a dose of 0.05 mmol/kg BW suffices at low field strength. Received: 7 June 2000 Revision requested: 22 August 2000 Revision received: 8 September 2000 Accepted: 21 September 2000     

Comment on ‘Predicting recurrence in axillary node negative breast cancer patients’, by Rosner and Lane

on behalf of the Nottingham Breast Unit     

Prevalence of behaviour disorders in low birthweight infants

OBJECTIVE--To determine the prevalence of behaviour disorders in low birthweight infants. DESIGN--Children of birth weight < or = 2000 g born to mothers resident in Merseyside in 1980-1 assessed using the Rutter parent and teacher behaviour questionnaires and the Conner modification of the Rutter teacher questionnaire. Children attending normal schools were assessed with controls matched for age, sex, and class in school. Children attending special schools were assessed unmatched. SUBJECTS--233 matched case-control pairs attending normal primary schools and 46 unmatched children attending special schools. SETTING--Primary and special schools. MAIN OUTCOME MEASURES--Emotional, conduct, and undifferentiated behaviour disorders and hyperactivity. RESULTS--On the parental questionnaire screen, 36% of the cases and 22% of the controls had a behaviour disorder and on the teacher questionnaire the proportions were 27% and 12% respectively. Hyperactivity was significantly more common among male cases than their controls (21% v 5.0%) but differed little among female cases and controls (9% v 7%). CONCLUSIONS--Improving neonatal survival of low birthweight infants is accompanied by a higher prevalence of behaviour disorders. The long term implications for psychiatric morbidity and other adult disease must be monitored.     

BENIGN GASTROCOLIC FISTULA ASSOCIATED WITH PERITONITIS

SUMMARY Gastrocolic fistula is most often related to malignancy or previous gastric surgery. It is an uncommon complication of benign gastric ulceration in patients who have not had a previous operation. Benign gastrocolic fistula associated with peritonitis is extremely rare — this case is only the fourth ever reported. The patient presented with an acute abdomen, and subsequent investigations demonstrated a gastrocolic fistula of benign aetiology.     

Lower extremity: low-dose contrast agent intraarterial MR angiography in patients--initial results

Institutional review board approval and patient consent were obtained. A low-dose injection protocol for intraarterial three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiography was derived from femoral flow phantom studies and prospectively evaluated in patients with peripheral arterial occlusive disease (PAOD). All MR angiograms were obtained at 1.5 T with a T1-weighted gradient-echo sequence. MR angiograms of a gadolinium dilution series (0.8-200.0 mmol/L) were acquired in a femoral phantom at different flow rates. Signal-to-noise ratios (SNRs) above the 75% threshold of the measured maximum were considered optimal. The lowest optimal concentration was injected intraarterially in nine patients to obtain 3D MR angiograms of the thigh and calf station. Contrast-to-noise ratios (CNRs) were calculated for four arterial segments. The low optimal concentration of 50 mmol/L (20-mL bolus volume), about 5% of the total permissible dose, showed SNRs larger than the 75% threshold in the phantom study. In patients, this concentration led to high-spatial-resolution angiograms with mean CNRs of 70.0 +/- 14.5 (+/- standard deviation) for the superficial femoral artery and 47.5 +/- 13.4 at the infrapopliteal level. Low-dose contrast agent intraarterial 3D MR angiography showed high arterial enhancement, enabling assessment of lower extremity arteries in patients with PAOD and multiple injections--a crucial precondition for MR-guided endovascular interventions.     

Modality-based navigation

Modality-based navigation (MBN) means the interactive tracking of instruments in a co-ordinate system defined by an imaging modality, eg, CT, MR, or a fluoroscope. During the registration process, a transformation matrix between the two co-ordinate systems of the digitizer and imaging modality is calculated. Navigation can start immediately after collection of the images without an intraprocedural registration process. Since the imaging modality belongs to the OR or the intervention suite, image update can be performed at any time. Following a step-by-step procedure with navigation and image update in a reasonable sequence, the risk for a virtual-real mismatch is minimized. For CT-MBN, we obtained a freehand absolute positioning accuracy of 1.9+/-1.1 mm in vitro. The in vivo freehand absolute positioning accuracy in pelvic fracture fixation was determined to be 3.1 mm (unpublished data). From our point of view, modality-based navigation is an efficient and safe alternative tool for computer aided interventions.