Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography

The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study.     

Effect of bite tray impression technique on relocation accuracy in frameless stereotactic radiotherapy.

A previously developed method for achieving patient relocation in fractionated stereotactic radiotherapy (attachment of an infrared fiducial system to a bite tray) relies on the integrity of a bite tray system that incorporates moulding to the patient's upper dentition. Reproducible and accurate patient positioning requires stability of the bite tray and mould during the full treatment process, both during the time the bite tray is inserted in the patient's mouth, and between separate bite tray insertions. The optimum construction method for a stable reproducible tray has not been sufficiently investigated. We undertook a study to identify factors which might influence the integrity of the hard palate bite tray system. Reprosil Fast Set Putty was used to construct 3 impression conditions; teeth only; teeth and alveolar sulcus; and teeth, alveolar sulcus, and the hard palate. Reproducibility was assessed by volunteers inserting the impressions multiple times and recording the locations of 8 standard reference points. Our results showed the optimal impression technique (i.e., the one that led to the smallest ranges in positional and rotational errors) was that which incorporated the teeth, alveolar sulcus, and hard palate.     

FM sonography in diffuse liver disease: prospective assessment and blinded analysis

FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease.     

Epidemiology of migraine headache in Santiago, Chile: a prevalence study

Objective . To describe the importance of migraine in Santiago, Chile, by analyzing its prevalence, clinical features and impact by age, gender and socioeconomic status. Methods . In 1993, a representative sample of 1,540 adults of the province of Santiago were interviewed using a standard questionnaire. A total of 1,385 (89.9%) subjects responded to the survey. Initially, a designated member of each household responded to the questionnaire. Subsequently, each household member with headaches was asked to respond to questions about severity, frequency, location, duration, associated symptoms and impact in work and social activities of their most frequent headaches. Migraine diagnoses were determined in accordance with the International Headache Society (IHS) criteria of 1988. Results. Recurrent headaches in the past year were found in 516 (36.82%) respondents, 145 (28.1%) males and 371 (71.9%) females. Total prevalence of migraine was found to be 7.3% (95%, CI 5.9–8.6); 11.9% (95% CI 9.6–14.2) in females and 2.0% (95% CI 0.9–3.0) in males. Overall, migraine constituted 19.6% (101/516) of all headaches reported in this sample. The prevalence did not vary significantly by age groups or socioeconomic status (SES). Migraine with aura had an overall prevalence of 3.5% (CI 0.8–7.1), and was significantly more frequent in females. In 60–70% of cases the attacks lasted 2–6 h and the frequency was 3.3 and 3.4 per month in females and males respectively. Both males and females reported significantly high percentages of attacks during work. Conclusions . Migraine prevalence in a sample of adults of Santiago is similar to that reported in previous studies using IHS criteria. Women of all socioeconomic levels are at an increased risk.     

Characterization of antibody and selection of alternative drug therapy in hydrochlorothiazide-induced immune hemolytic anemia

The authors report the clinical and laboratory findings of a patient who had severe immune hemolytic anemia due to hydrochlorothiazide (HCTZ). In this case, the HCTZ antibody reacted not only with other thiazide and thiazide-like drugs, but also with a chemically unrelated diuretic, ethacrynic acid. These results indicate that HCTZ antibody activity is not restricted solely to the thiazides and imply that therapy with any of the reactive drugs would be contraindicated for this patient. The serologic screening for drug reactivity may be useful for selecting alternative therapy for patients with drug-induced immune hemolytic anemia.     

The pharmacokinetics of 125I-atrial natriuretic factor in anaesthetized rats. Effects of neutral endopeptidase inhibition with candoxatrilat and of ANF-C receptor blockade.

The effects of candoxatrilat (cis-4-([2-carboxy-3-(2-methoxyethoxy)propyl]-1-cyclopentanecarbonyla mino)- 1-cyclohexane carboxylic acid) and the ring-deleted atrial natriuretic factor (ANF) analogue C-ANF4-23 (des[Gln18, Ser19, Gly20, Leu21, Gly22]ANF4-23-NH2) on the clearance of (3-[125I]iodotyrosyl28)ANF (125I-ANF) were studied in both intact and nephrectomized anaesthetized rats. HPLC analysis was used to verify that the 125I-labelled material isolated by solid phase extraction of rat plasma was intact ANF. In intact animals, clearance of 125I-ANF was biphasic with a T1/2 alpha of 17 sec and T1/2 beta of 95 sec. Volume of distribution (Vd) was 564 mL/kg and plasma clearance (Clp) 248 mL/min/kg. Candoxatrilat, over the dose range 0.01-10 mg/kg i.v., increased T1/2 beta (by a maximum of 56%) and decreased Clp (by up to 52%) with no effect on T1/2 alpha or Vd. C-ANF4-23 (10 micrograms/kg+1 microgram/kg/min i.v.) reduced Vd (by 57%) and Clp (by 54%) with no effect on T1/2 beta, whilst abolishing the T1/2 alpha phase in over 50% of animals. Increasing the dose of C-ANF4-23 did not increase the effect on any of these parameters, apart from a small increase in T1/2 beta. Combining the two agents resulted in a substantial decrease in Clp (76%) whilst the reduction in Vd and increase in T1/2 beta were comparable to those seen with C-ANF4-23 and candoxatrilat alone, respectively. In nephrectomized rats, the pharmacokinetics of 125I-ANF and the changes induced by candoxatrilat were similar to those observed in intact animals, whilst the effects of C-ANF4-23 alone were greater than in intact animals. The combination of C-ANF4-23 and candoxatrilat again produced a substantial increase in T1/2 beta (153%) and decreases in Vd (55%) and Clp (78%) in nephrectomized animals, although these changes could not be distinguished from those seen in intact animals treated with the same combination. Our studies indicate that neutral endopeptidase and ANF-C receptors are both major, and approximately equal, clearance mechanisms for 125I-ANF, together accounting for at least 75% of the total clearance of this peptide in the rat.