Respiration resolved imaging with continuous stable state 2D acquisition using linear frequency SWEEP.

PURPOSE: To investigate the potential of continuous radiofrequency (RF) shifting (SWEEP) as a technique for creating densely sampled data while maintaining a stable signal state for dynamic imaging. METHODS: We present a method where a continuous stable state of magnetization is swept smoothly across the anatomy of interest, creating an efficient approach to dense multiple 2D slice imaging. This is achieved by introducing a linear frequency offset to successive RF pulses shifting the excited slice by a fraction of the slice thickness with each successive repeat times (TR). Simulations and in vivo imaging were performed to assess how this affects the measured signal. Free breathing, respiration resolved 4D volumes in fetal/placental imaging is explored as potential application of this method. RESULTS: The SWEEP method maintained a stable signal state over a full acquisition reducing artifacts from unstable magnetization. Simulations demonstrated that the effects of SWEEP on slice profiles was of the same order as that produced by physiological motion observed with conventional methods. Respiration resolved 4D data acquired with this method shows reduced respiration artifacts and resilience to non-rigid and non-cyclic motion. CONCLUSIONS: The SWEEP method is presented as a technique for improved acquisition efficiency of densely sampled short-TR 2D sequences. Using conventional slice excitation the number of RF pulses required to enter a true steady state is excessively high when using short-TR 2D acquisitions, SWEEP circumvents this limitation by creating a stable signal state that is preserved between slices.

Treatment of Salmonella gastroenteritis with ampicillin, amoxicillin, or placebo.

In a randomized, prospective, double-blind study infants and children with uncomplicated Salmonella gastroenteritis were treated with ampicillin (15 patients), amoxicillin (15 patients), or placebo (14 patients). The dosage of antibiotics was 100 mg/kg/day in four equally divided doses given for five days. There was no significant benefit from antibiotic therapy on the duration of diarrhea (means 8.8, 7.3, and 7.2 days, respectively) or on the duration of recovery of Salmonella from stool cultures (means 41.3, 37.0, and 20.9 days, respectively). Bacteriologic relapse was not observed in placebo-treated patients but eight patients given ampicillin (53%) and eight given amoxicillin (53%) had relapse (P = .003). Salmonella isolated in relapse were still susceptible in vitro to the antibiotics. Of the 16 patients with bacteriologic relapse six (38%) had concomitant recurrence of diarrhea. It is concluded that ampicillin or amoxicillin therapy provides no benefit to patients with uncomplicated Salmonella gastroenteritis and substantially increases the risk of bacteriologic and symptomatic relapse.

Treatment of acute otitis media of infancy with cefaclor.

The emergence of ampicillin-resistant Haemophilus as a clinical problem in otitis media necessitates a search for alternative, effective therapy. An orally absorbable cephalosporin derivative, cefaclor, is equally effective in vitro against ampicillin-susceptible and -resistant Haemophilus and against other bacteria that cause acute otitis media. Two dosage schedules of cefaclor (40 and 60 mg/kg/day) were evaluated in 95 infants with acute otitis media. Bacterial origin was determined by a culture of tympanocentesis fluid. Success rates using the smaller dosage were inferior to those using the larger dosage. Results of therapy for pneumococcal and Haemophilus infection with 60 mg/kg/day were comparable to those previously found with amoxicillin trihydrate or with combinations of trisulfapyrimadines with erythromycin or penicillin V. One patient with an ampicillin-resistant Haemophilus infection responded well to cefaclor and did not have a relapse. Cefaclor was well tolerated and caused an acceptably low incidence of minor, adverse effects. Cefaclor deserves further testing as a candidate for preferred status as a single-drug treatment of acute otitis media.

Otitis media of infancy and early childhood. A double-blind study of four treatment regimens.

A double-blind, randomized trial of four antimicrobial regimens was conducted in 383 infants and children with acute otitis media. The drugs used were penicillin V, amoxicillin trihydrate, erythromycin estolate, and erythromycin estolate with trisulfapyrimidines. Aspiration of middle ear fluid for culture was done before treatment and repeated during treatment if fluid persisted. Etiologic bacteria were most commonly pneumococci (31%) or Haemophilus sp (22%), and an additional 5% of patients had both organisms. Amoxicillin was the most effective in promoting initial response in pneumococcal infection. For Haemophilus infections, the cure rates with amoxicillin and the erythromycin-trisulfapyrimidines mixture were significantly better than with the other two regimens, and serous otitis did not occur during the follow-up period; however, new episodes of otitis were comparable in the four groups. Amoxicillin and the erythromycin estolate-trisulfapyrimidines combination appear to be somewhat more effective than penicillin V or erythromycin estolate.

Comparison of trimethoprim-sulfamethoxazole and ampicillin theraphy for shigellosis in ambulatory.

One-hundred seventy-four infants and children with acute diarrhea were treated as ambulatory patients with either ampicillin (100 mg/kg/day orally in four divided doses) or trimethoprim sulfamethoxazole (10 mg TMP and 50 mg SMX/KG/day orally in two divided doses). There were 65 patients with shigellosis. Responses of those treated with TMP/SMX and of those with susceptible Shigella treated with ampicillin were comparable. Patients with resistant organisms failed to respond to ampicillin. All Shigella, including ampicillin-resistant strains, were suseptible in vitro to TMP/SMX, and patients with ampicillin-resistant strains responded favorably to treatment with TMP/SMX. TMP/SMX appears to be the best, currently available drug for the treatment of shigellosis.

Trimethoprim-sulfamethoxazole therapy for shigellosis.

Twenty-eight infants and children hospitalized for severe shigellosis were treated orally either with ampicillin trihydrate (100 mg/kg/day administered in divided doses every six hours) or with trimethoprim-sulfamethoxazole (trimethoprim, 10 mg; sulfamethoxazole, 50 mg/kg/day in divided doses every 12 hours) for five days. Four patients with ampicillin-resistant shigellae continued to have diarrhea and positive stool cultures during therapy. Patients with susceptible shigellae treated with ampicillin and all patients treated with trimethoprim-sulfamethoxazole responsed promptly and comparably within an average of 1.6 and 1.7 days, respectively, until stool cultures were negative, and 3.1 and 2.9 days, respectively, until diarrhea stopped. Patients with ampicillin-resistant shigellae responded to treatment with trimethoprim-sulfamethoxazole. It is concluded that trimethoprim-sulfamethoxazole is the best currently available drug for treatment of shigellosis in areas where multiple antibiotic resistance of shigellae is common.