PubMed Health⌕ Search

Biomedical subjects

John C Leonidas

Publications and source records attributed to John C Leonidas.

12 recordsLinked to original sources
PubMed2005

Comparison of lung area by chest radiograph, with estimation of lung volume by helium dilution during prone and supine positioning in mechanically ventilated preterm infants: a pilot study.

Measurement of lung volume may be useful in determining the degree of lung disease and for optimizing an infant's mechanical ventilator settings. A chest radiograph (CXR) is often used to estimate lung volume, because direct measurement, e.g., functional residual capacity (FRC), is neither practical nor possible in the neonatal intensive care unit. In supinely positioned infants, good correlation was found between lung area determined by CXR and lung volume, e.g., functional residual capacity (FRC). Whether this is true for the prone position is unknown. Since positioning may affect oxygenation and pulmonary function, we studied the relationship between lung area measured from CXR and FRC during both supine and prone positioning in 14 mechanically ventilated preterm infants. Lung area was determined from CXRs using computed radiography and FRCs obtained by helium dilution at end-expiration in both supine and prone positions. Reproducibility of lung area measurements was demonstrated by high correlations between two observers (R2 = 0.92 and 0.99 for supine and prone, respectively). When supine, lung area was 15.4 +/- 3.1 cm2, and FRC was 19.5 +/- 7.3 ml. In prone position, lung area was 16.7 +/- 4.2 cm2, and FRC 23.0 +/- 9.4 ml. There was a moderate to strong positive correlation between lung area and FRC for both positions (supine: r = 0.57, P < 0.03; prone: r = 0.63, P < 0.02). Lung area measured by computed radiography is a reproducible and practical method for estimating lung volume from routine chest X-rays in both supine and prone positions in mechanically ventilated preterm infants.

Female↗
PubMed2004

Coincidence-detection FDG-PET versus gallium in children and young adults with newly diagnosed Hodgkin's disease.

UNLABELLED: Coincidence-detection 18F-FDG-PET (PET) and 67Ga whole-body and SPECT (Ga) were compared in children and young adults with newly diagnosed Hodgkin's disease (HD). MATERIALS AND METHODS: Thirty patients with histologically confirmed HD underwent PET with attenuation correction 1 h after injection of 150-220 MBq 18F-FDG and whole-body and SPECT imaging 72 h after injection of 250-370 MBq 67Ga citrate. Two experienced readers retrospectively reviewed PET and Ga scans, grading 13 anatomic regions from one (normal) to five (abnormal). Numerical stages were assigned based on Ann Arbor classification. Comparison was made with disease sites (established by biopsy or two or more of the following: physical examination, conventional imaging studies, radionuclide studies, and follow-up studies) and clinical stages. Sensitivity, specificity, and accuracy were calculated and significance of differences determined using McNemar's test. RESULTS: PET detected 120/138 (87%) disease sites and Ga 109/138 (79%). PET and Ga were concordant for 103/138 (75%) sites. Accuracies were not significantly different for supradiaphragmatic disease. PET was more accurate than Ga for detecting splenic (0.91 vs 0.61, P = 0.012), infradiaphragmatic (0.89 vs 0.75, P = 0.042), and all disease sites combined (0.95 vs 0.91, P = 0.039). PET stage agreed with clinical stage in 79% of patients and Ga in 71%. CONCLUSION: PET was superior to Ga for evaluating children and young adults with newly diagnosed HD.

Adolescent↗
PubMed2003

The role of gadolinium enhanced magnetic resonance imaging for children with suspected acute pyelonephritis.

PURPOSE: The diagnosis of pyelonephritis is primarily clinical. However, the history and physical findings can be confusing in children, leading to adjunctive nuclear renal cortical scintigraphic studies (99mtechnetium dimercapto-succinic acid [DMSA]) to confirm the diagnosis. Nonetheless, ambiguity occurs when differentiating between acute pyelonephritis and chronic scarring. We report our initial experience with gadolinium enhanced inversion recovery magnetic resonance imaging (MRI) to diagnose acute pyelonephritis. MATERIALS AND METHODS: Nine patients 7 months to 18 years old (mean age 81 months) underwent MRI to confirm radiographically a clinical suspicion of acute pyelonephritis. All patients had at least 1 prior episode of clinical pyelonephritis. Data were collected to determine whether acute pyelonephritic changes could be differentiated from chronic pyelonephritis on the basis of MRI characteristics. RESULTS: Of the 9 patients 4 were identified as having acute pyelonephritis on MRI (persistently high signal intensity after gadolinium), 2 demonstrated evidence of postpyelonephritic scar (parenchymal loss without change in signal intensity), 1 had evidence of acute pyelonephritis and chronic changes, and 2 had a completely normal examination (decreased signal intensity after gadolinium). At our institution the billable cost of MRI to the patient is $1,329, while the billable cost of 99mtechnetium DMSA is $1,459. All patients younger than 6 years required intravenous sedation for MRI, whereas 70% of those younger than 6 years require intravenous sedation for DMSA scanning at our institution. MRI provided greater anatomical detail regarding the renal architecture without radiation exposure, and allowed the unambiguous diagnosis of acute versus chronic pyelonephritis scar in a 1-time (versus often multipart for DMSA) imaging study. CONCLUSIONS: In cases where adjunctive imaging studies are useful to make a diagnosis gadolinium enhanced inversion recovery magnetic resonance imaging allows the detection of acute pyelonephritis rapidly, cost-effectively and safely in the pediatric population.

Acute Disease↗
PubMed2003

18F-FDG PET versus CT for evaluating the spleen during initial staging of lymphoma.

UNLABELLED: The purpose of this study was to compare (18)F-FDG PET to CT for evaluating the spleen during the initial staging of lymphoma. METHODS: Seven patients with newly diagnosed lymphoma underwent (18)F-FDG PET and CT. Splenic uptake of (18)F-FDG, diffuse or focal, greater than hepatic uptake was interpreted as consistent with tumor. CT demonstrating a positive splenic index or focal hypodensities was classified as positive for tumor. PET and CT results were compared with final diagnoses, which were confirmed surgically for 6 patients and at autopsy for 1 patient. RESULTS: Five of 7 patients had lymphomatous involvement of the spleen. (18)F-FDG PET was true-positive for all 5 patients with splenic disease and true-negative for both patients without splenic disease. CT, in contrast, was true-positive for 4 of the 5 patients with splenic disease and false-positive for the 2 patients without splenic disease. The accuracies of (18)F-FDG PET and CT for evaluating the spleen were 100% and 57%, respectively. CONCLUSION: (18)F-FDG PET correctly identified all patients with and without splenic disease and was superior to CT for this purpose.

Adolescent↗