Multispectral analysis of magnetic resonance images

Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study.     

Orbital exenteration reconstruction with rectus abdominis microvascular free flap

OBJECTIVES: To determine the course of reconstructive treatment and outcomes with use of the rectus abdominis free flap after orbital exenteration with or without total maxillectomy. STUDY DESIGN: Retrospective chart review of treatment and outcomes of patients who had rectus abdominis free-tissue transfer for orbital exenteration with or without total maxillectomy at the Mayo Clinic between 1994 and 2004. METHODS: Charts of patients who had rectus abdominis free flap reconstruction after orbital exenteration were retrospectively reviewed and the surgical technique evaluated. An explanation of the surgical technique for rectus abdominis free-tissue transfer to the orbital cavity is provided, along with a discussion of the advantages and disadvantages of this reconstructive method. RESULTS: Twelve of 13 patients who underwent reconstruction with rectus abdominis free-tissue transfer had a successful outcome (flap viability 92%). Cosmetic results were acceptable both to patients and to surgeons. CONCLUSIONS: Rectus abdominis microvascular free-tissue transfer for repair of orbital exenteration defects is a safe and reliable alternative to the use of the temporalis or the pectoralis major muscle as a pedicle flap; it provides a larger volume of well-vascularized tissue and greater placement flexibility without associated orientation problems; and the long vascular pedicle facilitates the use of multiple donor vessels within the head and neck, which is an advantage in previously irradiated patients. Postoperative care and the donor site defect are well tolerated. The flap allows reliable obturation of the oral maxillectomy defect, and it negates the need for cavity care in these patients.     

Cerebral cortical oxygenation: a pilot study

BACKGROUND: Cerebral hypoxia (cerebral cortical oxygenation [Pbro2] < 20 mm Hg) monitored by direct measurement has been shown in animal and small clinical studies to be associated with poor outcome. We present our preliminary results observing Pbro2 in patients with traumatic brain injury (TBI). METHODS: A prospective observational cohort study was performed. Institutional review board approval was obtained. All patients with TBI who required measurement of intracranial pressure (ICP), cerebral perfusion pressure (CPP), and Pbro2 because of a Glasgow Coma Scale score < 8 were enrolled. Data sets (ICP, CPP, Pbro2, positive end-expiratory pressure (PEEP), Pao2, and Paco2) were recorded during routine manipulation. Episodes of cerebral hypoxia were compared with episodes without. Results are displayed as mean +/- SEM; t test, chi2, and Fisher's exact test were used to answer questions of interest. RESULTS: One hundred eighty-one data sets were abstracted from 20 patients. Thirty-five episodes of regional cerebral hypoxia were identified in 14 patients. Compared with episodes of acceptable cerebral oxygenation, episodes of cerebral hypoxia were noted to be associated with a significantly lower mean Pao2 (144 +/- 14 vs. 165 +/- 8; p < 0.01) and higher mean PEEP (8.8 +/- 0.7 vs. 7.1 +/- 0.3; p < 0.01). Mean ICP and CPP measurements were similar between groups. In a univariate analysis, cerebral hypoxic episodes were associated with Pao2 < or = 100 mm Hg (p < 0.01) and PEEP > 5 cm H2O (p < 0.01), but not ICP > 20 mm Hg, CPP < or = 65 mm Hg, or Pac2 < or = 35 mm Hg. CONCLUSION: Cerebral oxymetry is confirmed safe in the patient with multiple injuries with TBI. Occult cerebral hypoxia is present in the traumatic brain injured patient despite normal traditional measurements of cerebral perfusion. Further research is necessary to determine whether management protocols aimed at the prevention of cerebral cortical hypoxia will affect outcome.     

The effect of methadone treatment on the quantity and quality of human fetal movement

OBJECTIVE: To evaluate the effect of daily maternal methadone maintenance treatment on the quality and quantity of fetal movement. METHODS: At 34-37 weeks gestation, real-time ultrasound recordings were obtained from 17 methadone treated and 17 non-opioid-dependent mothers at two time points relative to the methadone mothers' daily dose of methadone. The first observation was just prior to the mother taking her daily dose (Time A) and the second was 1-h postdose (Time B). The incidence and pattern of fetal breathing movements (FBMs), fetal trunk movements (FTMs) and total fetal activity (TFA) were obtained from these ultrasounds. RESULTS: A time by group effect was found for measures of FBM and TFA, Fs(1,32)=6.06 and 4.94, P<0.05. At Time A and Time B for these measures t-tests showed no difference in the incidence of FBM (47.9% vs. 55.4%) and TFA (56% vs. 64%) at Time A between the methadone and comparison groups; however, at Time B the incidence of FBM (16.6% vs. 53.5%) and TFA (27% vs. 65%) was decreased for the methadone group. In addition, there was a between-group difference for two qualitative measures of fetal breathing. A slower rate of fetal breathing (40.3 vs. 47.2 breaths/min) and fewer FBMs per breathing episode (51.7 vs. 92.4) were found for the methadone group regardless of time since the mothers' daily dose. CONCLUSION: Taken together these results suggest that daily maternal methadone maintenance treatment altered both quantitative and qualitative measures of fetal activity that have been found to be related to normal fetal development.     

Smoking,nicotine and tar and risk of small for gestational age babies

AIMS: To assess the effect of maternal smoking and environmental tobacco smoke (ETS) on risk of small for gestational age infants (SGA). METHODS: Case-control study of 844 cases and 870 controls. RESULTS: Maternal smoking in pregnancy was associated with an increased risk of SGA (adjusted odds ratio (OR)= 2.41; 95% confidence interval (CI) = 1.78, 3.28). We could not detect an increased risk of SGA with paternal smoking, or with other household smokers when the mother was a non-smoker, but did find an increased risk with exposure to ETS in the workplace or while socializing. Infants of mothers who ceased smoking during pregnancy were not at increased risk of SGA, but those who decreased but did not stop remained at risk of SGA. There was no evidence that the concentration of nicotine and tar in the cigarettes influenced the risk of SGA. CONCLUSIONS: Maternal smoking in pregnancy is a major risk factor for SGA. This study suggests that mothers should be advised to cease smoking completely during pregnancy, and that a reduction in the number of cigarettes smoked or smoking low tar or nicotine concentration cigarettes does not reduce the risk of SGA.     

Estimation and implications of random errors in whole-body dosimetry for targeted radionuclide therapy

For targeted radionuclide therapy, the level of activity to be administered is often determined from whole-body dosimetry performed on a pre-therapy tracer study. The largest potential source of error in this method is due to inconsistent or inaccurate activity retention measurements. The main aim of this study was to develop a simple method to quantify the uncertainty in the absorbed dose due to these inaccuracies. A secondary aim was to assess the effect of error propagation from the results of the tracer study to predictive absorbed dose estimates for the therapy as a result of using different radionuclides for each. Standard error analysis was applied to the MIRD schema for absorbed dose calculations. An equation was derived to describe the uncertainty in the absorbed dose estimate due solely to random errors in activity-time data, requiring only these data as input. Two illustrative examples are given. It is also shown that any errors present in the dosimetry calculations following the tracer study will propagate to errors in predictions made for the therapy study according to the ratio of the respective effective half-lives. If the therapy isotope has a much longer physical half-life than the tracer isotope (as is the case, for example, when using 123I as a tracer for 131I therapy) the propagation of errors can be significant. The equations derived provide a simple means to estimate two potentially large sources of error in whole-body absorbed dose calculations.