Non-iterative partial view 3D ultrasound to CT registration in ultrasound-guided computer-assisted orthopedic surgery

Purpose

In image-guided orthopedic surgery, rigid registration of intra-operative ultrasound (US) to a pre-operative plan, developed using computed tomography (CT) scans, is an important step for providing real time surgical guidance. The ability to perform this registration accurately, automatically, and in real time is critical for enabling more effective image guidance and anatomic restoration in a number of orthopedic procedures. Several surface-based and intensity-based registration methods have been proposed before to align the US and CT data. Although relatively successful results were reported, both methods require accurate segmentation or localization of the bone surface in US data, which is a challenging task. Furthermore, typically, only partial views of the three-dimensional (3D) bone anatomy are visible in US data, and registration would only converge if a good estimation of the initial alignment between the US and CT datasets is known.

Methods

We propose a 3D rigid CT to US registration method based on the alignment of local phase bone image projections. The registration is achieved by transforming the local phase bone features, calculated using 3D Log-Gabor filters, to a projection space obtained using 3D Radon transform. Validation experiments show the capability of the method in registering partial view US volumes to full view CT volume.

Results

Feasibility experiments, carried out on a phantom and ten volunteer subjects, show an average surface registration, in the region where the US scans were acquired, of 0.42 and 0.78  mm, respectively.

Conclusions

The proposed US to CT registration method is fully automatic, non-iterative and requires no initial alignment between the two registering datasets.     

Routine CT screening of psychiatry inpatients

During a 3-year period, all inpatients in the psychiatry unit underwent routine screening computed tomography (CT) in an effort to detect clinically unsuspected intracranial abnormalities. Of 261 patients examined who had no focal neurologic deficits, 103 had schizophrenia, 71 had depression, 48 had bipolar disorders, and 39 had paranoid delusions. Findings on 230 (88.1%) of the CT scans were within normal limits, and 27 (10.4%) showed only cortical atrophy. The remaining four cases (1.5%) demonstrated basal ganglia calcification (n = 2), old lacunar infarction (n = 1), or osteoma arising from the inner table of the skull (n = 1), all of which were considered to be clinically unrelated to the patients' psychiatric conditions. In the absence of focal neurologic deficits or other findings suggesting an intracranial abnormality (eg, papilledema, seizures, persistent or increasing headaches), there is no justification for routine CT scanning in patients admitted to the hospital for psychiatric disorders.     

Prognostic significance of argyrophilic nucleolar organizer region (AgNOR) in resected non-small cell lung cancer (NSCLC)

The expression of the nucleolar organizer regions (NORs) was quantified in paraffin sections of tumors and lymph node metastasis, by means of digital image analysis, in 75 patients with resected non-small cell lung cancer (NSCLC). Patients were divided in two groups: early stage (stages I and II) and advanced stage (stages IIIa, IIIb and IV). The prognostic significance of AgNOR expression was tested by Cox regression analysis in models controlled for age, sex, vital status, stage and histological type. Tumors at early stages had a lower expression of AgNOR than those at more advanced diseases. The mean values obtained for NORs in advanced disease were almost the same as those in the primary tumors when compared with the corresponding lymph node metastasis (r = 0.90; p < 0.01; linear regression). The prognostic role of AgNOR was significant only for tumors at stages I and II and not for advanced neoplasms (stages IIIa, IIIb and IV). These results encourage the inclusion of AgNOR quantitation in routine material, especially in early lung cancer.      

Morphine pharmacokinetics in premature and mature newborn infants

The pharmacokinetics of a single dose of morphine was investigated in five term infants (gestational age 37–40 weeks) and eight preterm infants (gestational age 25–32 weeks). In the five term infants, median (range) volume of distribution at steady state (Vd_β) was 1758 (634–2700) ml/kg, plasma clearance (Cl) was 4.73 (1–75–6.61) ml/kg/min and terminal half-life (T1/2) was 224 (107–394) min. In the eight preterm infants, Vd_β was 2366 (1662–2876) ml/kg, Cl was 2.82 (1.88–6.60) ml/kg/min and T1/2 was 556 (248–834) min. No correlation was found between clearance and gestational age, but we found a significant negative correlation between T1/2 and gestational age. We conclude that there is considerable variation in the pharmacokinetic properties of morphine in both term and preterm newborn infants. Because of this variation, careful individual assessment of the clinical effect of therapy with morphine in newborn infants should be exercised.     

Systemic chemotherapy induces microsatellite instability in the peripheral blood mononuclear cells of breast cancer patients

Introduction  

Systemic chemotherapy is an important part of treatment for breast cancer. We conducted the present study to evaluate whether systemic chemotherapy could produce microsatellite instability (MSI) in the peripheral blood mononuclear cell fraction of breast cancer patients.     

High-level mupirocin resistance in Staphylococcus aureus: evidence for two distinct isoleucyl-tRNA synthetases.

Mupirocin resistance in Staphylococcus aureus results from changes in the target enzyme, isoleucyl-tRNA synthetase (IRS). Twelve strains of S. aureus comprising four susceptible (MICs < or = 4 micrograms/ml), four intermediate level-resistant (MICs between 8 and 256 micrograms/ml), and four highly resistant (MICs > or = 512 micrograms/ml) isolates were examined for their IRS content and the presence of a gene known to encode high-level mupirocin resistance. Ion-exchange chromatography of cell extracts showed a single IRS active peak in mupirocin-susceptible strains, with 50% inhibitory concentrations (IC50s) of 0.7 to 3.0 ng of mupirocin per ml. In strains showing intermediate mupirocin resistance, similar single IRS activity peaks were observed, but these were less sensitive to inhibition, and the mupirocin IC50s for them were 19 to 43 ng/ml. Strains that were highly resistant to mupirocin displayed two distinct peaks; one was similar to that found with susceptible strains (IC50, 0.9 to 2.5 ng/ml), but an additional peak with an IC50 of 7,000 to 10,000 ng/ml was also observed. A strain cured of the plasmid encoding high-level mupirocin resistance lacked the resistant IRS peak. Restriction digests, produced by endonuclease NcoI, of total bacterial DNA isolated from the highly resistant strains hybridized with a mupirocin resistance gene probe, whereas DNA isolated from the intermediate level-resistant and susceptible strains did not. These results demonstrate that two different IRS enzymes were present in highly mupirocin-resistant S. aureus strains. In strains expressing intermediate levels of resistance, only a chromosomally encoded IRS which was inhibited less by mupirocin than IRS from fully susceptible strains was detected.     

Effects of propofol, etomidate, and pentobarbital on critical oxygen delivery

OBJECTIVE: To test the hypothesis that propofol, etomidate, and pentobarbital increase critical oxygen delivery in a dose-dependent manner during progressive hemorrhage. DESIGN: Prospective, randomized laboratory investigation. SETTING: University laboratory. SUBJECTS: A total of 40 anesthetized, paralyzed, and mechanically ventilated dogs weighing 29.2+/-4.6 kg. INTERVENTIONS: Dogs were randomly assigned to be anesthetized with propofol (n = 13), etomidate (n = 13), or pentobarbital (n = 14) at either low or high dosages. At 30 mins after splenectomy, the dogs underwent progressive hemorrhage by successive withdrawals of 3-5 mL/kg arterial blood. MEASUREMENTS AND MAIN RESULTS: At each step of hemorrhage, oxygen consumption and oxygen delivery were determined. Oxygen consumption was obtained from expired gas analysis, and oxygen delivery was determined from thermodilution cardiac output and calculated arterial oxygen content. In each animal, critical oxygen delivery and critical oxygen consumption were obtained from a plot of oxygen consumption vs. oxygen delivery as the point of intersection of the two best-fit regression lines determined by a least sum of squares method. Critical oxygen extraction was obtained by dividing critical oxygen consumption by critical oxygen delivery. In the three groups, animals receiving the higher anesthetic infusion had a significantly higher critical oxygen delivery (propofol: 10.5+/-0.8 vs. 13.9+/-2.5 mL/min/m2, p < .05; etomidate: 10.1+/-0.7 vs. 13.4+/-3.0 mL/min/m2, p < .05; pentobarbital: 7.8+/-1.0 vs. 12.3+/-2.5 mL/min/m2, p < .01) attributable to a lower critical oxygen extraction ratio (propofol: 41.1+/-6.4% vs. 54.2+/-2.5%, p < .01; etomidate: 42.7+/-10.2% vs. 60.6+/-7.1%, p < .01; pentobarbital: 42.2+/-7.2% vs. 64.3+/-8.8%, p < .01). CONCLUSIONS: This study indicates that propofol, etomidate, and pentobarbital increased critical oxygen delivery in a dose-dependent manner. This effect was mainly related to a decrease in tissue oxygen extraction capabilities.     

A needs assessment of surgical residents as teachers.

OBJECTIVE: To determine the needs of surgical residents as teachers of clinical clerks. DESIGN: A needs assessment survey. SETTING: Department of Surgery, University of Toronto. PARTICIPANTS: Clinical clerks and surgical residents and staff surgeons. METHODS: Three stakeholder groups were defined: staff surgeons, surgical residents and clinical clerks. Focus-group sessions using the nominal group technique identified key issues from the perspectives of clerks and residents. Resulting information was used to develop needs assessment surveys, which were administered to 170 clinical clerks and 190 surgical residents. Faculty viewpoints were assessed with semi-structured interviews. Triangulation of these 3 data sources provided a balanced approach to identifying the needs of surgical residents as teachers. RESULTS: Response rates were 64% for clinical clerks and 66% for surgical residents. Five staff surgeons were interviewed. Consensus was noted among the stakeholder groups regarding the importance of staff surgeon role modelling and feedback, resident attitude, time management, knowledge of clerks' formal learning objectives, and appropriate times and locations for teaching. Discrepancies included a significant difference in opinion regarding the residents' capacity to address clerks' individual learning needs and to foster good team relationships. Residents indicated that they did not receive regular feedback regarding their teaching and that staff did not place an emphasis on their teaching role. CONCLUSIONS: This study has, from a multi-source perspective, assessed the needs of surgical residents as teachers. These needs include enhancing residents' education regarding how and what to teach medical students on a surgical rotation, and a need for staff surgeons to increase feedback to residents regarding their teaching.