Computer assisted pelvic surgery: registration based on a modified external fixator.

A fundamental step in Computer Assisted Surgery (CAS) is the registration, when the preoperative virtual data and the corresponding operative anatomy of the region of interest are merged. To provide exact landmarks for anatomical registration, a tubular external fixator was modified. Two intact pelvic bones (one artificial foam pelvis and one cadaver specimen) were used for the experimental setup. Registration was carried out using a standardized protocol for anatomy-based registration in the control group; anatomical registration was achieved using a modified external fixator in the study group. This external fixator had titanium fiducials wedged into the fixator carbon tubes serving as landmarks for paired-point registration. The tubes were used for surface registration. The standard anterior pelvis fixator assembly was augmented with additional bilateral tubes oriented towards the posterior, enabling registration of the sacroiliac areas. The accuracy of registration was checked by "reversed verification", where the examiner used only the screen display to control the virtual position of the pointer tip in relation to selected landmarks. By virtual matching, the real distance was measured with a digital caliper. We defined the verification as "accurate" when the residual distance was less than 1 mm; "acceptable" when it was between 1 mm and 2 mm; and "insufficient" when it exceeded 2 mm. The paired T-test with significance levels of p < 0.05 was used for statistical analysis. The anatomical registration based on the external fixator landmarks was statistically as accurate as that obtained using anatomical landmarks on the pelvic bone. This study concludes that the external fixator, a conventional tool in the management of acute traumatic pelvic instability, can also be useful for landmark registration in CAS.     

Effect of haemodialysis on visual-evoked potential parameters

SUMMARY: Different papers have emphasized the presence of visual-evoked potential (VEP) abnormalities in metabolic disorders. The aim of this study was to perform pattern VEP (PVEP) recordings in patients with chronic renal failure just before and 24 h after dialysis to test the effect of this procedure on visual pathway generated parameters. Twenty-four haemodialysis patients (M/F:14/10; mean age: 48.8 ± 14.1 years) were examined. None of them were complaining from visual difficulties or from visual loss. The recording sessions were performed just before and 24 h after dialysis. The control group consisted from 27 healthy subjects matched for age and sex. Eight (33%) patients demonstrated abnormal P100 latency prolongation in at least one tested eye (six patients in one tested eye, two in both eyes) in the recording session just prior to dialytic treatment. In the post-treatment session, it was found that the abnormal P100 latencies that were present in six patients (75%) before dialysis had returned to normal, while in the remaining two (25%), the latency abnormality persisted. No correlation was found between VEP parameters and dialysis duration, serum blood urea nitrogen (BUN), creatinine, parathyroid hormone and haematocrit levels. However, a positive correlation in the intradialytic percentage variation of bodyweight with P100 latencies was found . Visual evoked potential is a reliable, simple and non-invasive technique that can be used for the investigation and follow up of subclinical involvement of visual pathways in patients with chronic renal failure. Detected abnormalities in some uraemic patients are reversible by using dialysis.     

Purulent pericarditis complicating septicaemia: report of two cases

Intrapericardial (Pericardial) abscess is quite rare as a complication of sepsis and as a cardiac complication of typhoid septicaemia. It is rapidly fatal if untreated. We report two cases of a schoolboy eight years old with septicaemia from pyomyositis of the right thigh and another of nine and a half years with typhoid perforation and typhoid septicaemia that developed pericardial abscesses. In well-developed centres, computerised tomography, ultrasonography and other radiological investigations are employed for both diagnosis and therapy. We emphasise that these can be accomplished by good clinical examination, radiography of chest and the use of 18-G intra-venous cannula for percutaneous pericardiocentesis without aggressive surgical intervention.     

Increasing trend of ciprofloxacin resistance amongst common bacterial isolates at Mymensingh Medical College and Hospital

Ciprofloxacin resistance among common bacterial pathogen comprising Esch.coli, Staph.aureus and Pseudomonas spp. isolated from different clinical samples of Mymensingh Medical College Hospital during the periods of September, 1999 to March, 2001 and September, 2001 to August, 2002 were recorded. Values of two periods were compared and increased rate of ciprofloxacin resistance were noted in every bacterial species, e.g. 32.0% in Esch.coli, 8.7% in Staph.aureus and 5.1% in Pseudomonas spp. It was suggested to be aware and careful regarding use of ciprofloxacin in clinical practice so as to limit emergence of bacterial strains resistance towards the drug.     

Mixed-signal template-based reduction scheme for stimulus artifact removal in electrical stimulation

Simultaneous electrical stimulation and recording are used to gain insights into the function of neuronal circuitry. However, artifacts produced by the electrical stimulation pulses prevent the recording of neural responses during, and a short period after, the stimulation duration. In this work, we describe a mixed-signal recording topology with template subtraction for removing the artifact during the stimulation pulse. Emulated artifacts generated from a lumped electrical circuit model and experimental artifacts in cardiac cell cultures are used to evaluate the topology. The simulations show that delays between the emulated artifact and its estimated compensation template represent the largest error source of the analog template subtraction. The quantization error appears like random noise and determines the threshold level for the action potential detection. Simulations show that removal of the artifacts is possible, allowing the detection of action potentials during the stimulation pulsing period, even for high-amplitude saturating artifacts. Measurement results with artifacts elicited in cardiac cell cultures show feasible applications of this topology. The proposed topology therefore promisingly opens up a previously unavailable detection window for improving the analysis of the neuronal activity.     

Better retention of Malaysian opiate dependents treated with high dose methadone in methadone maintenance therapy

Background  

Methadone is a synthetic opiate mu receptor agonist that is widely used to substitute for illicit opiates in the management of opiate dependence. It helps prevent opiate users from injecting and sharing needles which are vehicles for the spread of HIV and other blood borne viruses. This study has the objective of determining the utility of daily methadone dose to predict retention rates and re-injecting behaviour among opiate dependents.