Surgical simulation – a new tool to evaluate surgical incisions in congenital heart disease?

We introduce a new concept for preoperative planning and surgical education in congenital heart disease: surgical simulation. Recent advances in three-dimensional image acquisition have provided a new means to virtually reconstruct accurate morphological models while computer visualisation hardware now allows simulation of elastic tissue deformations interactively. Incision simulation is performed in two patients with complex congenital heart disease to preoperatively evaluate potential corrective surgical strategies. The relevant cardiac morphology was correctly depicted by the virtual models on which arbitrary incisions could be performed. By visualising the morphology in respect to each incision, different surgical strategies could be evaluated pre-operatively. We have taken the first step towards a clinically useful incision simulator for procedures in congenital heart disease and made an initial evaluation. With further developments it is likely that new tools for patient-specific preoperative planning and surgical training will emerge based on the presented ideas.

A new virtual reality approach for planning of cardiac interventions

A novel approach to three-dimensional (3D) visualization of high quality, respiratory compensated cardiac magnetic resonance (MR) data is presented with the purpose of assisting the cardiovascular surgeon and the invasive cardiologist in the pre-operative planning. Developments included: (1) optimization of 3D, MR scan protocols; (2) dedicated segmentation software; (3) optimization of model generation algorithms; (4) interactive, virtual reality visualization. The approach is based on a tool for interactive, real-time visualization of 3D cardiac MR datasets in the form of 3D heart models displayed on virtual reality equipment. This allows the cardiac surgeon and the cardiologist to examine the model as if they were actually holding it in their hands. To secure relevant examination of all details related to cardiac morphology, the model can be re-scaled and the viewpoint can be set to any point inside the heart. Finally, the original, raw MR images can be examined on line as textures in cut-planes through the heart models.

Oxygen transport through methacrylate-based hydrogels with potential biological capability

The permeability to oxygen of hydrogels prepared from copolymers of 2-hydroxymethyl methacrylate and p-methacryloxyl-oxyacetanilide have been studied by using an oxygen electrode in combination with a permeometer. The transmissibility Dk/L and the permeability Dk (where D, k and L are, respectively, the diffusion coefficient, the Henry constant and the thickness of the hydrogel) are measured by a combination of steady state and transitory state measurements. Both transport coefficients increase with the water content, which in turn depends on the copolymer composition. The values of these quantities tend toward a limiting value for water-saturated hydrogels. The ratio of the characteristic volume for diffusion of the oxygen molecule to the free volume of water per mole water is found to be in the vicinity of 0.10, and this value increases slightly as the fraction of the hydrophilic comonomer in the hydrogel increases. A detailed comparison of the biogels studied with six commercial contact lenses has also been performed.

The penetration of cefazolin, erythromycin and methicillin into human bone tissue

The penetration of cefazolin, erythromycin and methicillin into normal bone was studied in 20 patients undergoing surgery for fracture in the trochanteric region of the femur. The antibiotic concentrations were determined in serum, bone marrow, and cancellous and cortical bone. For all three antibiotics the bone marrow concentrations were of the same order of magnitude as the serum concentrations. In the eight patients receiving erythromycin, detectable concentrations were found in all the cancellous bone specimens (ranging from 1/7 to 1/2 of the serum concentration) and in three cortical bone specimens (ranging from 1/50 to 1/5 of the serum concentration). In the six patients receiving cefazolin, a detectable concentration was found in only one cancellous bone sample. In the six patients receiving methicillin, detectable concentrations were found only in the blood contaminated specimens of one cancellous and two cortical bone samples. However, by the method used, the recoveries of standard solutions of methicillin in cancellous and cortical bone were about 50 per cent and 15 per cent, respectively.

The predominant E2F complex in human primary haemopoietic cells and in AML blasts contains E2F-4, DP-1 and p130

The E2F family of transcription factors are thought to play an important role in the control of cell cycle progression. There is now also increasing evidence that some family members may act as oncogenes or tumour suppressor genes. The characterization of these proteins in human primary haemopoietic cells and acute myeloid leukaemia (AML) blasts may thus give an insight to the molecular mechanisms governing proliferation and leukaemogenesis in these cells. Therefore we analysed the expression of E2F-DNA binding activity and the constituent proteins found in the complexes in human primary haemopoietic cells of various lineages. We also studied blasts from 18 patients with acute myeloid leukaemia (AML). On electromobility shift assays (EMSA) a single E2F-DNA binding complex was detected in T cells, B cells and monocytes which was shown to contain E2F-4, DP-1 and p130, indicating that all quiescent haemopoietic cells have the same complex. Examination of 18 AML samples by EMSA revealed the presence of E2F binding and no gross abnormalities were detected. An E2F-4/p130 complex was detected in representative samples of all FAB types analysed. Thus abnormalities of E2F function are unlikely to play a primary pathogenic role in AML.

Fast 4D cone-beam CT from 60 s acquisitions

Background & purpose

Four dimensional Cone beam CT (CBCT) has many potential benefits for radiotherapy but suffers from poor image quality, long acquisition times, and/or long reconstruction times. In this work we present a fast iterative reconstruction algorithm for 4D reconstruction of fast acquisition cone beam CT, as well as a new method for temporal regularization and compare to state of the art methods for 4D CBCT.

Materials & methods

Regularization parameters for the iterative algorithms were found automatically via computer optimization on 60 s acquisitions using the XCAT phantom. Nineteen lung cancer patients were scanned with 60 s arcs using the onboard image on a Varian trilogy linear accelerator. Images were reconstructed using an accelerated ordered subset algorithm. A frequency based temporal regularization algorithm was developed and compared to the McKinnon-Bates algorithm, 4D total variation and prior images compressed sensing (PICCS).

Results

All reconstructions were completed in 60 s or less. The proposed method provided a structural similarity of 0.915, compared with 0.786 for the classic McKinnon-bates method. For the patient study, it provided fewer image artefacts than PICCS, and better spatial resolution than 4D TV.

Conclusion

Four dimensional iterative CBCT reconstruction was done in less than 60 s, demonstrating the clinical feasibility. The frequency based method outperformed 4D total variation and PICCS on the simulated data, and for patients allowed for tumor location based on 60 s acquisitions, even for slowly breathing patients. It should thus be suitable for routine clinical use.

The effect of intra-articular instillation of bupivacaine on postarthroscopic morbidity: a placebo-controlled, double-blind trial

Forty patients undergoing diagnostic arthroscopy of the knee were included in a randomized double-blind study to investigate the effect of bupivacaine on postarthroscopic morbidity. The arthroscopies were performed under local anesthesia using 1% lidocaine with adrenaline. At the conclusion of the arthroscopic examination, 10 ml 0.5% bupivacaine with adrenaline or 10 ml placebo was instilled and left in the joint cavity. The two groups of patients were compared with regard to postarthroscopic duration of the anesthesia, degree of postarthroscopic pain, number of analgesic tablets taken, need for crutches or other walking aids, and days away from work. There was no difference between the patients receiving bupivacaine and patients receiving placebo for any of the parameters investigated.

Bactericidal activity of gentamicin against S. aureus. In vitro study questions value of prolonged high concentrations

Bactericidal activity of gentamicin against 4 strains of Staphylococcus aureus was investigated in vitro using Mueller-Hinton broth (MH) and surgical wound fluid (WF) as test media. 6 concentrations of gentamicin were tested ranging from 1-1024 micrograms/mL. During the first hour of incubation, there was a marked concentration-dependent kill rate, approximately 3 x 10(3) times in WF and 10(2) times in MH. After the first hour of incubation, the kill rate was independent of the concentration in both media. Our study questions the benefit of the prolonged and high wound concentrations of gentamicin obtained after application of gentamicin-containing PMMA.

Fractures of the shaft of the tibia treated with Hoffmann external fixation

Ninety-six compound or unstable fractures of the tibial shaft were treated with external fixation of different mountings. The median healing time was 10 months without a statistically significant difference between the healing time after treatment with unilateral frames and quadrilateral frames. The rate of pin-track infection was 36%, which is comparable to those of other published series. Seven cases of chronic osteitis and four pseudarthroses required further surgical management. We had no primary or secondary amputations in this series.

Pharmacokinetics of topical gentamicin in total hip arthroplasty

Two different ways of administering topical gentamicin were examined in patients undergoing total hip arthroplasty. 160 mg gentamicin, dissolved in isotonic saline, was instilled into the wounds of five out of ten patients. In the other five patients, the components of the prostheses were inserted by means of gentamicin-containing cement, 0.5 g per 40 g powder. Both the serum concentrations and the wound concentrations of gentamicin were determined constantly during the postoperative period. The average half-lives of gentamicin in the surgical wounds of the two groups of patients were found to be 3 1/2 and 25h, respectively. The average wound concentration was found to be higher than the minimum inhibitory concentration for staphylococci and aerobic Gram-negative rods for 18 and 11 h, respectively, in the group of patients treated with gentamicin solution compared with 160 and 67 h, respectively, in the group treated with the gentamicin-containing cement.

Elimination of cefuroxime and gentamicin during and after open heart surgery

In eight consecutive adult heart surgery patients, serum concentrations of cefuroxime and gentamicin were studied during and after operation. Repeated doses of cefuroxime 1.5 g and gentamicin 80 mg were given. Intra-operative concentrations were deemed adequate (cefuroxime Cmin: 16-45 mg/l, gentamicin Cmin: 1.6-2.8 mg/l), and no differences (P = 0.05) could be demonstrated between elimination rates during and after open heart operation (cefuroxime T1/2 101 vs 111 min, gentamicin T1/2 191 vs 193 min).

Orthopedic wound infections. 182 cases after 8913 operations during an 8-year survey

We performed a surveillance of postoperative wound infections at our department for a period of 8 years. The surveillance was based on forms completed by the surgeons at the department. Retrospectively, by scrutinizing the records of patients with recorded infections, the criteria for infections used by the surgeons were compared with the criteria recommended by the Centers for Disease Control, USA, for routine infection surveillance studies: 1) pus present in the wound, 2) bacteria isolated from the wound, 3) spontaneous wound breakdown or surgical intervention due to suspected infection; if culture is performed, it must be positive, 4) evidence of infection at reoperation or at radiologic or histopathologic examination (restricted to deep infections) or 5) diagnosis of infection by a surgeon. 182 infections were recorded; in 106 (58%) pus was present, drained either spontaneously or by surgical intervention, in 24 (13%) no pus was seen, but the culture was positive. In 116 cases, surgical intervention was performed or wounds spontaneously broke down; pus was found in 101 of these and culture of non-purulent material was positive in 13 and negative in 2. In 52 (29%) patients, only criterion 5 was fulfilled. In surveillance studies where the recordings are based on several observers, the subjective criterion 5 may, as in our study, give a falsely high number of infections, also preventing comparison between studies. We recommend that all suspected infections are cultured and that only criteria 1, 2 and 4 are used.

Mechanical prophylaxis against deep vein thrombosis in Charnley hip arthroplasty

A retrospective study of 521 Charnley hip replacements involving 471 patients is presented, assessing the effect of mechanical prophylaxis against deep vein thrombosis. During the operation venous flow was stimulated in all cases by passive movement at the ankle joint. In addition, all patients used Flowtron leggings--a non-invasive, intermittent pneumatic compression device - on the unoperated leg during the operation and on both legs during the first 24 hours after the operation. The patients were mobilized as soon as possible with weight-bearing on the operated leg from the second postoperative day. As indicated by the results, the above combination of early mobilization, peroperative stimulation of the venous flow and the use of Flowtron leggings lowered the incidence of thromboembolic complications to 3.6 per cent.

Complications following osteotomy of the greater trochanter in total hip replacement arthroplasty using the lateral approach

In a consecutive series of 365 hip replacement arthroplasties ad modum Charnley in 309 patients migration of the trochanteric fragment was encountered in 4.9 per cent of the cases. The predisposing factors were wire-breakage, trochanteric fractures and excessive weight. Men were more apt than women to develop migration. Early mobilization with weight-bearing on the operated leg did not increase the risk of migration. The migration rarely gave rise to complaints, and if so only mild ones. Trochanteric union did not pose problems, and at the end of 2 years 98 per cent had united. After 5 years no case of non-union was detected.

Overcoming foetal motion using interactive real-time magnetic resonance imaging

OBJECTIVE

Foetal MRI has become an established image modality in the prenatal diagnosis of CNS anomalies, but image quality can be severely affected by foetal movements. The objective was to overcome these inherent motion problems by applying interactive real-time MRI and to evaluate the diagnostic usefulness of the applied real-time MRI sequence in relation to standard protocols.

METHODS

Ten healthy foetuses (gestation week 21·3 ± 0·5) were scanned using a system, which allowed visual feedback and interactive slice positioning in real time. The data were compared to a control group of 14 healthy foetuses (gestation week 21·0 ± 0·8) who had previously been scanned using standard MRI. Comparisons were carried out by two radiologists with regard to cerebral anthropometric sizes, presence of important brain structures, degree of movement, clinical image value, image quality and ability to obtain correct slice planes.

RESULTS

Two out of eight anthropometric sizes were statistically different between the two groups. Representation of cerebral structures was found in 70-100% in the real-time group. No statistically differences were found in clinical image value and image quality. The mean ability to obtain optimal slice planes was higher in the real-time group, but it was not significant.

CONCLUSION

Imaging of the foetal brain using the proposed interactive real-time MRI system is a promising alternative to traditional foetal MRI for anthropometrics or as a supplement for the representation of foetal brain structures in cases in which foetal motion causes challenges in relation to obtaining optimal slice planes using conventional MRI techniques.