Limitations of the keyhole technique for quantitative dynamic contrast-enhanced breast MRI

The effect of keyhole data acquisition on quantitative analysis of dynamic MRI was examined. Experiments were performed retrospectively on raw data obtained from clinical dynamic contrast-enhanced breast imaging procedures. The effects of keyhole phase-encoding acquisition and type of reconstruction algorithm on the accuracy of derived quantitative parameters was assessed. Results indicate that the minimum keyhole size used should be restricted by the approximate minimum size of the expected lesions. Furthermore, reconstruction algorithms that offer improved image resolution do not circumvent this restriction.     

Laparoscopic versus open appendectomy: a prospective randomized trial of 81 patients

Objective

To compare the efficacy of laparoscopic appendectomy (LA) and open appendectomy (OA) in the treatment of acute appendicitis.

Design

A prospective randomized trial.

Setting

A university teaching hospital.

Patients

Eighty-one patients with a diagnosis of acute appendicitis were prospectively randomized to undergo either LA or OA. The two groups were matched for age and sex.

Interventions

LA or OA.

Main Outcome Measures

Number of days in hospital and time to full recovery.

Results

The mean hospital stay for LA was 3.23 days compared with 3.03 days for OA (p < 0.001). The mean number of narcotic injections required for patients in the LA group was 4.05 compared with 5.58 for patients in the OA group (p < 0.001). The mean time to complete recovery for patients in the LA group was 9.0 days compared with 16.2 days for patients in the OA group (p < 0.001). The mean operative time for LA was 73.8 minutes compared with 45.0 minutes for OA (p < 0.001). Three patients in the LA group had intra-abdominal abscesses (p > 0.25). No significant difference in wound infection rates was demonstrated (p > 0.05). Similarly, pain scores at 7 and 28 days showed no significant difference (p > 0.05).

Conclusions

With LA significantly fewer narcotic injections are required and there is a more rapid return to normal activities. LA takes longer to perform and was associated with three intra-abdominal abscesses. In cases of simple acute appendicitis the hospital stay for LA is significantly shorter.     

Elastic moduli of normal and pathological human breast tissues: an inversion-technique-based investigation of 169 samples

Understanding and quantifying the mechanical properties of breast tissues has been a subject of interest for the past two decades. This has been motivated in part by interest in modelling soft tissue response for surgery planning and virtual-reality-based surgical training. Interpreting elastography images for diagnostic purposes also requires a sound understanding of normal and pathological tissue mechanical properties. Reliable data on tissue elastic properties are very limited and those which are available tend to be inconsistent, in part as a result of measurement methodology. We have developed specialized techniques to measure tissue elasticity of breast normal tissues and tumour specimens and applied them to 169 fresh ex vivo breast tissue samples including fat and fibroglandular tissue as well as a range of benign and malignant breast tumour types. Results show that, under small deformation conditions, the elastic modulus of normal breast fat and fibroglandular tissues are similar while fibroadenomas were approximately twice the stiffness. Fibrocystic disease and malignant tumours exhibited a 3-6-fold increased stiffness with high-grade invasive ductal carcinoma exhibiting up to a 13-fold increase in stiffness compared to fibrogalndular tissue. A statistical analysis showed that differences between the elastic modulus of the majority of those tissues were statistically significant. Implications for the specificity advantages of elastography are reviewed.     

An inverse problem solution for measuring the elastic modulus of intact ex vivo breast tissue tumours

Soft tissue elasticity has been a subject of interest in biomedical applications as an aid to medical diagnosis since the dawn of medicine. More recently, this has led to the concept of elastography with the aim of imaging the spatial distribution of tissue elasticity. Interpreting elastography images requires reliable information pertaining to elastic properties of normal and pathological tissues. Such information is either very limited or not available in the literature. Elastic modulus measurement techniques developed for soft tissues generally require tissue excision to prepare samples for testing. While this may be done with normal tissues, tumour tissue excision is generally not permissible because tumour pathological assessment requires that the tumour be kept intact. To address this limitation, we developed a system to measure the Young's modulus of tumour specimens. The technique consists of indenting the tumour specimen while measuring indentation force and displacements. To obtain the Young's modulus from the measured force-displacement slope, we developed an iterative inversion technique that uses a finite element model of the piecewise homogeneous tissue slice in each iteration. Preliminary elasticity measurement results of various breast tumours are presented and discussed. These results indicate that the proposed method is robust and highly accurate. Furthermore, they indicate that a benign lesion and malignant tumours are roughly five times and ten times stiffer than normal breast tissues respectively.     

Voxel based versus region of interest analysis in diffusion tensor imaging of neurodevelopment

There are two main methods of quantitative analysis in diffusion tensor imaging (DTI) studies: manual region of interest (ROI) and automated voxel based. The purpose of this study is to compare the results of each of these methods applied to the same data set. Linear correlative analysis was performed for mean diffusivity (Trace/3 ADC) and for fractional anisotropy (FA) versus age within 8-12 years (N = 32) and within 21-27 years (N = 28), as well as a group comparison. SPM analysis identified more structures changing with age, partly due to the limited regions measured with ROI analysis. In general, ROI and voxel-based analysis methods produced comparable results for widespread reductions of Trace/3 ADC and increases of FA with age, particularly for group comparison. The discrepancies (i.e., missed regions) were likely related to problems of spatial normalization for SPM analysis, and masking localized changes by averaging all the voxels within a region of interest for ROI analysis. These two analysis methods for DTI offer complementary results, but neither one yields the complete story of neurodevelopment.     

Changes in energy during treatment of depression: an analysis of fluoxetine in double-blind, placebo-controlled trials

More than two thirds of patients with depression present with symptoms of fatigue, low energy, and listlessness. Because daytime sedation may be a concern in such patients, a "nonsedating" antidepressant should be considered. The authors examined the effects of fluoxetine on depression-related disturbances in energy. Data from seven double-blind, placebo-controlled clinical trials in 2,075 patients with major depression were retrospectively analyzed. The Hamilton Rating Scale for Depression (HAM-D) Retardation factor score (total of items 1, 7, 8, and 14) was used as the primary measure of energy improvement, whereas the HAM-D-17 total score was used to assess changes in overall depression. Elderly patients (aged 60 years and older) were included in the overall group and were also analyzed separately. In addition, a subgroup analysis was performed using the HAM-D Retardation factor score to categorize patients as having low (score < 8) or high (score > or = 8) levels of retardation at baseline. Beginning at week 3, fluoxetine-treated patients experienced statistically significant reductions in their HAM-D Retardation factor score compared with placebo-treated patients. The reductions for the elderly subgroup were less than those for the overall population, but they were still statistically significant beginning at week 4. Patients in both the low and high baseline retardation groups improved significantly. HAM-D-17 total scores for fluoxetine-treated patients in all groups (total, elderly, high retardation, and low retardation) improved significantly compared with placebo-treated patients. These findings demonstrate that fluoxetine-treated patients experience an improvement in energy symptoms as their overall depression improves.     

Exposure equalization radiography of the chest: clinical comparison of slit and raster scanning techniques

Exposure equalization radiography systems with scanning slit and raster geometries were constructed and tested with 75 patients. The scanning equalization radiography (SER) technique uses a detector, placed behind the patient, connected in a feedback loop to a microprocessor-controlled x-ray source. The detector monitors the transmitted radiation, and in turn the x-ray output is varied to equalize the radiographic film density over the entire image. The clinical evaluation of these systems included 25 posteroanterior (PA) chest radiographs by an SER slit-geometry system (5.0-sec scan time), 25 PA chest radiographs by an SER raster-geometry system with an 8.8-sec scan time, and 25 PA chest radiographs by an SER raster-geometry system with a 4.7-sec scan time. These SER radiographs were compared to conventional radiographs of the same patients by two radiologists. The observers noted that the SER slit radiographs had seriously overexposed areas in 80% of instances, and that any potential gains from this system were offset by the overexposure problems. The radiographs obtained by the SER raster technique with a 4.7-sec scan time showed more uniform and adequate exposure in 80% of instances and better visualization of normal anatomic detail in the lung (52%) and mediastinum (84%) than conventional radiographs. The radiographs obtained by the SER raster technique with an 8.8-sec scan time showed fewer peripheral lung markings in 15 of 25 cases, presumably due to motion. In all other respects, the images were similar in quality to the SER raster 4.7-sec radiographs.     

Electrostatic fields in ionography.

There is renewed interest in diagnostic radiology in electrostatic methods of imaging, such as xeroradiography and ionography. This is due to the fact that edge contrast can be achieved, aiding in the visualization of soft tissue tumors. In analyzing the image forming properties of these system, we chose to solve the electrostatic problems by the method of images. We present methods and recursion formulas for calculating electrostatic fields due to (a) any charge distribution on a slab of dielectric (the solution involves a single infinite series) or (b) the same as the above with the introduction of an additional ground plane parallel to the dielectric surface (the solution now involves double infinite series). Analysis of these fields suggests new methods of controlling edge contrast and development configurations where the field which penetrates through the foil is used to produce the final image rather than the field above the charged surface.     

The role of previously unmeasured organic acids in the pathogenesis of severe malaria

IntroductionSevere falciparum malaria is commonly complicated by metabolic acidosis. Together with lactic acid (LA), other previously unmeasured acids have been implicated in the pathogenesis of falciparum malaria.MethodsIn this prospective study, we characterised organic acids in adults with severe falciparum malaria in India and Bangladesh. Liquid chromatography-mass spectrometry was used to measure organic acids in plasma and urine. Patients were followed until recovery or death.ResultsPatients with severe malaria (n=138), uncomplicated malaria (n=102), sepsis (n=32) and febrile encephalopathy (n=35) were included. Strong ion gap (mean±SD) was elevated in severe malaria (8.2 mEq/L±4.5) and severe sepsis (8.6 mEq/L±7.7) compared with uncomplicated malaria (6.0 mEq/L±5.1) and encephalopathy (6.6 mEq/L±4.7). Compared with uncomplicated malaria, severe malaria was characterised by elevated plasma LA, hydroxyphenyllactic acid (HPLA), α-hydroxybutyric acid and β-hydroxybutyric acid (all P<0.05). In urine, concentrations of methylmalonic, ethylmalonic and α-ketoglutaric acids were also elevated. Multivariate logistic regression showed that plasma HPLA was a strong independent predictor of death (odds ratio [OR] 3.5, 95 % confidence interval [CI] 1.6–7.5, P=0.001), comparable to LA (OR 3.5, 95 % CI 1.5–7.8, P=0.003) (combined area under the receiver operating characteristic curve 0.81).ConclusionsNewly identified acids, in addition to LA, are elevated in patients with severe malaria and are highly predictive of fatal outcome. Further characterisation of their sources and metabolic pathways is now needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1023-5) contains supplementary material, which is available to authorized users.