Local T1-T2 distribution measurements in porous media.

A novel slice-selective T1-T2 measurement is proposed to measure spatially resolved T1-T2 distributions. An adiabatic inversion pulse is employed for slice-selection. The slice-selective pulse is able to select a quasi-rectangular slice, on the order of 1 mm, at an arbitrary position within the sample.The method does not employ conventional selective excitation in which selective excitation is often accomplished by rotation of the longitudinal magnetization in the slice of interest into the transverse plane, but rather a subtraction based on CPMG data acquired with and without adiabatic inversion slice selection. T1 weighting is introduced during recovery from the inversion associated with slice selection. The local T1-T2 distributions measured are of similar quality to bulk T1-T2 measurements. The new method can be employed to characterize oil-water mixtures and other fluids in porous media. The method is beneficial when a coarse spatial distribution of the components is of interest.

Local diffusion and diffusion-T2 distribution measurements in porous media.

Slice-selective pulsed field gradient (PFG) and PFG-T2 measurements are developed to measure spatially-resolved molecular diffusion and diffusion-T2 distributions. A spatially selective adiabatic inversion pulse was employed for slice-selection. The slice-selective pulse is able to select a coarse slice, on the order of 1cm, at an arbitrary position in the sample. The new method can be employed to characterize oil-water mixtures in porous media. The new technique has an inherent sensitivity advantage over phase encoding imaging based methods due to signal being localized from a thick slice. The method will be advantageous for magnetic resonance of porous media at low field where sensitivity is problematic. Experimental CPMG data, following PFG diffusion measurement, were compromised by a transient ΔB0(t) field offset. The off resonance effects of ΔB0(t) were examined by simulation. The ΔB0 offset artifact in D-T2 distribution measurements may be avoided by employing real data, instead of magnitude data.

B(1) mapping with a pure phase encode approach: quantitative density profiling.

In MRI, it is frequently observed that naturally uniform samples do not have uniform image intensities. In many cases this non-uniform image intensity is due to an inhomogeneous B1 field. The 'principle of reciprocity' states that the received signal is proportional to the local magnitude of the applied B1 field per unit current. Inhomogeneity in the B1 field results in signal intensity variations that limit the ability of MRI to yield quantitative information. In this paper a novel method is described for mapping B1 inhomogeneities based on measurement of the B1 field employing centric-scan pure phase encode MRI measurements. The resultant B1 map may be employed to correct related non-uniformities in MR images. The new method is based on acquiring successive images with systematically incremented low flip angle excitation pulses. The local image intensity variation is proportional to B1(2), which ensures high sensitivity to B1 field variations. Pure phase encoding ensures the resultant B1 field maps are free from distortions caused by susceptibility variation, chemical shift and paramagnetic impurities. Hence, the method works well in regions of space that are not accessible to other methods such as in the vicinity of conductive metallic structures, such as the RF probe itself. Quantitative density images result when the centric scan pure phase encode measurement is corrected with a relative or absolute B1 field map. The new technique is simple, reliable and robust.

Centric scan SPRITE magnetic resonance imaging: optimization of SNR, resolution, and relaxation time mapping.

Two strategies for the optimization of centric scan SPRITE (single point ramped imaging with T1 enhancement) magnetic resonance imaging techniques are presented. Point spread functions (PSF) for the centric scan SPRITE methodologies are numerically simulated, and the blurring manifested in a centric scan SPRITE image through PSF convolution is characterized. Optimal choices of imaging parameters and k-space sampling scheme are predicted to obtain maximum signal-to-noise ratio (SNR) while maintaining acceptable image resolution. The point spread function simulation predictions are verified experimentally. The acquisition of multiple FID points following each RF excitation is described and the use of the Chirp z-Transform algorithm for the scaling of field of view (FOV) of the reconstructed images is illustrated. Effective recombination of the rescaled images for SNR improvement and T*2 mapping is demonstrated.

Water content profiles with a 1D centric SPRITE acquisition.

The purpose of this work is to develop a rapid MRI method amenable to profiling with minimal or no T(1) relaxation weighting. The behavior of a signal during a centric SPRITE acquisition is analyzed. It is shown that the technique can be made immune to a broad range of T(1) changes. In a properly executed measurement, only T(2)* and proton density parameters define the image intensity. A T(2)* mapping technique can be easily applied, separating T(2)* and proton density contributions to the image. A drying soil sample with low initial water content is experimentally studied as a demonstration of the technique. A characteristic baseline artifact is easily removed from the profiles by a simple operation.

Prospective clinical study of Hydron, a synthetic dressing, in delivery of an antimicrobial drug to second-degree burns.

This clinical trial prospectively evaluates the potential beneficial effects of antimicrobial drug delivery from a synthetic dressing (Hydron-AgSD) formed on second-degree burn wounds. A paste composed of polyethylene glycol-400, poly 2-OH ethylmethacrylate, and silver sulfadiazine (AgSD 1%-3%) matured within one hour to form a solid dressing. In 27 patients, comparable areas of second-degree wounds on the same patient were selected at random for test and control (silver sulfadiazine 1% only) sites. The mean total time of the synthetic dressing application per patient was about nine days, and each dressing remained in place for nearly four days. During this interval the control sites required four dressings changes. In 17 tests for infections, the control areas were contaminated but no bacteria were detected under the synthetic dressing; in three tests, the controls had no bacteria, whereas the synthetic dressing did. Healing of burns was similar under both types of dressing. Benefits of Hydron treatment included increased patient comfort because of the reduced number of dressing changes and, in some cases, greater freedom from contaminating bacteria.

Biosynthetic skin substitute versus frozen human cadaver allograft for temporary coverage of excised burn wounds.

During the past 2 years a multicenter study was performed comparing Biobrane (Woodroof) and frozen cadaver allograft as temporary dressings on freshly excised full-thickness burns before the application of autograft. Each biologic dressing was evaluated with respect to the other on the same patient. Seventy-one patients were evaluated. The mean burn size was 35 +/- 20% with a mean full-thickness burn of 28 +/- 20%. Mean patient age was 34 +/- 21 years. Overall survival was 82%. The mean time of wound coverage was 10.2 +/- 6.7 days. There was no significant difference in the number of dressing changes, area changed, purulence, autograft take, and final results between allograft- and Biobrane-covered sites. There were no complications following use of either Biobrane or allograft. We conclude that Biobrane is as effective as frozen human cadaver allograft for the temporary coverage of freshly excised full-thickness burn wounds before autografting.

Ecthyma gangrenosum in a burned child.

The history of ecthyma gangrenosum has been presented, as well as its pathological diagnosis, prognosis and natural history. The history of forms of treatment has been outlined and the grave prognosis is emphasized. A case presentation introduces the experience at the Cincinnati Shriners Burns Institute. From a review of the literature and the experience at the Shriners Burns Institute, a suggestion for optimal treatment has been proposed. The particulars of this treatment include: early recognition, general nutritional and metabolic support, as well as high-dose aminoglycoside and semi-synthetic penicillin therapy, administered parentally and by sub-eschar clysis. Despite the grave prognosis, attention to these factors should result in optimal survival of patients with ecthyma gangrenosum.

An evaluation of Aquaphor Gauze dressing in burned children.

Aquaphor Gauze was evaluated as a dressing for skin graft donor sites, for partial thickness burn injuries and for split thickness skin grafts. Control dressings consisted of: fine mesh gauze for skin graft donor sites. silver sulphadiazine (Silvadene) on coarse mesh gauze for the partial thickness burns, and nitrofurazone cream (Furacin) on fine mesh gauze for the skin grafts. The Aquaphor Gauze was found to be inferior to the fine mesh gauze for donor site dressings. No statistically significant difference was identified between Aquaphor Gauze and controls for the treatment of partial thickness burns. As a dressing for skin grafts the Aquaphor Gauze was significantly superior to the control dressing as measured by graft take and reduced patient pain. We would recommend that Aquaphor Gauze be used as a dressing for skin grafts where the risk of infection is not excessive.

Failure of topical steroids and vitamin E to reduce postoperative scar formation following reconstructive surgery.

One hundred fifty-nine operative procedures for postburn contractures of interdigital webs (96), the axilla (46), or the neck (17) were prospectively randomized to be treated postoperatively for four months with a topical steroid (Aristocort A), topical vitamin E, or the base cream carrier for these drugs. The nature of the medication was blinded both to the patient and to the evaluator. Patients were followed for one year. Observations were made for range of motion, scar thickness, change in graft size, and ultimate cosmetic appearance. No beneficial effect of either vitamin E or topical steroid could be demonstrated. However, adverse reactions occurred in 16.4% of patients receiving active drug, compared to 5.9% treated only with base cream. Interestingly, the grafts initially contracted and subsequently grew to be a size larger (about 20%) than the original graft by one year. It is concluded that neither topical steroid nor topical vitamin E is effective in reducing scar formation after grafting procedures for reconstruction for postburn contractures.

Regeneration of full layer necrosis of the skull following high voltage electrical injury.

Scalp and skull necrosis often follow high voltage electrical injury to the head. Classically reconstruction of the scalp and skull is performed after sequestration of the necrotic bone. The relatively frequent complication of epidural infection, however, detracts from this approach. As an alternative we have attempted to induce regeneration of devitalized bone by covering it with a vascular tissue flap. A typical patient is described in this report with results which indicate that at least partial regeneration of the necrotic tissue can occur, thus one-stage management of such wounds is possible.

Surgical treatment of elbow contractures in postburn children.

One-hundred and forty-six postburn elbow contractures in children were classified into four categories--simple band, complex band (crosses shoulder and/or wrist joint), diffuse scar, and limited scar--to assess the results of surgical treatment. The best results were seen in children less than 5 years of age and in children with less than 50 percent third-degree total body surface area burns. Types of release included skin grafts, local flaps (with or without graft), and deep releases. Generally, good to excellent results were seen regardless of technique of release, and in no case was the postoperative contracture worse than the preoperative contracture. Full extension was restored in 82 percent of contractures that were less than 50 degrees and in 50 percent of contractures greater than 50 degrees. Major complications were uncommon, with 4 of 171 elbows requiring reoperation because of skin-graft or flap loss. Repeat releases were of minimal functional benefit.

Acute upper airway obstruction in the postburn period.

Upper airway obstruction in the severely burned patient is a well-known problem that is due to mucosal edema secondary to the effects of toxic substances and heat on the laryngeal and tracheal mucosa. Herein, we report a different cause of airway obstruction seen in the late postburn period during the induction of anesthesia for reconstructive procedures. This obstruction is due to the presence of severe burn-scar contractures of the neck that prevent successful endotracheal intubation. We have seen this occur 17 times in 13 patients. All of the patients were successfully treated by an emergency neck release, after which most of the patients could be intubated and the release then skin grafted. Surgeons operating on patients with scar contractures of the neck should be aware of this condition and its appropriate treatment.

Role of escharotomy and fasciotomy as a first aid measure in the early treatment of an electrically burned arm and wrist.

The saving of the hand and forearm of a patient with a deep circumferential electrical burn of the wrist and forearm following contact with 10 000 V AC demonstrates the important role played by escharotomy and fasciotomy in the early treatment of electrically injured extremities.

Early vascular grafting to prevent upper extremity necrosis after electrical burns. Commentary on indications for surgery.

Early vascular grafting is the only effective form of treatment for electrical burns of the wrist which are severe enough to impair blood flow to the hand. Failure to appreciate the significance of early changes in blood flow and to take prompt appropriate action may result in the irreversible loss of blood supply and subsequent amputation. This report analyses the problems encountered in six patients where the early signs of impaired blood flow were not appreciated and amputations were subsequently required.

Classification and management of burned thumb contractures in children.

Based on the position of the thumb metacarpal, 102 burned thumb contractures in children were classified into four categories: adduction, opposition, extension and flexion. The contractures were further classified as mild, moderate or severe, based on the amount of motion lost. All thumbs were surgically released. Coverage was obtained with local flaps or Z-plasties, skin grafts or a combination of local flaps and skin grafts. Factors influencing the results were as follows: Classification category: Extension contractures generally did poorly, whereas flexion contractures did well. Severity of contracture: The more severe the contracture, the worse the final results. Complexity of contracture: Contractures with a subluxated or dislocated joint did not do as well as those with undisturbed bony alignment. Type of surgical release: There was a trend towards better results when skin grafts (as opposed to local flaps) were used, especially in the treatment of moderate and severe contractures.

Candida parapsilosis fungemia in burn patients: report of three cases.

Three patients with Candida parapsilosis septicemia, secondary to large burns, are reported. All patients sustained large burns with inhalation injuries and were treated with various topical antibiotics. All had sepsis with various bacterial organisms and had received treatment with systemic antibiotics prior to the development of the Candida episode. Once a positive blood culture for Candida parapsilosis was obtained, treatment was carried out with amphotericin-B. Sensitivity data indicated that this was the appropriate systemic agent. All patients recovered uneventfully after a 10-day course of amphotericin-B therapy.