PubMed Health⌕ Search

Biomedical subjects

J A Jensen

Publications and source records attributed to J A Jensen.

At least 19 recordsLinked to original sources
PubMed1992

Factors affecting mammographic visualization of the breast after augmentation mammaplasty.

OBJECTIVE: To measure the effect of various parameters on mammographic visualization of the breast after augmentation mammaplasty. DESIGN: Preoperative and postoperative mammography was performed in patients undergoing augmentation mammaplasty. The area of breast tissue visualized on each film was measured. Changes in the area visualized were correlated with a variety of different parameters. SETTING: The Breast Center, Van Nuys, Calif, a free-standing multidisciplinary breast diagnostic and treatment facility. PATIENTS: The 68 women (126 breasts) represent a consecutive sample of patients undergoing augmentation mammaplasty for whom preoperative and postoperative mammograms were available. MAIN OUTCOME MEASURES: Area visualized was correlated with degree of capsular contracture, implant position, type of mammography, preoperative breast size, implant size, and implant type. RESULTS: The major factor affecting mammography is capsular contracture. Little or no capsular contracture results in a 30% reduction in the area visualized; moderate or severe contracture results in a 50% reduction. Other important factors include implant position (improved visualization with implant beneath pectoral muscle) and type of mammography performed (slightly more tissue seen with displacement technique). Very small preoperative breast size yields increased visualization. Implant size and type have little or no effect. CONCLUSIONS: In most women with breast implants, there is a decrease in measurable breast tissue on the postaugmentation mammogram. Capsular contracture and implant position exert a profound effect; type of mammography performed and preoperative breast size are also significant.

Adult↗
PubMed1992

An improved technique for creation of the inframammary fold in silicone implant breast reconstruction.

A "lipo-fascial" flap is described for creation of the inframammary fold in patients undergoing breast reconstruction with silicone implants. We have employed this technique in 13 patients. The fold has been enhanced in all cases, and we have not encountered any significant complications. This technique is a useful adjunct to breast reconstruction with a silicone implant, and we recommend that it be considered in appropriate patients.

Female↗
PubMed1992

Deconvolution of ultrasound images.

Based on physical models, it is indicated that the received pressure field in ultrasound B-mode images can be described by a convolution between a tissue reflection signal and the emitted pressure field. This result is used in a description of current image formation and in formulating a new processing scheme. The suggested estimator can take into account the dispersive attenuation, the temporal and spatial variation of the pulse, and the change in reflection strength and signal-to-noise ratio. Details of the algorithm and the estimation of parameters to be used are given. The performance is indicated by two examples. One is for a synthetic signal and the other is for data measured from a tissue mimicking phantom. The last example shows a finer speckle pattern, giving an increased resolution.

Algorithms↗
PubMed1991

Cigarette smoking decreases tissue oxygen.

Subcutaneous wound-tissue oxygen (PsqO2) tension in eight volunteers fell rapidly and significantly in response to smoking, and remained low for 30 to 50 minutes. Sham "smoking" had no effect. These data suggest that a typical "pack-per-day" smoker experiences tissue hypoxia during a significant portion of each day. The degree of hypoxia found in these subjects has been associated with poor wound healing in animal and human studies. The onset and duration of tissue hypoxia paralleled the well-established plasma pharmacokinetics of nicotine. This suggests that peripheral vasoconstriction, induced by the adrenergic effects of nicotine, may contribute to the observed decrease in PsqO2.

Connective Tissue↗
PubMed1991

Assessment of hybrid speckle reduction algorithms.

A consequence of employing coherent detection methods in medical ultrasound imaging systems is the occurrence of interference effects in the received echo field, which produce the speckle artefact. Speckle can severely degrade the information content of the image, and its efficient removal from ultrasound pulse-echo images is the focus of a number of research projects. Traditionally, the approach towards speckle reduction in pulse-echo images has been based on two classes of technique, either employing some form of spatial/frequency compounding or a data (image) filter. Both approaches have inherent shortcomings, and two alternative techniques are suggested here: 'local frequency diversity' and 'frequency differencing'. These algorithms deterministically identify where speckle occurs, and correct for speckle only within short, localized, corrupted segments of the A-line. This provides the potential for real-time implementation. Simulated and clinical in vivo images have been obtained, and the capabilities of the alternative speckle reduction algorithms are assessed against the more conventional approaches.

Algorithms↗
PubMed1991

Tissue oxygenation, anemia, and perfusion in relation to wound healing in surgical patients.

Oxygen tension and collagen deposition were measured in standardized, subcutaneous wounds in 33 postoperative surgical patients. Pertinent clinical and wound parameters were analyzed by Pearson's correlation test and sequential linear regression analysis. Collagen deposition was directly and significantly proportional to wound oxygen tension and measures of perfusion. There were no significant correlations with hematocrit, estimated blood loss, length of operation, smoking, age, weight, sex, or urine output. This study in humans confirms animal experiments showing that collagen deposition and tensile strength in wounds are limited by perfusion and tissue oxygen tension. It appears unnecessary to maintain hemoglobin at normal levels to support repair, provided that peripheral perfusion can be maintained at a high level in compensation for anemia. These circumstances reflect the fact that although oxygen is essential to many aspects of healing, and must be delivered at adequate partial pressures, reparative tissue consumes relatively little of it.

Anemia↗
PubMed1991

Comparative experience with smooth and polyurethane breast implants using the Kaplan-Meier method of survival analysis.

Smooth-walled silicone implants have been widely used in breast surgery. Capsular contracture, causing undesirable firmness and spherical deformity, has been a common problem. Recent studies suggest that polyurethane-covered breast implants are associated with a lower incidence of capsular contracture. The statistical methodology employed in some of these studies, however, may be subject to criticism. Between July of 1984 and June of 1990 (72 months), 427 polyurethane breast implants were used in 279 patients and 439 smooth prostheses were used in 250 patients for a variety of aesthetic and reconstructive procedures. The occurrence of capsular contracture was carefully monitored and then analyzed using the Kaplan-Meier method of survival analysis. This method is particularly well suited to analysis of these types of clinical data because it allows for the fact that contractures occur at varying intervals after surgery and that follow-up of patients is incomplete. The probability of capsular contracture with smooth-walled prostheses was found to be significantly greater than with polyurethane-covered implants in each group of patients studied (p less than 0.05). Other complications occurred at a similar rate regardless of prosthesis type. This study supports the belief that polyurethane breast implants have a lower contracture rate; furthermore, it introduces the Kaplan-Meier method for analyzing the outcome of alternative plastic surgical therapies.

Breast↗
PubMed1991

A model for the propagation and scattering of ultrasound in tissue.

An inhomogeneous wave equation is derived describing propagation and scattering of ultrasound in an inhomogeneous medium. The scattering term is a function of density and propagation velocity perturbations. The integral solution to the wave equation is combined with a general description of the field from typical transducers used in clinical ultrasound to yield a model for the received pulse-echo pressure field. Analytic expressions are found in the literature for a number of transducers, and any transducer excitation can be incorporated into the model. An example is given for a concave, nonapodized transducer in which the predicted pressure field is compared to a measured field.

Acoustics↗
PubMed1991

The wound healing curve as a practical teaching device.

Fundamental concepts of clinical wound healing are commonly misunderstood. A hypothetical curve that describes the relationship between wound perfusion and risk of infection is constructed as a teaching device. Although many factors influence this curve, the most important are the presence of bacteria, dead space, necrotic tissue and motion. Subjecting the curve to clinical illustrations enhances its value as a tool for medical education.

Audiovisual Aids↗
PubMed1991

Tissue oxygen tension and other indicators of blood loss or organ perfusion during graded hemorrhage.

Currently employed clinical indicators of perfusion provide inadequate warning of developing hazards caused by marginal perfusion in certain vital organs or "peripheral" tissues that are pivotal to postsurgical wound healing. In this study, mean arterial blood pressure, cardiac output, and transcutaneous and subcutaneous oxygen tensions (PtcO2 and PsqO2) were investigated during serial hemorrhage, as indicators of the degree of both hypovolemia and perfusion to specific tissues. Blood was removed in stages (10%, 20%, 30%, 40%, 55%, 60%, and 65% of original volume) from anesthetized dogs. Injections of variously radiolabeled microspheres allowed assessment of blood flow at each stage of hemorrhage in bone, brain, colon, heart, kidney, liver, muscle, pancreas, skin, small intestine, spleen, stomach, and subcutaneous tissue. PsqO2 was correlated more highly with blood volume lost than was PtcO2. Furthermore PsqO2 was more sensitive to blood loss than was either cardiac output or PtcO2 and, also during the early loss (0% to 40%), was more sensitive than mean arterial pressure. Some organs (e.g., pancreas) appeared to lose considerable blood flow with only small loss of blood volume, but their blood flow then stabilized at a low level despite further hemorrhage. Other organs, notably the kidney, appeared to be relatively unaffected by substantial loss of blood volume (20% to 40%), after which, however, their blood flow quite abruptly became sensitive to further hypovolemia. This explains why blood flow-related performance of the kidney (e.g., urine volume) may not adequately predict a developing hazard or peripheral perfusion. Some indicators were found to be better indexes of blood flow in some organs than in others (e.g., cardiac output and PsqO2 correlated more closely with skin, spleen, and intestinal flows [and one another] than with vital organ flows).

Animals↗
PubMed1987

Assessment of perfusion in postoperative patients using tissue oxygen measurements.

Subcutaneous tissue oxygen tension was measured as an index of perfusion in 44 postoperative patients. Hypoperfusion was defined as suboptimal tissue oxygen tension unresponsive to increased inspired oxygen but becoming responsive after increased fluid infusion. Twelve of thirty patients who underwent major abdominal and flank operations were found to be suboptimally perfused by this definition despite adequate fluid maintenance according to standard clinical criteria including urine output. Apparently, a significant number of postoperative abdominal surgery patients are not optimally perfused, and this state is not recognized by the present clinical criteria. Tissue oximetry may be a useful objective method of assessing tissue perfusion.

Blood Gas Analysis↗
PubMed1987

The influence of a brief preoperative illness on postoperative healing.

In a study of wound healing at high altitude, subcutaneously implanted PTFE tubes were used to stimulate and measure accumulation of wound hydroxyproline (an index of collagen) in 26 patients who had appendectomy and in 38 patients who had cholecystectomy. Patient age, length of surgery, and postoperative recovery seemed to predict better healing in patients who had appendectomy, but there was a difference in the preoperative illness of the two groups: acute cholecystitis was treated medically and cholecystectomy performed after resolution of the acute phase of illness, whereas patients who had appendectomy were taken to surgery as soon as a diagnosis was made. It was observed that patients who had appendectomy accumulated 20% less hydroxyproline than patients who had cholecystectomy (p less than 0.02), and that the depression of hydroxyproline accumulation was significantly related to length of preoperative illness (p = 0.008). This decrease in wound hydroxyproline accumulation is attributed to the acute preoperative illness. Conceptually, this is a unique situation since the brief illness did not produce lasting debility, and the source of illness, the inflamed appendix, was not present during healing. This indicates that even a brief preoperative illness has a more prolonged influence on postoperative healing than usually anticipated.

Adult↗
PubMed1987

Cardiac cryolesions as an experimental model of myocardial wound healing.

The standard coronary ligation model for experimental myocardial infarction results in variable areas and patterns of necrosis; therefore, the healing of such infarctions is also variable. The authors developed an experimental myocardial injury model using simple cryoinjury, which allows standardization of the size, depth, and location of the wound. Thirty-eight left ventricular cryolesions were created in 19 dogs, which were then killed from 3 to 35 days after injury. A consistent decrease in the depth of scar (p less than 0.005) and accumulation of collagen (p less than 0.0001) over time characterized this healing myocardial wound. Histologic examination revealed that the cellular pattern of healing myocardial cryolesions is similar to that of a healing myocardial infarction but with less variability. The authors advocate the use of cardiac cryolesions as a model of experimental myocardial wound healing.

Animals↗
PubMed1987

Subcutaneous tissue oxygen tension falls during hemodialysis.

The effect of hemodialysis on subcutaneous tissue oxygen tension was studied in nine patients. During hemodialysis, blood pressure decreased, pulse increased, and all patients lost weight. Arterial blood oxygen tension fell insignificantly, from 79 to 73 mm Hg. Subcutaneous oxygen tension decreased from 52 to 28 mm Hg (p less than 0.001). Because adequate tissue oxygenation is necessary for wound healing and resistance to infection, we postulate that hemodialysis may contribute to the wound morbidity frequently seen in dialyzed patients.

Adult↗
PubMed1987

Umbilical fistulas in Crohn's disease.

Four patients with enteroumbilical fistulas complicating Crohn's disease are described herein. We recommend that, in such patients, the affected small intestine be excised and the umbilical sinus debrided.

Adolescent↗
PubMed1986

The second component (C2n) of the nurse shark complement system: purification, physico-chemical characterization and functional comparison with guinea pig C4.

C2n was isolated and purified from nurse shark serum by initial cold low ionic strength precipitation, followed by chromatography on DE-52 cellulose, hydroxylapatite and filtration on BioGel A-0.5. The molecular weight, determined by gel filtration and PAGE, was 170K daltons and 180K daltons respectively. The molecule retained 100% activity after heating for 2 hours at 56 degrees C. Optimal temperature and time for C2n fixation was 30 degrees C and 20 minutes respectively. Experiments were carried out to determine whether C2n and C4gp could replace each other in the lysis of cellular intermediate EAnC1n (with which both components are compatible) when the remaining homologous and heterologous complement components were supplied. Results showed that lysis only occurred with the homologous components indicating an incompatibility between C2n and C2gp and C4gp and C3n. Results from interference studies indicated that C4gp and C2n interfere with each others binding and/or interaction with EAnC1n.

Animals↗
PubMed1986

Effect of lactate, pyruvate, and pH on secretion of angiogenesis and mitogenesis factors by macrophages.

Macrophages secrete substances that stimulate angiogenesis and mitogenesis at wound sites. To test whether metabolic characteristics of the wound such as high lactate concentration and low pH may regulate the expression of these substances, macrophages were cultured in lactalbumin hydrolysate and then in increasing concentrations of lactate, pyruvate, and hydrogen ions, and cell-free supernatants were collected. Cultures incubated in concentrations of lactate approximating those observed in wounds secreted an angiogenesis factor or factors, but cultures incubated in equivalent concentrations of pyruvate or at pH 6.2 did not. These observations seem to be specific to macrophages because capillary endothelial cells and fibroblasts failed to secrete an angiogenesis factor when cultured under hypoxic conditions or in high concentrations of lactate. None of these conditions changed the expression of macrophage mitogens.

Angiogenesis Inducing Agents↗