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Molecular dynamics and transmission electron microscopy are employed to study the formation and evolution of interstitial dislocation loops due to nearby growing helium bubbles. The study reveals a novel mechanism that suppresses further formation of loops. Mass transport of self-interstitial atoms between the bubbles is observed, followed by the loop formation, resulting in a loop-bubble complex in which the Burgers vector may rotate between <100> and 1/2 <111>. Such a complex can absorb free loops, effectively influencing the evolution of loop number density. These results provide a new understanding of loop-bubble complex formation and saturation of the loop density under continuous helium implantation in materials. [ABSTRACT FROM AUTHOR]

Tailored metal alloy thin film-oxide interfaces generated using molecular beam epitaxy (MBE) deposition of alloy thin films on a single crystalline oxide substrate can be used for detailed studies of irradiation damage response on the interface structure. However, the presence of nanoscale phase separation in the MBE grown alloy thin films can impact the metal-oxide interface structure. Due to nanoscale domain size of such phase separation, it is very challenging to characterize by conventional techniques. Therefore, laser assisted atom probe tomography (APT) was utilized to study the phase separation in epitaxial Cr0.61Mo0.39, Cr0.77Mo0.23, and Cr0.32V0.68 alloy thin films grown by MBE on MgO(001) single crystal substrates. Statistical analysis, namely frequency distribution analysis and Pearson coefficient analysis of experimental data was compared with similar analyses conducted on simulated APT datasets with known extent of phase separation. Thus, the presence of phase separation in Cr-Mo films, even when phase separation was not clearly observed by x-ray diffraction, and the absence of phase separation in the Cr-V film were confirmed. [ABSTRACT FROM AUTHOR]

Ab initio calculations based on density functional theory have been performed to determine the properties of self-interstitial atoms (SIAs), vacancies, and single H and He atoms in hcp-Er. The results show that the most stable configuration for a SIA is a basal octahedral configuration, while the octahedral (O), basal split, and crowdion (C) interstitial configurations are less stable, followed by the split <0001> dumbbell and tetrahedral configurations. For both H and He defects, the formation energy of an interstitial atom is less than that of a substitutional atom in hcp-Er. Furthermore, the tetrahedral interstitial position is more stable than an octahedral position for both He and H interstitials. The hybridization of the He and H defects with Er atoms has been used to explain the relative stabilities of these defects in hcp-Er. [ABSTRACT FROM AUTHOR]

The effects of using different interatomic potentials in molecular dynamics (MD) simulations of the formation of He-vacancy clusters within displacement cascades in α-Fe are investigated using two sets of potentials. Simulations of cascades produced by primary knock-on atoms of energy Ep=1–20 keV were performed in α-Fe containing a concentration of substitutional He atoms varying from 1 to 5 at. % at an irradiation temperature of 100 K. Although the effects of interatomic potentials on the nucleation of He-vacancy clusters induced by cascades are relatively small, the number and size of He-vacancy clusters produced are significantly different for the different potentials employed in this study. Thus, these differences may influence the microstructural evolution predicted in damage accumulation models that use the results from MD cascade simulations as input. The observed differences in postcascade configurations can be attributed mainly to the differences in the Fe–Fe and Fe–He potentials. [ABSTRACT FROM AUTHOR]

The interactions of He and vacancy defects with 〈111〉 screw dislocations in alpha-Fe were modeled using molecular statics, molecular dynamics and transition state energy determinations. The formation energies and binding energies of interstitial He atoms, vacancies and He-vacancy clusters near and within dislocations in alpha-Fe were determined at various locations relative to the dislocation core. Using the dimer transition state method, the migration energies and trajectories of the He and vacancy defects near and within the screw dislocation were also determined. Both interstitial He atoms and single vacancies are attracted to and trapped in the dislocation core region, and they both migrate along the dislocation line with a migration energy of about 0.4 eV, which is about half the migration energy of vacancies in the perfect crystal and about five times the migration energy for interstitial He in the perfect crystal. Divacancies and He-divacancy complexes have migration properties within the dislocation core that are similar to those in the perfect crystal, although the stability of these defects within the dislocation may be somewhat less than in the perfect crystal. [ABSTRACT FROM AUTHOR]

Atomic recoil events on free surfaces orthogonal to two different anti-phase boundaries (APBs) and two grain boundaries (GBs) in Ni 3 Al are simulated using molecular dynamics methods. The threshold energy for sputtering, E sp , and adatom creation, E ad , are determined as a function of recoil direction. The study is relevant to FEG STEM (a scanning transmission electron microscope fitted with a field emission gun) experiments on preferential Al sputtering and/or enhancement of the Ni–Al ratio near boundaries. Surfaces intersected by {110} and {111} APBs have minimum E sp of 6.5&ThickSpace;eV for an Al atom on the Ni–Al mixed (M) surface, which is close to the value of 6.0&ThickSpace;eV for a perfect M surface. High values of E sp of an Al atom generally occur at a large angle to the surface normal and depend strongly on the detailed atomic configuration of the surface. The mean E sp , averaged over all recoil directions, reveals that APBs have a small effect on the threshold sputtering. However, the results for E ad imply that an electron beam could create more Al adatoms on surfaces intersected by APBs than on those without. The equilibrium, minimum energy structures for a (001) surface intersected by either Σ5[001](210) or Σ25[001](340) symmetric tilt grain boundaries are computed. E sp for surface Al atoms near these GBs increases monotonically with increasing recoil angle to the surface normal, with a minimum value, which is only about 1&ThickSpace;eV different from that obtained for a perfect surface. Temperature up to 300&ThickSpace;K has no effect on this result. It is concluded that the experimental observations of preferential sputtering are due to effects beyond those for E sp studied here. Possible reasons for this are discussed. [ABSTRACT FROM AUTHOR]

During sliding, the grain-boundary (GB) energy depends on the atomic structures produced during relative translation of the two grains. The variation in the GB energy within the two-dimensional boundary unit cell (BUC) constitutes the GB-γ surface. Maxima in the slope of the γ surface determines the sliding resistance, that is the stress required to move the system over the lowest saddle points along a particular path within the BUC. In this paper we present the results of an atomistic study of the γ surfaces for two types of boundaries in a fcc metal. One of the boundaries is a Σ = 11, <110>{131} which is a low-energy boundary and has a simple γ surface with a single stable configuration located at the corners and centre of the BUC. The resistance to sliding was determined by chain-of-states methods along four shear vectors connecting equivalent states within the BUC and is found to be very high in all cases. The asymmetric, Σ = 11, <110>{252}-{414} GB, has a higher GB energy and its γ surface is much more complex, with distinctly different structures appearing at various locations in the BUC. At certain locations, more than one structure is found for the asymmetric GB. Although complex, a chain-of-states calculation along one path across the BUC suggests that the shear strength of this GB is also quite high. Extrinsic GB dislocations are found to lower the resistance to shear considerably and, therefore, to perform the same role in shear of GBs as do glide dislocations in slip of the lattice. The existence of multiple configurations has significant implications for the interaction of lattice dislocations with GBs, the core structure of GB dislocations, the temperature dependence of GB properties, and the GB sliding resistance, which we discuss. [ABSTRACT FROM AUTHOR]

A computer simulation was performed to examine the role of extrinsic grain, boundary (GB) defects in the sliding of the Sigma11 101 {131} symmetric tilt boundary in aluminium by means of an embedded-atom method potential. The sliding resistance of the equilibrium GB was determined from a computation of the dependence of the boundary energy on in-plane translation of one grain relative to the other. Low-energy faulted structures were found that correspond to unstable intermediate states and the presence of stable partial GB dislocations. Extrinsic dislocations and disconnections were found to lower significantly the sliding stress relative to the equilibrium GB. [ABSTRACT FROM AUTHOR]

A computer simulation was performed to investigate the structure and properties of extrinsic grain-boundary (GB) defects in the Sigma11, <101>{131} symmetric tilt boundary. An embedded-atom method potential was employed to represent aluminium. Standard molecular dynamics relaxation techniques were used to compute low-temperature (about 0 K) equilibrium structures. Extrinsic GB dislocations were introduced into the models by application of the exact anisotropic elastic displacement field for a bicrystal interface. Some dislocations were accompanied by geometrically necessary steps (in which case the pair form a disconnection) to avoid formation of GB faults. The structure and properties of the equilibrium GB were compared with GBs containing steps, dislocations and disconnections. A broad range of GB defects was studied in order to characterize their potential effect on GB sliding resistance. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) methods are utilized to study the formation of vacancy clusters created by displacement cascades in α-Fe containing different concentrations of substitutional He atoms. Primary knock-on atom energies, Ep, from 500 eV to 20 keV are considered at a temperature of 100 K, and the results are compared with those performed in pure α-Fe. There are distinct differences in the number and size of vacancy clusters within displacement cascades with and without substitutional helium atoms. It is found that many large vacancy clusters can be formed within cascade cores in α-Fe with helium atoms, in contrast to a few small vacancy clusters observed in pure α-Fe. The number and size of helium/vacancy clusters generally increase with increasing helium concentration and PKA energy. One of the striking results is that the number of self-interstitial atoms (SIAs) and the size of interstitial clusters are much smaller than those in pure α-Fe. [ABSTRACT FROM AUTHOR]

Complex states of nanoscale interstitial dislocation loop can be described by its habit plane and Burgers vector. Using atomistic simulations, we provide direct evidences on the change of the habit plane of a 1/2〈1 1 1〉 loop from {1 1 1} to {1 1 0} and {2 1 1}, in agreement with TEM observations. A new {1 0 0} habit plane of this loop is also predicted by simulations. The non-conservation of the Burgers vector is approved theoretically for: (1) dislocation reactions between loops with different Burgers vectors and (2) the transition between 〈1 0 0〉 loops and 1/2〈1 1 1〉 loops. The rotation from a 1/2〈1 1 1〉 to a 〈1 0 0〉 loop has also been explored, which occurs at 570 K for time on the order of 10 s. The dislocation-precipitate phase duality and change of habit plane are then proposed as new features for nano-scale dislocation loops.

A self-adaptive accelerated molecular dynamics method is developed to model infrequent atomic-scale events, especially those events that occur on a rugged free-energy surface. Key in the new development is the use of the total displacement of the system at a given temperature to construct a boost-potential, which is slowly increased to accelerate the dynamics. The temperature is slowly increased to accelerate the dynamics. By allowing the system to evolve from one steady-state configuration to another by overcoming the transition state, this self-evolving approach makes it possible to explore the coupled motion of species that migrate on vastly different time scales. The migrations of single vacancy (V) and small He-V clusters, and the growth of nano-sized He-V clusters in Fe for times in the order of seconds are studied by this new method. An interstitial-assisted mechanism is first explored for the migration of a helium-rich He-V cluster, while a new two-component Ostwald ripening mechanism is suggested for He-V cluster growth.

To develop a model system containing regularly spaced misfit dislocations for studies of the radiation resistance of nanoscale defects, epitaxial thin films of Cr, Mo, and Cr(x)Mo(1-x) alloys were deposited on MgO(001) by molecular beam epitaxy. Film compositions were chosen to vary the lattice mismatch with MgO. The film structure was investigated by x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) and scanning transmission electron microscopy (STEM). Epitaxial films with reasonably high crystalline quality and abrupt interfaces were achieved at a relatively low deposition temperature, as confirmed by STEM. However, it was found by XRD and RBS in the channeling geometry that increasing the Mo content of the CrMo alloy films degraded the crystalline quality, despite the improved lattice match with MgO. XRD rocking curve data indicated that regions of different crystalline order may be present within the films with higher Mo content. This is tentatively ascribed to spinodal decomposition into Cr-rich and Mo-rich regions, as predicted by the Cr(x)Mo(1-x) phase diagram.

Background: Appendectomy can be performed using either a laparoscopic or an open technique. This study compares the outcome of patients treated for acute appendicitis by open appendectomy with the outcome of those undergoing laparoscopic appendectomy., Methods: Patients undergoing appendectomy at The Mount Sinai Hospital between 1994 and 1998 were studied. Outcome of patients having open appendectomy was compared with that of patients having laparoscopic appendectomy., Results: Seven hundred fifty-eight patients underwent appendectomy for acute appendicitis during the 5-year study period. Two hundred seventy-one (36%) had open appendectomy and 487 (64%) had laparoscopic appendectomy. Patients subsequently found to have a normal appendix had the highest rate of laparoscopic appendectomy, whereas those with gangrenous appendicitis were most likely to have open appendectomy (P <0.05). There was a significant decline in the postoperative length of stay for open cases during the length of the study. In the final year, the difference in length of stay between open and laparoscopic appendectomy was only 1 day. Patients with gangrenous appendicitis had a significantly longer length of stay than did patients with a normal appendix or suppurative appendicitis. The hospital cost of laparoscopic appendectomy was greater than that for open appendectomy but the extra expenditure in the operating room was offset by the longer length of stay of the patients having open surgery., Conclusions: Differences in outcome between open and laparoscopic appendectomy are minor. In this study, more difficult cases with gangrenous appendicitis were more likely to require open appendectomy whereas milder forms of appendicitis, especially in women, were more likely to be treated by laparoscopy. Savings from the slightly shorter hospital stay after laparoscopic appendectomy are offset by the higher surgical cost of the laparoscopic equipment.

Fifty-two patients with ulcerative colitis and colorectal cancer undergoing colectomy at the Mount Sinai Hospital between 1973 and 1988 were studied retrospectively to determine the correlation of age, sex, duration of colitis, tumor location, number of cancers, tumor differentiation, colloid content, presence of signet ring cells, Dukes' classification, and DNA ploidy with survival. The mean age was 45 years, with a mean duration of colitis of 21 years. Five patients (10%) had Dukes' A lesions, 17 (33%) had Dukes' B lesions, 17 (33%) had Dukes' C lesions, and 13 (25%) had distant metastases. Thirty patients (58%) had well- or moderately differentiated tumors, whereas tumors were poorly differentiated in 22 (42%). Twenty-eight patients (54%) had colloid tumors, and, in 14 (27%), signet ring cells were present. Thirty-one patients (60%) had nondiploid tumors. Actuarial analysis revealed that the 5-year survival rate was significantly worse for patients with nondiploid tumors (76% versus 32%). When stratified by stage, only patients with Dukes' C lesions showed a significant difference in survival for diploid versus nondiploid tumors. Multivariate analysis showed that the Dukes' classification was the best prognostic indicator, followed by tumor differentiation and DNA ploidy. Tumor location, colloid content, number of cancers, duration of disease, age, and sex did not correlate with the prognosis.

Sixteen patients with polyposis coli and cancer were studied retrospectively to determine the incidence of DNA ploidy abnormalities in the tumors and synchronous polyps. Six patients (37 percent) had nondiploid tumors. Nondiploid tumors were more likely to be advanced and had a significantly worse prognosis (17 percent vs. 76 percent 5-year survival; P less than 0.01). Only 4 of 20 polyps studied were nondiploid. There was no association between tumor and polyp ploidy. All nondiploid polyps were found in patients with synchronous diploid cancers. Patients with nondiploid polyps were more likely to be older and have more advanced tumors than those with diploid polyps. DNA ploidy abnormalities seem to occur with the same frequency in polyposis coli as in the nonpolyposis population, and tumor ploidy correlates with prognosis.

A contemporary dilemma in nursing is the order to care in a society that refuses to value caring. The authors analyze the historical creation of this dilemma and its consequences for nursing. In addition, they explore the meaning of the concept of caring from a nursing perspective, along with the impact of technology on patients, providers, and caring. Finally, a framework and strategies for the promotion of caring within the discipline of nursing are presented.

Several studies have shown that the presence of DNA content abnormalities, measured by flow cytometry, may correlate with a poor prognosis in a variety of cancers. The predictive value of DNA content in patients with small rectal cancers has not been well determined. Thirty-nine patients with primary rectal adenocarcinoma smaller than 3 cm were studied in a comparison of DNA content with established prognostic variables. The following covariates were evaluated for their prognostic value: sex, age, tumor size, location, distal margin, Dukes' classification, tumor differentiation, and DNA content. DNA content was assessed by flow cytometric analysis, and each tumor was categorized as diploid or nondiploid. Of the parameters studied, Dukes' classification and tumor DNA content were found to be independent prognostic indicators. Determination of DNA content seems to provide additional useful prognostic information in patients with small rectal tumors.

A retrospective review of 24 patients with gallstone ileus from our institutions during the period from 1947 through 1981 has been presented. The study was undertaken in an attempt to refine the diagnosis and treatment of this rare entity. The patients ranged in age from 58 to 84 years, and 19 patients were women. The correct preoperative diagnosis was made in 74 percent of the patients using various combinations of clinical history, plain film roentgenograms, and barium contrast upper gastrointestinal series. After an average preoperative hospital stay of 4.5 days, 23 patients required operation. Wound infection developed in nine patients and resulted in wound dehiscence in two. There were four deaths in the patients over 73 years of age (p less than 0.01). Age was the only factor found to correlate with mortality.

Echogenicity can be created by the admixture of any acoustically dissimilar substances. Experiments performed in vitro using mineral oil and water and in vivo examining 24 pathologically proven echogenic abnormalities show that echogenicity cannot be ascribed to a specific tissue, but rather is a property of all substances. In addition, when dissimilar histologic and pathologic substances have similar echo appearances and are adjacent, they become indistinguishable. This loss of structural definition can be termed the sonographic "masking sign," comparable in masking qualities to the established radiographic "silhouette sign." When this phenomenon occurs, an abnormality can be detected only through displacement of an organ or distortion of its internal anatomy. A thorough understanding of echogenicity and the sonographic masking sign will allow a more accurate evaluation of masses and infiltrating processes.

The prolate ellipse formula has been shown to be inaccurate and inconsistent in the calculation of total uterine volume. The stepped area-to-volume technique has proven to be both accurate and consistent and provides a value equal to the true uterine volume. When these true volumes were plotted on previously published graphs of total uterine volume derived from the prolate ellipse formula, the graphs were found to be inaccurate. New graphs based on normal values have been constructed, comparing total uterine volume with both biparietal diameter and average gestational age. When 26 abnormal values were plotted on the total uterine volume versus biparietal diameter graph, almost all fell outside the 90 per cent confidence limits. Seven of the abnormal value were from fetuses found to have growth retardation. Six of these cases, including two not appreciated either clinically or ultrasonographically, were detected by this method. The stepped area-to-volume technique should allow reconsideration of the total uterine volume concept and aid in the detection of the subtle changes in uterine size.

All patients with gallstone ileus admitted to our institutions between 1938 and 1982 were retrospectively analyzed by grouping the patients into 10-year periods. Forty-five patients were studied, of whom 39 required operation. When hospital statistics for admissions, length of stay, and mortality rates from the Mount Sinai Hospital were compared to the gallstone ileus data, it was found that there has been no significant change in the admission rate for these patients. The mortality rate and length of stay of gallstone ileus patients has also remained constant over the past 25 years despite the general hospital decrease in both of these numbers. There has been no change in the complication rate, duration of symptoms prior to admission, or the preoperative diagnostic rate of gallstone ileus during the duration of this study.

In an attempt to identify factors contributing to survival of free fall and impact, we evaluated the records of four patients who survived a jump from the Brooklyn Bridge into the East River in New York Harbor between 1977 and 1985. All four patients were male and ranged in age from 22 to 67 years. They had free falls of between 41.0 and 48.8 meters. All of the patients were brought to the hospital within 24 minutes of entering the water. Three of the four had emergency surgical treatment and the fourth patient had only minor injuries. All four patients survived the suicide attempts. The length of the hospital stay ranged from two to 26 days.

Inaccuracies in total intrauterine volumes calculated using the prolate ellipse equation have been reported. No previous study has examined all the sources of error. In this study, a comprehensive approach was undertaken. Measurements were obtained from scans of the pregnant uterus in the prone position using an automated water-path scanner (Octoson) and in the supine position using standard static B-mode scanners. Several conclusions could be drawn: 1) From the Octoson prone scans, uterine volumes obtained using the prolate ellipse formula were markedly different from the true uterine volumes obtained by the summation of stepped areas. This showed that the prolate ellipse formula was inaccurate. 2) From the static supine scans, many observer inconsistencies were found in uterine volumes obtained from the prolate ellipse formula. This made the prolate ellipse formula unreliable. 3) Previously published graphs calculated from the prolate ellipse equation, comparing fetal age with total intrauterine volume, were found to vary accuracy, presumably as a result of 1 and 2. A more accurate approach is proposed. Using the outer uterine wall as the boundary, the stepped area-to-volume values of transverse scans taken at 3-cm intervals were found to closely approximate true volumes, with an average error of only 3.5 per cent. Since these measurements encompass the intrauterine contents and the myometrium, it is suggested that the term "total uterine volume" be used instead of "total intrauterine volume."

A technique for performing mucosal proctectomy in patients with ulcerative colitis using ultrasonic fragmentation is described. Twenty-eight patients undergoing colectomy and ileoanal anastomosis were studied. Removal of the mucosal layer of the distal rectum was performed using a titanium probe vibrating at 23 kHZ with an amplitude of 300 microns. This method produces complete mucosal destruction and the resulting debris and irrigating fluid is removed through the hollow central portion of the probe. Healing of the ileoanal anastomosis does not appear to be adversely affected by the use of this technique. Because ultrasonic fragmentation is not dependent on the integrity of the submucosal plane, it may be advantageous in those cases in which severe inflammation and submucosal scarring make manual dissection of the rectal mucosa difficult to perform.

Several studies have shown that the presence of DNA ploidy abnormalities, measured by flow cytometry, may correlate with a poor prognosis in a variety of cancers. The predictive value of these DNA abnormalities in young patients with colorectal cancer has not been well studied. Fifty patients aged 40 years and younger with colorectal adenocarcinoma were studied to determine the correlation of tumor DNA abnormalities with survival. DNA content was determined by flow cytometric analysis and each tumor was categorized as diploid or nondiploid. Of the parameters studied, Dukes' classification and tumor DNA ploidy were found to be significant prognostic indicators. Determination of DNA content seems to provide additional useful prognostic information in young patients with colorectal cancer.

The surgical treatment of patients with familial polyposis coli and ulcerative colitis often requires removal of the rectum. Abdominoperineal resection, however, has a substantial morbidity. Ultrasonic fragmentation allows complete removal of the distal rectal mucosa with preservation of the surrounding muscularis. Ten adult mongrel dogs underwent ultrasonic mucosal proctectomy with resection of the proximal rectum and end colostomy. Two months later, the animals were sacrificed and the remaining rectum was removed and examined. The rectal remnant had shrunk and there was fibrous healing of the muscular wall with obliteration of the lumen. There was no mucosal regeneration. Ultrasonic mucosal proctectomy appears to achieve the same results as abdominoperineal resection of the rectum without the morbidity of the perineal dissection. This procedure may be useful in those patients where removal of the rectum is necessary for benign disease and endorectal pull-through is not indicated.

Mesenteric and retroperitoneal cysts are rare intra-abdominal tumors. Ten new patients are presented as well as 152 other cases reported in the English literature. These 162 cases were then analyzed for significant trends. Patients under 10 years of age were significantly different from the older group with respect to a shorter duration of symptoms, a higher number of patients requiring an emergency operation, a lower number of recurrences and the location of the cyst. Patients with retroperitoneal cysts were more likely to have incomplete excision of the cyst and therefore had a higher incidence of recurrence. They also required marsupialization more often. Retroperitoneal cysts should be considered a different entity from mesenteric cysts even though they present clinically in a similar fashion. The outcome of surgical treatment is less satisfactory in patients with retroperitoneal cysts.

Various formulas have been employed to compute the circumference of an ellipse. These formulas can be separated into three groups: formulas for a circle, formulas for an incorrect ellipse, and a very complicated formula for a correct ellipse. The errors caused by the first two groups are termed systematic because they occur every time that one of these formulas is used. When measuring fetal head circumference, the errors increase as the fetal head is more ellipsoid, becoming more than 1% when the ratio of the biparietal to fronto-occipital diameter decreases to less than .70. Near term, when the fetal head is large, this could create an error in predicting gestational age of almost .8 weeks. The third group is associated with mathematical random errors because of the difficulty in using a cumbersome equation. All of these formulas and their shortcomings are analyzed. A calculation for the correct circumference of an ellipse is proposed using the simple formula for a circle times a correction factor. The correction factor depends solely on the ratio of the biparietal to fronto-occipital diameter. This formula should minimize random errors and eliminate systematic errors in the calculation of fetal head circumference and will permit a more accurate analysis of fetal age.

We report a new technique for mucosal proctectomy that does not require manual separation of the mucosa and submucosa from the underlying muscularis. Mucosal proctectomy using ultrasonic fragmentation of the rectal mucosa was performed in four patients. Three had severe ulcerative colitis, and one patient had radiation proctitis with a rectal stricture. In all cases an endorectal pullthrough with anastomosis to the area of the dentate line was performed. Healing after ultrasonic mucosal proctectomy occurred without infection or retraction. Ultrasonic fragmentation offers an alternative to the standard technique of mucosal proctectomy. This new method is useful in those patients in whom separation of the rectal mucosal layer is difficult to perform.

Mucosal proctectomy is becoming the operation of choice in the surgical treatment of patients with ulcerative colitis and familial polyposis coli. Dissection of the rectal mucosa and submucosa from the underlying muscularis is often difficult and, in some instances, impossible to perform. The feasibility of using an ultrasonic device to perform mucosal protectomy was studied in eight dogs. This technique produced coagulative necrosis of the mucosa and muscularis mucosa with marked edema and congestion of the submucosa. The muscularis propria remained intact. Complete destruction of the distal 7 cm of rectal mucosa required a total duration of exposure to the ultrasonic probe of at least 12 minutes. In another five dogs, total colectomy was performed above the area of the mucosal proctectomy followed by endorectal pull-through of the ileum. Follow-up studies revealed healing of the ileonal anastomosis without retraction or stricture. This technique should allow mucosal proctectomy to be performed in those patients in whom standard dissection is not possible due to fibrosis of the submucosal plane.