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Results for “Learning Curve”

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PubMed2007

The learning curve in the training of percutaneous nephrolithotomy.

OBJECTIVES: To investigate the learning curve in the training of percutaneous nephrolithotomy (PCNL). METHODS: A total of 104 PCNL cases were included in this evaluation to define the learning curve of a surgeon with no previous experience at performing solo PCNL. Two parameters of expertise were reviewed, namely the operation and fluoroscopic screening times. The operation time was calculated as the beginning of access with the needle until the nephrostomy tube was placed and secured. PCNL procedures were analyzed in seven sets of 15 cases regarding the operation and fluoroscopy times, stone size, stone clearance rate, blood transfusion rate, and estimated blood loss. RESULTS: The mean operation time was 2.4 h for the first 15 patients. It decreased to a mean of 1.5 h for cases 46 through 60. No further decrease in the operation time was observed after case 60. The fluoroscopic screening time was a peak of 17.5 min in the first 15 cases, whereas it dropped to a mean of 8.9 min for cases 46 through 60. The decline in the mean fluoroscopy screening time continued in cases 61 to 104, but the decline was not significant. There was no significant difference in stone size, stone clearance rate, blood transfusion rate, and estimated blood loss among each set of cases. CONCLUSIONS: This study suggests that the surgical competence in PCNL can be reached after 60 cases. PCNL and fluoroscopy times drop to a steady-state level after performing 60 procedures.

Clinical Competence↗

PubMed2000

Learning curve of transrectal ultrasound.

PURPOSE: Transrectal ultrasound is the most accurate means of assessing the degree of invasion for rectal neoplasms. A learning curve for performing and interpreting these studies exists, but it is unknown how long or steep it is. We reviewed our initial results with transrectal ultrasound to determine our accuracy and to define the learning curve. METHODS: All patients undergoing transrectal ultrasound during our initial 30 months of experience were included. Each patient was staged with transrectal ultrasound and, after resection, the histopathologic stage was compared with transrectal ultrasound staging. The accuracy of transrectal ultrasound was calculated at intervals as experience was gained. RESULTS: A total of 42 examinations were performed on 41 neoplasms in 41 patients. Comparison between transrectal ultrasound and the pathologic stage could be made in 36 studies. Overall accuracy of degree of wall invasion was 78 percent. Overstaging occurred with eight neoplasms, and one lesion was understaged. Accuracy of transrectal ultrasound staging improved with time: 58 percent of the initial 12 studies were staged correctly compared with 87.5 percent accuracy in the remaining 24 examinations (P = 0.048). CONCLUSION: A definite learning curve was apparent. We conclude that transrectal ultrasound is a relatively simple procedure to learn and, once a moderate degree of experience is gained, should be routinely incorporated into the evaluation of rectal neoplasms.

Adult↗

PubMed2006

Robotic assistance provides excellent outcomes during the learning curve for laparoscopic Roux-en-Y gastric bypass: results from 100 robotic-assisted gastric bypasses.

BACKGROUND: Laparoscopic Roux-en-Y gastric bypass (LRYGB) has a reported learning curve of 100 cases. Robotic-assisted surgery decreases the learning curve in complex laparoscopic surgeries. We hypothesize that robotic-assisted, hand-sewn gastrojejunostomy during a LRYGB will improve results during the initial 100 cases when compared with the literature. METHODS: Our first 100 robotic-assisted gastrojejunostomies performed during LRYGB were reviewed from a prospective database. Patient demographics, operative times, length of stay, reoperations, anastomotic leak, pulmonary embolus, and death were all evaluated. RESULTS: The mean age and body mass index were 42 and 50, respectively. Operative times ranged from 148 minutes to 437 minutes (mean = 254). There were no leaks or deaths. Four patients had complications, including reoperation (1), incisional hernia (1), pulmonary embolus (1), and recurrent umbilical hernia (1). CONCLUSIONS: Robotic-assisted LRYGB is feasible and safe, as evidenced by the excellent outcomes from this series during the initial learning curve for LRYGB.

Adult↗

PubMed2005

Learning curves for stochastic gradient descent in linear feedforward networks.

Gradient-following learning methods can encounter problems of implementation in many applications, and stochastic variants are sometimes used to overcome these difficulties. We analyze three online training methods used with a linear perceptron: direct gradient descent, node perturbation, and weight perturbation. Learning speed is defined as the rate of exponential decay in the learning curves. When the scalar parameter that controls the size of weight updates is chosen to maximize learning speed, node perturbation is slower than direct gradient descent by a factor equal to the number of output units; weight perturbation is slower still by an additional factor equal to the number of input units. Parallel perturbation allows faster learning than sequential perturbation, by a factor that does not depend on network size. We also characterize how uncertainty in quantities used in the stochastic updates affects the learning curves. This study suggests that in practice, weight perturbation may be slow for large networks, and node perturbation can have performance comparable to that of direct gradient descent when there are few output units. However, these statements depend on the specifics of the learning problem, such as the input distribution and the target function, and are not universally applicable.

Neural Networks, Computer↗

PubMed2001

Learning curve for stereotactic breast biopsy: how many cases are enough?

OBJECTIVE: The objective of this study was to evaluate the learning curve for stereotactic breast biopsy. MATERIALS AND METHODS: Retrospective review was performed of 923 consecutive lesions that underwent stereotactic breast biopsy performed by one of six radiologists. Four hundred fourteen lesions had 14-gauge automated core biopsy, and 509 subsequent lesions had vacuum-assisted biopsy (14-gauge in 163 and 11-gauge in 346). Medical records were reviewed to determine the technical success rate and false-negative rate as a function of operator experience. RESULTS: For 14-gauge automated core biopsy, a significantly lower technical success rate was seen for the first five cases of each radiologist than for subsequent cases (25/30 = 83.3% versus 366/384 = 95.3%, p < 0.02) and for the first 20 cases than for subsequent cases (90/100 = 90% versus 284/296 = 95.9%, p < 0.05). For 11-gauge vacuum-assisted biopsy, a significantly lower technical success rate was seen for the first five cases than for subsequent cases (17/20 = 85.0% versus 310/322 = 96.3%, p < 0.05) and for the first 15 cases than for subsequent cases (54/60 = 90.0% versus 273/283 = 96.5%, p = 0.03). The false-negative rate was higher for the first 15 cases compared with subsequent cases both for stereotactic 14-gauge automated core biopsy (4/31 = 12.9% versus 3/115 = 2.6%, p < 0.04) and for stereotactic 11-gauge vacuum-assisted biopsy (2/27 = 7.4% versus 0/85 = 0%, p < 0.06). CONCLUSION: A learning curve exists for stereotactic breast biopsy. Significantly higher technical success rates and lower false-negative rates were observed after the first five to 20 cases for 14-gauge automated core biopsy and after the first five to 15 cases for 11-gauge vacuum-assisted biopsy. Even after a radiologist has experience with stereotactic biopsy, changes in equipment may result in a new learning curve.

Biopsy, Needle↗

PubMed2006

Clinical outcomes and learning curve of a laparoscopic adrenalectomy in 103 consecutive cases at a single institute.

OBJECTIVE: We examined the clinical outcomes and the learning curve for a laparoscopic adrenalectomy (LA) in 103 consecutive cases performed by three surgeons at our institute, according to the type of adrenal disorder. PATIENTS AND METHODS: One hundred and three patients with adrenal tumors, including 38 cases of primary aldosteronism, 33 cases of Cushing syndrome (including preclinical Cushing syndrome), 15 cases of pheochromocytoma, and nine cases of non-functioning adenoma were evaluated, while focusing on the approaches, intraoperative and postoperative data, and the learning curve of LA, according the type of adrenal disorder. RESULTS: There was no significant difference in the operation time, estimated blood loss, incidence of conversion to open surgery and blood transfusion, or postoperative recovery among the patients treated by LA for aldosteronoma, Cushing adenoma, pheochromocytoma, and non-functioning adenoma. In the cases of aldosteronoma and Cushing adenoma, the learning curve for the operation time and blood loss in each operator tended to decrease as the number of operations increased. On the other hand, in the cases treated by LA for pheochromocytoma, no trends in either the operation time or blood loss were observed. However, there has been neither any conversion to open surgery nor blood transfusion in cases treated by LA since 1998 (our 42nd case), even after the changes in the operators. CONCLUSIONS: Our results clearly indicate that LA is becoming safer than before, probably due to improvements in the technique, education, and training of surgeons, in addition to the increased number of cases now treated by LA.

Adrenal Gland Neoplasms↗

PubMed2003

Learning curves for mutual information maximization.

An unsupervised learning procedure based on maximizing the mutual information between the outputs of two networks receiving different but statistically dependent inputs is analyzed [S. Becker and G. Hinton, Nature (London) 355, 161 (1992)]. For a generic data model, I show that in the large sample limit the structure in the data is recognized by mutual information maximization. For a more restricted model, where the networks are similar to perceptrons, I calculate the learning curves for zero-temperature Gibbs learning. These show that convergence can be rather slow, and a way of regularizing the procedure is considered.

Journal Article↗

PubMed2003

Learning curve for the detection of axillary sentinel lymph node in breast cancer.

AIM: Sentinel axillary lymph node (SALN) detection is a new technique. Surgeons must progress up a learning curve in order to guarantee quality and safety equivalent to axillary lymphadenectomy. To ensure accurate staging of patients this learning curve must include SALN detection and an axillary lymphadenectomy. The aim of our work was to validate the principles and evaluate the consequences of learning curve for SALN detection from a prospective series of 200 consecutive patients. METHOD: Prospective assessment was made of the detection and false negative rates, post operative morbidity as abcess and seroma, and length of hospital stay. RESULTS: We evaluated the performance from the first to the hundredth case for each surgeon. Detection rate improved to 85% after patient number 10. False negative rate was less than 6%. Post operative axillary morbidity included 11% of seromas and 2% of abcess. Mean hospital stay was 2.8 days. CONCLUSION: Multidisciplinary validation of the learning period contributes to an accurate and safe SALN.

Adult↗

PubMed2005

Learning curve for laparoscopic Roux-en-Y gastric bypass with totally hand-sewn anastomosis: analysis of first 600 consecutive patients.

BACKGROUND: Laparoscopic Roux-en-Y gastric bypass (LRYGB) is a challenging operation for the treatment of morbid obesity with well-demonstrated effectiveness in weight lost. There are several variations to the technique. METHODS: From September 2000 to July 2004, 600 consecutive patients underwent surgery for morbid obesity at our institution. The surgical technique employed was LRYGB with totally hand-sewn gastrojejunal anastomosis (GJA). All patients were considered candidates for laparoscopic approach regardless of age, gender, body mass index (BMI), or previous bariatric or digestive surgery. RESULTS: Mean BMI was 44.4 +/- 7.6 kg/m2. Thirty-two patients had undergone previous failed bariatric procedures. Conversion to an open procedure was necessary in three patients. Seventy-two patients (12%) developed early complications, including 23 (3.8%) leaks at the GJA (eight in the first 18 patients). Mortality rate was 1.1% (one death was related to GJA leakage). Early and late reoperation rates were 5.3 and 1.8%, respectively. Rate plateau of morbidity and mortality was reached after the first 18 patients when the surgical technique was fully standardized. CONCLUSIONS: LRYGB is a technically demanding procedure for the surgical treatment of morbid obesity with significant morbidity during the learning curve. The learning curve can be soon overcome, reaching a rate plateau of complications after adequate training. Morbidly obese patients should be operated on in expert bariatric surgical laparoscopic units to obtain the best results.

Adolescent↗

PubMed2004

Impact of fellowship training on the learning curve for laparoscopic gastric bypass.

BACKGROUND: We have previously shown that the learning curve for laparoscopic Roux-en-Y gastric bypass (LRYGBP) is approximately 75 cases. Patients have worse outcomes during the learning curve. Our aim was to evaluate the impact of fellowship training on outcomes during a surgeon's early experience with LRYGBP. METHODS: The study population consisted of the first 75 consecutive LRYGBP operations attempted by two laparoscopic surgeons, one with laparoscopic gastric bypass fellowship training (Group A) and one without laparoscopic bypass fellowship training (Group B). OUtcome parameters included mortality, major perioperative complications, operative time, and conversion to an open operation. RESULTS: Age, BMI, and gender distribution were similar in both groups. Operative time was significantly longer in Group B (189 min. vs 122 min., P<0.05). Conversion to an open procedure occurred uncommonly in both groups (3%). Major complications occurred more frequently in Group B (13% vs 8%, P=NS). In addition, the complications in Group B were more severe, resulting in 2 deaths. No deaths occurred in Group A. CONCLUSION: Laparoscopic bypass fellowship training improves perioperative outcomes during a surgeon's early experience with LRYGBP.

Adolescent↗

PubMed2004

Cumulative sum failure analysis of the learning curve with endovascular abdominal aortic aneurysm repair.

PURPOSE: The purpose of this study was to evaluate the importance of experience and the learning curve with endovascular abdominal aortic aneurysm (AAA) repair. METHODS: A retrospective analysis was performed of all elective endovascular AAA repairs attempted by an individual surgeon and radiologist over a 4-year period. The primary outcome variable was achievement and 30-day maintenance of initial clinical success as defined by the Society for Vascular Surgery/American Association of Vascular Surgery reporting standards. Following standard statistical analysis, the cumulative sum (CUSUM) method was used to analyze the learning curve, with a predetermined acceptable failure rate of 10% and calculated 80% alert and 95% alarm lines. RESULTS: Ninety-six elective endovascular AAA repairs were attempted by this team between 1998 and 2002 (mean age 74 +/- 0.8 years; mean aneurysm diameter 5.98 +/- 0.8 cm). Initial clinical success was achieved and maintained in 85 of 96 patients (88.5%). Although results were acceptable throughout the study period, improved results with respect to the target failure rate (10%) were not achieved until 60 patients were treated. The learning or CUSUM curves did not differ for different device manufacturers, with improved results being achieved following 20 implantations of each device. The results did differ when comparing aortouniiliac grafts (n = 27) and bifurcated grafts (n = 64). Results with bifurcated grafts remained consistent throughout the study period, whereas with aortouniiliac grafts, results improved after only a few procedures in comparison with the target failure rate. CONCLUSION: Success rates with endovascular aneurysm repair will improve with an individual's experience. The CUSUM method is a valuable tool in the evaluation of this learning curve, which has credentialing and training implications. Although acceptable results were obtained throughout the study period, this analysis indicates that 60 endovascular aneurysm repairs, or 20 with an individual device, are necessary before optimal rates of initial clinical success can be achieved. These results can be achieved more readily with aortouniiliac grafts than with bifurcated grafts.

Aged↗

PubMed2000

Defining the pediatric spinal thoracoscopy learning curve: sixty-five consecutive cases.

STUDY DESIGN: Consecutive case prospective chart and radiographic review. OBJECTIVES: The purpose of this study was to define the learning curve of spinal thoracoscopy. SUMMARY OF BACKGROUND DATA: Thoracoscopy is an alternative to open thoracotomy in the treatment of pediatric spinal deformity. The learning curve for spinal thoracoscopy has not been described. METHODS: In this prospective study 65 consecutive cases of thoracoscopic anterior release with discectomy and fusion performed by one surgeon for the treatment of pediatric spinal deformity were reviewed. The patients were, on average, 14 +/- 3 years old and had the following diagnoses: idiopathic scoliosis (n = 13), Scheuermann's kyphosis (n = 9), neuromuscular spinal deformity (n = 35), congenital scoliosis (n = 4), and tumor/syrinx (n = 4). RESULTS: The average operative time for the thoracoscopic procedure was 161 +/- 41 minutes (range, 50-240 minutes). There was a slight decrease in the average operative time as the series progressed. The average number of discs excised was 6.5 +/- 1.5 (range, 3-10), and the number increased as the series progressed. The average operative time per disc was 29.3 +/- 7.7 minutes in the first 30 patients compared with 22.3 +/- 4.7 minutes in the next 35 patients (P < 0.01). The average blood loss during the thoracoscopic procedure was 301 +/- 322 mL (range, 25-2000 mL) and did not decrease as the series progressed. Initial postoperative scoliosis and kyphosis corrections were 59% +/- 17% and 92% +/- 12%, respectively. Complications occurred in six patients (cases 4, 8, 17, 31, 39, and 46) and were evenly distributed throughout the series. CONCLUSIONS: The learning curve for thoracoscopy is substantial, but not prohibitive. This technique provides a safe and effective alternative to thoracotomy in the treatment of pediatric spinal deformity.

Adolescent↗

PubMed1985

Changed learning curve for percutaneous transluminal coronary angioplasty. Implication for the future treatment of coronary artery disease.

As with all skilled techniques, there is a learning curve for percutaneous coronary angioplasty. This curve has been well described in the literature and it is generally quoted that an initial success rate of 70 to 75 percent in reaching and crossing lesions is to be expected during the first 20 cases. However, the introduction of the steerable or guidewire-directed dilation catheter has altered the learning curve. After an initial experience of six nonsteerable percutaneous transluminal coronary angioplasty procedures, 20 consecutive steerable percutaneous transluminal coronary angioplasty procedures were performed without a single failure to reach or cross a lesion. These 20 consecutive steerable coronary angioplasty procedures included eight single left anterior descending lesions, two double (lesions located in series) left anterior descending lesions, six single right coronary lesions, one double (lesions located in series) right coronary lesion, and three single circumflex lesions. It is concluded that the introduction of the steerable system for percutaneous transluminal coronary angioplasty has shifted the learning curve, and that skilled and experienced coronary angiographers beginning a coronary angioplasty program can expect an initial success rate in reaching and crossing obstructive coronary lesions far in excess of the figures quoted in the literature. This may have significant implication for the ultimate availability of percutaneous transluminal coronary angioplasty to patients with coronary artery disease.

Adult↗

PubMedDate not supplied

Learning curves, acquisition, and retention of skills trained with the endoscopic sinus surgery simulator.

BACKGROUND: As an initial step in evaluating the effectiveness of training otolaryngology residents on an endoscopic sinus surgery simulator (ES3), we have assessed the ability of the ES3 to train persons inexperienced in sinus surgery (medical students) to perform certain simulated procedural tasks needed in endoscopic sinus surgery (ESS). METHODS: A total of 26 medical students were enrolled and trained on the ES3 following a preset protocol in the three levels of difficulty and complexity (novice, intermediate, and advanced modes). RESULTS: In the novice mode (three-dimensional abstract images are used to teach the use of endoscopic surgical equipment), medical students displayed a steep learning curve within three to five trials on the simulator and after an additional four to five trials, they reached a plateau in their learning curves to within 90% of that of experienced sinus surgeons. In the intermediate mode (ESS is performed on a simulated patient with teaching aids), medical students were able to reach a plateau in their learning curves to within 80% of that of experienced surgeons. This performance was sustained in the advanced mode (simulated sinus surgery without teaching aids). We observed that medical students, who had novice or intermediate mode training interrupted with an interval of 11-60 days, were able to resume their training without deviation from their prior learning curves. CONCLUSION: Intensive, proctored training on the ES3 can train inexperienced persons to perform simulated ESS within a reasonable approximation of the performance of experienced sinus surgeons on the ES3 and the training that an inexperienced person receives on the simulator is not short term but is retained over a period of at least 2 months.

Adult↗

PubMed1996

Retroperitoneal lymphadenectomy for clinical stage I nonseminomatous testicular tumor: laparoscopy versus open surgery and impact of learning curve.

PURPOSE: Laparoscopic retroperitoneal lymphadenectomy for clinical stage I nonseminomatous testicular tumors was compared to open surgery, taking into account the impact of the learning curve. MATERIALS AND METHODS: Between August 1992 and September 1995, 29 consecutive patients underwent laparoscopic retroperitoneal lymphadenectomy. Open surgical retroperitoneal lymphadenectomy was performed on 30 patients between January 1988 and July 1992. RESULTS: A comparison of the 14 initial and 15 subsequent laparoscopies showed a steep learning curve (operative time shorter by 36%, blood loss decreased by 50% and postoperative hospital stay shorter by 27%). When comparing the last 15 laparoscopic procedures to the open operations, the latter were superior only in terms of operative time (shorter by 18%). With regard to all other parameters open surgery was inferior (increased blood loss by 38%, longer postoperative hospital stay by 166%, more serious complications and a greater complication rate). Antegrade ejaculation was preserved after all laparoscopic and after 28 of the 30 open operations. There were no retroperitoneal recurrences in either group (mean followup 16 months after laparoscopy and 54 months after open surgery). CONCLUSIONS: Laparoscopic retroperitoneal lymphadenectomy is a demanding operation that is superior to open surgery once the learning curve has been overcome. However, this is possible only if laparoscopic retroperitoneal lymphadenectomy is performed on a regular basis.

Adult↗

PubMed2005

Laparoscopic radical prostatectomy: prospective evaluation of the learning curve.

OBJECTIVE: We prospectively evaluated the learning curve (LC) of laparoscopic radical prostatectomy (L-RPE) regarding the improvements in operative times (OT) and technical difficulty in one-operator-practice as it compares with open RPE. METHODS: Over 18 months, 50 L-RPE were performed by an inexperienced surgeon in laparoscopy but skilled in open surgery. Difficulty scores were obtained at the completion of each L-RPE comparing L-RPE to open RPE. OT, estimated blood loss (EBL), length of stay, and catheterization time were also obtained. RESULTS: In the ablative part of L-RPE the median difficulty score was significantly higher (p<0.001) for the first 10 cases, decreased dramatically by case 11 becoming equivalent (p=0.3) to open RPE and by case 31 the L-RPE becomes significantly easier than open RPE (p=0.002). The difficulty scores for the urethrovesical anastomosis performance is always uniformly higher for the whole patient series (p<0.001). Median OT decreased significantly from 293 minutes in the first 10 cases to 114 minutes in the last 10 cases (p<0.001). Catheterization time and length of hospitalization, decreased significantly with the progression of the LC. EBL remained stable throughout the patient cases. Obesity, prior surgery, and extension of the procedure (lymphadenectomy, nerve-sparing) significantly increased the OT. CONCLUSION: Although the ablative part of L-RPE has a relatively short LC for a skilled open surgeon reflected by the rapid decrease in difficulty scores and OT by case 21, the performance of anastomosis shows a longer LC. Intensive training on anastomosis may be necessary to master this skill.

Aged↗

PubMed1962

On the form of learning curves.

In a wide variety of learning experiments, cumulated measures of performance turn out to be a power function of practice time or number trials, typically with an exponent between 1 and 2. The effects of various conditions on the course of learning can frequently be described in terms of the two constants of the function.

Humans↗

PubMed2005

Prospective evaluation of learning curve for laparoscopic radical prostatectomy: identification of factors improving operative times.

OBJECTIVES: To evaluate the time required for each component of laparoscopic radical prostatectomy (LRP) performed by a single surgeon to identify the factors that expedite the learning curve. LRP is a technically demanding procedure with a lengthy learning curve. METHODS: The LRP procedure was divided into 12 steps, and the time for each step was prospectively recorded during the first 50 consecutive patients undergoing LRP by a single surgeon. The operations were divided into five groups of 10, and the average times for each step were compared and correlated with surgeon observations and changes in surgical technique. RESULTS: Statistically significant progressive improvement was seen in the total time of the LRP procedure (269.4 minutes in period 1 versus 205.4 minutes in period 4, P < 0.05). Regarding the specific steps, improvement occurred in the time needed for dissection of the vas deferens and seminal vesicles (51.8 minutes for period 1 versus 25.3 minutes for period 4, P < 0.01 and 31.2 minutes for period 5, P < 0.03), apical incision (16.7 minutes for period 1 versus 6.3 minutes for period 4, P < 0.03 and 5.7 minutes for period 5, P < 0.02), and division of the rectourethralis (13.5 minutes for period 1 versus 3.4 minutes for period 5, P < 0.05). The time needed for vesicourethral anastomosis remained unchanged throughout the study (average 48.5 minutes). CONCLUSIONS: With experience, the operative times for defined components of LRP improve. Patient selection for a low body mass index and smaller prostate may expedite the procedure. Application of a fixed retractor system, early identification of the vas deferens beneath the peritoneum in a more lateral position, and slow meticulous dissection and ligation of the dorsal vein complex are factors that may expedite the learning curve for LRP.

Clinical Competence↗