Effect of WEDM Process Parameters on Surface Morphology of Nitinol Shape Memory Alloy.

Nickel-titanium shape memory alloys (SMAs) have started becoming popular owing to their unique ability to memorize or regain their original shape from the plastically deformed condition by means of heating or magnetic or mechanical loading. Nickel-titanium alloys, commonly known as nitinol, have been widely used in actuators, microelectromechanical system (MEMS) devices, and many other applications, including in the biomedical, aerospace, and automotive fields. However, nitinol is a difficult-to-cut material because of its versatile specific properties such as the shape memory effect, superelasticity, high specific strength, high wear and corrosion resistance, and severe strain hardening. There are several challenges faced when machining nitinol SMA with conventional machining techniques. Noncontact operation of the wire electrical discharge machining (WEDM) process between the tool (wire) and workpiece significantly eliminates the problems of conventional machining processes. The WEDM process consists of multiple input parameters that should be controlled to obtain great surface quality. In this study, the effect of WEDM process parameters on the surface morphology of nitinol SMA was studied using 3D surface analysis, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. 3D surface analysis results indicated a higher value of surface roughness (SR) on the top of the work surface and a lower SR on the bottom portion of the work surface. The surface morphology of the machined sample obtained at optimized parameters showed a reduction in microcracks, micropores, and globules in comparison with the machined surface obtained at a high discharge energy level. EDX analysis indicated a machined surface free of molybdenum (tool electrode).

Surface Analysis of Wire-Electrical-Discharge-Machining-Processed Shape-Memory Alloys.

Shape-memory alloys such as nitinol are gaining popularity as advanced materials in the aerospace, medical, and automobile sectors. However, nitinol is a difficult-to-cut material because of its versatile specific properties such as the shape-memory effect, superelasticity, high specific strength, high wear and corrosion resistance, and severe strain hardening. Anunconventional machining process like wire-electrical-discharge-machining (WEDM) can be effectively and efficiently used for the machining of such alloys,although the WEDM-induced surface integrity of nitinol hassignificant impact on material performance. Therefore, this work investigated the surface integrity of WEDM-processed nitinol samples using digital microscopy imaging, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. Three-dimensional analysis of the surfaces was carried out in two different patterns (along the periphery and the vertical plane of the machined surface) andrevealed that surface roughness was maximalat the point where the surface was largely exposed to the WEDM dielectric fluid. To attain the desired surface roughness, appropriate discharge energy is required that,in turn, requires the appropriate parameter settings of the WEDM process. Different SEM image analyses showed a reduction in microcracks and pores,and in globule-density size at optimized parameters. EDX analysis revealed the absence of wire material on the machined surface.

Multi-Response Optimization of WEDM Process Parameters for Machining of Superelastic Nitinol Shape-Memory Alloy Using a Heat-Transfer Search Algorithm.

Nitinol, a shape-memory alloy (SMA), is gaining popularity for use in various applications. Machining of these SMAs poses a challenge during conventional machining. Henceforth, in the current study, the wire-electric discharge process has been attempted to machine nickel-titanium (Ni55.8Ti) super-elastic SMA. Furthermore, to render the process viable for industry, a systematic approach comprising response surface methodology (RSM) and a heat-transfer search (HTS) algorithm has been strategized for optimization of process parameters. Pulse-on time, pulse-off time and current were considered as input process parameters, whereas material removal rate (MRR), surface roughness, and micro-hardness were considered as output responses. Residual plots were generated to check the robustness of analysis of variance (ANOVA) results and generated mathematical models. A multi-objective HTS algorithm was executed for generating 2-D and 3-D Pareto optimal points indicating the non-dominant feasible solutions. The proposed combined approach proved to be highly effective in predicting and optimizing the wire electrical discharge machining (WEDM) process parameters. Validation trials were carried out and the error between measured and predicted values was negligible. To ensure the existence of a shape-memory effect even after machining, a differential scanning calorimetry (DSC) test was carried out. The optimized parameters were found to machine the alloy appropriately with the intact shape memory effect.

Two- vs three-drug combination chemotherapy in advanced or recurrent head and neck cancer: a single institution experience of 361 patients.

Head and neck squamous cancer is a major concern in India. The proportion of advanced cases is significantly high, and these patients have dismal survival prospects despite aggressive therapy. Often surgical resection and/or radiotherapy are not feasible in these patients. Hence, we decided to explore the option of neoadjuvant chemotherapy using effective agents like ifosfamide and paclitaxel in combination with cisplatin in these patients. A total of 361 patients were evaluable at the end of study. Of these, 207 had received ifosfamide and cisplatin and 154 had received taxanes (paclitaxel or docetaxel) in addition to ifosfamide and cisplatin. The ifosfamide-cisplatin group had an overall response rate of 66.67% (CR, 16.42%; PR, 50.24%) and the median duration of response was 5.5 mo; whereas the group in which taxanes were added, showed an overall response rate of 73.37% (CR, 7.79%; PR, 65.58%) with a median duration of response of 10 mo. The toxicity in both the groups was acceptable and there was no mortality. We conclude that taxane-based combinations have a significant activity in advanced head and neck squamous cancer and warrant further studies.

Neoadjuvant chemotherapy with ifosfamide and cisplatin combination in advanced head and neck cancer: a retrospective analysis of 519 patients: a single institution experience.

Advanced head and neck cancer is a major therapeutic problem in India. Ifosfamide has shown significant activity as a single agent in head and neck squamous carcinoma. In this study, we present our experience with two cycles of ifosfamide and cisplatin in the neoadjuvant setting given to a total of 519 patients. The complete response rate was 20% and the overall response rate was 80%. The treatment was well tolerated, there was no need for dose reduction, and there were no life-threatening side effects. We feel that this high response rate is sufficient to warrant more studies using ifosfamide-based combinations in a neoadjuvant setting for squamous carcinoma of the head and neck.

Evidence-based protocols for the management of well-differentiated carcinomas of the thyroid.

OBJECTIVES: In recent years, well-differentiated carcinomas of the thyroid have been stratified into low-risk and high-risk groups. The pattern of thyroid cancer in India is different from that seen in the West. Moreover, patients present with more advanced stages of the disease. Our aim was to develop protocols for the management of well-differentiated thyroid cancer, based on the analysis of our data and our experience. METHODS: Cases of thyroid carcinoma, which were surgically treated at the Tata Memorial Hospital during 1970-5, were studied. The survival curves were plotted according to the Kaplan-Meier method. Univariate analysis was done using the log rank test. The prognostic factors analyzed were age, sex, tumour size, extra-thyroid extension, distant metastases and lymph node metastases. Multivariate analysis using the Cox regression model was performed. Analyses were separate for follicular and papillary carcinomas. RESULTS: Four hundred and seventeen cases were entered in the study, of which 198 were follicular and 219 were papillary. Based on the evidence derived from this study, we stratified our cases into low- and high-risk groups. The low-risk group consisted of patients below 40 years of age, nodules smaller than 5 cm, absence of extra-thyroidal spread and absence of distant metastases. For follicular carcinoma, the low-risk group had 100% survival at 15 years, compared with 40% for the high-risk group. (p < 0.001). For papillary carcinomas, the survival at 15 years was 95% for the low-risk group and 40% for the high-risk group (p < 0.001). CONCLUSIONS: We recommend lobectomy for the low-risk group, and total thyroidectomy for the high-risk group and for cases with lymph node metastases. In the latter, total thyroidectomy facilitates the use of 131I.

Prognosticators of survival in differentiated thyroid carcinoma.

Differentiated carcinoma of the thyroid has good prognosis, even in patients presenting in the late stage and with distant metastasis. In India, the incidence of papillary carcinoma and follicular carcinoma are in the ratio of 60∶40. A retrospective study was carried out to determine the impact of patient and tumor factors on survival, and to develop a simple rish group staging system to predict survival in patients with differentiated thyroid carcinomas. Four hundred and seventeen (417) patients undergoing primary treatment at our hospital between 197-1985, were entered to the study. There were 198 follicular carcinomas and 219 papillary carcinomas. Impact of patient and tumor variables were studied by drawing Kaplan Meier curves and comparing them by the Chi Sq Test. Age<=40 years (p=0.00001), tumor size <5cms (p=0.01), extrrathyroidal spread (p=0.001) and distant metastasis (p=0.00001) had significant impact on survival. These finding were true for a subset analysis follicular and papillary carcinomas separately. A Cox Regression Analysis was also performed and this showed the above factors to impact significantly on survival. Basing on the regression analysis we devised a simple risk group system and classified the patients as high and low risk. Low risk group patients had a significant survival advantage. Our findings show that the incidence of follicular carcinoma is significantly high in india (48%) and that 65% of our patients are in the high risk group. Incidence of contralateral lobe disease on completion thyroidectomy is as high as 53%. Hence, a more aggressive treatment policy is warranted and total thyroidectomy is the appropriate treatment of choice in our patients.

Surgery in early cancer of the oral tongue (Tl-2). Wide excision versus hemiglossectomy.

Cancer of the oral tongue is a common disease. Thirty five (35%) percent of patients seen at our hospital are in Stages I&II. The choice of surgical treatment is a wide excision of the lesion (WE) or a hemiglossectomy (HG). This study was carried out to compare the local recu-rrences and survival in patients undergoing either a WE or HG for early cancer of the tongue. One hundred and twenty six (126) patients were evaluated, 40 underwent a WE and 86 HG. The local recurrence was higher in the WE group, 25% compared with 9% in the HG group; which is statistically significant (p=0.02). This was also seen in the Tl subgroup (p=0.003). Survival were better in the HG group (p=0.005), which was also seen for the Tl subgroup (p=0.004). Our study demonstrates that there is a lower incidence of local recurrences following a hemiglossectomy for Tl-2 tumours of the oral tongue with improved survivals. Our recommendation is that hemi-glossectomy should be the optimal surgery performed for early cancer of the oral tongue.

CO2 LASER - A NEW TOOL IN THE SURGEONS ARMAMENTARIUM.

One hundred and sixty five patients, treated with carbondioxide (CO2) laser for benign and malignant lesions of the head and neck were studied. Alveolo-buccal complex (68/165) had the majority of benign and malignant tumors followed by larynx (23/165) and tongue (21/165). All lesions were widely excised, none were reconstructed and all defects healed well with minimal scarring. The post-operative morbidity was minimal and the hospitalization period was 1 to 5 days. Complications were not serious and could be managed easily. This study confirms the usefulness of CO2 laser surgery for both benign and malignant conditions in head and neck.

EARLY CARCINOMA TONGUE - SURGICAL OPTIONS.

A retrospective analysis of 127 surgically treated cases of T-1, T-2 carcinoma of oral tongue during the period 1987-1990 was undertaken. 68.5 per cent (87) underwent hemiglossectomy and 31.5 per cent (40) underwent wide excision. There were loco-regional recurrences in 22 per cent (27). In the hemiglossectomy group 9 per cent (8 of 87) had local recurrences compared to 25 per cent (10 of 40) of wide excision group, (P = 0.01). Mean disease free survival was 40 months and 33 months for hemiglossectomy group and wide excision group respectively, (P = 0.006). It is seen that local recurrences are significantly less for the hemiglossectomy group compared to the wide excision group.

Histologic trends in thyroid cancer 1969-1993: a clinico-pathologic analysis of the relative proportion of anaplastic carcinoma of the thyroid.

BACKGROUND: It was observed that new presentations of anaplastic carcinoma of the thyroid had become infrequent in the last two decades. METHODS: All cases of thyroid cancer seen at our centre between 1969-1993 (n = 2921) were classified as papillary 49%, follicular 34%, medullary 7.5%, anaplastic 4.7%, and other 4.8%. The total number of thyroid cancers show a 3.5-fold rise. RESULTS: The differentiated thyroid cancers show a significant rising trend as against the relative proportion of anaplastic carcinoma, which shows a significant decline (P = 0.002). Clinicopathologic data on 124 patients of anaplastic carcinoma revealed 50% patients had either long-standing goitres, previous thyroid abnormalities, or associated differentiated thyroid carcinoma on histology. CONCLUSIONS: The decline in the relative proportion of anaplastic carcinoma may in part be explained by the clinicopathologic findings or it may be attributed to histological reclassification.

Prognostic factors in follicular carcinoma of the thyroid: a study of 198 cases.

BACKGROUND: Prognostic parameters for papillary carcinoma of the thyroid have been defined by several groups. However, no such study has been reported for follicular carcinoma. METHODS: We undertook a retrospective study of well-differentiated carcinoma of the thyroid operated at the Tata Memorial Hospital during the period 1970-1985. In our series, follicular carcinoma formed 48% of the well-differentiated carcinomas of the thyroid. The variables age, sex, size, extrathyroidal spread, distant metastases, and lymph node metastases were evaluated. The survival was plotted according to the Kaplan-Meier method, and graphs compared by log-rank test. Univariate and multivariate analyses were performed. RESULTS: Based on our experience we stratified the cases into low-risk and high-risk groups. The low-risk group included: age below 40 years, tumor size less than 5 cm. and no extrathyroidal extension or metastases. This low risk group had 100% survival at 15 years, compared with 40% survival for the high-risk group (P <.001). Seventy-three percent (73%) of our cases were in the high-risk group. CONCLUSIONS: Based on our findings that the majority of our patients were in the high-risk group, we advocate a total or near-total thyroidectomy in treatment of follicular carcinoma of the thyroid. There is a need to arrive at a universally acceptable classification of risk groups in follicular carcinoma of the thyroid gland.

Reconstruction with different free flaps in oro-facial cancer patients.

In 75 patients following ablative surgery of head and neck cancer, reconstruction was attempted with free tissue transfer techniques under magnification. It was possible to do free tissue transfers in 69 cases. In 6 cases it was not possible to harvest free flaps successfully and alternative reconstructive procedure was carried out due to unavoidable circumstances and various reasons: 1. unsuitable venous drainage, as in Anterior Rib Osteomyocutaneous Composite Flap, AROCF (2 cases), 2. injury to vessels during flap harvest, as in parascapular flap (1 case), 3. residual disease unable to excise (2 cases) and 4. unsuitable proposition (1 case), due to emergency curfew imposed suddenly. These 6 cases were not included in the study. Free tissue transfer was successful in 64 cases (92.7%) and there was a total failure in 5 cases where delayed secondary salvage surgery was performed. Out of 69 cases, in 65 cases reconstructions were carried out immediately, primarily as one-stage operative procedure. Their functional, cosmetic results and complications during the operative and post-operative period are analyzed and discussed. Inter-maxillary fixation was never used to maintain the bite alignment. All cases were given a bite guide prosthesis in the early post-operative period, to improve the bite alignment when it was necessary.

Laryngectomy: a quality of life assessment.

Cosmetic disfigurement and loss of voice following a total laryngectomy can cause major psychosocial problems. Fifty patients who had undergone a total laryngectomy and completed more than six months following surgery, were randomly selected during a routine follow-up, and asked to answer a questionnaire, to asses their degree of disability and extent of rehabilitation. The questionnaire have five main components viz. general information, functional evaluation, vocal rehabilitation, social assessment and economic sequelae. Results revealed that these patients suffered from a significant decrease in social acceptance (70%), social activity (82%), sexual activity (62%), ability to communicate vocally (58%), and severe financial repercussions (78%). A large number of patients (40%) were dissatisfied with the present level of rehabilitation offered. Inspite of these problems the majority (80%) were willing to accept a total laryngectomy as treatment of their cancer. This emphasizes the need for greater interaction between the treating surgeon, speech therapist, occupational therapist, and psychotherapist to rehabilitate these patients adequately.

Extent of lymph node dissection in T3/T4 cancer of the alveolo-buccal complex.

BACKGROUND: Cancer of the alveolo-buccal complex even when locally advanced is amenable to curative resection. However, the extent of lymph node dissection remains controversial. METHODS: A total of 181 patients with T3/T4 cancer of the alveolo-buccal complex who underwent a radical neck dissection (RND) were analyzed retrospectively to determine the incidence and pattern of lymph node involvement and to define the extent of neck dissection required in these cancers. RESULTS: Lymph node involvement was as follows: level I (85%), II (51%), III (19%), IV (18%), V (5%). Levels I and II were most commonly involved (94%). Skip metastases occurred in 13%. Levels IV and V were involved in 2% and 20% when levels I, II, and III were uninvolved and involved, respectively. CONCLUSION: A supraomohyoid neck dissection (SOHD) should be performed and subjected to a frozen section evaluation in every patient. If lymph nodes are negative, then SOHD is adequate. If levels I, II, or III are positive, then a RND should be performed.

Perioperative chemotherapy in patients with oral cancer.

In the final report of a prospective, randomized controlled clinical trial, we report the results of using adjuvant perioperative chemotherapy in patients with oral cancer. Our study is based on the hypothesis of Goldie and Coldman. A total of 135 patients with alveolobuccal carcinoma, classified as clinically stage III and IV, were entered on the protocol. After a curative resection, they were randomized. The patients in the test arm of the study received methotrexate 50 mg/m2 on the 3rd, 10th, and 17th postoperative days. The patients in the control arm underwent observation. This analysis at 24 months showed a disease-free survival rate of 61% in the test arm versus 37% in the control arm, which is statistically highly significant (P < 0.01). Analysis of the recurrence pattern showed that recurrence at the primary site was dramatically reduced during the first 6 postoperative months (P = 0.002). Our study provided further clinical evidence in support of the concepts of Goldie and Coldman that the timing of chemotherapeutic drugs is critical for a successful end result.

Malignant peripheral nerve sheath tumors of the head and neck: a clinicopathological study.

Twenty-seven cases of malignant peripheral nerve sheath tumors involving the head and neck region over a period of 7 years were reviewed. They were graded from 1-3 based on necrosis, mitosis, cellularity, and pleomorphism. Mean age of occurrence was 42 years, with a range of 12-70 years. Male preponderance was noted (M:F = 3.5:1). The most common site of involvement was the neck (44.6%). The main presenting symptom was an enlarging mass. The nerve of origin could be identified in 33% of patients. Treatment consisted of wide excision. The 5-year observed survival was 33%. Fifty-two percent of patients developed local recurrence of disease. Fifteen percent of patients died due to advanced local disease within 18 months of treatment. Distant metastasis was seen in 18.5% of patients. Lymph node metastasis was not seen. At the end of 5 years 15% of patients remained disease free. Large tumor size (> 5 cm) adversely affected the prognosis (P = < 0.1). No significant correlation was noted between the grade of tumor and survival.

Tracheal tear during laryngopharyngectomy with gastric transposition.

Tracheal rupture occurred in 7 of 174 (4%) patients undergoing laryngopharyngectomy with gastric transposition. Tracheal tears were classified as proximal if they involved the upper two-thirds of the trachea (five patients), or distal if they extended into the lower one-third of the trachea (two patients) and their clinical features and management analyzed. Predisposing factors, including prior radiotherapy (three patients) and preoperative tracheostomy (1 patient) did not influence the site or severity of tracheal injury. Proximal tears were detected incidentally in four patients, but in one patient, manifested postoperatively with subcutaneous emphysema and pneumothorax. Distal tears manifested dramatically with a ventilatory leak. Adequate access for repair of distal tears may necessitate a right thoracotomy while proximal tears may be sutured through the cervical incision. Gastric transposition alone did not prevent air leak in two patients. Postoperative complications included prolapse of the stomach and bilateral pneumothoraces in one patient. Close interaction between the surgeon and the anesthesiologist ensured a successful outcome in six patients. There was one mortality.

Phase II study of high-dose ifosfamide as a single agent and in combination with cisplatin in the treatment of advanced and/or recurrent squamous cell carcinoma of head and neck.

152 patients with histologically proven squamous cell carcinoma of the head and neck (advanced and/or recurrent) were treated with a single drug therapy of ifosfamide 1.5 g/m2 by intravenous drip for half an hour in 125 ml of dextrose saline for 5 days and mesna 20% of the total ifosfamide dose in 3 doses for 5 days, or in combination with cisplatin 10 mg/m2 by intravenous infusion for 5 days following the ifosfamide drip. The courses of treatment were repeated at the interval of every 4 weeks, and a total of 3 cycles was given. Out of 152 patients 64 received ifosfamide alone, and 88 received ifosfamide with cisplatin. 6 complete and 25 partial remissions (total response 53%) were observed in 58 evaluable patients of the ifosfamide group, and 10 complete and 40 partial remissions (total response 65.7%) were observed in 76 evaluable patients of the combination group. Nausea, vomiting, alopecia and leucopenia were experienced by all patients.

Malignant mixed tumor of the salivary gland with bone metastasis: a case report and literature review.

Malignant mixed salivary tumors are rare, accounting for 2%-10% of all mixed salivary tumors. Rarer still are metastasis from a malignant mixed salivary tumor. A case of malignant mixed salivary tumor occurring in the parotid gland and presenting as a parapharyngeal mass; with asymptomatic multiple bony metastasis is presented with a brief review of literature.