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Biomedical subjects

G M Onik

Publications and source records attributed to G M Onik.

17 recordsLinked to original sources
PubMed2000

Percutaneous diskectomy in the treatment of herniated lumbar disks.

APLD and the minimally invasive approach to spine surgery has stood the test of time successfully. With the advent of new imaging technologies to aid in the guidance of spine procedures, such as three-dimensional ultrasound, interventional MR imaging, and fluoroscopic CT, and the development of flexible instruments that can be navigated within the disk, the stage is now set for major breakthroughs in the treatment of herniated lumbar disks (i.e., the minimally invasive removal of extruded and free disk fragments). With the active role of radiologists and sophisticated imaging, minimally invasive spinal intervention has a bright and exciting future.

Diskectomy↗
PubMed1999

Cryosurgery for prostate cancer: improved glandular ablation by use of 6 to 8 cryoprobes.

OBJECTIVES: To describe and assess the efficacy for increased glandular destruction by using 6 to 8 cryoprobes in place of the traditional 5 probes. METHODS: In April 1996, a revised method for cryosurgery was begun that uses 6 to 8 cryoprobes, and by July 1997, 81 men had been treated. This group was compared retrospectively to our last 82 cases done before April 1996 using 5 cryoprobes. All cases were consecutive. To ensure that the groups were similar, comparison was performed of entrance prostate-specific antigen (PSA), clinical stage, and Gleason score. Six months after cryosurgery, PSA and residual epithelial acini were compared between the two groups. RESULTS: The two groups were comparable for all the above parameters (P >0.05). The degree of overall glandular kill was greater for the 6 to 8-probe method (P = 0.023). Complete glandular ablation for the 5-probe and 6 to 8-probe methods was 39% and 53%, respectively, and the difference was not significant (P = 0.072). However, when one combined the complete glandular ablation group with the none to few residual acini group, 67.5% for the 5-probe method and 88.9% for the 6 to 8-probe method, a significant difference was found (P = 0.001). The odds of having many remaining acini versus having none to few were 3.5 times greater in the 5-probe group than in the 6 to 8-probe group. The mean and median PSA for the 5- and 6 to 8-probe groups were 0.19 and 0.1 versus 0.11 and 0.07 ng/mL, respectively, a significant difference (P = 0.02). No difference was found in rates of tumor persistence or complications. CONCLUSIONS: A revised method for cryosurgery using 6 to 8 cryoprobes has proved to be more effective for near-glandular ablation than the traditional 5-probe method. It was easily applied, had a wide margin of safety, and even shortened learning time. These innovations have permitted a closer approach to the goal of complete glandular destruction.

Cryosurgery↗
PubMed1998

Nuances in percutaneous discectomy.

This article presents an update of the field of percutaneous discectomy and a perspective as to where percutaneous discectomy currently fits in the treatment of patients with herniated discs. The future of minimally invasive disc surgery is also entertained, and a novel approach to lumbar disc surgery is presented.

Diskectomy, Percutaneous↗
PubMed1997

Minimally invasive disc surgery. Nucleotomy versus fragmentectomy.

There is continued debate as to the optimum surgical management of a herniated disc with sciatica. There are proponents of conventional microdiscectomy as well as those who advocate minimally invasive approaches, including central disc decompression or nucleotomy as well as arthroscopic lumbar microdiscectomy and fragmentectomy. In this controversy (I), Dr. Gary Onik takes the position that central disc decompression is both safe and efficacious and may be the procedure of choice for recurrent disc herniations (II). Dr. Parvis Kambin takes the opposing position and advocates arthroscopically assisted fragmentectomy as the procedure of choice.

Diskectomy↗
PubMed1994

US-guided percutaneous cryoablation of prostate cancer.

A tailored approach to cryosurgery of prostate cancer is presented. The authors have performed 214 cryoprocedures to date with use of this protocol. The technique requires pretreatment with androgen ablation therapy, preoperative diagnosis and staging with ultrasound (US)-guided biopsies, and detailed knowledge of prostate and rectal anatomy. Five cryoprobes are placed in the prostate under US guidance in a configuration that depends on tumor location, sites of extracapsular extension, the size of the tumor, and gland geometry. Freezing starts anteriorly to keep from obstructing the ultrasound beam. Two freezes are performed at the known cancer site, and additional freezes are performed, if necessary, to include the remainder of the gland. Thermosensors enable monitoring of the cryosurgical ice ball and determination of the number of freezes. Cryosurgery is always performed by a urologist and a radiologist working together.

Cryosurgery↗
PubMed1993

Transrectal ultrasound-guided percutaneous radical cryosurgical ablation of the prostate.

BACKGROUND: The two major treatments for prostate cancer, radical prostatectomy and radiation therapy, are associated with considerable morbidity and variable results. This article presents the preliminary results using percutaneous radical cryosurgical ablation under ultrasound guidance to treat prostate cancer. METHODS: The patient group consisted of all patients with localized prostate cancer who underwent cryosurgery between June 1, 1990 and May 1, 1992. Patients in Group 1 were treated by freezing of the tumor with two cryoprobes placed multiple times. Group 2 patients were treated by freezing of the tumor with five cryoprobes placed simultaneously. Cryoprobes (3 mm in diameter) were placed percutaneously with a transperineal approach. Cryoprobe placement and freezing were monitored using the transrectal ultrasound. RESULTS: Of the 55 patients (68 procedures) undergoing treatment, 23 have 3 months of follow-up with associated biopsy (Group 1, 8 patients; Group 2, 15 patients). In Group 1, three (37.5%) patients had residual disease. In Group 2, one (6.7%) patient had residual disease, whereas 14 (93.3%) patients did not. Combining both groups, 19 (82.6%) patients had no residual disease, whereas 4 (17.4%) patients had positive results on postoperative biopsy. Complications included rectal freezing, urethrorectal fistula, sloughing urethral tissue, impotence, perineal ecchymosis, penile edema, and ileus. CONCLUSIONS: Preliminary results indicate that percutaneous transperineal ultrasound-guided prostate cryosurgery may be an effective treatment for prostate cancer with minimal associated morbidity.

Biomarkers, Tumor↗
PubMed1993

Hepatic cryosurgery with and without the Bair Hugger.

Hypothermia is a significant clinical problem during hepatic cryosurgery, which at times causes the procedure to be halted until the patient's body temperature can be raised. This study examines the effects of the Bair Hugger (a warming device) on body temperature during hepatic cryosurgery. Twenty-eight cases of hepatic cryosurgery were performed without the Bair Hugger, while 44 cases included the Bair Hugger. The lowest mean temperature was significantly lower in the group without the Bair Hugger (34.2 degrees C vs. 35.3 degrees C; P < 0.0001). In addition, this group showed a significantly greater mean change in temperature during the procedure (1.81 degrees C vs. 0.73 degrees C; P < 0.0001). No patient in the Bair Hugger group reached the point of clinically significant hypothermia. In conclusion, the Bair Hugger is safe and very effective in regulating body temperature and it is an essential piece of equipment performing hepatic cryosurgery.

Cryosurgery↗
PubMed1993

Monitoring cryosurgery in the brain and in the prostate with proton NMR.

This brief communication reports the results of preliminary studies performed to evaluate the feasibility of using NMR imaging to monitor the freezing of tissue during cryosurgery. Two tissues were studied, rabbit brain and dog prostate. NMR imaging of these tissues provided a clear distinction between frozen and unfrozen tissue and an accurate assessment of the extent of freezing in real time.

Animals↗
PubMed1993

Ultrasound characteristics of renal cryosurgery.

The ability to visualize renal cryosurgery using ultrasound was tested in an animal model. Five dogs underwent open laparotomy and ultrasound-monitored cryosurgery of both kidneys. On each kidney two cryolesions were made. The borders of the frozen region were identified on ultrasound as a hyperechoic rim created by the interface between frozen and unfrozen tissue. The thawed cryolesion appeared hyperechoic compared with the unfrozen kidney. Excellent correlation between the ultrasound and autopsy measurements of the cryolesions was obtained. Knowing this, renal cryosurgery under ultrasound monitoring may be possible.

Animals↗
PubMed1989

Mechanical aspiration of hematomas in an in vitro model.

A modified Nucleotome (Surgical Dynamics, San Leandro, California) was used to aspirate blood clot in an in vitro model of intracerebral hematoma. This machine was successful in removing the clot at a reasonably rapid rate. It aspirates normal rat brain far more slowly. It therefore shows promise for being effective and safe in removing intracerebral hematomas in humans.

Adult↗
PubMed1986

Ultrasound monitored hepatic cryosurgery: longevity study on an animal model.

Ultrasound imaging has been proposed to monitor the amount of frozen tissue during hepatic cryosurgery of primary and metastatic tumors. In this follow-up study, a cryolesion was produced in an adult pig under ultrasound monitoring. The animal was allowed to recuperate for 3 days before being sacrificed. Pathologic and histologic evaluation showed extremely close correlation with the ultrasound image. The necrotic region was clearly observable in the sonogram after 3 days. Ultrasonography can accurately represent the extent of the cryolesion both during as well as following cryosurgery.

Animals↗
PubMed1985

Real time ultrasonic monitoring of hepatic cryosurgery.

Cryosurgery has a number of advantages that make it particularly appealing in the treatment of liver cancer. However, a major problem in the clinical application of hepatic cryosurgery is the lack of a precise means of monitoring the freezing process in situ. Preliminary investigations on simulated tissue have shown that standard ultrasonography is capable of accurately determining the amount of frozen material during a cryosurgical procedure. To extend these results to living tissue, cryosurgery was performed, in vivo, on the livers of four mongrel dogs. An ultrasound imaging device using a new intraoperative ultrasound transducer monitored the entire process in real time. The results indicate that the entire freezing and thawing cycle can be monitored easily using real time ultrasound. During freezing, the solidification interface can be seen to move through the tissue allowing clear imaging of the cryolesion. After complete thawing, the cryolesion became less echogenic than before freezing and was therefore distinguishable under ultrasound. Postsurgical pathologic examination showed excellent correlation between the lesion size and its ultrasonic image.

Animals↗
PubMedDate not supplied

Cryosurgery of liver cancer.

Cryosurgery, the in situ destruction of tissue using subzero temperatures, has been used to treat hepatic metastases. Because it is a focal treatment, cryosurgery can be used in patients with unresectable lesions due to location (next to major blood vessels) or multiplicity. In this study, 57 patients with unresectable hepatic metastases were treated with cryosurgery (with at least a 6-month follow-up). The number of lesions treated ranged from 1-16 with a mean of 4.6. Forty-three patients (73%) had bilobar disease, while 25 patients (42%) were treated with a combination of resection and cryosurgery. The disease-free survival rate (patients with normal computed tomography [CT] scans and carcinoembryonic antigen [CEA] levels) was 27% with a mean follow-up of 21 months. This is comparable to other hepatic cryosurgery studies that have found survival rates of 25-37.5%. Although the results are still short-term, this study indicates that hepatic cryosurgery offers the hope of long-term survival in patients with unresectable hepatic metastases.

Colonic Neoplasms↗