Neodymium-yttrium Aluminum Garnet Laser Research Articles

Changing patterns in interventional bronchoscopy

Many interventional tools for airway disorders can now be delivered via flexible bronchoscopy (FB), including neodymium-yttrium aluminium garnet laser, electrocautery, argon plasma coagulation, cryotherapy, balloon dilatation and metal or hybrid stents. Comparison of outcomes for patients undergoing rigid bronchoscopy (RB) with those treated using FB highlights the usefulness of the FB approach. A retrospective medical record review of all interventional bronchoscopy procedures performed at Lahey Clinic over the past 8 years was conducted. Patients were categorized into two groups according to the procedure used, that is, RB (251 patients), and FB (161 patients) groups. Patients with malignancies were included as a separate subgroup, comprising 178 RB and 117 FB patients. For every procedure, the location of the lesion, patient survival from the first interventional procedure performed, and in patients with malignancy, additional treatments received such as chemotherapy and radiation were recorded. Ninety per cent of RB procedures were performed in patients with tracheal or main stem lesions, while over half the patients undergoing FB had more distal lesions. A trend towards increasing use of FB for interventional procedures in recent years was noted. FB is a valuable alternative to RB for treating less advanced malignant disease or distal airway lesions.

Results of intraocular lens implantation with capsular tension ring in subluxated crystalline or cataractous lenses in children

Purpose:To evaluate the outcome of intraocular lens (IOL) implantation using capsular tension ring (CTR) in subluxated crystalline or cataractous lenses in children.Setting:Tertiary care settingMaterials and Methods:We prospectively studied 18 eyes of 15 children with subluxation of crystalline or cataractous lenses between 90° up to 210° after phacoemulsification, CTR and IOL implantation. Each child was examined for IOL centration, zonular dehiscence and posterior capsular opacification (PCO).Results:Age of the patient ranged between five to 15 years. Out of 18 eyes, seven had traumatic and 11 had spontaneous subluxation of crystalline or cataractous lens. Phacoemulsification was successfully performed with CTR implantation in the capsular bag. Intraoperative zonular dialysis occurred in two eyes. Anterior vitrectomy was performed in six eyes to manage vitreous prolapse. IOL implanted was polymethyl methacrylate (PMMA) in eight eyes, hydrophobic acrylic in seven and hydrophilic acrylic in three. Follow-up ranged from 24 months to 72 months. Sixteen eyes had a best corrected visual acuity of 20/40 or better. Nine eyes developed significant PCO and were managed with Neodymium Yttrium Aluminum Garnet (Nd:YAG) laser posterior capsulotomy. One eye with acrylic IOL in the capsular bag had IOL dislocation after two years which was managed with vitrectomy and secondary trans-scleral fixation of IOL.Conclusions:Phacoaspiration with CTR implantation makes capsular bag IOL fixation possible in most of the eyes with subluxated crystalline or cataractous lenses. PCO still remains a challenge in children with successful phacoaspiration with CTR implantation

Venous Malformation of the Eyelid Treated With Pulsed-Dye-1064-nm Neodymium Yttrium Aluminum Garnet Sequential Laser: An Effective and Safe Treatment

Venous malformations of the skin and subcutaneous tissue are compressible, blue-purple tumors that are present at birth. According to the location and symptoms caused, venous malformations can be treated with surgery, sclerotherapy, or a combination of both. Laser therapy can also be used, especially when surgery is contraindicated. We report the case of a 24-year-old man who presented with a venous malformation on the upper and lower left eyelids, which provoked a mechanical ptosis. Treatment with sequential pulsed-dye neodymium yttrium aluminum garnet (PDL-Nd:YAG) laser was performed. After 2 treatments, a marked reduction of volume and blanching of the venous malformation was observed, with satisfactory cosmetic results. The sequential PDL-Nd:YAG laser seems to be an effective and safe therapy for the treatment of cutaneous venous malformations. It penetrates deeper than pulsed-dye laser alone, and because it allows the use of lower fluencies than Nd:YAG laser alone, it reduces the risk of adverse effects.

Prognostic significance of tumor-infiltrating cytotoxic T-cells in colorectal cancer

Limited evidence exists regarding the role of scaling and root planning (SRP) with adjunct neodymium yttrium aluminum garnet (Nd:YAG) laser therapy in reducing periodontal parameters (plaque index [PI], bleeding on probing [BOP] and probing pocket depth [PPD]) and levels of proinflammatory cytokines in the gingival crevicular fluid (GCF) among patients with periodontal disease (PD). The aim was to assess the effect of SRP with and without adjunct Nd:YAG laser therapy on clinical periodontal parameters and GCF interleukin 1-beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) levels among patients with PD.Demographic data was collected using a questionnaire. Mandibular right and left quadrants were randomly divided into test- (SRP + Nd:YAG laser) and control-sites (SRP alone). PI, BOP and PPD were assessed and GCF IL-1β and TNF-α levels were measured at baseline and at 3- and 6-month follow-up. Level of significance was set at P < 0.05.Twenty-eight male patients with PD were included. At 3- and 6-month follow-up, PI (P < 0.01), BOP (P < 0.01) and PPD (P < 0.01) were significantly higher in the control-sites than test-sites. In the test-sites, PI, BOP and PPD and GCF IL-1β and TNF-α levels were comparable at 3- and 6-month follow-up. At 6-month follow-up, IL-1β (P < 0.05) and TNF-α (P < 0.05) levels were significantly higher in control-sites than test-sites at 3- and 6-month follow-up.At 3- and 6-month follow-up, SRP + Nd:YAG therapy was more effective in reducing periodontal inflammatory parameters and GCF IL-1β and TNF-α levels compared with SRP alone.

Intraluminal bronchial carcinoid resection by bronchoscopy

Pulmonary carcinoid tumour is an uncommon malignant neoplasm derived from the surface or glandular epithelium of the conducting or transitional airways. It is a neuroendocrine neoplasm that arises from the enterochromaffin cells of the amine precursor uptake and decarboxylation system of bronchial mucosa. They represent 1-2 % of all pulmonary neoplasms [1, 2, 3, 4]. The carcinoid tumours can be divided into two clinicopathological types, typical and atypical. They behave like low grade malignant tumours and have a high rate of resectability and better prognosis [5]. The prognosis depends on size of tumour, histological type, nodal involvement and the presence of metastasis. Majority of carcinoids are located centrally within the trachea and mainstem bronchi and are reachable with flexible bronchoscope [3, 4, 5]. Curative surgical resection with focus on lung sparing or bronchoplastic surgery is the treatment of choice [1, 2, 5]. Endobronchial laser resection via rigid or flexible bronchoscope can photocoagulate and vaporize lesions. The potassium titanyl phosphate (KTP), argon dye, yttrium aluminium pevroskite (YAP), neodymium-yttrium aluminium garnet (Nd:YAG) and diode lasers are suitable for use in fibreoptic bronchoscopes. The Nd:YAG laser is currently preferred for airway resection because of its predictable effect on living tissue (photocoagulation or vaporization), depending on the amount of energy applied [6,7]. At 980 nm diode laser shows a smaller optical penetration depth than the Nd:YAG laser at 1064 nm. Thus with identical application parameters, higher temperatures are produced with the diode in most tissues at superficial and interstitial applications. Most experts use flexible bronchoscope for laser photoresection [6]. We report a case of bronchial carcinoid in the left main bronchus causing collapse of left lung. The endobronchial resection via diode laser resulted in complete removal of obstruction with an excellent result.

Neodymium:Yttrium Aluminum Garnet laser for mini-percutaneous treatment of upper urinary tract stones

To observe the efficacy and safety of mini-percutaneous nephrolithotomy with Neodymium: Yttrium Aluminum Garnet (Nd-YAG) laser in the treatment for upper urinary tract stones, from December 2005 to September 2006, 31 patients with renal stones, 15 patients with ureteral stones and 7 patients with renal and ureteral stones underwent mini-percutaneous nephrolithotomy with Nd-YAG laser by combination of rigid ureteroscope and flexible ureteroscope under B-ultrasound guidance. Clinical data including operation time, lithotripsy time, complications and stone-free rate were analyzed retrospectively. Our study showed that the percutaneous renal access (F14-F18) was successfully established under B-ultrasound guidance in all cases. Immediate phase: lithotripsy was performed in 47 cases through single tract, and in one case through two tracts. Delayed phase II lithotripsy was done in 5 cases of renal stones. Operation time ranged from 55 to 180 min with an average time of 100+/-15 min. Lithotripsy time was from 25 to 135 min and the average lithotripsy time was 65+/-11 min. No severe complications occurred in our series. Complex renal stones were cleared in 34 of 38 cases (89.5%). All ureteral stones were completely removed in 15 cases (100%). It was concluded that mini-percutaneous nephrolithotomy with Nd:YAG laser for the treatment of upper urinary tract stones by combination of rigid ureteroscope and flexible ureteroscope has the advantages of effectiveness, mini-invasion, shorter operative time and safety.

Continuum generation in water and carbon tetrachloride using a picosecond Nd-YAG laser pulse

We have measured the continuum generated in two non-linear media, distilled water and carbon tetrachloride, pumped by a 36 ps Neodymium Yttrium Aluminium Garnet laser pulse operating at 1.06 μm. We show that the induced spectral broadening extends from 400 nm to 850 nm in both media. However, we find that continuum spectra of carbon tetrachloride exhibit an oscillatory structure with an energy range of about 445 cm −1 which corresponds to the fundamental Raman component. This behaviour is due to a spectral non-overlapping of the Raman anti-Stokes components photoinduced in this medium.

Acute painful visual loss from accelerated hypertensive choroidopathy

32-year-old man presented witha 2-day history of redness,severe pain and reduced vision in theright eye. Best corrected visual acuity(VA) was 6⁄9 and 6⁄6 in the right andleft eyes, respectively. He had no pastmedical or ophthalmic history. Slit-lamp examination showed right con-junctiva injection and the anteriorchamber (AC) was considerably shal-low with no cornea and pupil abnor-malities. His left eye was normal.Intraocular pressure (IOP) was20 mmHg in both eyes. Gonioscopyrevealed the iridocorneal angle in theright eye to be closed, whereas that inthe left eye was wide open. Fundusexamination confirmed hypertensiveretinopathy in both eyes (Fig. 1A, B),with haemorrhagic ciliochoroidaldetachment in the right eye (Fig. 1C).The subject’s blood pressure raisedto 220⁄150 mmHg. An ultrasoundB-scan of the right eye (Fig. 1D)showed diffuse shallow haemorrhagicchoroidal detachment in the temporalquadrant. Neodymium yttrium alu-minium garnet (Nd:YAG) laser per-ipheral iridotomy failed to deepen theright AC. The subject was managedmedically with topical intensive ster-oid and oral analgesics. Acetazola-mide 250 mg three times daily wasadded for 1 day to prevent a postNd:YAG IOP spike. He was referredurgently to a physician for control ofsystemic hypertension. One monthlater, best corrected VA in the righteye was 6⁄6 and the AC was deep.The haemorrhagic ciliochoroidaldetachment had resolved with mini-mum retinal pigment epithelium(RPE) changes at the macula.Spontaneous choroidal detachmentcausing secondary angle-closure glau-coma has numerous associations, suchas uveal effusion syndrome, scleritis,carotid cavernous fistulas, Harada’sdisease and acquired immunodefi-ciency syndrome (Pesin et al. 1990).Renal hypertension presenting asacute angle-closure glaucoma secon-dary to serous retinal detachment ingrade IV hypertensive retinopathy hasbeen reported previously (Arora et al.1991; Pierro et al. 1991).Acute angle closure due to haemor-rhagic ciliochoroidal detachment as acomplication of hypertensive choroid-opathy is unusual (Pesin et al. 1990).It induced transient myopia andintractable ocular pain in our patient,who had previously undetected accel-erated hypertension. The mechanismof angle closure involved forward bul-ging of the iris lens diaphragm follow-ing haemorrhagic ciliochoroidaldetachment. The painful visual loss isattributed to ciliochoroidal ischaemiaand haemorrhagic infarction (Kiny-oun & Kalina 1986). The symptomswere highly suggestive of anteriorischaemic ocular syndrome or ‘ocularangina’. The underlying causes of thechoroidal haemorrhage were suddenincreasing blood pressure, increasingsympathetic tone, fragility of choroi-dal vessels and haemorrhagic choroi-dal infarction.Accelerated essential hypertensionwas the only associated condition inthis patient after endocrine, renal andcollagen vascular diseases had beenexcluded. He had been unaware of hishypertension until he presented withacute visual loss. Nd:YAG peripheraliridotomy was attempted to preventperipheral anterior synechiae and sec-ondary glaucoma, but was ineffective.With hindsight, achieving control ofblood pressure prior to undergoingYAG peripheral iridotomy might havebeen preferable as the subject’s IOPwas normal at presentation.Hypertensive choroidopathy is asimportant a fundus change as hyper-tensive retinopathy (Hayreh et al.1986). In hypertensive choroidopathy,the choroidal vascular bed showsextensive occlusion and ischaemicchanges (Hayreh et al. 1986). LateRPE changes in the macula are asequaela to RPE infarction associatedwith occlusion of choroidal capillaries.Massive spontaneous choroidal hae-

Endoscopic removal of eroded bands in vertical banded gastroplasty: a novel use of endoscopic scissors (with video)

Vertical banded gastroplasty (VBG) as a surgical therapy for morbid obesity was first described in 1982. VBG involves partitioning the stomach with a vertical staple line and restricting the outlet pouch with a Gortex band. Complications of VBG include partial and total erosion of the band through the vertical staple line or through the lesser curvature into the gastric pouch. Band erosion occurs after surgery in 1% to 3% of patients, and patients may present with symptoms of obstruction, weight gain, nausea, pain, and bleeding. Unless a band has freely eroded from the stomach wall, allowing spontaneous elimination or simple endoscopic retrieval, surgical removal has been required heretofore. Previous attempts at endoscopic removal of eroded bands have included the use of neodymium-yttrium aluminum garnet laser ablation and other electrosurgical devices. Endoscopic scissors transection to remove an eroded laparoscopic band has been described in Europe but has not been performed in the United States. In this series, we describe the endoscopic removal of partially eroded bands embedded in the gastric wall by using flexible endoscopic scissors to sever and subsequently withdraw the bands endoscopically through the mouth. Eroded gastric bands have been safely removed endoscopically in 2 ambulatory outpatients. Case series. Tertiary-care academic center. Efficacy and safety. Highly selected motivated patient population.

Treatment of Small Congenital Nevocellular Naevi Using a Combination of Ultrapulse Carbon Dioxide Laser and Q-Switched Frequency-Doubled Nd-YAG Laser

This report describes treatment combining Ultrapulse CO(2) laser and Q-switched frequency-doubled neodymium:yttrium-aluminum-garnet (Nd-YAG) laser for a number of congenital nevocellular naevi (CNN). The Ultrapulse CO(2) laser removes the superficial component, which contains most of the color, preserving the integrity of the reticular dermis. At a later stage, any residual color is targeted using the Nd-YAG laser. To date, a total of 10 histologically proven CNNs have been treated at the Laser Suite. The median age of the patients was 18 years (range, 13-24 years). All the patients were white females. The patients accepted for treatment had relatively small lesions (mean surface area, 352 mm(2); range, 50-1,092 mm(2)), but the lesions were either cosmetically sensitive or located in an anatomically critical area in which excision could result in a scar that would be unpredictable. The median follow-up period was 24 months. The overall results have been satisfactory, with reduction of color and no significant scarring. The minor textural and pigmentary changes were acceptable to the patients.

Does the Source of Laser Energy Influence the Coagulation of Chorionic Plate Vessels? Comparison of Nd:YAG and Diode Laser on an ex vivo Placental Model

Objectives: To compare the histological effects of diode and Neodymium-Yttrium Aluminium Garnet (Nd:YAG) laser coagulation of chorionic plate vessels. Methods: In selected chorionic plate vessels in an ex vivo term placenta perfused with warm saline solution, diode (wavelength 940 nm) and Nd:YAG (wave length 1,064 nm) laser were used with an output of 30, 40, and 50 W, and 55 and 70 W respectively using preset energy and duration of impact. All vessels were examined histologically blindly to the procedures’ characteristics. Results: A total of 23 vessels were coagulated. Similar histological lesions were observed using diode and Nd:YAG lasers. The lesions were compatible with an acceptable clinical effect at all power outputs tested. The results were not related to the diameter or type of vessels. Lesions of the endothelium and reduction of the vessel lumen were best achieved with a diode laser at 40 W. Conclusion: Nd:YAG and Diode laser induce significant and comparable changes in chorionic plate vessels compatible with an efficient coagulation process under the experimental condition used.

Use of silicone stents for the management of post-tuberculosis tracheobronchial stenosis

The role of bronchoscopic management in post-tuberculosis tracheobronchial stenosis is not well defined. To investigate the role of bronchoscopic intervention, including silicone stenting, in the management of post-tuberculosis tracheobronchial stenosis, the current retrospective study was conducted at a tertiary referral hospital. Under rigid bronchoscopy, 80 patients underwent ballooning, neodymium-yttrium aluminium garnet laser resection and/or bougienation as first-line methods of airway dilatation between January 2000 and December 2003 inclusive, and were followed for a median of 41 months. Silicone stents were required in 75 out of 80 (94%) patients to maintain airway patency. Bronchoscopic intervention provided immediate symptomatic relief and improved lung function in 88% of the patients. After airway stabilisation, stents were removed successfully in 49 out of 75 (65%) patients at a median of 14 months post-insertion. Three patients out of 75 (4%) eventually underwent surgical management. Acute complications included: excessive bleeding (n = 1); pneumothorax (n = 5); and pneumomediastinum without mortality (n = 2). Stent-related late complications, such as migration (51%), granuloma formation (49%), mucostasis (19%) and re-stenosis (40%), were controllable during a median follow-up of 41 months. In conclusion, bronchoscopic intervention, including silicone stenting, could be a useful and safe method for treating post-tuberculosis tracheobronchial stenosis.

Endoscopic transection of distally migrated biliary self-expanding metallic stents by using argon plasma coagulation: a report of 2 cases (with video)

Metallic biliary stents have been shown to have higher patency rates and a decreased need for repeat endoscopic intervention than plastic stents in patients with unresectable pancreatic and biliary malignancies. Distal malposition or migration of self-expanding metallic biliary stents occurs rarely but may lead to stent malfunction, mucosal trauma, or ulceration secondary to impaction into the opposite wall of the duodenum. Surgical and percutaneous transhepatic removal of distally migratedmetallic stents has been reportedbut is excessively invasive andcarries apotential for substantial morbidity. While late endoscopic removal of covered stents has been described and is usually feasible, en bloc removal of uncoveredmetallic stents is usually impossible, because they become imbedded in the biliary epithelium; piecemeal extraction of uncovered stents has been reported but is cumbersome and not always possible. Endoscopic transection of metallic stents has been reportedwhen using a neodymium-yttrium aluminum garnet laser, but this technology is not widely available and raises concerns about inadvertent tissue injury and perforation. Argon plasma coagulation (APC) is a widely available method for tissue coagulation. Use of APC to transectmetallic stents has been described from a single institution in Europe but has not been described in the United States. We describe our initial experience when using APC for the transection of distally migrated self-expanding metallic stents.

The Combined Occluding Effects of Fluoride-Containing Dentin Desensitizer and Nd-yag Laser Irradiation on Human Dentinal Tubules: an In Vitro Study

The purpose of the present study was to evaluate the combined occluding effects of fluoride-containing dentin desensitizer and neodymium:yttrium aluminum garnet (Nd-YAG) laser irradiation on human dentinal tubules. All six of the groups of dentin samples (A-F) included in this study received applications of fluoride-containing dentin desensitizer. Groups B, D, and F also received Nd-YAG laser irradiation. Groups A and B served as controls, to allow observations of the occluding effects on the dentinal tubules before and after Nd-YAG laser irradiation. Groups C and D were treated with 0.5 M vitamin C solution, whereas groups E and F underwent brushing with an electric toothbrush. Scanning electron microscopy (SEM) revealed that the fluoridated dentinal tubule-occluding agent (FDTOA) formed a fine crystalline deposit on the dentin surface. After soaking in 0.5 M vitamin C solution for 3 hours, the crystalline deposit of the FDTOA was completely dissolved. Furthermore, brushing of the teeth 3,600 times removed most of the occluding agent. When the application of FDTOA was combined with Nd-YAG laser irradiation, the dentin melted and then recrystallized. The occluding agent was thus 'burned into' the dentinal tubules, and could neither be dissolved by vitamin C solution nor removed by brushing. Therefore, we concluded that the FDTOA combined with Nd-YAG laser irradiation burns the occluding agent into the dentinal tubules, thereby resisting the effects of an acidic diet and brushing, and increasing the duration of the desensitizing effect.

Poor palliation of colorectal malignancy with the neodymium yttrium-aluminium-garnet laser.

The neodymium yttrium-aluminium-garnet (NdYAG) laser was used to palliate the symptoms of 38 patients with rectal carcinoma unsuitable for radical surgery. All patients with small tumours (n = 6) reported resolution of their symptoms. In contrast, those with large tumours frequently showed little improvement (n = 18) and alternative surgical management was necessary in 12 patients. The overall early mortality rate (less than 1 month after first treatment) was 21 per cent. The NdYAG laser offers good palliation and may even cure small colorectal tumours in patients who are unsuitable for surgery. For large circumferential tumours, those associated with obstruction and those close to or involving the anal sphincters, however, the results are poor and better symptom control may be achieved by other means.

Focal Hyperthermia Produces Progressive Tumor Necrosis Independent of the Initial Thermal Effects

Focal hyperthermia, produced using laser, radio frequency, and microwave, is used to treat liver tumors. The exact mechanisms of tissue destruction using focal hyperthermia are, however, unknown. Clinical and experimental studies suggest a progression of injury after cessation of the initial heat stimulus. This study investigates the mechanisms and time sequence of progressive tissue necrosis induced using focal hyperthermia in a murine model of colorectal liver metastases. Focal hyperthermia produced using a neodymium-yttrium aluminum garnet (Nd-YAG) laser source was applied to the normal liver and colorectal cancer liver metastases in inbred male CBA strain mice. The extent of direct lethal thermal injury was assessed histochemically using vital stain for nicotinamide adenine dinucleotide (NADH) diaphorase immediately after laser application. Tissue injury at subsequent time points was assessed using both NADH diaphorase staining and routine histology to determine the temporal relationship between tissue necrosis and time. Thermal injury occurring immediately after the application of 100 joules of energy was greater in the tumor tissue than in the normal liver (mean [standard error of the mean (SEM)]), measuring 23.5 (3.4) and 16.3 (2.6) mm(3), respectively (P=0.046), despite similar tissue temperature profiles. There was a significant increase in tissue necrosis after initial injury that was greater in the normal liver than in the tumor tissue. In the normal liver, the peak volume of necrosis was 137.4 (9.8) mm(3) and occurred at 3 days, whereas in the tumor tissue the peak was 49.0 (3.5) mm(3) at 4.5 days (P < 0.001). Focal hyperthermia produces tissue necrosis that occurs in two phases. The first phase is caused by the direct lethal thermal injury followed by a second phase involving a progression of necrosis beyond the initial thermal effects. The normal liver and the tumor tissue responded differently to focal hyperthermia. In the tumor tissue, the direct injury is more pronounced, whereas the progression of injury is more rapid and extensive in the normal liver.

Laparoscopic laser sterilisation: An alternative option

SummaryThe aim of this prospective study was to evaluate the safety and efficacy of female laparoscopic laser tubal sterilisation. A total of 265 women underwent laparoscopic laser sterilisation as a day-case procedure at Princess Royal University Hospital in Kent between 1996 and 2001. The fallopian tube was divided at the isthmic portion using a neodymium-yttrium aluminium garnet (Nd:YAG) laser probe. All procedures were completed laparoscopically and patients were discharged within 6 h of surgery. No perioperative complications were encountered. The mean follow-up duration was 36 months (range 2 – 7 years) and no intra- or extrauterine pregnancies were reported throughout the entire follow-up period. We conclude that laparoscopic Nd:YAG laser sterilisation appears to be a safe and effective day-case method of female sterilisation. Larger studies with longer follow-up are needed to further define its role as a reliable long-term contraceptive method.

Use of laser for rectal lesions in poor-risk patients

Background This study evaluates laser ablation of large polyps and cancer of the rectum in poor-risk surgical patients. Methods We performed a retrospective review of treatment of rectal lesions with the neodymium yttrium aluminium garnet (Nd:YAG) laser. Biopsy was performed before the first and subsequent therapies. Large lesions were initially debulked by diathermy snare. Biopsies were performed on suspicious areas at follow-up after completion of therapy. Results Three patients with unresectable rectal cancer had symptom control over a mean period of 15.7 months and 12 patients with large polyps over 60.6 months since the start of therapy. Indications in polyps were carpeting of the rectum (n = 3), proximity to sphincter (n = 1), or comorbidity (n = 8). No complication occurred; however, there was 1 treatment failure. None of the patients with polyps developed cancer during a mean follow-up interval of 14 months after final treatment. Conclusions Outpatient laser therapy is safe, repeatable, and effective in the local control of rectal lesions.

Experimental application of thermosensitive paramagnetic liposomes for monitoring magnetic resonance imaging guided thermal ablation

The use of a liposomal paramagnetic agent with a T(1)-relaxivity that increases markedly at temperatures above the phase transition temperature (T(m)) of the liposomal membrane was evaluated during magnetic resonance imaging (MRI) guided hyperthermia ablation. A neodymium-yttrium aluminum garnet (Nd-YAG) laser unit and a radiofrequency ablation system were used for tissue ablation in eight rabbit livers in vivo. One ablation was made in each animal prior to administration of the liposomal agent. Liposomes with a T(m) of 57 degrees C containing gadodiamide (GdDTPA-BMA) were injected iv, and two additional ablations were performed. T(1)-weighted scans were performed in heated tissue, after tissue temperature had normalized, and 15-20 min after normalization of tissue temperature. Increase in signal intensity (DeltaSI) for ablations prior to injection of the agent was 13.0% (SD = 5.7) for the laser group and 9.1% (SD = 7.9) for the radiofrequency group. Signal intensity after administration of the agent unrelated to heating was not statistically significant (DeltaSI = 1.4%, P = 0.35). For ablations made after injection of the agent, a significant increase was found in the laser (DeltaSI = 34.5%, SD = 11.9) and radiofrequency group (DeltaSI = 21.6%, SD = 22.7). The persistent signal enhancement found in areas exposed to a temperature above the threshold temperature above T(m) allows thermal monitoring of MRI guided thermal ablation.

Liver ablation therapy.

The first description of percutaneous ethanol injection (PEI) was published in 1986, a small series of just 14 patients with small, non-resectable hepatocellular carcinoma (HCC) [1]. Thermal techniques were first performed in the liver at our institution in 1989, initially using single bare tip neodymium yttrium aluminium garnet (NdYAG l 1064 nm) laser fibres placed under ultrasound guidance [2]. 15 years on there are hundreds of centres performing thousands of ablations mostly using radiofrequency (RF). The most common site for treatment remains the liver but ablation has been performed in many other sites including lung, renal, adrenal, pleura, bone, pelvic tumours and nodal masses. Two particularly promising areas of development are RF ablation for inoperable lung cancer and as a minimally invasive, nephron sparing technique in renal cell carcinoma. This article looks at liver ablation; the different technologies available, the clinical results and current status of ablation in patients with colorectal liver metastases, neuroendocrine metastases and non-colorectal, non-neuroendocrine metastases, e.g. breast, and HCC.