Image-guided Laser Ablation Research Articles

Near-IR image-guided laser ablation of demineralization on tooth occlusal surfaces.

Studies have shown that reflectance images at near-IR wavelengths coincident with higher water absorption are well-suited for image-guided laser ablation of carious lesions since the contrast between sound and demineralized enamel is extremely high and interference from stains is minimized. The objective of this study was to demonstrate that near-IR reflectance images taken at a wavelength range of 1,500-1,700 nm can be used to guide a 9.3 μm CO(2) laser for the selective ablation of early demineralization on tooth occlusal surfaces. The occlusal surfaces of ten sound human molars were used in this in vitro study. Shallow simulated caries lesions with random patterns and varying depth and position were produced on tooth occlusal surfaces. Sequential near-IR reflectance images at 1,500-1,700 nm were used to guide the laser for the selective removal of the demineralized enamel. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess selectivity. Images taken before and after lesion removal suggest that the demineralized areas were removed with high selectivity. Although the estimated volume of tissue ablated was typically higher than the initial lesion volume measured with PS-OCT, the volume of enamel removed by the laser correlated well with the initial lesion volume. Sequential near-IR reflectance images at 1,500-1,700 nm can be used to guide a 9.3 μm CO(2) laser for the selective ablation of early demineralization on tooth occlusal surfaces.

Outcomes and Risk Factors for Complications of Laser Ablation for Thyroid Nodules: A Multicenter Study on 1531 Patients.

Image-guided laser ablation therapy (LAT) of benign thyroid nodules demonstrated favorable results in randomized trials with fixed modalities of treatment. The aim of this retrospective multicenter study was to assess the effectiveness, tolerability, and complications of LAT in a large consecutive series of patients from centers using this technique in their routine clinical activity. Clinical records of 1534 consecutive laser-treated nodules in 1531 patients from eight Italian thyroid referral centers were assessed. Inclusion criteria were as follows: solid or mixed nodules with fluid component up to 40%; benign cytological findings; and normal thyroid function. LAT was performed with a fixed-power protocol, whereas the number of applicators and illumination times were different according to target size. From one to three illuminations with pullback technique and with a total energy delivery based on the nodule volume were performed during the same session. Patients were evaluated during LAT, within 30 days, and 12 months after the procedure. Total number of treatments was 1837; 1280 (83%) of nodules had a single LAT session. Mean nodule volume decreased from 27 ± 24 mL at baseline to 8 ± 8 mL 12 months after treatment (P < .001). Mean nodule volume reduction was 72% ± 11% (range 48%-96%). This figure was significantly greater in mixed nodules (79% ± 7%; range 70%-92%) because they were drained immediately before laser illumination. Symptoms improved from 49% to 10% of cases (P < .001) and evidence of cosmetic signs from 86% to 8% of cases (P < .001). Seventeen complications (0.9%) were registered. Eight patients (0.5%) experienced transitory voice changes that completely resolved at the ear-nose-throat examination within 2-84 days. Nine minor complications (0.5%) were reported. No changes in thyroid function or autoimmunity were observed. Real practice confirmed LAT as a clinically effective, reproducible, and rapid outpatient procedure. Treatments were well tolerated and risk of major complications was very low.

Image-guided removal of occlusal caries lesions with a λ= 9.3-µm CO2 laser using near-IR transillumination.

Previous studies have shown that near-IR transillumination is well suited for imaging deep occlusal lesions. The purpose of this study was to determine if near-IR images can be used to guide a CO2 laser for the selective removal of natural occlusal lesions on extracted teeth. Near-IR occlusal transillumination images of extracted human teeth with natural occlusal caries lesions were acquired using an InGaAs camera and near-IR light at wavelengths from 1290 to 1470-nm from a filtered tungsten halogen source. A CO2 laser operating at 9.3-µm with a pulse duration of 10-15-µs and a pulse repetition rate of 100-300-Hz was used for caries removal. Optical Coherence tomography was used to confirm lesion presence and serial scans were used to assess selective removal. Teeth were also sectioned for histological examination using polarized light microscopy. This study suggests that near-infrared transillumination is a promising method for the image guided laser ablation of occlusal caries lesions but the use of serial near-IR transillumination imaging for monitoring lesion removal was limited.

Selective removal of demineralized enamel using a CO2 laser coupled with near-IR reflectance imaging.

Detection and diagnosis of early dental caries lesions can be difficult due to variable tooth coloration, staining of the teeth and poor contrast between sound and demineralized enamel. These problems can be overcome by using near-infrared (NIR) imaging. Previous studies have demonstrated that lasers can be integrated with NIR imaging devices, allowing image-guided ablation. The aim of this study was to demonstrate that NIR light at 1500 - 1700 nm can be used to guide a 9.3-μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. The occlusal surfaces of ten sound human molars were used in this in-vitro study. Shallow simulated caries lesions of varying depth and position were produced on tooth occlusal surfaces using a demineralization solution. Sequential NIR reflectance images at 1500 - 1700 nm were used to guide the laser for selective ablation of the lesion areas. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess the selectivity of removal. This study demonstrates that high contrast NIR reflectance images can be used for the image-guided laser ablation of early demineralization from tooth occlusal surfaces.

MR‐guided laser‐induced thermotherapy (LITT) in patients with liver metastases of uveal melanoma

Evaluation of the local tumour control rate and survival data for magnetic resonance (MR) imaging-guided laser ablation of uveal malignant melanoma liver metastases by using laser-induced interstitial thermotherapy (LITT). The LITT was performed in 18 patients with liver metastases (n = 44) from uveal malignant melanoma. All patients tolerated this intervention well. With the Kaplan-Meier method, the survival rates were calculated. Indications for the procedure were defined for patients with no more than five metastases, none of which were larger than 5 cm in diameter: The Indication for LITT treatment were recurrent liver metastases after partial liver resection (22%), locally non-resectable tumours (17%) or metastases in both liver lobes (61%). The mean survival rate for all treated patients was 3.6 years (95% CI: 2.19, 5.06). We started the calculation on the date of diagnosis of the metastases treated with LITT. The median survival was 1.83 years; 1-year survival, 88%; 3-year survival 47%, 5-year survival 17%. Calculated after the first LITT treatment the median survival was 2.8 years (95% CI: 1.0, 5.0). 10 patients were treated by transarterial chemoembolization before LITT. MR-guided LITT treatment shows a high local tumour control and survival rates in patients with liver metastases of uveal malignant melanoma.

Molecular Bioluminescence Imaging as a Noninvasive Tool for Monitoring Tumor Growth and Therapeutic Response to MRI-Guided Laser Ablation in a Rat Model of Hepatocellular Carcinoma

The objective of this study was to quantitatively compare tumor imaging by magnetic resonance imaging (MRI) and molecular bioluminescence imaging (BLI) and test the feasibility of monitoring the effect of MRI-guided laser ablation on tumor viability by 2-dimensional BLI and 3-dimensional diffuse luminescence tomography (3D DLIT) in an orthotopic rat model of hepatocellular carcinoma. This study was approved by the animal care committee. Rats underwent injection of N1S1 cells stably transfected with an empty vector (n = 3) or a heat shock element luciferase reporter (HSE-luc; n = 4) into the liver. All rats underwent MRI to assess tumor establishment and volume and 2-dimensional BLI to assess tumor luminescence at day 7 with subsequent MRI and 2D BLI and 3D DLIT in select animals at days 14 and 21. Magnetic resonance imaging-guided laser ablation of the tumor was performed with preablation and postablation 2D BLI and/or 3D DLIT (n = 2). The tumors underwent histopathologic analysis to assess tumor viability. The MRI scans demonstrated hyperintense T2-weighted lesions at 3 of 3 and 4 of 4 sites in the empty vector and HSE-luc rats, respectively. Two-dimensional BLI quantitation demonstrated 23.0-fold higher radiance in the HSE-luc group compared with the empty vector group at day 7 (P < 0.01) and a significant correlation with tumor volume by MRI (r = 0.86; P < 0.03). Tumor dimensions by 3D DLIT and MRI demonstrated good agreement. Three-dimensional DLIT quantitation demonstrated better agreement with the percentage of nonviable tumor by histopathology than did 2D BLI quantitation after the MRI-guided laser ablation. Bioluminescence imaging is feasible as a noninvasive, quantitative tool for monitoring tumor growth and therapeutic response to thermal ablation in a rat model of hepatocellular carcinoma.

Magnetic Resonance Imaging–Guided Laser Ablation of Bone Tumors

Image-guided thermal ablation of bone tumors is gaining acceptance in the oncology community. Computed tomography-guided radiofrequency ablation and cryoablation are widely available and are used in clinical practice. However, a potentially devastating complication of these techniques is thermal injury to the spinal cord and nerve roots in patients with tumors involving the vertebra, paraspinal tissues, or pelvis. Magnetic resonance imaging-guided laser ablation with quantitative magnetic resonance temperature imaging is a novel technique that allows for accurate imaging of the tumor, real-time placement of laser fibers, and real-time monitoring of the ablation zone. With this technique, target temperature thresholds are placed on critical neural elements to provide real-time feedback that allows for automatic deactivation of the laser when the threshold temperature is reached. The ablation zone is generated quickly, with sharp and well-demarcated boundaries. As such, magnetic resonance imaging-guided laser ablation may be a safer technique for ablating bone tumors in the vicinity of the spinal cord, nerve roots, and peripheral nerves.

Feasibility of 3.0T Magnetic Resonance Imaging-guided Laser Ablation of a Cadaveric Prostate

To demonstrate the feasibility of 3.0T magnetic resonance imaging (MRI)-guided laser ablation of the prostate. MRI-guided laser ablations in the intact prostate gland were performed in 5 cadavers. The cadavers were brought into the MRI suite and placed in a supine headfirst position. A needle guide grid was placed against the perineum, and MRI was performed to co-localize the grid with the prostate imaging data set. Using the guidance grid and 14-gauge Abbocath catheters, the laser applicators were placed in the prostate with intermittent MRI guidance. After confirmation of the position of the laser applicators, 2-minute ablations were performed with continuous MRI temperature feedback. Using the relative change in temperature and the Arrhenius model of thermal tissue ablation, the ablation margins were calculated. Laser ablation was successfully performed in all 5 cadaveric prostates using 15- and 30-W laser generators. Thermal mapping in the axial, sagittal, and coronal planes was performed with calculated ablation margins projected back onto the magnitude MR images. Deviations of the needles from the template projections ranged from 1.0 to 4.1 mm (average 2.1) at insertion depths of 75.5-116.5 mm (average 98.2). In the 2 cadavers for which histologic correlation was available, the extent of the ablation zone corresponded to the temperature mapping findings and the ablation transition zones were identifiable on hematoxylin-eosin staining. Transperineal laser ablation of the prostate gland is possible using 3.0T MRI guidance and thermal mapping and offers the potential for precise image-guided focal targeting of prostate cancer.

Near-infrared image-guided laser ablation of dental decay

Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO(2) laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO(2) laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO(2) laser ablation system for the selective removal of dental caries.

Image-Guided Laser Ablation of Osteoid Osteoma in Pediatric Patients

We aimed to evaluate the effectiveness of image-guided laser ablation for the treatment of osteoid osteomas in pediatric patients. From June 1994 to June 2006, 68 patients aged 3 to 18 years (mean age, 12.1 +/- 4.2 years) with a diagnosis of osteoid osteoma underwent laser ablation in our department. Among them, 3 patients had prior unsuccessful attempt of surgical resection. Procedures were performed under spinal or general anesthesia with combined computed tomographic and fluoroscopic guidance. An 18-gauge needle was placed in the nidus after bone drilling when required, and an optical fiber was inserted through it. An average energy of 1200 J was delivered using an infrared diode laser generator. Patients were discharged the next day and followed up with assessment of pain, medication intakes, and potential complications. Clinical success was defined by complete pain relief without need for medication intake. Technical success was achieved in all but 1 of our first patients, which was subsequently treated by percutaneous resection. Overall clinical success was 98%. Primary clinical success was obtained in 60 patients (88%). In 7 patients, recurrence of symptoms at 4 to 27 months from the initial procedure was managed by repeat laser ablation, resulting in secondary success (10%). No complications related to the procedure were observed. Follow-up ranged 16 to 146 months (mean, 83 months). Currently, image-guided laser ablation is a safe and effective procedure that can be proposed as the mainstay treatment of osteoid osteomas in pediatrics. Therapeutic case series study level IV.

Near-infrared image-guided laser ablation of artificial caries lesions.

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. The objective of this study was to test the hypothesis that two-dimensional NIR images of demineralized tooth surfaces can be used to guide CO(2) laser ablation for the selective removal of artificial caries lesions. Highly patterned artificial lesions were produced by submerging 5 × 5 mm(2) bovine enamel samples in demineralized solution for a 9-day period while sound areas were protected with acid resistant varnish. NIR imaging and polarization sensitive optical coherence tomography (PS-OCT) were used to acquire depth-resolved images at a wavelength of 1310-nm. An imaging processing module was developed to analyze the NIR images and to generate optical maps. The optical maps were used to control a CO(2) laser for the selective removal of the lesions at a uniform depth. This experiment showed that the patterned artificial lesions were removed selectively using the optical maps with minimal damage to sound enamel areas. Post-ablation NIR and PS-OCT imaging confirmed that demineralized areas were removed while sound enamel was conserved. This study successfully demonstrated that near-IR imaging can be integrated with a CO(2) laser ablation system for the selective removal of dental caries.

Breast cancer metastases in liver: laser-induced interstitial thermotherapy--local tumor control rate and survival data.

To evaluate the local tumor control rate and survival data for magnetic resonance (MR) imaging-guided laser ablation of breast cancer liver metastases by using laser-induced interstitial thermotherapy (LITT). MR-guided LITT was performed in 232 female patients with 578 liver metastases from breast cancer. Survival rates were calculated with the Kaplan-Meier method. Indications for the procedure were defined for patients with no more than five metastases, none of which were larger than 5 cm in diameter, as follows: recurrent liver metastases after partial liver resection (8.2%), metastases in both liver lobes (45.2%), locally nonresectable tumors (19%), general contraindications for surgery (2.6%), or refusal to undergo surgical resection (25%). Local recurrence rate at 6-month follow-up after LITT was 2.3% (five of 213) for metastases up to 2 cm in diameter, 4.3% (seven of 162) for metastases 2-3 cm in diameter, 3.2% (two of 63) for metastases 3-4 cm in diameter, and 1.9% (one of 52) for metastases larger than 4 cm in diameter. No additional local tumor progression was observed beyond 6 months. The mean survival rate for all treated patients, with calculation started on the date of diagnosis of the metastases treated with LITT, was 4.9 years (95% confidence interval: 4.3, 5.4). The median survival was 4.3 years; 1-year survival, 96%; 2-year survival, 80%; 3-year survival, 63%; and 5-year survival, 41%. The mean survival after the first LITT treatment was 4.2 years (95% confidence interval: 3.6, 4.8). MR-guided LITT yields high local tumor control and survival rates in patients with liver metastases from breast cancer.

MR imaging-guided laser ablation of osteoid osteomas with the use of optical instrument guidance at 0.23 T

MR imaging-guided laser ablation of osteoid osteomas with the use of optical instrument guidance at 0.23 T

MR imaging-guided laser ablation of osteoid osteomas with use of optical instrument guidance at 0.23 T.

The purpose of this study was to determine the feasibility and features of low-field MR imaging in performing interstitial laser ablation of osteoid osteomas. Between September 2001 and April 2002, five consecutive patients with clinical and imaging findings suggesting osteoid osteoma and referred for removal of osteoid osteoma were treated with interstitial laser treatment. A low-field open-configuration MRI scanner (0.23 T, Outlook Proview, Philips Medical Systems, Finland) with optical instrument guidance hardware and software was used. Laser device used was of ND-Yag type (Fibertom medilas, Dornier Medizin Technik, Germany). A bare laser fiber (Dornier Medizin Technik, Germany) with a diameter of 400 microm was used. Completely balanced steady-state (CBASS; true fast imaging with steady precession) imaging was used for lesion localization, instrument guidance, and thermal monitoring. A 14-G (Cook Medical, USA) bone biopsy drill was used for initial approach. Laser treatment was conducted through the biopsy canal. All the lesions were successfully localized, targeted, and treated under MRI guidance. All the patients were symptom free 3 weeks and 3 months after the treatment. There was one recurrence reported during follow-up (6 months). The MRI-guided percutaneous interstitial laser ablation of osteoid osteomas seems to be a feasible treatment mode.