Design and evaluation of a fiberoptic fluorescence guided laser recanalization system

A nanometer-sized protease inhibitor for precise cancer diagnosis and treatment

Inhibition of pro-cancer proteases is a potent anticancer strategy. However, protease inhibitors are mostly developed in the forms of small molecules or peptides, which normally suffer from insufficient metabolic stability. The fast clearance significantly impairs the antitumor effects of these inhibitors. In this study, we report a nanometer-sized inhibitor of a pro-cancer protease, suppressor of tumorigenicity 14 (st14), which has been reported as a potent prognostic marker for multiple cancers. This st14 inhibitor was fabricated by conjugating a recombinant st14 inhibitor (KD1) with carbon quantum dots (CQDs). CQD-KD1 not only demonstrated high potency of inhibiting st14 activity in biochemical experiments, but also remarkably suppressed the invasion of breast cancer cells. In contrast to the original recombinant KD1, CQD-KD1 demonstrated a prolonged retention time in plasma and at the tumor site because of the reduced renal clearance. Consistently, CQD-KD1 demonstrated enhanced efficacies of suppressing tumor growth and cancer metastases in vivo. In addition, CQD-KD1 precisely imaged tumor tissues in cancer-grafted mice by specifically targeting the over-expressed st14 on the tumor cell surface, which indicates CQD-KD1 as a potent probe for the fluorescence guided surgery of tumor resection. In conclusion, this study demonstrates that CQD-KD1 is a highly potent diagnostic and therapeutic agent for cancer treatments.

Spectroscopic characterisation of carotid atherosclerotic plaque by laser induced fluorescence

BACKGROUND AND OBJECTIVE

An effort has been made to distinguish the composition of carotid atherosclerotic plaques (CAP) from patients undergoing carotid endarterectomy, by laser induced fluorescence spectroscopy.

STUDY DESIGN/MATERIALS AND METHODS

Different excitation wavelengths were used: 476, 488, and 458 nm of a continuous wave krypton/argon ion laser, and 337 nm of a pulsed nitrogen laser. Twenty-three CAP samples from different patients were investigated and several spectra from each plaque were obtained.

RESULTS

Results were crossed-examined with conventional histologic techniques, which showed three areas of different composition on the pathologic samples: fibrous tissue, lipid constituents, and calcified plaque. Gaussian fittings were performed to reproduce the fluorescence spectra as a correlation of multiple Gaussian curves.

CONCLUSION

The accuracy for discrimination of the heterogeneous composition of the atherosclerotic plaque is still limited, due to superposition of the fluorescence emission of various plaque components.

Single-laser approach for fluorescence guidance of excimer laser angioplasty at 308 nm: evaluation in vitro and during coronary angioplasty

BACKGROUND AND OBJECTIVE

Spectroscopic guidance of laser angioplasty has been attempted using a diagnostic He-Cd laser in addition to the therapeutic laser system. This study evaluated a single-laser approach for simultaneous ablation and fluorescence excitation.

STUDY DESIGN/MATERIALS AND METHODS

A spectroscopy system was coupled to a clinical XeCl excimer laser. Ablation of 162 human aortic samples in saline and blood with 45 mJ/mm2 per pulse yielded 676 fluorescence spectra validated histologically. The same equipment was used in 16 patients for angioplasty of 18 coronary stenoses applying 500 to 1,725 pulses with 45 to 60 mJ/mm2 under saline flushing. A total of 783 spectra were recorded and validated by intracoronary ultrasound (categories: atheroma, fibrous plaque, calcified lesion).

RESULTS

In vitro, 5 types of spectra could be differentiated: (1) atheroma, (2) fibrous plaque, (3) calcified lesion in saline, (4) media, and (5) calcified lesion in blood. Discriminant analysis prospectively classified 576 validation spectra with the following sensitivity and specificity for each type: (1) 83.5 and 97.1%, (2) 85.7 and 96.8% (3) 100 and 98.5%, (4) 98.1 and 99.3%, (5) 98.9 and 100%, respectively. In vivo type 1, 2, 3, and 5 spectra were also observed, but not the media spectrum. The predominant sonographic category also prevailed in spectroscopy. Calcified lesions yielded type 3 and 5 as well as mixed spectra.

CONCLUSIONS

Using an excimer laser for angioplasty allows combining ablation and fluorescence excitation without a diagnostic laser. Principal types of atherosclerotic lesions and the media can be differentiated spectroscopically with this approach.

Fluorescence spectrum analysis of atherosclerotic plaque using doxycycline

Using doxycycline (DOXY), fluorescence spectrum analysis was performed on arteriosclerotic lesions, and the efficacy of this method was examined in basic and clinical studies. In the basic study, DOXY 50 mg was administered intravenously to arteriosclerotic rabbits, and the thoracoabdominal aorta removed. Fluorescence spectral analysis was performed on each specimen, and the fluorescence spectral pattern, peak intensity and degree of intimal hypertrophy were studied. In the clinical study, DOXY 200 mg was administered intravenously to 6 human subjects with stable angina and coronary arterial stenosis of greater than 90%, and coronary angiography, coronary angioscopy and fluorescence spectral analysis were performed. DOXY accumulation in the arteriosclerotic intima of rabbit aortae was confirmed. The fluorescence spectrum was monomodal, peaking at around 532 nm. In the noncalcification group, significant correlation was observed between peak intensity and arteriosclerotic intimal thickness. Using DOXY as a fluorescent marker, it was possible to assess the level of arteriosclerotic intimal hypertrophy. Clinically, it was possible to obtain the DOXY spectrum of the coronary arteries.

[Development and evaluation of a spectroscopy system for classification of laser-induced arterial fluorescence spectra]

The present study evaluated the potential of fluorescence guidance of laser angioplasty without using a second laser for fluorescence excitation. A prototype spectroscopy system with a grating spectrograph, microchannel plate, CCD array and digital image processor on a personal computer was developed and coupled to a clinical XeCl excimer laser. Using multifibre catheters, specimens of human aorta were ablated in physiological saline and blood. The spectra thus generated were recorded and validated histologically. Five types of spectra could be differentiated. Based on a training set, classification algorithms were developed using multiple linear regression and linear discriminant analysis with intensity ratios as predictor variables. Discriminant analysis yielded prospective classification of the remaining validation spectra with high sensitivity and specificity for each type. These data demonstrate that fluorescence spectroscopy during excimer laser ablation at 308 nm does not require a diagnostic laser. Principal types of atherosclerotic lesions and the media can be differentiated spectroscopically in physiological saline and blood.

Evaluation of a fluorescence feedback system for guidance of laser angioplasty

BACKGROUND AND OBJECTIVE

Laser-induced fluorescence spectroscopy (LIFS) may be capable of guiding laser angioplasty by discriminating normal and atherosclerotic artery and by determining catheter-tissue environment. Previous optical multichannel analyzer based LIFS systems have been expensive and cumbersome. To simplify LIFS, a system based on photomultiplier tubes was developed and evaluated.

STUDY DESIGN/MATERIALS AND METHODS

Tissue fluorescence was induced by a helium cadmium laser (wavelength = 325 nm, power = 0.2-0.5 mW), collected by clinical multifiber laser angioplasty catheters and directed through one of two filters (10 nm bandpass, 380 nm or 440 nm peak transmission) to a photomultiplier tube. An LIFS ratio was defined as the relative intensity at 380:440 nm after calibration with an elastin fluorescence spectrum; 157 coronary artery cadaveric specimens were evaluated spectroscopically and histologically. To evaluate the utility of LIFS to optimize catheter position by determining catheter-tissue contact, by determining saline dilution of blood, and by orienting eccentric multifiber catheters a new variable, the total fluorescence intensity (TFI) was defined as the sum of arterial fluorescence intensities at 380 nm and 440 nm. TFI was recorded in vitro through multifiber catheters from 20 arterial specimens in vitro in blood and evaluated as a function of the catheter-to-tissue distance (d) over a range from 0 to 400 mu.

RESULTS

Defining normal specimens as those with an intimal thickness < or = 200 mu, and atherosclerotic as those with an intimal thickness > 200 mu, 47/50 (94%) normal and 85/107 (79%) atherosclerotic specimens were correctly classified using a threshold LIFS ratio of 2.0. Mean (+/- SE) normal ratio was 1.76 +/- 0.02 and mean atherosclerotic ratio was 2.78 +/- 0.08 (P < or = 0.01). The classification accuracy of atherosclerotic specimens increased with intimal thickness so that 95% of atherosclerotic specimens (69/73) with intimal thickness > or = 400 mu were correctly classified. TFI was capable of determining catheter-tissue contact as maximal TFI was recorded with the catheter in contact with the tissue (d = 0 mu) and decreased markedly with distance (to 52 +/- 6% at d = 100 mu, 19 +/- 4% at d = 200 mu, and 3 +/- 1% at d = 300 mu). TFI was recorded from ten arterial specimens in blood/saline mixtures ranging in hematocrit from 0% (saline) to 50% (whole blood). TFI was capable of detecting saline hemodilution of blood as TFI decreased markedly at higher hematocrits such that TFI could only by recorded at hematocrits < 10% for catheter-to-tissue distances > or = 300 mu. TFI was recorded through ecentric multifiber catheters from 25 arterial specimens and eval-uated as a function of the degree of catheter-tissue overlap. TFI was capable of detecting maximal catheter-tissue overlap as TFI correlated linearly with the area (A) of overlap (TFI = 1.12 A + .07, r = 0.92).

CONCLUSIONS

By discriminating atherosclerotic from normal tissue and by confirming catheter-tissue contact and saline hemodilution, fluorescence feedback should minimize irradiation of normal tissue and/or blood and enhance the safety and efficacy of laser angioplasty.

Effect of midinfrared holmium: YAG laser angioplasty with and without balloon angioplasty on acute outcome and restenosis in atherosclerotic femoral arteries in rabbits

BACKGROUND AND OBJECTIVE

Pulsed laser may lessen vascular damage and reduce restenosis. This study examined the acute and chronic effects of midinfrared laser angioplasty with and without balloon angioplasty in atherosclerotic femoral arteries in rabbits.

STUDY DESIGN/MATERIALS AND METHODS

Atherosclerosis was induced in arteries by air desiccation and cholesterol feeding. Arteries were assigned to one of four groups: (1) laser angioplasty with a Thullium/Holmium/Chromium:YAG infrared laser (Eclipse), (2) balloon angioplasty, (3) laser followed by balloon angioplasty, and (4) no intervention. Arteries were examined angiographically and histologically at 2 hours and 28 days.

RESULTS

Intervention groups had significant initial gain, but this gain was less with laser alone than after balloon or after laser plus balloon. At 2 hours, laser alone caused greater arterial damage and thrombosis compared to controls. At 28 days, arteries treated with laser plus balloon had greater narrowing compared with arteries treated with balloon angioplasty. By multivariate regression analysis, the severity of the pre-intervention stenosis (P = 0.001) and intervention with laser plus balloon (P = 0.01) correlated independently with the severity of luminal narrowing at 28 days.

CONCLUSION

Midinfrared Ho:YAG laser angioplasty resulted in substantial acute damage with increased frequency of thrombus formation in this rabbit model. arteries treated with laser alone had suboptimal initial gain and more obstruction by plaque at 28 days compared to nonintervened arteries. The adjunctive use of balloon angioplasty improved initial gain, but correlated with smaller luminal diameters and more severe narrowing by plaque at 28 days.

Cardiovascular applications of laser technology

Laser technology has been evaluated for the treatment of coronary artery disease, ventricular and supraventricular arrythmias, hypertrophic cardiomyopathy, and congenital heart disease. Developments in laser angioplasty, laser thrombolysis, transmyocardial laser revascularization, photochemotherapy, laser treatment of arrhythmias and/or laser diagnostics are directed at improving upon conventional non-laser approaches, and providing new therapeutic and diagnostic options. This review will summarize the current status of the multiple applications of laser technology for cardiovascular diagnosis and therapy.

Coronary laser angioplasty

With the widespread growth of percutaneous transluminal coronary angioplasty (PTCA), the realization of limitations of balloon angioplasty stimulated the development of alternative revascularization approaches such as laser angioplasty. PTCA is best suited for the treatment of discrete atherosclerotic stenoses, with lower success rates and more difficult application in patients with diffuse atherosclerotic disease or total occlusions [1-3]. Moreover, despite an initially high primary success rate, coronary angioplasty is still plagued by a restenosis rate as high as 57% [4]. The potential advantages of laser angioplasty address the limitations of PTCA. In contrast to balloon angioplasty where the plaque material is compressed or displaced, laser angioplasty ablates the plaque material [5]. This bulk removal of plaque material could improve acute procedural success rates, decrease complication rates, treat "untreatable" lesions, and decrease restenosis rates. Because laser energy can vaporize atherosclerotic plaque, there may be no requirement for a preexisting channel, and therefore laser angioplasty may have a high success rate for the treatment of coronary occlusions. In its best embodiment, laser angioplasty offers the potential for passing a fiberoptic catheter through the entire length of the coronary circulation to vaporize all atherosclerotic plaque along the arterial wall. This applicability for the treatment of diffuse atherosclerotic disease would offer treatment opportunities currently unavailable with conventional bypass surgery or angioplasty.

Autofluorescence spectroscopy using a XeCl excimer laser system for simultaneous plaque ablation and fluorescence excitation

Laser-induced fluorescence may be used to guide laser ablation of atherosclerotic lesions. This study was performed to evaluate arterial autofluorescence spectroscopy in vitro using a single XeCl excimer laser (308 nm) for simultaneous tissue ablation and fluorescence excitation. The laser beam was coupled to a 600-microns silica fiber transmitting 40-50 mJ/mm2 per pulse. The fluorescence radiation emanating retrogradely from the fiber was collected by a concave mirror spectroscopic analysis over a range of 321-657 nm. The arterial media (n = 26), lipid plaques (n = 26), and calcified lesions (n = 27) of aortic specimens from ten human cadavers were investigated in air, saline, and blood. Whereas the spectrum of calcified lesions changed with the surrounding optical medium, the other spectra remained constant. In air and blood, the spectra of arterial media, lipid plaques, and calcified lesions could be differentiated qualitatively and quantitatively (P < 0.0001). In saline, there was no clearcut spectroscopic difference between lipid plaques and calcified lesions. However, normal arterial media and atherosclerotic lesions (lipid plaques plus calcified lesions) could still be discriminated. Thus spectroscopy and plaque ablation can be combined using a single XeCl excimer laser. These encouraging results should stimulate further studies to determine the potential use of this approach to guide laser angioplasty in humans.

Lasers in neurosurgery

Lasers have been used in neurosurgery for the past 25 years, undergoing modifications to suit the specific needs of this medical discipline. The present report reviews the current use of lasers in neurosurgical practice and examines the pros and cons of lasers in specific neurosurgical applications. In spite of their advantages, laser use is still not widespread in neurosurgery. One reason is the continued lack of complete control over real-time laser interactions with neural tissue. A greater acceptance and use of lasers by neurosurgeons will depend upon automated control over defined specific parameters for laser applications based upon the type of tissue, the desired effect on tissue, and application to the clinical situation without loss of precision and a lot of expense. This will require the integration of newer lasers, computers, robotics, stereotaxy, and concepts of minimally invasive surgery into the routine management of neurosurgical problems.

Assessing Photofrin uptake in atherosclerosis with a fluorescent probe: comparison with photography and tissue measurements

The purpose of this study was to assess Photofrin porfimer sodium (P*) concentration in atherosclerotic plaque (ASP) using a fluorescence detector (Fluoroprobe) compared with fluorescent photography and chemical extraction of P*. ASP was created in the aortoiliac segments of Yucatan miniswine by a combination of balloon endothelial injury and 2% cholesterol and 15% lard diet for 7 weeks. At that time, swine were given P* I.V. in one of the following single dosages: Group I, 2.5; Group II, 1.0; or Group III, 0.5 mg/kg. Swine were sacrificed 24 hours later and aortoiliac and control carotid artery segments removed. Fluorescence was determined from these segments using photographic techniques, the Fluoroprobe, and a spectrofluorometer after chemical extraction. ASP were identified in all swine using photography and the Fluoroprobe. The intensity of fluorescence measured with the Fluoroprobe for Groups I to III was 1,098 +/- 524, 471 +/- 337, and 295 +/- 173 units, respectively (P < 0.01). The tissue concentration of P* in ASP from each group was 130.4 +/- 82.7, 10.0 +/- 1.2, and 9.1 +/- 0.6 ng/g, respectively (P < 0.01). There was a linear correlation between the fluorescence intensity measured with the Fluoroprobe and the extracted tissue concentration (r = 0.88, P < 0.0001). This study showed that a fluorescent detector such as the Fluoroprobe accurately detects the uptake of P* into atherosclerotic plaque.

Vascular applications of lasers

There have been major advances in laser technology and in our understanding of the effects of laser energy on blood vessels. This, in turn, has led to the many clinical applications of lasers in patients with vascular disease. The clinical results of laser endarterectomy, laser angioplasty, laser-assisted balloon angioplasty, laser-assisted vascular anastomoses, and the future of lasers in cardiovascular disease are discussed.

New technologies and future applications of surgical lasers. The right tool for the right job

The real future of surgical lasers, and indeed of surgery itself, will depend on the integration of the surgeon into a system incorporating real-time tissue sensors, computer-directed robotic manipulation, and laser-tissue interactions that are customized to the clinical task. The human surgeon will operate as the central judgmental element in this mechanized and semiautomated laser surgical system. Only then will we really be able to make use of the subtle and varied laser-tissue effects now being discovered.

Detection of calcified atherosclerotic plaque by laser-induced plasma emission

The use of fluorescence spectroscopy to discriminate atherosclerotic from normal tissue is limited by a lower sensitivity for calcified than noncalcified atherosclerotic plaque (65% vs. 93%, respectively). To evaluate plasma emission as a means to detect calcified plaque, 325 normal and atherosclerotic cadaveric aortic sites were irradiated through a 100-micron silica fiber in blood by a pulsed holmium laser (lambda = 2.1 microns, fluence = 4 J/mm2). A photodiode positioned near the proximal end of the fiber detected plasma emission during a laser pulse. Plasma emission was detected at 0% (0/110) of normal, 0% (0/107) of noncalcified atherosclerotic tissue, and 91% (98/108) of calcified atherosclerotic sites. Spectroscopic analysis confirmed the presence of calcium lines in the plasma emission from calcified atherosclerotic plaque. Although ablative fluences (greater than 3 J/mm2) were required for plasma generation, a single laser pulse ablated only to a depth of 67 +/- 16 microns in normal tissue. In an additional 10 calcified atherosclerotic sites, laser ablation was continued as long as plasma emission was detected. In all cases, plaque ablation was terminated before arterial perforation. Furthermore, the adjunctive use of plasma detection improved the accuracy of fluorescence spectroscopic classification of normal and atherosclerotic tissue. In conclusion, plasma detection has a high sensitivity (91%) and specificity (100%) for calcified atherosclerotic plaque and may be a useful adjunct for laser angioplasty guidance. Furthermore, plasma detection can be implemented both simply and inexpensively.