Stomach wall structure and vessels imaging by acoustic resolution photoacoustic microscopy.

AIM: To image stomach wall blood vessels and tissue, layer-by-layer. METHODS: We built up the acoustic resolution photoacoustic microscopy (AR-PAM) system for imaging layered tissues, such as the stomach wall. A tunable dye laser system was coupled to a fiber bundle. The fibers of the bundle were placed in nine directions with an incident angle of 45° around a high-frequency ultrasound transducer attached to the acoustic lens. This structure formed a dark field on the tissue surface under the acoustic lens and the nine light beams from the fibers to be combined near the focal point of the acoustic lens. The sample piece was cut from a part of the porcine stomach into a petri dish. In order to realize photoacoustic depth imaging of tumor, we designed a tumor model based on indocyanine green (ICG) dye. The ICG solution (concentration of 129 µM/mL) was mixed into molten gel, and then a gel mixture of ICG (concentration of 12.9 µM/mL) was injected into the stomach submucosa. The injection quantity was controlled by 0.1 mL to make a small tumor model. RESULTS: An acoustic resolution photoacoustic microscopy based on fiber illumination was established and an axial resolution of 25 µm and a lateral resolution of 50 µm in its focal zone range of 500 µm has been accomplished. We tuned the laser wavelength to 600 nm. The photoacoustic probe was driven to do B-scan imaging in tissue thickness of 200 µm. The photoacoustic micro-image of mucosa and submucosa of the tissue have been obtained and compared with a pathological photograph of the tissue stained by hematoxylin-eosin staining. We have observed more detailed internal structure of the tissue. We also utilized this photoacoustic microscopy to image blood vessels inside the submucosa. High contrast imaging of the submucosa tumor model was obtained using ICG dye. CONCLUSION: This AR-PAM is able to image layer-by-layer construction and some blood vessels under mucosa in the stomach wall without any contrast agents.

Label-free cell nuclear imaging by Grüneisen relaxation photoacoustic microscopy.

Photoacoustic microscopy (PAM) with ultraviolet (UV) laser illumination has recently been demonstrated as a promising tool that provides fast, label-free, and multilayered histologic imaging of human breast tissue. Thus far, the axial resolution has been determined ultrasonically. To enable optically defined axial resolution, we exploit the Grüneisen relaxation (GR) effect. By imaging mouse brain slices, we show that GRUV-PAM reveals detailed information about three-dimensional cell nuclear distributions and internal structures, which are important diagnostic features for cancers. Due to the nonlinear effect, GRUV-PAM also provides better contrast in images of cell nuclei.

A Multimodal Biomicroscopic System based on High-frequency Acoustic Radiation Force Impulse and Multispectral Imaging Techniques for Tumor Characterization Ex vivo.

We report a multimodal biomicroscopic system which offers high-frequency ultrasound B-mode, acoustic radiation force impulse (ARFI), and multispectral imaging for qualitative tumor characterization ex vivo. Examinations of resected tissues from diseased regions such as tumors are crucial procedures during surgical operations to treat cancer. Particularly, if tiny tumors remain at surgical sites after tumor resection, such tumors can result in unwanted outcomes, such as cancer recurrence or metastasis to other organs. To avoid this, accurate characterizations of tumors resected during surgery are necessary. To this end, we devised a multimodal biomicroscopic system including high-frequency ultrasound B-mode, ARFI, and multispectral imaging modalities to examine resected tumors with high levels of accuracy. This system was evaluated with tissue-mimicking phantoms with different mechanical properties. In addition, colorectal tumors excised from cancer patients were examined. The proposed system offers highly resolved anatomical, mechanical, chemical information pertaining to tumors, thus allowing the detection of tumor regions from the surface to deep inside tissues. These results therefore suggest that the multimodal biomicroscopic system has the potential to undertake qualitative characterizations of excised tumors ex vivo.

Ex vivo detection of macrophages in atherosclerotic plaques using intravascular ultrasonic-photoacoustic imaging.

Macrophages are excellent imaging targets for detecting atherosclerotic plaques as they are involved in all the developmental stages of atherosclerosis. However, no imaging technique is currently capable of visualizing macrophages inside blood vessel walls. The current study develops an intravascular ultrasonic-photoacoustic (IVUP) imaging system combined with indocyanine green (ICG) as a contrast agent to provide morphological and compositional information about the targeted samples. Both tissue-mimicking vessel phantoms and atherosclerotic plaque-mimicking porcine arterial tissues are used to demonstrate the feasibility of mapping macrophages labeled with ICG by endoscopically applying the proposed hybrid technique. A delay pulse triggering technique is able to sequentially acquire photoacoustic (PA) and ultrasound (US) signals from a single scan without using any external devices. The acquired PA and US signals are used to reconstruct 2D cross-sectional and 3D volumetric images of the entire tissue with the ICG-loaded macrophages injected. Due to high imaging contrast and sensitivity, the IVUP imaging vividly reveals structural information and detects the spatial distribution of the ICG-labeled macrophages inside the samples. ICG-assisted IVUP imaging can be a feasible imaging modality for the endoscopic detection of atherosclerotic plaques.

In Vivo Near Infrared Virtual Intraoperative Surgical Photoacoustic Optical Coherence Tomography.

Since its first implementation in otolaryngological surgery nearly a century ago, the surgical microscope has improved the accuracy and the safety of microsurgeries. However, the microscope shows only a magnified surface view of the surgical region. To overcome this limitation, either optical coherence tomography (OCT) or photoacoustic microscopy (PAM) has been independently combined with conventional surgical microscope. Herein, we present a near-infrared virtual intraoperative photoacoustic optical coherence tomography (NIR-VISPAOCT) system that combines both PAM and OCT with a conventional surgical microscope. Using optical scattering and absorption, the NIR-VISPAOCT system simultaneously provides surgeons with real-time comprehensive biological information such as tumor margins, tissue structure, and a magnified view of the region of interest. Moreover, by utilizing a miniaturized beam projector, it can back-project 2D cross-sectional PAM and OCT images onto the microscopic view plane. In this way, both microscopic and cross-sectional PAM and OCT images are concurrently displayed on the ocular lens of the microscope. To verify the usability of the NIR-VISPAOCT system, we demonstrate simulated surgeries, including in vivo image-guided melanoma resection surgery and in vivo needle injection of carbon particles into a mouse thigh. The proposed NIR-VISPAOCT system has potential applications in neurosurgery, ophthalmological surgery, and other microsurgeries.

Anterior chamber depth studies.

PURPOSE: To compare the anterior chamber depth (ACD; corneal epithelium to lens) using 3 modalities and compare the change 1 day and 3 months postoperatively. SETTING: Private practice, Santa Monica, California, USA. DESIGN: Nonrandomized prospective series. METHODS: The mean optical pachymetry and immersion ultrasound (US) of the ACD and partial coherence interferometry (PCI) were measured. Optical pachymetry ACD was measured in 675 eyes postoperatively at 1 day and 3 months. RESULTS: The optical pachymetry ACD in 492 eyes was 3.17 mm ± 0.42 (SD); by immersion US, it was 2.99 ± 0.51 mm (0.18 mm deeper; P < .0001). In 178 eyes, the optical pachymetry ACD was 3.23 ± 0.45 mm; the PCI was 3.19 ± 0.48 mm (0.04 mm deeper), which was not statistically different (P > .05). In 675 eyes, optical pachymetry ACD preoperatively was 3.19 ± 0.40 mm. The postoperative 1-day optical pachymetry ACD was 4.35 ± 0.35 mm with a mean refractive error of -0.30 diopter (D); the final 3-month optical pachymetry ACD was 4.47 ± 0.31 mm, with a mean refractive error of -0.07 D (P < .0001). This is a mean intraocular lens (IOL) position shift of +0.12 mm posteriorly; the +0.23 D change represents a ratio of 1.92 D/mm of IOL axial movement. CONCLUSIONS: The PCI ACD was comparable with optical pachymetry, but careful immersion US led to a 0.18 mm shorter ACD reading that cannot be corrected by sound velocity. The posterior capsule contracted and moved the IOL posteriorly 0.12 mm, resulting in 0.23 D hyperopic shift. FINANCIAL DISCLOSURE: Dr. Hoffer owns the registered trademark name "Hoffer(®)" and receives royalties for its commercial use from Alcon Laboratories, Inc., Appasamy Associates, Carl Zeiss Meditec AG, DGH Technology, Inc., Ellex iScience, Inc., Haag-Streit AG, Nidek Co., Ltd., Tomey Corp., Topcon Medical Systems, Inc., and Ziemer USA, Inc., as well as royalties from Slack, Inc. for the textbook IOL Power. Neither author has a financial or proprietary interest in any material or method mentioned.

Quantitative phase imaging with molecular sensitivity using photoacoustic microscopy with a miniature ring transducer.

We present a dual-modality system for both structural and molecular cell imaging based on coregistered quantitative phase imaging (QPI) and photoacoustic microscopy (PAM). The QPI system was based on off-axis holography, whereas the PAM system comprised a sinusoidally modulated optical source for excitation and a narrow-band low profile and low-cost ring ultrasonic transducer for detection. This approach facilitated a simple confocal alignment of the excitation beams of both modalities and the ultrasonic detector. This system was demonstrated by imaging endogenous molecules in red blood cells (RBCs) as well as by imaging exogenous molecular labels on cancer cells using gold nanoparticles (GNPs) functionalized to target epidermal growth factor receptor. QPI provided high resolution imaging of the cellular structures while PAM provided molecular contrast. This dual-modality microscopy method can potentially be implemented as a compact and low cost cellular diagnostic assay.

Macrophage with gold nanorod visualized by optical-resolution and acoustic-resolution photoacoustic microscopes.

Macrophages play a key role in inflammation and they are frequently observed in vulnerable atherosclerotic plaque. In the present study, macrophages phagocytosing gold nanorod (AuNR) were observed by optical-resolution (OR) and acoustic-resolution (AR) photoacoustic microscope (PAM). The OR-PAM consisted of diode laser optically focused to 60 micron and planar ultrasonic transducer with the central frequency of 8 MHz placed under the object. AR-PAM consisted of concave ultrasonic transducer with the central frequency of 20 MHz and optical fiber through the center hole of the transducer for laser irradiation. First, PA signal from gold, silver and copper wire were measured in order to determine the best metal substrate for enhancing PA contrast. Gold generated largest PA signal. AuNR with the resonance wavelength of 1064 nm was co-cultured with the macrophages for phagocytosis. PA signal was successfully detected from macrophages with AuNR by both OR-PAM and AR-PAM. PA imaging of the macrophages with AuNR indicates inflammation in the vulnerable plaque and AR-PAM method would be applicable for clinical settings.

Handheld photoacoustic microscopy to detect melanoma depth in vivo.

We developed handheld photoacoustic microscopy (PAM) to detect melanoma and determine tumor depth in nude mice in vivo. Compared to our previous PAM system for melanoma imaging, a new light delivery mechanism is introduced to improve light penetration. We show that melanomas with 4.1 and 3.7 mm thicknesses can be successfully detected in phantom and in in vivo experiments, respectively. With its deep melanoma imaging ability and handheld design, this system can be tested for clinical melanoma diagnosis, prognosis, and surgical planning for patients at the bedside.

Detection and quantification of bacterial biofilms combining high-frequency acoustic microscopy and targeted lipid microparticles.

BACKGROUND: Immuno-compromised patients such as those undergoing cancer chemotherapy are susceptible to bacterial infections leading to biofilm matrix formation. This surrounding biofilm matrix acts as a diffusion barrier that binds up antibiotics and antibodies, promoting resistance to treatment. Developing non-invasive imaging methods that detect biofilm matrix in the clinic are needed. The use of ultrasound in conjunction with targeted ultrasound contrast agents (UCAs) may provide detection of early stage biofilm matrix formation and facilitate optimal treatment. RESULTS: Ligand-targeted UCAs were investigated as a novel method for pre-clinical non-invasive molecular imaging of early and late stage biofilms. These agents were used to target, image and detect Staphylococcus aureus biofilm matrix in vitro. Binding efficacy was assessed on biofilm matrices with respect to their increasing biomass ranging from 3.126 × 103 ± 427 UCAs per mm(2) of biofilm surface area within 12 h to 21.985 × 103 ± 855 per mm(2) of biofilm matrix surface area at 96 h. High-frequency acoustic microscopy was used to ultrasonically detect targeted UCAs bound to a biofilm matrix and to assess biofilm matrix mechanoelastic physical properties. Acoustic impedance data demonstrated that biofilm matrices exhibit impedance values (1.9 MRayl) close to human tissue (1.35 - 1.85 MRayl for soft tissues). Moreover, the acoustic signature of mature biofilm matrices were evaluated in terms of integrated backscatter (0.0278 - 0.0848 mm(-1) × sr(-1)) and acoustic attenuation (3.9 Np/mm for bound UCAs; 6.58 Np/mm for biofilm alone). CONCLUSIONS: Early diagnosis of biofilm matrix formation is a challenge in treating cancer patients with infection-associated biofilms. We report for the first time a combined optical and acoustic evaluation of infectious biofilm matrices. We demonstrate that acoustic impedance of biofilms is similar to the impedance of human tissues, making in vivo imaging and detection of biofilm matrices difficult. The combination of ultrasound and targeted UCAs can be used to enhance biofilm imaging and early detection. Our findings suggest that the combination of targeted UCAs and ultrasound is a novel molecular imaging technique for the detection of biofilms. We show that high-frequency acoustic microscopy provides sufficient spatial resolution for quantification of biofilm mechanoelastic properties.

The sound of orthopaedic surgery--the application of acoustic emission technology in orthopaedic surgery: a review.

Acoustic emission technology has been developed and extensively used as a non-destructive method of testing within engineering. In recent years, acoustic emission has gained popularity within the field of Orthopaedic research in a variety of situations. It is an attractive method in the detection of flaws within structures due its high sensitivity and non-destructive nature. The aim of this article is firstly to critically review the research conducted using acoustic emission testing in a variety of Orthopaedic-related situations and to present the technique to the wider Orthopaedic community. A summary of the principles and practical aspects of using acoustic emission testing are outlined. Acoustic emission has been validated as a method of early detection of aseptic loosening in femoral components in total hip arthroplasty in several well-conducted in vitro studies [1-3]. Other studies have used acoustic emission to detect microdamage in bone and to assess the biomechanical properties of bone and allografts [9]. Researchers have also validated the use of acoustic emission to detect and monitor fracture healing [4]. Several studies have applied acoustic emission to spinal surgery and specifically to assess the biomechanical environment in titanium mesh cages used in spinal surgery [10, 11]. Despite its growing popularity within Orthopaedic research, acoustic emission remains are relatively unfamiliar technique to the majority of Orthopaedic surgeons.

Simultaneous follow-up of mouse colon lesions by colonoscopy and endoluminal ultrasound biomicroscopy.

AIM: To evaluate the potential use of colonoscopy and endoluminal ultrasonic biomicroscopy (eUBM) to track the progression of mouse colonic lesions. METHODS: Ten mice were treated with a single azoxymethane intraperitoneal injection (week 1) followed by seven days of a dextran sulfate sodium treatment in their drinking water (week 2) to induce inflammation-associated colon tumors. eUBM was performed simultaneously with colonoscopy at weeks 13, 17-20 and 21. A 3.6-F diameter 40 MHz mini-probe catheter was used for eUBM imaging. The ultrasound mini-probe catheter was inserted into the accessory channel of a pediatric flexible bronchofiberscope, allowing simultaneous acquisition of colonoscopic and eUBM images. During image acquisition, the mice were anesthetized with isoflurane and kept in a supine position over a stainless steel heated surgical waterbed at 37 °C. Both eUBM and colonoscopic images were captured and stored when a lesion was detected by colonoscopy or when the eUBM image revealed a modified colon wall anatomy. During the procedure, the colon was irrigated with water that was injected through a flush port on the mini-probe catheter and that acted as the ultrasound coupling medium between the transducer and the colon wall. Once the acquisition of the last eUBM/colonoscopy section for each animal was completed, the colons were fixed, paraffin-embedded, and stained with hematoxylin and eosin. Colon images acquired at the first time-point for each mouse were compared with subsequent eUBM/colonoscopic images of the same sites obtained in the following acquisitions to evaluate lesion progression. RESULTS: All 10 mice had eUBM and colonoscopic images acquired at week 13 (the first time-point). Two animals died immediately after the first imaging acquisition and, consequently, only 8 mice were subjected to the second eUBM/colonoscopy imaging acquisition (at the second time-point). Due to the advanced stage of colonic tumorigenesis, 5 animals died after the second time-point image acquisition, and thus, only three were subjected to the third eUBM/colonoscopy imaging acquisition (the third time-point). eUBM was able to detect the four layers in healthy segments of colon: the mucosa (the first hyperechoic layer moving away from the mini-probe axis), followed by the muscularis mucosae (hypoechoic), the submucosa (the second hyperechoic layer) and the muscularis externa (the second hypoechoic layer). Hypoechoic regions between the mucosa and the muscularis externa layers represented lymphoid infiltrates, as confirmed by the corresponding histological images. Pedunculated tumors were represented by hyperechoic masses in the mucosa layer. Among the lesions that decreased in size between the first and third time-points, one of the lesions changed from a mucosal hyperplasia with ulceration at the top to a mucosal hyperplasia with lymphoid infiltrate and, finally, to small signs of mucosal hyperplasia and lymphoid infiltrate. In this case, while lesion regression and modification were observable in the eUBM images, colonoscopy was only able to detect the lesion at the first and second time-points, without the capacity to demonstrate the presence of lymphoid infiltrate. Regarding the lesions that increased in size, one of them started as a small elevation in the mucosa layer and progressed to a pedunculated tumor. In this case, while eUBM imaging revealed the lesion at the first time-point, colonoscopy was only able to detect it at the second time-point. All colonic lesions (tumors, lymphoid infiltrate and mucosal thickening) were identified by eUBM, while colonoscopy identified just 76% of them. Colonoscopy identified all of the colonic tumors but failed to diagnose lymphoid infiltrates and increased mucosal thickness and failed to differentiate lymphoid infiltrates from small adenomas. During the observation period, most of the lesions (approximately 67%) increased in size, approximately 14% remained unchanged, and 19% regressed. CONCLUSION: Combining eUBM with colonoscopy improves the diagnosis and the follow-up of mouse colonic lesions, adding transmural assessment of the bowel wall.

Single-cell photoacoustic thermometry.

A novel photoacoustic thermometric method is presented for simultaneously imaging cells and sensing their temperature. With three-seconds-per-frame imaging speed, a temperature resolution of 0.2°C was achieved in a photo-thermal cell heating experiment. Compared to other approaches, the photoacoustic thermometric method has the advantage of not requiring custom-developed temperature-sensitive biosensors. This feature should facilitate the conversion of single-cell thermometry into a routine lab tool and make it accessible to a much broader biological research community.

In vivo endoluminal ultrasound biomicroscopic imaging in a mouse model of colorectal cancer.

RATIONALE AND OBJECTIVES: The gold-standard tool for colorectal cancer detection is colonoscopy, but it provides only mucosal surface visualization. Ultrasound biomicroscopy allows a clear delineation of the epithelium and adjacent colonic layers. The aim of this study was to design a system to generate endoluminal ultrasound biomicroscopic images of the mouse colon, in vivo, in an animal model of inflammation-associated colon cancer. MATERIALS AND METHODS: Thirteen mice (Mus musculus) were used. A 40-MHz miniprobe catheter was inserted into the accessory channel of a pediatric flexible bronchofiberscope. Control mice (n = 3) and mice treated with azoxymethane and dextran sulfate sodium (n = 10) were subjected to simultaneous endoluminal ultrasound biomicroscopy and white-light colonoscopy. The diagnosis obtained with endoluminal ultrasound biomicroscopy and colonoscopy was compared and confirmed by postmortem histopathology. RESULTS: Endoluminal ultrasound biomicroscopic images showed all layers of the normal colon and revealed lesions such as lymphoid hyperplasias and colon tumors. Additionally, endoluminal ultrasound biomicroscopy was able to detect two cases of mucosa layer thickening, confirmed by histology. Compared to histologic results, the sensitivities of endoluminal ultrasound biomicroscopy and colonoscopy were 0.95 and 0.83, respectively, and both methods achieved specificities of 1.0. CONCLUSIONS: Endoluminal ultrasound biomicroscopy can be used, in addition to colonoscopy, as a diagnostic method for colonic lesions. Moreover, experimental endoluminal ultrasound biomicroscopy in mouse models is feasible and might be used to further develop research on the differentiation between benign and malignant colonic diseases.

In vivo validation of a bimodal technique combining time-resolved fluorescence spectroscopy and ultrasonic backscatter microscopy for diagnosis of oral carcinoma.

Tissue diagnostic features generated by a bimodal technique integrating scanning time-resolved fluorescence spectroscopy (TRFS) and ultrasonic backscatter microscopy (UBM) are investigated in an in vivo hamster oral carcinoma model. Tissue fluorescence is excited by a pulsed nitrogen laser and spectrally and temporally resolved using a set of filters/dichroic mirrors and a fast digitizer, respectively. A 41-MHz focused transducer (37-µm axial, 65-µm lateral resolution) is used for UBM scanning. Representative lesions of the different stages of carcinogenesis show that fluorescence characteristics complement ultrasonic features, and both correlate with histological findings. These results demonstrate that TRFS-UBM provide a wealth of co-registered, complementary data concerning tissue composition and structure as it relates to disease status. The direct co-registration of the TRFS data (sensitive to surface molecular changes) with the UBM data (sensitive to cross-sectional structural changes and depth of tumor invasion) is expected to play an important role in pre-operative diagnosis and intra-operative determination of tumor margins.

In vivo photoacoustic microscopy with 7.6-µm axial resolution using a commercial 125-MHz ultrasonic transducer.

Photoacoustic microscopy has achieved submicron lateral resolution, but its axial resolution is much lower. Here an axial resolution of 7.6 µm, the highest axial resolution validated by experimental data, has been achieved by using a commercial 125 MHz ultrasonic transducer for signal detection followed by the Wiener deconvolution for signal processing. Limited by the working distance, the high-frequency ultrasonic transducer can penetrate 1.2 mm into biological tissue from the ultrasound detection side. At this depth, the signal-to-noise ratio decreases by 11 dB, and the axial resolution degrades by 36%. The new system was demonstrated in imaging melanoma cells ex vivo and mouse ears in vivo.

High-resolution ultrasound imaging of human skin in vivo by using three-dimensional ultrasound microscopy.

Observing the morphology of human skin is important in the diagnosis of skin cancer and inflammation and in the assessment of skin aging. High-frequency ultrasound imaging provides high spatial resolution of the deep layers of the skin, which cannot be visualized by optical methods. The objectives of the present study were to develop a three-dimensional (3-D) ultrasound microscope and to observe the morphology of normal human skin in vivo. A concave polyvinylidene fluoride transducer with a central frequency of 120 MHz was excited using an electric pulse generated by semiconductor switching. The transducer was scanned two-dimensionally by using two linear motors on the region-of-interest and the ultrasonic reflection was digitized with 2-GHz sampling. Consecutive B-mode images perpendicular to the skin surface were reconstructed to generate multiplanar reconstructed images and 3-D volume-rendering images clearly showing microstructures such as sebaceous glands and hair follicles. The 3-D ultrasound microscope could be used to successfully image the morphology of human skin noninvasively and may provide important information on skin structure.

Corneal thickness measurement using Orbscan, Pentacam, Galilei, and ultrasound in normal and post-femtosecond laser in situ keratomileusis eyes.

PURPOSE: To compare corneal pachymetry assessment using slit scanning imaging (Orbscan), rotating Scheimpflug imaging (Pentacam), dual Scheimpflug system (Galilei), and ultrasound pachymetry in normal and post-femtosecond (FS) laser in situ keratomileusis (LASIK) eyes. METHODS: Sixty eyes of 60 patients were enrolled for this study, which consisted of 30 unoperated eyes (normal corneas) and 30 eyes after FS-LASIK (post-LASIK corneas). Central corneal thickness was measured sequentially using Orbscan II, Pentacam, Galilei, and ultrasound pachymetry, and the average value of measurements obtained by the 4 different methods were compared in each group. RESULTS: In normal corneas, corneal thickness measurements were not different by all 4 methods [P = 0.202, 1-way analysis of variance (ANOVA)]. In post-LASIK corneas, the measurement was significantly different among those achieved by 4 methods (P < 0.001, 1-way ANOVA). Orbscan measurement was thinner than those yielded by Galilei, Pentacam, or ultrasound pachymetry with average of 47.7, 38.5, and 34.4 µm, respectively (all P values < 0.001, 1-way ANOVA and the Tukey multiple comparisons test) in post-LASIK corneas. Orbscan, Pentacam, and Galilei measurements showed good agreement with ultrasound pachymetry data in both groups, except Orbscan data in post-LASIK corneas showed a statistically significant difference from ultrasound pachymetry measurements (P value = 0.001, 1-way ANOVA and the Tukey multiple comparisons test). CONCLUSIONS: Any of central corneal thicknesses obtained by all 4 measurement modalities might be acceptable before refractive surgery. However, in post-FS-LASIK eyes, measurements using Orbscan were thinner than those obtained with other modalities; in contrast, those with Pentacam or Galilei were comparable with ultrasound pachymetry.

Comparison of anterior chamber depth measurements by 3-dimensional optical coherence tomography, partial coherence interferometry biometry, Scheimpflug rotating camera imaging, and ultrasound biomicroscopy.

PURPOSE: To evaluate the congruity of anterior chamber depth (ACD) measurements using 4 devices. SETTING: Saneikai Tsukazaki Hospital, Himeji City, Japan. DESIGN: Comparative case series. METHODS: In 1 eye of 42 healthy participants, the ACD was measured by 3-dimensional corneal and anterior segment optical coherence tomography (CAS-OCT), partial coherence interferometry (PCI), Scheimpflug imaging, and ultrasound biomicroscopy (UBM). The differences between the measurements were evaluated by 2-way analysis of variance and post hoc analysis. Agreement between the measurements was evaluated using Bland-Altman analysis. To evaluate the true ACD using PCI, the automatically calculated ACD minus the central corneal thickness measured by CAS-OCT was defined as PCI true. Two ACD measurements were also taken with CAS-OCT. RESULTS: The mean ACD was 3.72 mm ± 0.23 (SD) (PCI), 3.18 ± 0.23 mm (PCI true), 3.24 ± 0.25 mm (Scheimpflug), 3.03 ± 0.25 mm (UBM), 3.14 ± 0.24 mm (CAS-OCT auto), and 3.12 ± 0.24 mm (CAS-OCT manual). A significant difference was observed between PCI biometry, Scheimpflug imaging, and UBM measurements and the other methods. Post hoc analysis showed no significant differences between PCI true and CAS-OCT auto or between CAS-OCT auto and CAS-OCT manual. Strong correlations were observed between all measurements; however, Bland-Altman analysis showed good agreement only between PCI true and Scheimpflug imaging and between CAS-OCT auto and CAS OCT manual. CONCLUSION: The ACD measurements obtained from PCI biometry, Scheimpflug imaging, CAS-OCT, and UBM were significantly different and not interchangeable except for PCI true and CAS-OCT auto and CAS-OCT auto and CAS-OCT manual. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.