Image-guided near-infrared fluorescent sentinel lymph node mapping in human breast cancer

e11591

Background: Breast cancer surgery is presently performed without real-time image-guidance. We have developed a novel optical imaging system for image-guided surgery that uses invisible near-infrared (NIR) fluorescent light to highlight structures on the surgical field with high sensitivity, specificity, and contrast. We have also performed the first human clinical trial of the imaging system in women undergoing SLN mapping for breast cancer. Methods: We used a portable imaging system with an articulating arm that has 6 degrees of freedom, high power LED light source, custom optics, custom software, and sterile drape. The imaging system provided simultaneous and real-time imaging of color video and NIR fluorescence at up to 15 frames per second. N = 6 women with biopsy- confirmed breast cancer undergoing SLN mapping gave informed consent. All subjects received conventional mapping with Tc-99m sulfur colloid using a handheld gamma probe as well as NIR fluorescence-guided SLN mapping using a mixture of indocyanine green (ICG) diluted to a final concentration of 10 μM in human serum albumin (ICG:HSA). Results: The imaging system was easy to position in the operating room, with the articulating arm providing 50” horizontal reach and 70” vertical reach. Working distance to the patient was 18”. NIR fluorescence excitation was 20 mW/cm2 at 760 nm. NIR-depleted white light was 40,000 lux. A total of 1.6 ml of ICG:HSA was injected intra-tumorally and peri-tumorally and the site massaged for 5 min. 8 of 9 SLNs identified by Tc- 99m sulfur colloid were also identified by NIR fluorescence. However, NIR fluorescence identified an SLN, confirmed to have cancer in it, that was not identified by Tc-99m sulfur colloid. These differences were consistent with asynchrony in the injection techniques. Unlike the gamma-ray probe, NIR fluorescence provided high-resolution, large area optical imaging of the surgical field, and helped guide surgical resection. Conclusions: In this 6-patient pilot study, a novel NIR fluorescence optical imaging system was used for the first time, and provided real-time image-guided surgery for SLN mapping of breast cancer.

No significant financial relationships to disclose.

[A head-mounted display system for augmented reality: initial evaluation for interventional MRI]

PURPOSE

To discuss the technical details of a head mounted display with an augmented reality (AR) system and to describe a first pre-clinical evaluation in interventional MRI.

METHOD

The AR system consists of a video-see-through head mounted display (HMD), mounted with a mini video camera for tracking and a stereo pair of mini cameras that capture live images of the scene. The live video view of the phantom/patient is augmented with graphical representations of anatomical structures from MRI image data and is displayed on the HMD. The application of the AR system with interventional MRI was tested using a MRI data set of the head and a head phantom.

RESULTS

The HMD enables the user to move around and observe the scene dynamically from various viewpoints. Within a short time the natural hand-eye coordination can easily be adapted to the slightly different view. The 3D perception is based on stereo and kinetic depth cues. A circular target with a diameter of 0.5 square centimeter was hit in 19 of 20 attempts. In a first evaluation the MRI image data augmented reality scene of a head phantom allowed good planning and precise simulation of a puncture.

CONCLUSION

The HMD in combination with AR provides a direct, intuitive guidance for interventional MR procedures.

A new method for the extraction of fetal ECG from the composite abdominal signal

We developed a wavelet transform-based method to extract the fetal electrocardiogram (ECG) from the composite abdominal signal. This is based on the detection of the singularities obtained from the composite abdominal signal, using the modulus maxima in the wavelet domain. Modulus maxima locations of the abdominal signal are used to discriminate between maternal and fetal ECG signals. Two different approaches have been considered. In the first approach, at least one thoracic signal is used as the a prior to perform the classification whereas in the second approach no thoracic signal is needed. A reconstruction method is utilized to obtain the fetal ECG signal from the detected fetal modulus maxima. The proposed technique is different from the classical time-domain methods, in that we exploit the most distinct features of the signal, leading to more robustness with respect to signal perturbations. Results of experiments with both synthetic and real ECG data have been presented to demonstrate the efficacy of the proposed method.

A spectral-discrimination method for tear-film lipid-layer thickness estimation from fringe pattern images

Examination of the tear-film lipid layer is often helpful in the prognosis of prospective contact lens patients and contact lens related problems, and in the analysis of symptomatic noncontact lens-wearing patients. In particular, the thickness of the lipid layer is considered to be an informative cue in studying the tear-film stability and uncovering of certain disorders. We propose a method for the accurate estimation of the lipid-layer thickness, exploiting the intensity and color information in Fizeau fringe images. The technique is based on a quantitative measure for discriminating among the spectra associated with different thicknesses. We propose an optical system for imaging the interference patterns, develop a mathematical model based on the physics of the fringe formation and sensing, and describe the calibration of the optical system using this model. The thickness extraction is readily carried out utilizing a lookup table. The proposed method would enable objective evaluation of the lipid layer characteristics, and provide a means for examining the dynamic changes in its thickness and spatial distribution during inter-blink periods.