Lab on a chip 2013 Nov 21
Authors: Göröcs Z, Ling Y, Yu MD, Karahalios D, Mogharabi K, Lu K, Wei Q, Ozcan A,
We demonstrate a new fluorescent imaging technique that can screen for fluorescent micro-objects over an ultra-wide field-of-view (FOV) of ~532 cm(2), i.e., 19 cm × 28 cm, reaching a space-bandwidth product of more than 2 billion. For achieving such a large FOV, we modified the hardware and software of a commercially available flatbed scanner, and added a custom-designed absorbing fluorescent filter, a two-dimensional array of external light sources for computer-controlled and high-angle fluorescent excitation. We also re-programmed the driver of the scanner to take full control of the scanner hardware and achieve the highest possible exposure time, gain and sensitivity for detection of fluorescent micro-objects through the gradient index self-focusing lens array that is positioned in front of the scanner sensor chip. For example, this large FOV of our imaging platform allows us to screen more than 2.2 mL of undiluted whole blood for detection of fluorescent micro-objects within <5 minutes. This high-throughput fluorescent imaging platform could be useful for rare cell research and cytometry applications by enabling rapid screening of large volumes of optically dense media. Our results constitute the first time that a flatbed scanner has been converted to a fluorescent imaging system, achieving a record large FOV.
PMID: 24080766 [PubMed - as supplied by publisher]
Spine 2013 Oct 15
Authors: Tabaraee E, Gibson AG, Karahalios DG, Potts EA, Mobasser JP, Burch S,
Cadaveric laboratory study.
To compare the accuracy, efficiency, and safety of intraoperative cone beam-computed tomography with navigation (O-ARM) with traditional intraoperative fluoroscopy (C-ARM) for the placement of pedicle screws.
Radiation exposure remains a concern with traditional methods of intraoperative imaging in spine surgery. The use of O-ARM has been proposed for more accurate and efficient spinal instrumentation. Understanding radiation imparted to patients and surgeons by O-ARM is important for assessing risks and benefits of this technology, especially in light of evolving indications.
Four surgeons placed 160 pedicle screws on 8 cadavers without deformity. Eighty pedicle screws were placed using O-ARM and C-ARM each. Instrumentation was placed bilaterally in the thoracic (T1-T6) spine and lumbosacral junction (L5-S1) using a standard open technique, whereas minimally invasive surgery technique was used at the lumbar 3 to 4 (L3-L4) level. A "postoperative" computed tomography (CT) scan was performed on cadavers where instrumentation was done using the C-ARM. An independent musculoskeletal radiologist assessed final images for screw position. Time required to set up and instrumentation was recorded. Dosimeters were placed on multiple aspects of cadavers and surgeons to record radiation exposure.
There were no differences in breach rate between the O-ARM and C-ARM groups (5 vs. 7, χ= 0.63, P = 0.4). The setup time for the O-ARM group was longer than that for the C-ARM group (592 vs. 297 s, P < 0.05). However, the average total time was statistically the same (1629 vs. 1639 s, P = 0.96). Radiation exposure was higher for surgeons in the C-ARM group and cadavers in the O-ARM group. When a "postoperative" CT scan was included in the estimation of the total radiation exposure, there was less of difference between the groups, but still more for the O-ARM group.
In cadavers without deformity, O-ARM use results in similar breach rates as C-ARM for the placement of pedicle screws. Time for instrumentation is shorter with the O-ARM, but requires a longer setup time. The O-ARM exposes less radiation to the surgeon, but higher doses to the cadaver.
PMID: 23883830 [PubMed - as supplied by publisher]
The spine journal : official journal of the North American Spine Society 2013 Aug
Authors: Shakur SF, Takagi I, Jacobsohn JA, Golden BM, Karahalios DG,
Spinal fibromatosis is a unique subset of fibromatosis that is only anecdotally described in the literature in sporadic case reports. According to our review of the literature, only 11 cases of spinal fibromatosis have been previously documented. This paucity of clinical data limits our understanding of its presentation and treatment.
The authors present the first two cases of spinal fibromatosis encountered at their institution, and review the literature of reported cases to elucidate the presentation and outcomes of patients with this rare tumor.
A report of two cases and review of the literature.
The two patients in our case report were women aged 45 and 38 years. Both of the patients presented to our clinic after previous excisional biopsy of a spinal mass, 17 years and 1 year later, respectively, with pain and paresthesias that recapitulated their former symptoms. Thirteen cases, including the two described in the current article, were culled from the literature.
Magnetic resonance imaging revealed an enhancing lesion in the posterior elements of the spinal column in the first case and a paraspinal soft tissue mass in the second case. The tumors were histologically defined by haphazardly arranged, elongated, and slender spindle cells separated by abundant collagen without mitoses or necrosis. Surgical management resulted in intralesional resection in the first case and en bloc resection in the second case. By 40 and 10 months after surgery, both patients remain without neurologic deficits.
Among 13 cases of spinal fibromatosis, pain with or without a mass is the most common symptom at presentation. Tumor etiology is evenly distributed between de novo origin and surgical trauma. Treatment outcomes, although, cannot be determined from the limited data currently available.
PMID: 23523438 [PubMed - as supplied by publisher]
The international journal of medical robotics + computer assisted surgery : MRCAS 2013 Jun
Authors: Karahalios DG, Mansour NH, Girardot EA, Turner RC,
Prior to the mobilization of patients with spinal fractures following treatment, it is important to confirm stability in the upright position.
A patient presented with T2 and T3 vertebral body fractures visible on recumbent CT. Supine and upright plain x-rays with additional swimmer's views were deemed suboptimal prior to mobilization. The default configuration of the O-arm was modified to enable imaging in the upright position.
Images utilizing the O-arm were satisfactory and anatomic alignment confirmed in an upright position. It is believed that this is the first time the O-arm has been used for upright diagnostic imaging (off-label application). Excellent visualization of the cervicothoracic junction and upper thoracic regions was obtained in the desired upright position.
The O-arm was used successfully to image spinal trauma in the upright position and may represent a new application of the device, potentially fulfilling a frequently unmet medical imaging need.
PMID: 23495167 [PubMed - as supplied by publisher]
Disease-a-month : DM 2011 Oct
Authors: Kaibara T, Karahalios DG, Porter RW, Kakarla UK, Reyes PM, Choi SK, Yaqoobi AS, Crawford NR,
To study the stability offered by a clamping lumbar interspinous anchor (ISA) for transforaminal lumbar interbody fusion (TLIF).
Seven human cadaveric lumbosacral specimens were tested: 1) intact; 2) after placing ISA; 3) after TLIF with ISA; 4) with TLIF, ISA, and unilateral pedicle screws-rod; 5) with TLIF and unilateral pedicle screws-rod (ISA removed); and 6) with TLIF and bilateral pedicle screws-rods. Pure moments (7.5 Nm maximum) were applied in each plane to induce flexion-extension, axial rotation, and lateral bending while recording angular motion optoelectronically. Compression (400 N) was applied while upright foraminal height was measured.
All instrumentation reduced angular range of motion (ROM) significantly from normal. The loading modes in which the ISA limited ROM most effectively were flexion and extension, where the ROM allowed was equivalent to that of pedicle screws-rods (P > .08). The ISA was least effective in reducing lateral bending, with this mode reduced to 81% of normal. TLIF with unilateral pedicle screws-rod was the least stable configuration. Addition of the ISA to this construct significantly improved stability during flexion, extension, lateral bending, and axial rotation (P < .008). Constructs that included the ISA increased the foraminal height an average of 0.7 mm more than the other constructs (P < .05).
In cadaveric testing, the ISA limits flexion and extension equivalently to pedicle screws-rods. It also increases foraminal height. When used with TLIF, a construct of ISA or ISA plus unilateral pedicle screws-rod may offer an alternative to bilateral pedicle screws-rods for supplemental posterior fixation.
PMID: 22036115 [PubMed - as supplied by publisher]
Journal of neurosurgery. Spine 2010 Apr
Authors: Karahalios DG, Kaibara T, Porter RW, Kakarla UK, Reyes PM, Baaj AA, Yaqoobi AS, Crawford NR,
An interspinous anchor (ISA) provides fixation to the lumbar spine to facilitate fusion. The biomechanical stability provided by the Aspen ISA was studied in applications utilizing an anterior lumbar interbody fusion (ALIF) construct.
Seven human cadaveric L3-S1 specimens were tested in the following states: 1) intact; 2) after placing an ISA at L4-5; 3) after ALIF with an ISA; 4) after ALIF with an ISA and anterior screw/plate fixation system; 5) after removing the ISA (ALIF with plate only); 6) after removing the plate (ALIF only); and 7) after applying bilateral pedicle screws and rods. Pure moments (7.5 Nm maximum) were applied in flexion and extension, lateral bending, and axial rotation while recording angular motion optoelectronically. Changes in angulation as well as foraminal height were also measured.
All instrumentation variances except ALIF alone reduced angular range of motion (ROM) significantly from normal in all directions of loading. The ISA was most effective in limiting flexion and extension (25% of normal) and less effective in reducing lateral bending (71% of normal) and axial rotation (71% of normal). Overall, ALIF with an ISA provided stability that was statistically equivalent to ALIF with bilateral pedicle screws and rods. An ISA-augmented ALIF allowed less ROM than plate-augmented ALIF during flexion, extension, and lateral bending. Use of the ISA resulted in flexion at the index level, with a resultant increase in foraminal height. Compensatory extension at the adjacent levels prevented any significant change in overall sagittal balance.
When used with ALIF at L4-5, the ISA provides immediate rigid immobilization of the lumbar spine, allowing equivalent ROM to that of a pedicle screw/rod system, and smaller ROM than an anterior plate. When used with ALIF, the ISA may offer an alternative to anterior plate fixation or bilateral pedicle screw/rod constructs.
PMID: 20367372 [PubMed - as supplied by publisher]
Journal of neurosurgery. Spine 2008 Oct
Authors: La Marca F, Zubay G, Morrison T, Karahalios D,
The occipital condyle has never been studied as a viable structure that could permit bone purchase by fixation devices for occipitocervical fusion. The authors propose occipital condyle screw placement as a possible alternative to conventional occipitocervical fixation techniques.
Six adult cadaver heads (12 total occipital condyles) were studied, and the StealthStation image-guidance system was used for preoperative planning of occipital condyle screw placement. Morphometric studies of the occipital condyle were performed. A 3.5-mm Vertex screw was then placed in the occipital condyle with image-guided assistance in 3 specimens. Operations in the remaining 3 specimens proceeded using anatomical markers and calculated degrees of angulation for screw placement with a free-hand technique. Postoperatively the cadaver heads were rescanned and reanalyzed to determine the success of screw placement and its effect on hypoglossal canal volume.
All screws were successfully placed with no sign of lateral or medial cortical breach. Two screws had bicortical purchase. There was no change in hypoglossal canal volume in any specimen.
Occipital condyle screw placement is a safe and viable option for occipitocervical fixation and could be a preferred procedure in selected cases. However, further biomechanical studies are required to compare its reliability to other more established techniques.
PMID: 18939920 [PubMed - as supplied by publisher]
Journal of neurosurgery. Spine 2007 Oct
Authors: Lekovic GP, Potts EA, Karahalios DG, Hall G,
The goal of this study was to compare the accuracy of thoracic pedicle screw placement aided by two different image-guidance modalities.
The charts of 40 consecutive patients who had undergone stabilization of the thoracic spine between January 2003 and January 2005 were retrospectively reviewed. Three patients were excluded from the study because, on the basis of preoperative findings, small pedicle diameter precluded the use of pedicle screws. Thus, a total of 37 patients had 277 screws placed with the aid of either virtual fluoroscopy or isocentric C-arm 3D navigation. The indications for surgery included trauma, degenerative disease, and tumor, and were similar in both groups. All 37 patients underwent postoperative computed tomography scanning, and an independent reviewer graded all screws based on axial, sagittal, and coronal projections for a full determination of the placement of the screw in the pedicle.
The rate of unintended perforations was found to depend on pedicle diameter (p < 0.0001). There were no statistical differences between groups with regard to rate or grade of cortical perforations. Overall, the rate and grade of perforations was low, and there were no neurological or vascular complications.
The authors have shown that either image-guidance system may be used with a high degree of accuracy and safety. Because both systems were found to be comparably safe and accurate, the choice of image-guidance modality may be determined by the level of surgeon comfort and/or availability of the system.
PMID: 17933312 [PubMed - as supplied by publisher]
Neurosurgical focus 2006
Authors: Beringer WF, Mobasser JP, Karahalios D, Potts EA,
Adult high-grade degenerative spondylolisthesis represents the extreme end of the spectrum for spondylolisthesis and is consequently rarely encountered. Surgical management of high-grade spondylolisthesis requires constructs capable of resisting the shear forces at the slipped L5-S1 interspace. The severity of the slip, sacral inclination, and slip angle may make conventional approaches to 360 degrees fusion difficult or hazardous. Transdiscal pedicle screw fixation, transvertebral fibular graft fusion, and transvertebral cage fixation are techniques that have been developed to establish anterior column load sharing and to resist shear forces at the L5-S1 interspace, given the anatomical constraints accompanying high-grade spondylolisthesis. In this technical note the authors describe the procedure for implanting an in situ anterior L5-S1 transvertebral cage and performing L4-5 anterior lumbar interbody fusion, followed by placement of posterior S1-L5 vertebral body transdiscal pedicle screws for management of high-grade spondylolisthesis.
PMID: 16599423 [PubMed - as supplied by publisher]