Noninvasive patient tracker mask for spinal 3D navigation: does the required large-volume 3D scan involve a considerably increased radiation exposure?

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  • 1 Department of Neurosurgery, Medical Center–University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; and
  • | 2 Department of Neurosurgery, Cantonal Hospital St. Gallen, Switzerland
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OBJECTIVE

Intraoperative 3D imaging and navigation is increasingly used for minimally invasive spine surgery. A novel, noninvasive patient tracker that is adhered as a mask on the skin for 3D navigation necessitates a larger intraoperative 3D image set for appropriate referencing. This enlarged 3D image data set can be acquired by a state-of-the-art 3D C-arm device that is equipped with a large flat-panel detector. However, the presumably associated higher radiation exposure to the patient has essentially not yet been investigated and is therefore the objective of this study.

METHODS

Patients were retrospectively included if a thoracolumbar 3D scan was performed intraoperatively between 2016 and 2019 using a 3D C-arm with a large 30 × 30–cm flat-panel detector (3D scan volume 4096 cm3) or a 3D C-arm with a smaller 20 × 20–cm flat-panel detector (3D scan volume 2097 cm3), and the dose area product was available for the 3D scan. Additionally, the fluoroscopy time and the number of fluoroscopic images per 3D scan, as well as the BMI of the patients, were recorded.

RESULTS

The authors compared 62 intraoperative thoracolumbar 3D scans using the 3D C-arm with a large flat-panel detector and 12 3D scans using the 3D C-arm with a small flat-panel detector. Overall, the 3D C-arm with a large flat-panel detector required more fluoroscopic images per scan (mean 389.0 ± 8.4 vs 117.0 ± 4.6, p < 0.0001), leading to a significantly higher dose area product (mean 1028.6 ± 767.9 vs 457.1 ± 118.9 cGy × cm2, p = 0.0044).

CONCLUSIONS

The novel, noninvasive patient tracker mask facilitates intraoperative 3D navigation while eliminating the need for an additional skin incision with detachment of the autochthonous muscles. However, the use of this patient tracker mask requires a larger intraoperative 3D image data set for accurate registration, resulting in a 2.25 times higher radiation exposure to the patient. The use of the patient tracker mask should thus be based on an individual decision, especially taking into considering the radiation exposure and extent of instrumentation.

ABBREVIATIONS

CBCT = cone-beam CT; iCT = intraoperative CT.

OBJECTIVE

Intraoperative 3D imaging and navigation is increasingly used for minimally invasive spine surgery. A novel, noninvasive patient tracker that is adhered as a mask on the skin for 3D navigation necessitates a larger intraoperative 3D image set for appropriate referencing. This enlarged 3D image data set can be acquired by a state-of-the-art 3D C-arm device that is equipped with a large flat-panel detector. However, the presumably associated higher radiation exposure to the patient has essentially not yet been investigated and is therefore the objective of this study.

METHODS

Patients were retrospectively included if a thoracolumbar 3D scan was performed intraoperatively between 2016 and 2019 using a 3D C-arm with a large 30 × 30–cm flat-panel detector (3D scan volume 4096 cm3) or a 3D C-arm with a smaller 20 × 20–cm flat-panel detector (3D scan volume 2097 cm3), and the dose area product was available for the 3D scan. Additionally, the fluoroscopy time and the number of fluoroscopic images per 3D scan, as well as the BMI of the patients, were recorded.

RESULTS

The authors compared 62 intraoperative thoracolumbar 3D scans using the 3D C-arm with a large flat-panel detector and 12 3D scans using the 3D C-arm with a small flat-panel detector. Overall, the 3D C-arm with a large flat-panel detector required more fluoroscopic images per scan (mean 389.0 ± 8.4 vs 117.0 ± 4.6, p < 0.0001), leading to a significantly higher dose area product (mean 1028.6 ± 767.9 vs 457.1 ± 118.9 cGy × cm2, p = 0.0044).

CONCLUSIONS

The novel, noninvasive patient tracker mask facilitates intraoperative 3D navigation while eliminating the need for an additional skin incision with detachment of the autochthonous muscles. However, the use of this patient tracker mask requires a larger intraoperative 3D image data set for accurate registration, resulting in a 2.25 times higher radiation exposure to the patient. The use of the patient tracker mask should thus be based on an individual decision, especially taking into considering the radiation exposure and extent of instrumentation.

ABBREVIATIONS

CBCT = cone-beam CT; iCT = intraoperative CT.

In Brief

The authors compared the patient's radiation exposure during intraoperative thoracolumbar 3D scans using a mobile 3D C-arm with a large 30 × 30–cm and a smaller 20 × 20–cm flat-panel detector. The large C-arm displays an enlarged image area as required for the noninvasive patient tracker mask, but causes a 2.25 times higher radiation exposure to the patient. The application of the patient tracker mask and large 3D scans should be based on an individual decision, especially considering the radiation exposure and the extent of instrumentation.

Intraoperative 3D imaging and navigation is increasingly used in spine surgery, especially for navigated percutaneous placement of pedicle screws.1 For referencing the intraoperatively obtained 3D image data set, the invasive mounting of a referencing tracker, such as on a spinous process via a separate skin incision with detachment of autochthonous muscles, was necessary until recently. A currently available noninvasive patient tracker, which is adhered as a mask on the skin (Fig. 1), enables 3D navigation for minimally invasive surgery without the need for a separate skin incision with exposure of a spinous process.2,3 However, this noninvasive patient tracker mask requires a larger intraoperative 3D image data set for registration of a sufficient number of reference points. This necessitates a modern 3D C-arm with a large (e.g., 30 × 30 cm) flat-panel detector, which provides a fluoroscopy-based 3D image data set from consecutive 2D fluoroscopic images during a rotational scan. The correspondingly larger 3D image data set, in turn, suggests a higher radiation exposure to the patient.

FIG. 1.
FIG. 1.

Intraoperative use of a noninvasive patient tracker mask in the area of the lumbar spine. The patient tracker consists of multiple reference points and is attached to the skin as a rectangular mask to allow intraoperative 3D navigation. Figure is available in color online only.

The aim of this study is to determine the intraoperative radiation exposure to the patient during intraoperative fluoroscopy-based 3D scans using a modern 3D C-arm with a large flat-panel detector compared with a conventional 3D C-arm with a small flat-panel detector, to estimate the radiation exposure that is additionally required for noninvasive fluoroscopy-based 3D navigation.

Methods

Design

The recently introduced noninvasive patient tracker requires an enlarged 3D image data set. This retrospective, single-center study therefore investigates the intraoperative radiation exposure during intraoperative fluoroscopy-based 3D scans using a 3D C-arm with a suitable large flat-panel detector in comparison with a 3D C-arm with a conventional small flat-panel detector. Given the retrospective study design, which 3D C-arm was used for each operation was determined by the surgeon’s choice. Patients with intraoperative fluoroscopy-based 3D scans of the thoracolumbar spine between 2016 and 2019 were included. Excluded were patients without evaluable radiation exposure data.

Ethics Statement

The local ethics committee approved the study. The study was registered with the German Clinical Trials Register (www.drks.de; no. DRKS00019037). Included patients were informed about scientific use of the data and written consent was not considered necessary for retrospective analysis of the available data.

Outcome Measures

The primary outcome was the dose area product during intraoperative 3D scans of the thoracolumbar spine using a 3D C-arm with a large flat-panel detector (30 × 30 cm; Ziehm Vision RFD 3D, Ziehm Imaging)3 and a 3D C-arm with a small flat-panel detector (20 × 20 cm; Ziehm Vision FD Vario 3D, Ziehm Imaging).1 Secondary outcome measures were the fluoroscopy time and the number of fluoroscopic images per 3D scan.

3D C-Arm Specifications

Immediately prior to the automated 3D scan, single 2D fluoroscopic images are required to correctly position the 3D C-arm to the surgical field of the patient. This inevitable radiation exposure has therefore been included.

Large Flat-Panel Detector

The Ziehm Vision RFD 3D (referred to below as “RFD 3D”) generates a 3D image data set using a 30 × 30–cm digital flat-panel detector via a 180° scanning arc in 48 seconds (consisting of an initial 7.5° linear, followed by a 165° rotating, and a final 7.5° linear scan movement; Fig. 2A). The resulting 3D image data set has an edge length of 16 cm and a 3D scan volume of 4096 cm3,3 and can therefore display up to 6 lumbosacral vertebrae (Fig. 3A). This large 3D scan volume is essential for appropriate referencing of the noninvasive patient tracker mask (SpineMask, Stryker) that is attached to the skin for intraoperative 3D navigation2 (Fig. 1).

FIG. 2.
FIG. 2.

Juxtaposition of the two mobile 3D C-arms illustrating the large 30 × 30–cm digital flat-panel detector of the Vision RFD 3D (A) and the smaller 20 × 20–cm digital flat-panel detector of the Vision FD Vario 3D (B). Figure is available in color online only.

FIG. 3.
FIG. 3.

Triplanar visualization of intraoperatively generated fluoroscopy-based 3D image data sets. The large 30 × 30–cm flat-panel detector of the Vision RFD 3D (A) results in a 3D scan volume of 4096 cm3 and can display up to 6 lumbosacral vertebrae. The smaller 20 × 20–cm flat-panel detector of the Vision FD Vario 3D (B) results in a 3D scan volume of 2097 cm3 and can display up to 4 lumbosacral vertebrae. Figure is available in color online only.

Small Flat-Panel Detector

The previous model Ziehm Vision FD Vario 3D (referred to below as “FD Vario 3D”) generates a 3D image data set using a 20 × 20–cm digital flat-panel detector via a 135° rotational scan in 48 seconds (Fig. 2B). The resulting 3D image data set has an edge length of 12.8 cm and a 3D scan volume of 2097 cm3,1 and can therefore display up to 4 lumbosacral vertebrae (Fig. 3B).

Statistical Analysis

Statistical analyses were performed using Prism 6 for Mac (GraphPad Software Inc.). Variables rejected normality (Shapiro-Wilk normality test) and were analyzed using the Mann-Whitney U-test for comparing groups. Results were expressed as mean ± standard deviation. Statistical comparison for categorical values between groups was performed using the 2-tailed Fisher exact and chi-square tests. All p values < 0.05 were considered statistically significant.

Results

Patient Characteristics

Evaluable radiation exposure data were available for 62 large and 12 small intraoperative 3D image sets (Table 1). The mean BMI of the respective patients was 26.4 ± 5.7 kg/m2 (large RFD 3D) and 27.0 ± 6.0 kg/m2 (small FD Vario 3D) without a significant difference. The most frequently imaged region was the lower lumbar spine (59.5%), followed by the upper/middle thoracic spine (27.0%) and the thoracolumbar junction (13.5%). Of the 3D image sets, 87.8% were used for navigated percutaneous pedicle screw placement and 12.2% for navigated kyphoplasty.

TABLE 1.

Radiation exposure data

VariableRFD 3DFD Vario 3Dp Value
Distribution of patients, n
 T1–9182NS*
 T10–L2100
 L3–S23410
 Total6212
Mean BMI ± SD, kg/m2
 T1–923.3 ± 4.220.4 ± 7.0NS
 T10–L227.8 ± 3.4NA
 L3–S227.7 ± 6.428.3 ± 5.2NS
 Total26.4 ± 5.727.0 ± 6.0NS
Mean dose area product ± SD, cGy × cm2
 T1–9494.1 ± 386.5302.5 ± 147.8NS
 T10–L2895.5 ± 587.0NA
 L3–S21350.7 ± 806.9488.0 ± 92.1<0.0001
 Total1028.6 ± 767.9457.1 ± 118.90.0044
Mean fluoroscopy time ± SD, sec
 T1–955.2 ± 3.268.0 ± 4.20.0105
 T10–L254.6 ± 4.0NA
 L3–S254.9 ± 3.562.8 ± 10.00.0089
 Total54.9 ± 3.464.1 ± 9.00.0002
Mean no. of fluoroscopic images per 3D scan ± SD
 T1–9390.7 ± 3.5115.0 ± 9.90.0053
 T10–L2390.5 ± 3.7NA
 L3–S2387.6 ± 10.7117.6 ± 3.1<0.0001
 Total389.0 ± 8.4117.0 ± 4.6<0.0001
Procedures, n
 Percutaneous pedicle screw placement5411NS
 Kyphoplasty81

NA = not available; NS = not significant.

Data on radiation exposure are shown during 3D scans using the Vision RFD 3D (flat-panel 30 × 30 cm) or Vision FD Vario 3D (flat-panel 20 × 20 cm), categorized by spine regions within the thoracolumbar spine. In total, the average dose area product using the RFD 3D was 2.25 times higher across all spinal regions. Boldface type indicates statistical significance.

Chi-square test.

Mann-Whitney U-test.

Fisher exact test.

Radiation Exposure Data

The average dose area product using the RFD 3D was 2.25 times higher across all spinal regions (1028.6 ± 767.9 vs 457.1 ± 118.9 cGy × cm2, p = 0.0044). Fluoroscopy times using the RFD 3D were significantly lower in all spinal regions (total: mean 54.9 ± 3.4 vs 64.1 ± 9.0 seconds, p = 0.0002). However, the RFD 3D required more than three times the number of individual fluoroscopic images per 3D scan than the FD Vario 3D (389.0 ± 8.4 vs 117.0 ± 4.6 fluoroscopic images, p < 0.0001).

Discussion

Intraoperative 3D imaging and navigation is becoming more and more popular for minimally invasive surgical techniques, navigated implantation of pedicle screws, control of implants, and the application of virtual reality. These techniques have been made possible using mobile 3D C-arms for almost 2 decades, initially with small image intensifiers or flat-panel detectors.1 Until now, invasive mounting of a spinous process patient tracker was required to match the position of the patient’s spine with the intraoperatively acquired 3D image data set. This tracker was usually applied via a separate skin incision, with incision of the fascia and detachment of the paravertebral muscles down to the level of the lamina, thus contradicting the concept of minimally invasive surgical techniques. Therefore, a noninvasive patient tracker in the form of an adhesive mask has been developed to eliminate the need for an additional skin incision with detachment of the autochthonous muscles (Fig. 4). This, in turn, requires a larger volume of the 3D image data set for registration of a sufficient number of reference points in the noninvasive patient tracker mask.

FIG. 4.
FIG. 4.

Intraoperative view on the lower back during minimally invasive revision surgery. After previous fusion surgery of L4–5, adjacent-segment instability with stenosis occurred. Therefore, additional minimally invasive spondylodesis including decompression of the spinal stenosis was performed at L3–4 using the noninvasive patient tracker mask in combination with intraoperative fluoroscopy-based 3D navigation. Figure is available in color online only.

The drawback of this enlarged 3D image data set, as generated by the RFD 3D, is as expected and now proven by this study—that is, a significantly higher radiation exposure to the patient compared with a smaller 3D image data set, as generated by the Vision FD Vario 3D (2.25 times higher dose area product). Thus, the eliminated invasiveness of this new noninvasive tracker must be weighed against the increased radiation exposure to the patient with the following considerations.

From the perspective of radiation protection only, a 3D C-arm with a smaller flat-panel detector seems preferable for short-distance instrumentation, such as mono- or bilevel spondylodesis, so as not to expose the patient to increased radiation. A smaller 3D C-arm such as the Vision FD Vario 3D can capture up to 4 vertebrae per 3D scan (Fig. 3B). However, this setting still requires the mounting of an invasive spinous process patient tracker with the above-mentioned access-related tissue injury.

For multilevel instrumentation, an enlarged 3D scan volume may be required anyway, as provided by the large RFD 3D (4096 cm3), so that the simultaneous use of the noninvasive patient tracker mask does not per se lead to increased radiation exposure and therefore appears meaningful. A large 3D C-arm such as the RFD 3D is able to capture up to 6 lumbosacral vertebrae per 3D scan (Fig. 3A). Other manufacturers also offer mobile fluoroscopy-based devices for the intraoperative acquisition of 3D image data sets, of which the RFD 3D currently provides the largest 3D image data set.4

Consequently, the use of ionizing radiation–based imaging devices should always be tailored to the clinical needs of the individual case. In addition, there may be further aspects that influence the choice of C-arm device and type of patient tracker to be used. Imaging devices such as mobile 3D C-arms have been continuously developed and now allow imaging of increasingly larger spinal regions.5 Improved image quality and optimized handling of workflows and the devices themselves are also worthy of mention, even if they are not the subject of this investigation. Another decisive selection criterion is certainly the accuracy of the navigation equipment. There is currently no reliable data available on this topic for the noninvasive patient tracker mask. However, this aspect must be critically considered, especially because the tracker mask attached to the moveable skin may show a certain inaccuracy, especially in obese patients.

Independent of the use of a noninvasive patient tracker mask, all mentioned capabilities should be available in one single C-arm device to minimize the radiation exposure of the individual patient. Therefore, manufacturers should be encouraged to allow for manual adjustment of the edge length of the 3D image data set (similar to beam collimation for 2D fluoroscopic images) to fit the scan volume to the needs of the respective operation and thus minimize radiation exposure in the specific patient (Fig. 5).

FIG. 5.
FIG. 5.

Triplanar visualization of an intraoperative 3D image data set with superimposed illustration of a desirable individual adjustment of the 3D scan volume for an assumed monolevel instrumentation at L3–4 (arrows), similar to radiation collimation for 2D fluoroscopic images, to meet the requirements of the respective surgical procedure and to minimize radiation exposure to the corresponding patient. Figure is available in color online only.

There have been further efforts to reduce intraoperative radiation exposure. For instance, the utilization of radiation-sparing working methods and radiation-saving C-arms,6 as well as low-dose protocols,7 has been recommended. In addition, there are further intraoperative 3D imaging devices based on ionizing radiation, such as cone-beam CT (CBCT; e.g., O-arm, Medtronic) or intraoperative CT (iCT; e.g., Airo, Brainlab), which offer preconfigured low-dose protocols for radiation reduction. A fundamental problem for comparison purposes is that fluoroscopy-based devices such as the investigated mobile 3D C-arms or CBCT display the dose area product, whereas conventional CT and iCT use the CT dose index and dose length product; the corresponding units of these measures are different and not directly comparable. A conversion is very complex and can only be carried out with exact knowledge of the technical specifications and parameters as well as the characteristics of the object.8

Nevertheless, for a better understanding of the mean dose area product of 1028.6 cGy × cm2, which was assessed for a 3D scan using the RFD 3D in this study, and for comparing the radiation exposures to other devices and imaging techniques, the following approximations may serve as a basis for comparison. Assuming an appropriate conversion factor (e.g., 0.00228 mSv × cGy−1 × cm−2),9 the mean dose area product of 1028.6 cGy × cm2 of a 3D scan with the RFD 3D implies an effective dose of approximately 2.35 mSv. This corresponds to 75.7% of the average annual background radiation exposure of a US citizen from natural sources, which is about 3.1 mSv per year.10 Although this need not necessarily result in harm to the patient, this radiation exposure must be taken into account as there is no threshold dose below which ionizing radiation poses no risk according to the stochastic model for radiation injuries.11,12

For the CBCT O-arm, effective doses of 2.16, 1.08, and 0.68 mSv using a low-dose, very-low-dose, and ultra-low-dose protocol have been described, whereas a conventional CT was stated to produce 6.05 mSv.13 The 32-slice iCT scanner Airo was reported to cause an effective dose of 1.75 mSv at the thoracic spine using a low-dose protocol.14 The robotic 3D flat-panel fluoroscope (Artis zeego, Siemens) was reported to cause an effective dose of 4.4 mSv (high-dose protocol) or 1.0 mSv (low-dose protocol) at the thoracolumbar junction.15

In previous studies on an Alderson phantom using the Vision FD Vario 3D, a standard lumbar fluoroscopic image caused a radiation exposure of 0.018 mSv to the female gonad, and the radiation exposure of a lumbar 3D scan corresponded to 74 fluoroscopic images.6 With the RFD 3D, this radiation exposure was 0.133 mSv to the female gonad, resulting in a comparable radiation exposure of 47 fluoroscopic images as in a lumbar 3D scan.16

With regard to radiation protection, the present work adds to the recommendation that large-volume 3D scans, as generated by the RFD 3D, should only be performed for multilevel instrumentations. For the same reason, the noninvasive patient tracker mask should not be used for short-distance instrumentation (e.g., mono- or bilevel), as this requires a large-volume 3D scan (to appropriately reference this type of tracker), which considerably increases the radiation exposure.

Limitations

The present study intentionally focuses on the radiation exposure data of the 3D C-arms. Thus, other decisive characteristics of a C-arm, such as applicability or image quality, have not been considered. Likewise, this paper was not meant to describe the functionality, including advantages and disadvantages, of the noninvasive patient tracker mask itself. Finally, although the evaluated dose area product is widely accepted and frequently stated, it is not a true dosimetric assessment of the patient’s radiation exposure. Nevertheless, it can serve as a reasonable estimation of the differences in radiation exposure between various imaging devices or surgical techniques.

Conclusions

The noninvasive patient tracker mask eliminates the need for a further skin incision and the additional detachment of autochthonous muscles from a spinous process. However, the use of this patient tracker mask requires a larger intraoperative 3D image data set for accurate registration, whose acquisition results in a substantially higher radiation exposure to the patient. The use of the patient tracker mask should therefore be based on an individual decision, in particular in consideration of the radiation exposure and the extent of instrumentation. In addition, manufacturers should be encouraged to develop a technology of 3D collimation to adjust the 3D scan volume to the requirements of the specific surgical procedure to achieve full flexibility in the use of the 3D C-arm device and to minimize the radiation exposure to the patient.

Disclosures

The clinic had a cooperation agreement for system development with Ziehm Imaging and Stryker. Dr. Hubbe has received honoraria and travel expenditures for lectures from Ziehm Imaging.

Author Contributions

Conception and design: Klingler, Naseri. Acquisition of data: all authors. Analysis and interpretation of data: Klingler, Hubbe, Scholz, Naseri. Drafting the article: Klingler. Critically revising the article: Hubbe, Scholz, Volz, Hohenhaus, Vasilikos, Masalha, Watzlawick, Naseri. Reviewed submitted version of manuscript: Hubbe, Scholz, Volz, Hohenhaus, Vasilikos, Masalha, Watzlawick, Naseri. Approved the final version of the manuscript on behalf of all authors: Klingler. Statistical analysis: Klingler. Administrative/technical/material support: Klingler. Study supervision: Klingler.

Supplemental Information

Previous Presentations

Parts of this work were presented at the Annual Meeting of the Spine Section of the German Society of Neurosurgery (DGNC), September 14–15, 2018, in Hamburg, Germany, and at the Annual Meeting of the German Spine Society (DWG), December 6–8, 2018, in Wiesbaden, Germany.

References

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Images from Wemhoff et al. (pp 751–756).

Contributor Notes

Correspondence Jan-Helge Klingler: University of Freiburg, Germany. jan-helge.klingler@uniklinik-freiburg.de.

INCLUDE WHEN CITING Published online August 28, 2020; DOI: 10.3171/2020.5.SPINE20530.

Disclosures The clinic had a cooperation agreement for system development with Ziehm Imaging and Stryker. Dr. Hubbe has received honoraria and travel expenditures for lectures from Ziehm Imaging.

  • View in gallery

    Intraoperative use of a noninvasive patient tracker mask in the area of the lumbar spine. The patient tracker consists of multiple reference points and is attached to the skin as a rectangular mask to allow intraoperative 3D navigation. Figure is available in color online only.

  • View in gallery

    Juxtaposition of the two mobile 3D C-arms illustrating the large 30 × 30–cm digital flat-panel detector of the Vision RFD 3D (A) and the smaller 20 × 20–cm digital flat-panel detector of the Vision FD Vario 3D (B). Figure is available in color online only.

  • View in gallery

    Triplanar visualization of intraoperatively generated fluoroscopy-based 3D image data sets. The large 30 × 30–cm flat-panel detector of the Vision RFD 3D (A) results in a 3D scan volume of 4096 cm3 and can display up to 6 lumbosacral vertebrae. The smaller 20 × 20–cm flat-panel detector of the Vision FD Vario 3D (B) results in a 3D scan volume of 2097 cm3 and can display up to 4 lumbosacral vertebrae. Figure is available in color online only.

  • View in gallery

    Intraoperative view on the lower back during minimally invasive revision surgery. After previous fusion surgery of L4–5, adjacent-segment instability with stenosis occurred. Therefore, additional minimally invasive spondylodesis including decompression of the spinal stenosis was performed at L3–4 using the noninvasive patient tracker mask in combination with intraoperative fluoroscopy-based 3D navigation. Figure is available in color online only.

  • View in gallery

    Triplanar visualization of an intraoperative 3D image data set with superimposed illustration of a desirable individual adjustment of the 3D scan volume for an assumed monolevel instrumentation at L3–4 (arrows), similar to radiation collimation for 2D fluoroscopic images, to meet the requirements of the respective surgical procedure and to minimize radiation exposure to the corresponding patient. Figure is available in color online only.

  • 1

    Klingler JH, Sircar R, Scheiwe C, et al. Comparative study of C-arms for intraoperative 3-dimensional imaging and navigation in minimally invasive spine surgery part I: applicability and image quality. Clin Spine Surg. 2017;30(6):276284.

    • Search Google Scholar
    • Export Citation
  • 2

    Vaishnav AS, Merrill RK, Sandhu H, et al. A review of techniques, time demand, radiation exposure, and outcomes of skin-anchored intraoperative 3D navigation in minimally invasive lumbar spinal surgery. Spine (Phila Pa 1976). 2020;45(8):E465E476.

    • Search Google Scholar
    • Export Citation
  • 3

    Shaw JC, Routt MLC Jr, Gary JL. Intra-operative multi-dimensional fluoroscopy of guidepin placement prior to iliosacral screw fixation for posterior pelvic ring injuries and sacroiliac dislocation: an early case series. Int Orthop. 2017;41(10):21712177.

    • Search Google Scholar
    • Export Citation
  • 4

    Malham GM, Wells-Quinn T. What should my hospital buy next?-Guidelines for the acquisition and application of imaging, navigation, and robotics for spine surgery. J Spine Surg. 2019;5(1):155165.

    • Search Google Scholar
    • Export Citation
  • 5

    Malham GM, Parker RM. Early experience of placing image-guided minimally invasive pedicle screws without K-wires or bone-anchored trackers. J Neurosurg Spine. 2018;28(4):357363.

    • Search Google Scholar
    • Export Citation
  • 6

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