The accuracy of measurements of three-dimensional computed tomography reconstructions

Evaluation of photogrammetry for medical application in cardiology

Background: In the field of medicine, photogrammetry has played for long time a marginal role due to the significant amount of work required that made it impractical for an extended medical use. Developments in digital photogrammetry occurred in the recent years, that have steadily increased the interest and application of this technique. The present study aims to compare photogrammetry reconstruction of heart with computed tomography (CT) as a reference. Methods: The photogrammetric reconstructions of digital images from ECG imaging derived images were performed. In particular, the ventricles of 15 patients with Brugada syndrome were reconstructed by using the free Zephyr Lite software. In order to evaluate the accuracy of the technique, measurements on the reconstructions were compared to patient-specific CT scan imported in ECG imaging software UZBCIT. Result: The results showed that digital photogrammetry in the context of ventricle reconstruction is feasible. The photogrammetric derived measurements of ventricles were not statistically different from CT scan measurements. Furthermore, the analysis showed high correlation of photogrammetry reconstructions with CT scan and a correlation coefficient close to 1. Conclusion: It is possible to reproduce digital objects by photogrammetry if the process described in this study is performed. The reconstruction of the ventricles from CT scan was very close to the values of the respective photogrammetric reconstruction.

Development of a 3D printed surgical guide for Brugada syndrome substrate ablation

Background

Brugada syndrome (BrS) is a disease associated with ventricular arrhythmias and sudden cardiac death. Epicardial ablation has demonstrated high therapeutic efficacy in preventing ventricular arrhythmias. The purpose of this research is to define a workflow to create a patient-specific 3D-printed tool to be used as a surgical guide for epicardial ablation in BrS.

Methods

Due to their mechanical properties and biocompatibility, the MED625FLX and TPU95A were used for cardiac 3D surgical guide printing. ECG imaging was used to define the target region on the right ventricular outflow tract (RVOT). CT scan imaging was used to design the model based on patient anatomy. A 3D patient-specific heart phantom was also printed for fitting test. Sterilization test was finally performed.

Results

3D printed surgical models with both TPU95A and MED625FLX models were in agreement with pre-specified imputed measurements. The phantom test showed retention of shape and correct fitting of the surgical tool to the reproduced phantom anatomy, as expected, for both materials. The surgical guide adapted to both the RVOT and the left anterior descending artery. Two of the 3D models produced in MED265FLX showed damage due to the sterilization process.

Conclusions

A 3D printed patient-specific surgical guide for epicardial substrate ablation in BrS is feasible if a specific workflow is followed. The design of the 3D surgical guide ensures proper fitting on the heart phantom with good stability. Further investigations for clinical use are eagerly awaited.

Evaluation of the morphological changes in the mandible for dentate and totally edentate elderly population using cone-beam computed tomography

PURPOSE

The loss of teeth considerably modifies the mandibular shape. The aim of this study was to compare the morphological changes in the mandible for dentate and totally edentate elderly subjects using cone-beam computed tomography.

METHODS

In total, 50 cone-beam computed tomography patients (25 dentate, 25 edentate) without any maxilla-mandibular dysmorphosis were analyzed retrospectively. Panoramic representations of the mandible with superimposed axial slices and cross-sectional slices were developed with the cone-beam computed tomography scans. Values of the mandibular cortical index, bone quality index, gonial angle, antegonial angle, antegonial depth and condyle angle in the left and right side were measured.

RESULTS

There was a significant difference in the mandibular cortical index between the total edentate group and the dentate group in the left side of the mandible (p < 0.001). There was a significant difference in the bone quality index between the total edentate group and the dentate group in the right side and the left side (p < 0.001). There was a significant difference in the bone quality index between the right side and the left side (p < 0.005). When comparing gender, there was only a difference in the right side (p < 0.05).

CONCLUSIONS

Our study concluded that the mandibular basal bone morphology changes as a consequence of tooth loss. Cone-beam computed tomography is shown to be a good tool in investigating and achieving these results.

Quantification of regional interstitial lung disease from CT-derived fractional tissue volume: a lung tissue research consortium study

RATIONALE AND OBJECTIVES

Evaluation of chest computed tomography (CT) is usually qualitative or semiquantitative, resulting in subjective descriptions often by different observers over time and imprecise determinations of disease severity within distorted lobes. There is a need for standardized imaging biomarkers to quantify regional disease, maximize diagnostic yield, and facilitate multicenter comparisons. We applied lobe-based voxelwise image analysis to derive regional air (Vair) and tissue (Vtissue) volumes and fractional tissue volume (FTV = tissue/[tissue+air] volume) as internally standardized parameter for assessing interstitial lung disease (ILD).

MATERIALS AND METHODS

High-resolution CT was obtained at supine and prone end-inspiration and supine end-expiration in 29 patients with ILD and 20 normal subjects. Lobar Vair, Vtissue, and FTV were expressed along standard coordinate axes.

RESULTS

In normal subjects from end-inspiration to end-expiration, total Vair declined ~43%, FTV increased ~80%, but Vtissue remained unchanged. With increasing ILD, Vair declined and Vtissue rose in all lobes; FTV increased with a peripheral-to-central progression inversely correlated to spirometry and lung diffusing capacity (r(2) = 0.57-0.75, prone end-inspiration). Inter- and intralobar coefficients of variation of FTV increased 84-148% in mild-to-moderate ILD, indicating greater spatial heterogeneity, then normalized in severe ILD. Analysis of discontinuous images incurs <3% error compared to consecutive images.

CONCLUSIONS

These regional attenuation-based biomarkers could quantify heterogeneous parenchymal disease in distorted lobes, detect mild ILD involvement in all lobes and describe the pattern of disease progression. The next step would be to study a larger series, examine reproducibility and follow longitudinal changes in correlation with clinical and functional indices.

Evaluation of volumetry and density of mandibular symphysis bone grafts by three-dimensional computed tomography

PURPOSE

Bone grafting before implant placing can improve the treatment in traumatized or regular implant patients. The aim of this study was to evaluate the density and maximum amount of harvestable bone graft in the mandibular symphysis.

MATERIALS AND METHODS

Data from 15 CT-scans were obtained from 15 adult patients (10 male/five female) for the purposes of this study. The CT data, in DICOM format, were read into Mimics software from Materialize (Leuven, Belgium), with a slice thickness of 0.5 mm. The volume, density, and dimensions based on Hounsfield units (HU) were measured on the 3D symphyseal bone graft using Mimics software.

RESULTS

The average bone volume calculated from the mandibular symphysis was 3491.08 +/- 772.12 mm(3). The average sized corticocancellous block that was measured was 38.75 x 11.05 x 7.80 mm. The mean bone density was 958.95 +/- 98.11 HU.

CONCLUSION

The use of three-dimensional computed tomography (3D CT) in combination with a software program is a reliable means of determining the density of graft, evaluating maximal volume and dimensions of the graft that can be harvested from the mandibular symphysis region.

Three dimensional CT reconstruction: a comparison between 2D, 3D CT and original anatomical structures

Conventional two dimensional computed tomography has provided significant advancement in clinical diagnosis with information on cross-sectional anatomy of various parts of the body. However, three dimensional representations are not directly available. This is now made possible by recent development of CAD software and CT equipments and technique such as multiplanar reformation capable of providing 3D reconstruction using 2D CT data. This article evaluates the accuracy of measurements and dimensions in 3D CT reconstruction.

Validation of computed tomography protocols for simulated mandibular lesions: a comparison study

Computed tomography is the choice technique to assess oral and maxillofacial osseous lesions because it provides hard and soft tissues visualization in one examination without superimposition of surrounding structures. This examination offers a significant advance in maxillofacial lesions detection with an excellent anatomic resolution. The aim of this research was to evaluate the validity of two protocols, in axial sections, in simulated mandibular lesions. Two CT protocols were obtained in dry mandibles in which perforations were done simulating lesions. Two observers, previously calibrated, evaluated the images according to different parameters. The results indicated that the sensitivity and specificity in lesion detection were 100% for both protocols, but the detection of loci number of multilocular lesions and the location and detection of medullar invasion obtained reduced validity values, which were influenced by the acquisition protocol. We concluded that thinner axial slices and reconstructions were more effective in detecting early medullar invasion and loci number. Thicker protocols were not considered appropriate to detect multilocular lesions and early stages of medullar invasion.

The accuracy of 3-dimensional magnetic resonance 3D vibe images of the mandible: an in vitro comparison of magnetic resonance imaging and computed tomography

OBJECTIVE

The purpose of this study was to investigate in vitro the accuracy of three-dimensional (3D) magnetic resonance imaging (MRI) to measure the mandible.

STUDY DESIGN

The optimal MRI sequence for 3D mandible from the data of 2 volunteers was determined to be 3D vibe. MRI and computed tomography (CT) scans of tube, mandible, and hemimandible phantoms were obtained. MRI with 3D vibe and standard parameters used in clinical practice for 3D reconstructions of jawbones on CT were used. Pearson's correlation coefficient, standard deviation (SD), and accuracy in measurement on reconstructed 3D MRI and CT were compared to direct osteometric measurement of the phantoms.

RESULTS

The correlation coefficient between MRI and direct osteometry was high, with r = 0.85 to 0.99 (P < .001). The difference ranged from -1.5 to 0.7 mm (-8.9%-11.1%) on smaller distances, which is important for orthognathic surgery. The accuracy of MRI was similar to that of CT.

CONCLUSION

3D vibe MRI provided adequate dimensional accuracy and image quality during in vitro examination of the mandible.

CT-based analysis of malignant tumor volume and localization: a preliminary study

The purpose of this study was to correlate 3D-CT (3D computed tomography) volume measurements of malignant tumors with the response to treatment, and to observe bone invasion in these lesions applying a specific imaging protocol. We analyzed 17 individuals with maxillofacial malignant lesions who were submitted to spiral CT (2D-CT). The original data were transferred to an independent workstation using a 3D volume rendering package software, which was used by two examiners to obtain area and volume measurements of the lesions, independently, three times each, prior to and after treatment. The segmentation protocol was applied for the assessment of bone involvement. The difference between imaging and gold standard values was not considered significant (p > 0.05). Regarding bone invasion, three false-negatives were obtained using MPR-CT (multiplanar reconstruction) and no false-negatives were obtained using the 3D segmentation protocol. The use of 3D-CT may be a differential and important factor for expanding options regarding the localization, dimension, and clarification of lesion components.

3D CT evaluation of masseter muscle morphology after setback osteotomy for mandibular prognathism

OBJECTIVE

Following mandibular setback osteotomy, changes in the direction, length, and cross-sectional area of the masseter muscle were studied by means of computerized tomography (CT) images generated with a 3-dimensional (3D) reconstructive technique.

STUDY DESIGN

Pre- and postoperative CT examinations were performed on 17 prognathic patients treated by sagittal split ramus osteotomy with rigid osteosynthesis and 13 patients treated by intraoral vertical ramus osteotomy without osteosynthesis. The pre- and postoperative masseter muscle direction and length were evaluated using 3D CT images observed from a lateral viewing angle. The cross-sectional area of the masseter muscle was first measured on an axial CT image of a selected slice level, following which the right-angle cross-sectional area of the muscle was revised using the measured area from the axial image.

RESULTS

Postoperatively, anterior tilting of the masseter muscle was observed; however, masseter muscle length was unchanged. Three months postoperatively, a significant reduction in the cross-sectional area of the masseter muscle was seen. A tendency to revert back to the normal dimension was seen between 6 months and 1 year postoperatively. No significant difference was noted between the 2 surgical techniques.

CONCLUSIONS

Three-dimensional computed tomography is an adequate imaging modality for masseter muscle evaluation. The results of this study suggest the masseter muscle may undergo reversible atrophy after mandibular setback osteotomy.

The validation of 3D spiral CT-based measurements of simulated maxillofacial neoplasms

OBJECTIVE

The purpose of this study was to determine the precision and accuracy of 3-dimensional spiral computed tomography-based linear measurements of neoplasms associated with the mandible.

STUDY DESIGN

Four cadaver heads, each with 2 simulated tumors made of clay, containing contrast medium, and positioned medial to the mandible, were examined by means of a subsecond spiral computed tomography unit. The computed tomography data were transferred to a computer workstation and analyzed through use of 3-dimensional reconstructed images. Linear measurements of the length, width, and depth of the simulated tumors were made by 2 observers, twice each. The soft tissues were then removed and the same measurements made by means of calipers.

RESULTS

There were no statistically significant differences between the 3-dimensional computed tomography and physical measurements (P >.05). The mean difference was found to be less than 0.4 mm.

CONCLUSIONS

Spiral computed tomography imaging allows for precise and accurate 3-dimensional computed tomography-based measurements for neoplastic lesions in the mandible.

2-D and 3-D reconstructions of spiral computed tomography in localization of the inferior alveolar canal for dental implants

OBJECTIVE

The purpose of this study was to compare and validate the accuracy of measurements on 2-dimensional and 3-dimensional reconstructions from spiral computed tomography in localization of the inferior alveolar canal.

STUDY DESIGN

Four edentulous human cadaver heads with intact mandibles were imaged in a spiral computed tomography scanner. The data were transferred to a networked computer workstation to generate 2-dimensional orthoradially reformatted and 3-dimensional volumetric images. Linear measurements of the images were made from the superior border of the inferior alveolar canal to the alveolar crest. The specimens were then dissected at corresponding locations, and physical measurements were made.

RESULTS

There were no statistically significant differences between the 2-dimensional computed tomography measurements and the physical measurements or between the 3-dimensional computed tomography measurements and the physical measurements. However, we did find a statistically significant difference between the 2-dimensional and 3-dimensional computed tomography measurements.

CONCLUSIONS

2-dimensional and 3-dimensional computed tomography images allow accurate measurements for localization of the inferior alveolar canal.

In vitro analysis of the accuracy of subtraction radiography and computed tomography scanning for determination of bone graft volume

PURPOSE

This study evaluated the accuracy of digital subtraction radiography (DSR) and three-dimensional computed tomography (3D CT) for determination of bone graft volume in the maxillofacial region.

MATERIALS AND METHODS

Standardized bone defects were made on the top of the alveolar ridge in 10 dry pig mandibles. To resemble the clinical situation, a bone block was harvested from the symphyseal region of the mandible and fixed in the defect. True bone graft volume was determined by the water displacement technique (VOL I) and correlated to direct measurements by calipers (VOL II). The mean gray value of the bone graft as imaged by DSR was correlated to the directly measured thickness. Furthermore, VOL I was correlated to the 3D CT of the bone graft (VOL III) and to the 3D CT with the bone graft fixed in the defect (VOL IV).

RESULTS

There was a strong correlation between VOL I and VOL II (r = .95), whereas there was a poorer correlation between mean gray level in DSR and measured bone thickness (r = .63). A strong correlation was also registered between VOL I and VOL III (r = .97) and VOL I and VOL IV (r = .97).

Volumetry of bone grafts by three-dimensional computed tomographic reconstruction: an animal study in the minipig

OBJECTIVES

To evaluate the accuracy of 3D-CT reconstruction for determination of bone graft volume in an animal model.

MATERIALS AND METHODS

Eight minipigs had bone graft reconstruction of an alveolar ridge defect. The true volume of the graft (VOL I) was determined by Archimedes principle before reconstruction. Following fixation, axial CT-scans (1 mm slice thickness with 50% overlap) were performed and segmented into grafted and residual bone for 3D-reconstruction. Using the volume tool of the 3D program the volume (VOL II) was calculated.

RESULTS

There was a strong correlation between VOL I and VOL II (r = 0.93, P = 0.001). There was a tendency, which was not statistically significant, to overestimate the volume measured by 3D-CT.

CONCLUSION

The volume of a bone graft can be determined by 3D-CT. However, further refinements of the technique are needed to improve the accuracy.