Comparison of patient dose from imaging protocols for dental implant planning using conventional radiography and computed tomography

OBJECTIVES: To compare the radiation doses from imaging protocols for dental implant planning either using conventional radiography only (dental panoramic radiography (DPR), cephalometry and linear cross-sectional tomography) or involving computed tomography (CT). METHODS: Organ absorbed doses were measured using a female Rando anthropomorphic phantom loaded with lithium fluoride thermoluminescent dosemeters (TLD). Standard mandibular protocols for dental implant planning were followed using either a conventional dental radiographic unit (PM 2002 CC Planmeca, Helsinki, Finland) or CT scanner (Excel Twin Elscint, Haifa, Israel). Organ absorbed and effective doses were calculated. Effective dose was calculated using two approaches, one based on the ICRP method which excludes the salivary tissue from the remainder organs (designated E(exc)), and the other with its inclusion (E(inc)). RESULTS: The greatest individual organ doses for any examination were measured in the salivary tissue. E(exc) for panoramic, cephalometric and cross-sectional tomography using DPR was 0.004 mSv, 0.002 mSv and 0.002 mSv, respectively, whereas with CT it was 0.314 mSv. The value of E(inc) calculated using these data was between two and five times E(exc). CONCLUSIONS: E(inc) greatly increases the apparent radiation burden, especially with high dose procedures. CT techniques can provide excellent images, but at the cost of increased radiation detriment. DPR with a cross-sectional tomography facility may give adequate clinical information at a greatly reduced dose.     

Perioperative validation of localisation of the mental foramen.

AIM: To assess the accuracy of panoramic radiography and spiral or computed tomography for the localisation of the mental foramen. MATERIALS AND METHODS: The distance from the alveolar crest to the mental foramen was measured from panoramic radiographs, spiral tomograms and CT scans. The same distance was measured during implant surgery using a specially designed caliper. RESULTS: Panoramic radiography showed more deviation (+0.6 mm) from the perioperative measurements than either spiral or computed tomography (+0.4 and -0.3 mm respectively). The difference was significant (P<0.05). In general, distances were overestimated on the panoramic radiographs. CONCLUSIONS: Cross-sectional imaging techniques are recommended for the pre-operative planning of implants in the posterior mandible.     

Dental vertical root fractures: value of CT in detection

PURPOSE: To determine the value of computed tomography (CT) in the diagnosis of dental vertical root fractures relative to the value of conventional dental radiography. MATERIALS AND METHODS: Thirty-seven patients with 42 teeth in which vertical root fracture was clinically suspected underwent dental radiography and axial CT. Two radiologists evaluated the images independently and by consensus for a fracture line. The results were compared with intraoperative findings. RESULTS: Twenty-eight of the 42 teeth were proved intraoperatively to be fractured. The sensitivity and specificity averaged for the two reviewers in the assessment of vertical fractures were 23% and 70%, respectively, with dental radiography and 100% and 100%, respectively, with CT. Consensus reading showed sensitivities of 25% for dental radiography and 75% for CT. Eight (reviewer A) or nine (reviewer B) false-negative CT findings were encountered in cases in which metallic artifacts obscured parts of the root and in cases in which the root was very small in diameter. Interobserver agreement was 95% for dental radiography and 93% for CT. CONCLUSION: CT is superior to dental radiography in the detection of dental vertical root fractures.     

Mandibular osteoradionecrosis: a comparison of computed tomography with panoramic radiography.

OBJECTIVES: To compare the value of computed tomography (CT) with panoramic radiography in the diagnosis and presurgical evaluation of mandibular osteoradionecrosis (ORN). METHODS: Retrospective study comparing the diagnostic information from CT and panoramic radiography of 33 patients with clinical symptoms of ORN. In six patients the imaging was compared macroscopically with the resected mandible. RESULTS: Both panoramic radiography and CT revealed ORN in 31 cases. In 22 the anterior-posterior extent of the lesions could be estimated with equal reliability. In six patients the lesion appeared larger on CT and in three on panoramic radiography. Mono- or bicortical destruction, central necrosis and sequestration were better visualized by CT. Comparison between the imaging findings and the surgical resection showed that CT depicted the topography of the specimen more accurately. CONCLUSIONS: CT is superior to panoramic radiography in visualizing the features of mandibular ORN and the anterior-posterior extent of the lesion.     

The 3DX multi image micro-CT device in clinical dental practice

OBJECTIVES: To evaluate the usefulness of 3DX multi-image micro-CT device in clinical dental practice. METHODS: Images of 198 examinations performed with a 3DX device during a 6 month period in a private dental practice were evaluated retrospectively for the benefit of additional information compared with panoramic or intraoral radiographs. RESULTS: The main indication for the use of 3DX micro-CT was planning of dental implant placement in 49% of the examinations. Diagnosis or exclusion of dental infection or peri-implantitis represented 28% of the examinations and tooth, root or foreign body localization represented 13%. Temporomandibular joint (TMJ) imaging and cyst or tumour diagnosis represented 7.5% and 2.5% of the examinations, respectively. In implant planning and tooth, root or foreign body localization examinations, the required information was obtained in every case except three implant planning examinations, in which the exact measurements were hampered by artefacts caused by root fillings and retrograde fillings or metal posts. When compared with conventional radiography, additional radiographic information was obtained in 51% of the micro-CT examinations performed to confirm or exclude dental infection or peri-implantitis. Micro-CT also showed the bone structure of TMJs precisely. CONCLUSIONS: The 3DX micro-CT device visualizes bony anatomical structures precisely, which makes it a reliable tool for, for example, planning of implant treatment. The device is highly suitable for diagnosing dental infections. Dental restorations may cause disturbing artefacts and in 4.5% of the examinations the small imaging area resulted in re-examination.     

Current concepts in maxillofacial imaging

A review of state-of-the-art maxillofacial imaging is presented. Current imaging techniques include intra-oral radiographs, dental panoramic tomography, multidetector helical computed tomography, cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI). The commonest conditions encountered in clinical radiological practice are reviewed, including maxillofacial deformities, complicated dental impactions, maxillofacial trauma, jaw lesions (cysts, neoplasms, fibro-osseous lesions (FOLs) and infections), and temporomandibular joint pathology. Pre-operative assessment for dental implant placement is also briefly reviewed.     

Must radiation dose for CT of the maxilla and mandible be higher than that for conventional panoramic radiography?

We evaluated the feasibility of performing preoperative spiral CT of the maxilla and mandible with a radiation dose similar to that used for conventional panoramic radiography. The skin entrance doses of radiation used for spiral CT (collimation, 1 mm; pitch, 2; tube voltage, 80 kV; tube current, 40 mA) and for panoramic radiography (75 kV, 8 mA, 15 seconds) were measured in one patient by using thermoluminescent dosimeter chips. Results were 0.56 +/- 0.06 mGy for CT and 0.59 +/- 0.04 mGy for radiography. Image quality was adequate for preoperative implant planning. Spiral CT of the mandible and maxilla may therefore be feasible with a radiation dose of similar magnitude as that used for conventional panoramic radiography.     

Narrowing of the inferior dental canal in relation to the lower third molars

OBJECTIVES: To assess narrowing of the inferior dental canal in the lower third molar regions using computed tomography (CT) and to determine the value of radiographic markers on rotational panoramic radiographs in assessing the true relationships of the inferior dental canal. METHODS: Patients referred for CT assessment of impacted lower third molars were used in this study. The lower third molars were assessed using CT to determine the position and morphology of the inferior dental canal relative to the roots and the cortical plates. The radiographic markers on rotational panoramic radiographs were correlated with the CT findings when rotational panoramic radiographs were available. RESULTS: The patients referred had 202 lower third molars. Inferior positioning of the inferior dental canal was the most common location on CT. Narrowing of the inferior dental canal was found in relation to the lower third molars in 66.8% of cases. The chance of narrowing of the inferior dental canal as shown using CT increased when at least one of the radiographic markers, superimposition, narrowing, deviation or reduction in density was present on the rotational panoramic radiograph. Deviation of the inferior dental canal on rotational panoramic radiographs was found to be the most significant predictor of narrowing of the inferior dental canal and a close relationship to the roots, as shown in CT. CONCLUSIONS: Narrowing of the inferior dental canal is a common finding when impacted lower third molars are assessed using CT. On rotational panoramic radiographs deviation of the inferior dental canal is the best predictor of narrowing of the inferior dental canal and a close relationship to the roots.     

Computed tomography in dental implantology: medico-legal implications

Diagnostic imaging plays an important role in both the planning of dental implants and the follow-up evaluation of the procedure. It is widely known that computed tomography (CT) together with Dentascan software is the most accurate imaging technique in the planning of implant treatment. Unlike conventional radiological techniques, CT enables the three-dimensional evaluation of the bone without the overlapping of adjacent structures, as well as a precise measurement of the bone tissue available in the future implant site, contributing in this way to a significant reduction in unsuccessful treatment. CT also enables a qualitative evaluation of the bone structure together with a precise definition of the adjacent anatomical structures and possible associated pathologies. Finally, given the wealth of information provided by CT, it is clear that the technique can also be used for judging in retrospect the correctness of a dental implant procedure. The present paper describes the CT findings that are most relevant to the medicolegal assessment of professional liability in implantology.     

Diagnostic accuracy of cone-beam CT in the assessment of mandibular invasion of lower gingival carcinoma: Comparison with conventional panoramic radiography

Purpose

To evaluate the diagnostic accuracy of cone-beam CT in assessing mandibular invasion by lower gingival carcinoma and compare it with that of panoramic radiography.

Patients and methods

Fifty patients with squamous cell carcinoma of the lower gingiva who were examined by both panoramic radiography and cone-beam CT before surgery were included in this study. Five radiologists used a 6-point rating scale to independently evaluate cone-beam CT and panoramic images for the presence or absence of alveolar bone and mandibular canal involvement by tumor. Using the histopathogical findings as the gold standard, we calculated and compared the area under the receiver operating characteristic curve (Az value) and the sensitivity and specificity of the two imaging modalities.

Results

In evaluations of both alveolar bone and mandibular canal involvement, the mean Az value for cone-beam CT (0.918 and 0.977, respectively) was significantly higher than that for panoramic radiography (0.793 and 0.872, respectively). The mean sensitivity for cone-beam CT (89% and 99%, respectively) was significantly higher than that for panoramic radiography (73% and 56%, respectively). There was no significant difference in the mean specificity. While cone-beam CT could provide high-resolution three-dimensional images, the image quality around the alveolar crest was often hampered by severe dental artifacts and image noise, resulting in difficulties in detecting subtle alveolar invasion.

Conclusion

Cone-beam CT was significantly superior to panoramic radiography in evaluating mandibular invasion by lower gingival carcinoma. Its diagnostic value in detecting subtle alveolar invasion, however, may be limited by severe dental artifacts and image noise.     

Dental CT imaging: a look at the jaw

The jaw comprises two complex bony structures: the mandible and maxilla. Their curved or archlike configuration makes radiographic imaging difficult. Furthermore, the superimposition of dense teeth and roots may obscure underlying tissues, and streak artifacts from dental restorations often degrade computed tomographic (CT) images. Recently, dental CT reformatting programs that use thin transverse images of the jaw to reformat multiple panoramic and cross-sectional views were developed. Since images are reformatted, streak artifacts that degrade bone visualization at direct coronal CT are projected over the crowns of the teeth, permitting optimal viewing of bone. As a result, these programs have been successfully used to evaluate implants, cysts, tumors, and surgical procedures. They have created not only a new modality for viewing the jaw but also a new partnership between dentists and radiologists. Questions that cannot be answered in the dentist's office with conventional radiographs are now answered in radiology departments with dental CT scans. The objective of this article is to trace, with a series of examples, the effect that this imaging modality has had on radiographic evaluation of the jaw and to provide the reader with knowledge that should enable him or her to become more involved in imaging of the jaw.     

MSCT颌骨扫描技术在牙种植术前评估中的应用

目的 :探讨MSCT颌骨薄层扫描技术在牙种植术前检查与评估中的应用价值。方法 :应用GE 8排螺旋CT对牙种植术前预带定位模板的颌骨做螺旋 1.2 5mm层厚连续扫描 ,通过相应的牙科专用软件 (Dentascan)对扫描数据进行多平面重建 ,同时采用三维 ( 3D)立体重建技术观察牙种植术前颌骨全景结构形态、骨质密度和上颌窦、鼻腔底、鼻腭管以及下颌管等重要结构。结果 :Dentascan软件及 3D技术能够清晰显示种植区域颌骨的外部形态及内部重要结构 ,并能利用其图像上的标尺测量工具精确测量种植区的骨高度及宽度。结论 :颌骨扫描设计为口腔科牙种植医师制定最佳手术方案提供重要的依据     

A comparison of panoramic radiography with computed tomography in the planning of implant surgery

The accuracy of panoramic radiography and computed tomography (CT) in the evaluation of depth of the mandible at recipient implant sites was compared by measuring the distance between the edentulous bony crest and the superior border of the inferior alveolar canal in a group of ten patients. Distortion was calculated using the metal ball technique for the panoramic radiographs and the computer scale for the CT scans. The precise distance between the bony crest and inferior alveolar canal was determined from postoperative radiographs from the known length of the implants. It was found that although CT scans are more precise, panoramic radiography is sufficiently accurate for routine clinical purposes. CT scans have, however, an additional advantage in presurgical planning, since they reveal the horizontal dimension and shape of the mandible, and the topography and buccolingual location of the inferior alveolar canal.     

Dosimetry of 3 CBCT devices for oral and maxillofacial radiology: CB Mercuray, NewTom 3G and i-CAT

OBJECTIVES: Cone beam computed tomography (CBCT), which provides a lower dose, lower cost alternative to conventional CT, is being used with increasing frequency in the practice of oral and maxillofacial radiology. This study provides comparative measurements of effective dose for three commercially available, large (12') field-of-view (FOV), CBCT units: CB Mercuray, NewTom 3G and i-CAT. METHODS: Thermoluminescent dosemeters (TLDs) were placed at 24 sites throughout the layers of the head and neck of a tissue-equivalent human skull RANDO phantom. Depending on availability, the 12' FOV and smaller FOV scanning modes were used with similar phantom positioning geometry for each CBCT unit. Radiation weighted doses to individual organs were summed using 1990 (E(1990)) and proposed 2005 (E(2005 draft)) ICRP tissue weighting factors to calculate two measures of whole-body effective dose. Dose as a multiple of a representative panoramic radiography dose was also calculated. RESULTS: For repeated runs dosimetry was generally reproducible within 2.5%. Calculated doses in microSv [corrected] (E(1990), E(2005 draft)) were NewTom3G (45, 59), i-CAT (135, 193) and CB Mercuray (477, 558). These are 4 to 42 times greater than comparable panoramic examination doses (6.3 microSv [corrected] 13.3 mSv). Reductions in dose were seen with reduction in field size and mA and kV technique factors. CONCLUSIONS: CBCT dose varies substantially depending on the device, FOV and selected technique factors. Effective dose detriment is several to many times higher than conventional panoramic imaging and an order of magnitude or more less than reported doses for conventional CT.     

Radiation dose in dental radiology

The aim of this study was to compare radiation exposure in panoramic radiography (PR), dental CT, and digital volume tomography (DVT). An anthropomorphic Alderson-Rando phantom and two anatomical head phantoms with thermoluminescent dosimeters fixed at appropriate locations were exposed as in a dental examination. In PR and DVT, standard parameters were used while variables in CT included mA, pitch, and rotation time. Image noise was assessed in dental CT and DVT. Radiation doses to the skin and internal organs within the primary beam and resulting from scatter radiation were measured and expressed as maximum doses in mGy. For PR, DVT, and CT, these maximum doses were 0.65, 4.2, and 23 mGy. In dose-reduced CT protocols, radiation doses ranged from 10.9 to 6.1 mGy. Effective doses calculated on this basis showed values below 0.1 mSv for PR, DVT, and dose-reduced CT. Image noise was similar in DVT and low-dose CT. As radiation exposure and image noise of DVT is similar to low-dose CT, this imaging technique cannot be recommended as a general alternative to replace PR in dental radiology.     

Geometric accuracy of magnetic resonance imaging of the mandibular nerve

OBJECTIVES: Magnetic resonance imaging (MRI) is not routinely used for dental implant planning. A prerequisite for dental implant planning is the accurate imaging of risk structures like the mandibular nerve. The geometric accuracy of the imaging of the mandibular nerve was investigated. METHODS: Two human cadaver heads were scanned using MRI. Computed tomography (CT) scans of the same heads were used as a benchmark. Using a stereotactic frame, corresponding images of MRI and CT were superimposed and the concordance of the images of the mandibular nerve in MRI with those of the mandibular canal in CT was assessed. RESULTS: The geometric accuracy of the mandibular nerve in MRI was as good as that of the mandibular canal in CT imaging. CONCLUSIONS: MRI of the mandibular nerve is sufficiently accurate for the use of this imaging method in dental implant planning.     

Dosimetry in dental radiology: comparison of spiral computerized tomography and orthopantomography]

INTRODUCTION: Dental diagnosis still depends largely on diagnostic imaging for correct anatomical and radiological assessment. Many studies confirm the risk of ionizing radiations, especially if used in pediatric populations and with suboptimal control. We compared the doses absorbed by the dentomaxillary area in Spiral CT and panoramic radiography examinations. MATERIAL AND METHODS: Doses were measured at critical organs in neck, ocular and intracranial regions with lithium fluoride dosimeters calibrated on the national standard and then positioned on an anthropomorphic Rando phantom made of tissue-equivalent material covering a skeleton. Multiple measurements were made during Spiral CT with the Dentascan software and panoramic radiography, to calculate mean absorbed doses for both examinations. Acquisition technical parameters were similar to those used in vivo. RESULTS: The parotid, cerebellum and thyroid gland were the most irradiated organs with panoramic radiography, with the addition of the mandible with Spiral CT. The gonads did not receive major doses. CONCLUSIONS: Our dose measurements demonstrate that patients receive smaller doses with panoramic radiography than with Spiral CT with Dentascan. After allowing for some variations from instrumental differences, they are in substantial agreement with literature data. Further investigations are needed considering the radiobiological risk related to the growing spread of Dentascan examinations.     

The way we were (and how we got here): fifty years of technology changes in dental and maxillofacial radiology

The history of the last 50 years (1970–2020) of technological changes and progresses for equipment and procedures in dental and maxillofacial radiology is related from the insider perspective of an industrial physicist and technologist who has been instrumental at innovating and developing medical equipment in different parts of the world. The onset and improvement of all major categories of dental and maxillofacial radiographic equipment is presented, from the standpoint of their practical acceptance and impact among common dentists and maxillofacial radiologists: X-ray sources and detectors for intraoral radiography, and panoramic systems, both film-based and digital (including photo-stimulated phosphor plates); and cone beam CT.     

Dentascan in oral imaging

In the past, dental disease and lesions involving the jaw were either evaluated by plain radiography or tomography. The advent of spiral computed tomography (CT) and DentaScan is changing the imaging trend. It is now not only used for pre-implant assessment but also in the diagnosis of lesions affecting the jaw. This pictorial review discusses the role of DentaScan in the various abnormalities that may affect the mandible and maxilla.