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. 2023 Jan 18;52(3):20220336. doi: 10.1259/dmfr.20220336

The magnetic resonance imaging characteristics of radicular cysts and granulomas

Natnicha Wamasing 1, Supasith Yomtako 1,2,1,2, Hiroshi Watanabe 1,✉, Junichiro Sakamoto 1, Kou Kayamori 3, Tohru Kurabayashi 1
PMCID: PMC9944013  PMID: 36688723

Abstract

Objectives:

Limited studies have differentiated radicular cysts and granulomas with MRI. Therefore, we investigated the MRI characteristics of the two lesions and clarified features for distinguishing between them.

Methods:

We collected data of 27 radicular cysts and 9 granulomas definitively diagnosed by histopathology and reviewed the fat-saturated T2 weighted, T1 weighted, and contrast-enhanced fat-saturated T1 weighted images. We measured the maximum diameter and apparent diffusion coefficient values of the lesions. We employed Fisher’s exact test, the Mann–Whitney U test, and independent t-tests to compare the two lesions and created a decision tree for discriminating between them.

Results:

There were significant differences between radicular cysts and granulomas with respect to five imaging characteristics—signal intensity of the lesion centre on fat-saturated T2 weighted images; signal intensity, texture, and contrast enhancement of the lesion centre on contrast-enhanced fat-saturated T1 weighted images; and maximum diameter of the lesion. The cut-off diameter for radicular cysts was 15.9 mm. The area under the receiver operating characteristic curve, sensitivity, and specificity were 0.971, 85.2%, and 100%, respectively.

Conclusions:

From the decision tree analysis, maximum diameter, lesion centre contrast enhancement on contrast-enhanced fat-saturated T1 weighted images, and lesion centre signal intensity on fat-saturated T2 weighted images were important for discriminating between radicular cysts and granulomas.

Keywords: radicular cyst, granuloma, magnetic resonance imaging, histology, decision trees

Introduction

Bacterial infection of the necrotic dental pulp causes periapical inflammatory lesions, which occasionally progress to form periapical granulomas.1 Such lesions show apical radiolucency on intraoral periapical radiographs owing to rarefying osteitis and radiopacity in the surrounding cancellous bone due to osteosclerosis.2 Pathologically, the content of the lesion would be an inflammatory granuloma. However, the inflammatory response may stimulate the epithelial cell rests of Malassez and they may occasionally develop into a cyst in the periapical area.3,4 Nair et al reported that 85% of the periapical lesions analysed in their study were granulomas or abscesses, and the remainder were cysts.5 The incidence of radicular cysts is not very high among periapical lesions. However, true cysts that are pathologically characterised by an enclosed epithelium are less likely to be cured by non-surgical root canal treatment and often require surgical intervention, such as cystectomy.6 Therefore, it is important to correctly diagnose cysts among periapical lesions to ensure appropriate treatment.7–10

Radicular granulomas and cysts are usually examined using intraoral periapical radiographs, but their detection with this modality seems difficult even after contrast medium is applied.11–17 CBCT has recently been introduced in dental practice, and it is essentially employed to scrutinise periapical lesions. However, diagnosing periapical lesions with CBCT has been challenging, and there is little evidence of its reliability.18–21 Previous studies have shown that radicular cysts are significantly larger than granulomas22,23 and that periapical lesions of a certain size are not likely to heal after conventional root canal treatments.22,24A limitation of these studies that used intraoral periapical radiographs and CBCT is caused by the ability of these imaging modalities to detect changes in bone morphology but not differences in soft tissue content within cysts and granulomas.2 For soft tissue visualisation, medical CT or ultrasonography is considered better, but neither of them has offered any effective results.25,26 For this purpose, MRI is currently considered the best modality.

Most MRI examinations utilise the phenomenon of nuclear magnetic resonance with hydrogen nuclei, which are abundant in body water and fat, for generating images. Water and fat have different T1 and T2 relaxation times. Hence, it is possible to assess their contents in tissue on T1 weighted images (T1w) and T2 weighted images (T2w) with fat saturation (T2wFS).27 During many MRI procedures, contrast examination with gadolinium is often performed, which routinely distinguishes the spread of inflammation,28 cysts and tumours,29,30 and benign and malignant tumours.31,32 Additionally, there are diffusion-weighted images that can visualise and quantify the diffusion motion of water molecules. It was previously reported that cysts and malignant lymphomas33 and odontogenic tumours and cysts could be efficiently distinguished with this imaging technique.30 In this context, if the different features of these lesions can be clarified by MRI, it is expected that radicular cysts and granulomas would be distinguishable from each other with high accuracy using MRI. There are already two studies that support this hypothesis. Lizio et al reported that they established six criteria that could differentiate these lesions with a high accuracy of 74% or 79%, depending on the observers.34Juerchott et al also revealed that they could differentiate them, highlighting the characteristics of radicular cysts as homogeneity in the lesion centre (LC) and no soft tissue involvement on MRI.35 However, the former study employed 1.5 T MRI equipment, and the latter employed the latest 3 T equipment and based their conclusions on only 11 cases. In this study, we collected data from our database examined by 3 T MRI, analysed radicular cyst and granuloma cases, established the MRI characteristics of these two lesions, and compared our findings to previous reports. The aim of this study was to investigate the MRI characteristics of the two lesions and clarify features for distinguishing between them.

Methods

Patients

We collected 48 images of radicular granulomas and radicular cysts from an MRI database from June 2013 to March 2022. The cases were definitively diagnosed histopathologically. However, 12 cases were excluded owing to undetectable lesions on apparent diffusion coefficient (ADC) maps and/or severe motion/susceptibility artefacts on the images. The final population consisted of 27 cysts and 9 granulomas from 36 patients (26 men and 10 women; average age: 48 years, range: 24–75 years). This was a retrospective study that was conducted in accordance with the Declaration of Helsinki 1975 (as revised in 1983) and approved by the institutional review board (IRB) of Toky Medical and Dental University (IRB; No. D2020-066). Informed consent was waived by the IRB due to the nature of the study.

MRI protocols

In all cases, MRI was performed using one 3 T machine (Magnetom Spectra, Siemens Healthineers, Erlangen, Germany) with a 16-channel head and neck coil. A routine MRI protocol was applied for all the patients as follows: a T1 weighted turbo spin-echo sequence (echo time [TE]: 10 ms, repetition time [TR]: 650 ms, and number of signal averages [NSAs]: 1) in the axial and coronal planes; a T2weighted turbo spin-echo sequence (TE: 71 ms, TR: 5 400 ms, and NSA: 12 with fat suppression, using the two-point Dixon technique in the axial plane; and a post-contrast T1 weighted turbo spin-echo sequence (TE: 12 ms, TR: 640 ms, and NSA: 1) with fat suppression, using the two-point Dixon technique in the axial and coronal planes, after intravenous gadobutrol (Gadovist®, Bayer, Leverkusen, Germany) injection at a dose of 0.1 mmol/kg of body weight. All the images were obtained with a section thickness of 3.0 or 4.0 mm and an intersection gap of 0.9 or 1.0 mm, using a 230 × 187 mm2 field of view and a matrix of 384 × 312. A single-shot spin-echo echo-planar diffusion-weighted image sequence (TE: 85 ms, TR: 3 150 ms, and NSA: 2) was acquired with fat suppression by short tau inversion recovery in the axial plane, 4.0 mm section thickness, 1.0 mm intersection gap, 230 × 173 mm2 field of view, and matrix of 128 × 96 (interpolated to 256 × 192). Generalised auto-calibrating partially parallel acquisition was used for parallel imaging with an acceleration factor of 3. 10 b-values (0, 50, 100, 150, 200, 300, 500, 800, 1000, and 1500 s/mm2) were used, and a bipolar scheme was applied. The ADC maps were constructed from the diffusion-weighted images with all b-values by using the fit of a linear regression model.

Image analysis

The characteristics of the lesions were observed by focusing on the lesion margin and diameter, PR and LC features, soft tissue involvement on T2wFS and contrast-enhanced T1wFS (T1wFS + C), and average ADC values on ADC maps. All these were analysed by two independent observers on a syngo.via workstation (Siemens). Each observer performed the image analysis twice with an interval of more than 8 weeks and without knowing the histopathological results. Based on the lesion margin, we classified the lesions as well- or ill-defined. We evaluated the signal intensity of the lesions as hypo- or hyperintense compared with the adjacent masseter muscle and evaluated homogeneity as heterogeneous or homogeneous. We measured the maximum PR thickness of the lesion in subtracted pre- and post-contrast T1w. Contrast enhancement was evaluated by comparing T1w and T1wFS + C images, and it was sometimes observed in the subtracted image. We evaluated whether there was soft tissue involvement by observing signal changes in the surrounding tissues. These features were established by Juerchottet al,35 and we utilised them in this study. Additionally, we measured the lesion’s maximum diameter with a digital calliper on T1w and the average ADC value using a round-shaped region of interest on the ADC map. We recorded the radiological impression given at the time that MRI was performed for each lesion.

Decision tree analysis

We made a decision tree for discriminating radicular cysts from granulomas with the five significant factors as maximum diameter of lesion, contrast enhancement of the LC on T1wFS + C, signal intensity of the LC on T2wFS, signal intensity on T2wFS, and signal homogeneity on T2wFS using the χ2 automated interaction detection growing method (SPSS Statistics, IBM Corp., Armonk, NY).

Statistical analysis

Statistical analysis was performed using SPSS software v. 28.0.1.0. Normality was assessed with the Shapiro–Wilk test. We executed Fisher’s exact test for matrix tables and the Mann–Whitney U test for comparing maximum diameter and maximum PR thickness values between radicular cysts and granulomas. We used an independent sample t-test to compare the patients' age and average ADC value between the two lesions. Intra- and interobserver reliability was analysed with an intraclass correlation coefficient. A p-value less than 0.05 was considered statistically significant.

Results

We observed 36 cases of periapical lesions, including 27 cases of radicular cysts and 9 cases of periapical granulomas. The intra- and inter-observer agreements were judged as “moderate” or “excellent”, depending on previously established parameters.36 The characteristics of the lesions are summarised in Table 1. There were statistically significant differences in five imaging characteristics between radicular cysts and granulomas, namely: (1) the dominant signal intensity of the LC on T2wFS (Fisher’s exact test, p < 0.05), (2) dominant signal intensity of the LC on T1wFS + C (Fisher’s exact test, p < 0.05), (3) signal homogeneity of the LC on T1wFS + C (Fisher’s exact test, p < 0.05), (4) contrast enhancement status of the LC on T1wFS + C (Fisher’s exact test, p < 0.05), and (5) maximum diameter of the lesions (Mann–Whitney U test, p < 0.05). There were three cases of granuloma and one case of radicular cyst whose radiological diagnoses differed from their pathological diagnoses; hence, the total diagnostic accuracy of MRI in this study was 88.9%.

Table 1.

Demographic and radiographic characteristics of radicular granulomas and cysts

Granuloma Cyst p-value
Sex Male 5 21 0.226
Female 4 6
Age (years) Average 42 50 0.896
Minimum 24 27
Maximum 60 75
Lesion margin Ill-defined 2 1 0.148
Well-defined 7 26
PR features TFS Dominant signal Hypointense 2 0 0.057
Hyperintense 7 27
Texture Heterogenous 4 10 0.712
Homogenous 5 17
T1wFS + C Dominant signal Hypointense 0 0 NS
Hyperintense 9 27
Texture Heterogenous 5 5 0.079
Homogenous 4 22
Maximum thickness (mm) Average 1.72 1.93 0.089
Minimum 0.90 0.80
Maximum 4.20 3.20
Contrast-enhancement Yes 9 26 1.000
No 0 1
LC features T2wFS Dominant signal Hypointense 3 0 0.012
Hyperintense 6 27
Texture Heterogenous 5 12 0.706
Homogenous 4 15
T1wFS + C Dominant signal Hypointense 2 19 0.019
Hyperintense 7 8
Texture Heterogenous 7 8 0.019
Homogenous 2 19
Contrast-enhancement Yes 8 4 <0.001
No 1 23
ST involvement T2wFS Yes 5 8 0.235
No 4 19
T1wFS + C Yes 4 9 0.693
No 5 18
Maximum diameter (mm) Average 10.47 23.90 <0.001
Minimum 5.85 10.50
Maximum 14.70 40.90
ADC value (× 10−3 mm2/s) Average 1.108 1.018 0.513
Minimum 0.047 0.392
Maximum 1.463 2.139
Radiological impression by MRI Granuloma 6 1 <0.001
Cyst 3 26
Total number of cases 9 27
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ADC, apparent diffusion coefficient; LC, lesion center; NS, not significant; PR, peripheral rim; ST, soft tissue; T2wFS, T2 weighted with fat saturation;T1wFS+C, contrast-enhanced T1 weighted with fat saturation.

All radicular cysts showed a hyperintense signal in the LC on T2wFS; however, only three granulomas (33.3%) showed a low signal intensity in the LC. On T1wFS + C, most granulomas (8 out of 9 cases: 88.9%) showed contrast enhancement in the LC, while most radicular cysts (23 out of 27 cases: 85.2%) did not show any contrast enhancement in the LC. The average maximum diameter of radicular cysts was 23.9 mm, which was significantly larger than that of granulomas (10.5 mm) (Mann–Whitney U test, p < 0.05) as shown in Figure 1. A receiver operating characteristic curve analysis set the cut-off value for the diameter of radicular cysts as 15.9 mm, and the area under the curve was 0.971 (95% confidence interval = 0.90–1.00) with a sensitivity of 85.2% and specificity of 100% (as shown in Figure 2). Figure 3 demonstrates each type of lesion with its typical MRI features. The granuloma shows high signal intensity on T2wFS and enhancement of the lesion centre on T1wFS + C (Figure 3a), and the cyst shows high signal intensity on T2wFS but no lesion centre enhancement but rim enhancement on T1wFS + C (Figure 3b). Figures 4 and 5 demonstrate cases with atypical MRI features in the LC and PR, i.e. features that differed from the criteria established by Juerchott et al.35 Figure 6 shows a lesion that was misdiagnosed as a granuloma using MRI at the time of examination in Tokyo Medical and Dental Univeristy hospital. Figure 7 shows the decision tree for discriminating between radicular cysts and granulomas. The two lesions could be distinguished following the decision tree model by first measuring the maximum lesion diameter. If the diameter was larger than 17 mm, the lesion was considered a radicular cyst. Conversely, if the diameter was 17 mm or less, we further evaluated the LC contrast enhancement status on T1wFS + C. If the lesion showed an enhanced LC, it was considered a granuloma. If it showed a non-enhanced LC, we thoroughly investigated the LC signal intensity on T2wFS. A lesion that showed a hyperintense LC was considered a radicular cyst.

Figure 1.

Figure 1.

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A plot graph showing the maximum diameters of radicular cysts and granulomas. The horizontal lines indicate the averages. The differences in diameter between the two lesions are statistically significant based on Mann–Whitney U tests (p < 0.001).

Figure 2.

Figure 2.

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A receiver operating characteristic analysis based on the maximum diameters of the lesions. The cut-off value is set to 15.9 mm, and the area under the curve (grey area) is 0.971.

Figure 3.

Figure 3.

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Typical magnetic resonance images of a radicular granuloma (a) and a cyst (b). (a) Shows a radicular granuloma in the right mandible of a 54-year-old male, showing high signal intensity on T2wFS and enhancement of the lesion centre on T1wFS + C. (b) Shows a radicular cyst in the anterior left mandible of a 32-year-old male, showing high signal intensity on T2wFS and no lesion centre enhancement but rim enhancement on T1wFS + C. T1wFS + C, T1 weighted image with fat saturation with contrast media; T2wFS, T2 weighted image with fat saturation.

Figure 4.

Figure 4.

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“Atypical” lesion centre findings in a radicular granuloma (a) and a cyst (b). (a) Shows a radicular granuloma in the right mandible of a 36-year-old female. The lesion shows a hypointense signal on T1w but homogeneous high intensity on T2wFS. Heterogeneous relatively weak enhancement is shown on contrast-enhanced T1WFS + C. (b) Shows a cyst in the left molar of a 43-year-old female. The lesion shows a heterogeneous high-intensity signal in the lesion centre on T2wFS, whereas a homogeneous area is shown on T1wFS + C. T1wFS + C, T1 weighted image with fat saturation with contrast media; T2wFS, T2 weighted image with fat saturation.

Figure 5.

Figure 5.

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“Atypical” soft tissue involvement in a radicular granuloma (a) and a cyst (b). (a) Shows a radicular granuloma in the anterior right maxilla of a 29-year-old male, showing no soft tissue involvement on both T2wFS and contrast media-enhanced T1wFS + C. (b) Shows a radicular cyst in the right mandible of a 56-year-old female, showing soft tissue involvement on both T2wFS and T1wFS + C. T1wFS + C, T1 weighted image with fat saturation with contrast media; T2wFS, T2 weighted image with fat saturation.

Figure 6.

Figure 6.

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A radicular granuloma misdiagnosed as a cyst in a 24-year-old female. (a) Shows a panoramic view of dental CT showing a periapical lesion at the right mandibular canine periapical site. (b) Shows an axial T1 weighted image showing a hypointense signal in both the lesion centre and peripheral rim, with a maximum diameter of 10.2 mm. (c) Shows an axial T2 weighted image showing a heterogeneous high-intensity signal in the lesion centre and peripheral rim and soft tissue involvement. (d) Shows an axial contrast-enhanced T1 weighted image with fat saturation, and (e) shows a subtraction image of pre- and post-contrast T1 weighted image showing high signal intensity in the peripheral rim and soft tissue involvement. (f) Shows an axial ADC map showing high signal intensity in the lesion centre and an ADC value of 1.463 × 10–3 mm2/s. ADC, apparent diffusion coefficient.

Figure 7.

Figure 7.

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A decision tree for discriminating radicular cysts and granulomas. The tree was created with the five significant parameters, using the χ2 automated interaction detection growing method. LC, lesion centre; T1wFS + C, T1 weighted image with fat saturation with contrast media; T2wFS, T2 weighted image with fat saturation.

There were no statistically significant differences in the average ADC values (independent t-test, p > 0.05) or any other imaging characteristics between the two lesions.

Discussion

This retrospective study analysed the MRI features of 27 radicular cysts and 9 granulomas with the aim of distinguishing the two types of lesions. Radicular cysts constituted three-quarters of the total number of cases, which is consistent with previous studies.1,16 To the best of our knowledge, our study has the largest number of periapical lesions examined with 3 T MRI.

Recently, MRI features of radicular granulomas and cysts were investigated by Lizio et al34 and Juerchott et al.35 Juerchott et al concluded that the following six MRI characteristics could be used to distinguish radicular cysts from granulomas: (1) lesion margin, (2) PR texture on T1wFS + C, (3) LC texture on T2wFS, (4) soft tissue involvement on T2wFS, (5) soft tissue involvement on T1wFS + C, and (6) maximum PR thickness.35 Although they described their study as a pilot study, they were able to distinctly categorise their 11 cases into 2 types of lesions. However, the results of the present study did not show any statistically significant differences in these characteristics between radicular cysts and granulomas. In the present study, one radicular cyst showed an ill-defined margin with a thick PR, as shown in Figure 3b, and nine radicular cysts (33.3%) showed soft tissue involvement on T1wFS + C (Figure 5b). Additionally, four periapical granulomas (44.4%) showed homogeneity in the LC and PR on T2wFS (Figure 4a) and T1wFS + C (Figure 5a), respectively; however, according to the criteria used by Juerchott et al, these characteristics are supposed to be found in cysts.35 Moreover, we found that approximately half of the granulomas in this study showed no soft tissue involvement on T2wFS and T1wFS + C (as shown in Figures 4a and 5a).

Lizio et al clarified six criteria for differentiating radicular cysts and granulomas.34 They reported that the 34 cases in their study could be diagnosed by two observers with an accuracy of 74 and 79%. We applied these criteria to our cases, and the result was satisfactory, i.e. the accuracy of our results was 86.1%. However, none of our cases showed a low-intensity outline on T1w or T2w. Moreover, granulomas with well-defined margins were frequently observed (7 out of 9 cases: 77.8%), and they could have been mistaken as cysts if the criteria by Lizio et al34 had been applied; hence, it should be noted that lesion margin is not a distinctive parameter for identifying a radicular cyst or granuloma.

In this study, five significant MRI characteristics were used to identify granulomas and cysts. They are as follows:

  1. Maximum diameter of lesion: measurements of the lesion’s maximum diameter differentiated radicular cysts and granulomas, which is consistent with the findings of previous studies.22,37 All granulomas were smaller than 15.9 mm, whereas cysts had a wider diameter range of 10.5–40.9 mm, which is similar to the results of Juerchott et al.35 Although this finding could have been influenced by case selection bias, it may also indicate that there is a growth limitation in granulomas but not in cysts.38

  2. Signal intensity of the LC on T2wFS: low signal intensity in the LC was a characteristic found in three granulomas but not in any cysts. This may demonstrate the late healing stage of granulomas, which correlated with their pathological characteristics of fibroblasts and haemosiderin granule-rich status within a fibrous connective tissue stroma.39 Contrarily, the hyperintense signal found in all the cysts might reflect their fluid nature, which is in agreement with the result of a previous study.35 However, this characteristic does not confirm that a lesion is a cyst because two-thirds of granulomas also showed high signal intensity on T2wFS. Accordingly, we considered that the ADC value might be used to differentiate these two lesions by analysing the diffusion state of their water molecules,30,33 but this approach also failed as the average of the ADC values was not significantly different between the two lesions.

  3. Signal intensity, (4) signal homogeneity, and (5) contrast enhancement of the LC on T1wFS + C: the majority of the cystic lesions showed no enhancement in the LC, as expected, since they were non-vascularised, liquid-filled cavities.31 This finding is similar to that reported by Juerchott et al35 as all of their five radicular cysts showed no enhancement on T1wFS + C. However, four radicular cysts showed LC enhancement in the present study, which may be explained by the histopathological finding of haemosiderin within these lesions, indicating bleeding. In addition, one granuloma showed no contrast enhancement in the LC. Its pathological findings include fibrous tissue within the lesion, which may explain the non-enhanced LC on T1wFS + C and low signal intensity on T2wFS.27

The MRI characteristics clarified in this study are useful for differentiating radicular cysts and granulomas. However, there were a few inconsistent findings; hence, it is not practical for any of these characteristics to be used as a definitive discrimination point between radicular cysts and granulomas. We, therefore, established a decision tree for discrimination between these two lesions (as shown in Figure 7). The discriminative factors are easy to use and consistent with the pathological characteristics of the lesions. In this study, we assessed the radiological impression made at the time the MRI was performed, and its accuracy was 88.9%. This result means that the subjective assessment made by the interpreters based on the aforementioned objective characteristics, without measuring the lesion’s diameter, can provide an accurate diagnosis. However, 33.3% of the granulomas (3 out of 9) and 3.7% of the cysts (1 out of 27) were misdiagnosed. One of the misdiagnosed granulomas is shown in Figure 6. In this case, the lesion exhibited contrast enhancement in the LC on T1wFS + C (Figure 6d and e), and its maximum diameter was 10.2 mm. Based on the decision tree, it should be diagnosed as a granuloma. However, its average ADC value was as high as 1.46 × 10−3 mm2/s; therefore, the examiner suspected that it was a radicular cyst. The other two misdiagnosed granulomas also showed similar findings. The misdiagnosed radicular cyst had an inhomogeneous LC with a maximum diameter of 10.2 mm on T2wFS, as shown in Figure 4b; hence, the examiner considered it a granuloma. The lesion size, in this case, was too small to judge whether the LC was enhanced or not, which is a limitation of the current MRI.27 Recently, there has been an increasing number of attempts to make MRI more useful in dental practice. One of them is increasing the resolution of MRI. Specifically, many coils are placed outside the oral cavity,40 while some wiring or wireless intraoral coils are also being tested.39,41 These new methods will allow us to obtain images with higher resolution and signal-to-noise ratio to observe periapical structures in detail and, hopefully, accurately diagnose lesions such as the misdiagnosed radicular cyst in this study.

We successfully discriminated radicular cysts and granulomas in this study with the decision tree, yet the diagnosis of 14 cases (38.8%) depended on contrast medium enhancement. Although it is undeniable that gadolinium contrast examination has a significant impact on qualitative diagnosis with MRI, the administration of the contrast medium during the procedure may cause allergic reactions42 and/or induce systemic renal fibrosis,43 making it inapplicable to some patients. Therefore, careful administration is necessary. In cases where the contrast imaging technique cannot be used, the decision tree cannot be applied. According to our results, if the information on T1wFS + C had been ignored, six of the nine granulomas (66.7%) would have been misdiagnosed as cysts.

A limitation of this study is that there were few periapical granuloma cases. Nevertheless, our study still has the largest number of granuloma cases examined with 3 T MRI to our knowledge. Generally, granulomas tend to be small, as is evident here and supported by other studies22,23,35,37; hence, they are unlikely to be investigated using MRI and/or biopsy. Additionally, periapical granulomas are responsive to conventional endodontic treatments; therefore, MRI would not be necessary. The results of this study should be confirmed with further prospective studies. However, we believe our findings would be useful for differentiating radicular cysts from granulomas.

In summary, our findings indicate that a granuloma may not show inflammatory signs in soft tissue, and a cyst could possibly cause inflammation in soft tissue; hence, soft tissue involvement is not a key characteristic for distinguishing these two lesions. Furthermore, nearly half of the granuloma cases (4 out of 9: 44.4%) showed homogeneous high signal intensity on T2wFS; therefore, this feature is not a defining characteristic of radicular cysts. We conclude that this study clarified the MRI characteristics of radicular granulomas and cysts and demonstrated that MRI is a promising diagnostic modality for differentiating these two lesions.

Footnotes

Acknowledgements: We would like to thank Editage (www.editage.com) for English language editing.

Conflict of Interests: The authors declare no conflict of interests related to this study.

Contributor Information

Natnicha Wamasing, Email: nwamorad@tmd.ac.jp.

Supasith Yomtako, Email: suyo.orad@tmd.ac.jp.

Hiroshi Watanabe, Email: hiro.orad@tmd.ac.jp.

Junichiro Sakamoto, Email: sakajun.orad@tmd.ac.jp.

Kou Kayamori, Email: kayamori.mpa@tmd.ac.jp.

Tohru Kurabayashi, Email: kura.orad@tmd.ac.jp.

REFERENCES

  • 1. Diegues LL, Colombo Robazza CR, Costa Hanemann JA, Costa Pereira AA, Silva CO. Correlation between clinical and histopathological diagnoses in periapical inflammatory lesions. J Investig Clin Dent 2011; 2: 184–86. doi: 10.1111/j.2041-1626.2011.00053.x [DOI] [PubMed] [Google Scholar]
  • 2. Mallya SM, Lam EWN.. White and Pharoah’s oral radiology principles and interpretation (8th edn).Amsterdam.Elsevier, 2019.
  • 3. Nair PN. Apical periodontitis: a dynamic encounter between root canal infection and host response. Periodontol 2000. [DOI] [PubMed] [Google Scholar]
  • 4. Guo J, Simon JH, Sedghizadeh P, Soliman ON, Chapman T, Enciso R. Evaluation of the reliability and accuracy of using cone-beam computed tomography for diagnosing periapical cysts from granulomas. J Endod 2013; 39: 1485–90. doi: 10.1016/j.joen.2013.08.019 [DOI] [PubMed] [Google Scholar]
  • 5. Ramachandran Nair PN, Pajarola G, Schroeder HE. Types and incidence of human periapical lesions obtained with extracted teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996; 81: 93–102. doi: 10.1016/s1079-2104(96)80156-9 [DOI] [PubMed] [Google Scholar]
  • 6. Simon JH. Incidence of periapical cysts in relation to the root canal. J Endod 1980; 6: 845–48. doi: 10.1016/S0099-2399(80)80039-2 [DOI] [PubMed] [Google Scholar]
  • 7. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature -- part 2. influence of clinical factors. Int Endod J 2008; 41: 6–31. doi: 10.1111/j.1365-2591.2007.01323.x [DOI] [PubMed] [Google Scholar]
  • 8. Nair PN. New perspectives on radicular cysts: do they heal? Int Endod J 1998; 31: 155–60. doi: 10.1046/j.1365-2591.1998.00146.x [DOI] [PubMed] [Google Scholar]
  • 9. Berman LH, Hargreaves KM,Rotstein I. Cohen’s pathways of the pulp (12thedn).Amsterdam: Elsevier, 2020. [Google Scholar]
  • 10. Alantar A, Bloud C, Galéazzi J-M, Baranes M, Lévy G, Chapireau D, et al. Success rate and recurrence frequency of periapical surgery: prospective study on 132 cases. Med Buccale Chir Buccale 2010; 16: 15–22. doi: 10.1051/mbcb/2009038 [DOI] [Google Scholar]
  • 11. Becconsall-Ryan K, Tong D, Love RM. Radiolucent inflammatory jaw lesions: a twenty-year analysis. Int Endod J 2010; 43: 859–65. doi: 10.1111/j.1365-2591.2010.01751.x [DOI] [PubMed] [Google Scholar]
  • 12. Carrillo C, Penarrocha M, Ortega B, Martí E, Bagán JV, Vera F. Correlation of radiographic size and the presence of radiopaque lamina with histological findings in 70 periapical lesions. J Oral Maxillofac Surg 2008; 66: 1600–1605. doi: 10.1016/j.joms.2007.11.024 [DOI] [PubMed] [Google Scholar]
  • 13. Cunningham CJ, Penick EC. Use of a roentgenographic contrast medium in the differential diagnosis of periapical lesions. Oral Surg Oral Med Oral Pathol 1968; 26: 96–102. doi: 10.1016/0030-4220(68)90228-4 [DOI] [PubMed] [Google Scholar]
  • 14. Gbadebo SO, Akinyamoju AO, Sulaiman AO. PERIAPICAL pathology: comparison of clinical diagnosis and histopathological findings. J West Afr Coll Surg 2014; 4: 74–88. [PMC free article] [PubMed] [Google Scholar]
  • 15. Kizil Z, Energin K. An evaluation of radiographic and histopathological findings in periapical lesions. J Marmara Univ Dent Fac 1990; 1: 16–23. [PubMed] [Google Scholar]
  • 16. Ricucci D, Mannocci F, Ford TRP. A study of periapical lesions correlating the presence of A radiopaque lamina with histological findings. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006; 101: 389–94. doi: 10.1016/j.tripleo.2005.08.026 [DOI] [PubMed] [Google Scholar]
  • 17. Zain RB, Roswati N, Ismail K. Radiographic evaluation of lesion sizes of histologically diagnosed periapical cysts and granulomas. Ann Dent 1989; 48: 3–5. [PubMed] [Google Scholar]
  • 18. Bornstein MM, Bingisser AC, Reichart PA, Sendi P, Bosshardt DD, von Arx T. Comparison between radiographic (2-dimensional and 3-dimensional) and histologic findings of periapical lesions treated with apical surgery. J Endod 2015; 41: 804–11. doi: 10.1016/j.joen.2015.01.015 [DOI] [PubMed] [Google Scholar]
  • 19. Chanani A, Adhikari HD. Reliability of cone beam computed tomography as a biopsy-independent tool in differential diagnosis of periapical cysts and granulomas: an in vivo study. J Conserv Dent 2017; 20: 326–31. doi: 10.4103/JCD.JCD_124_17 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20. Kruse C, Spin-Neto R, Wenzel A, Kirkevang LL. Cone beam computed tomography and periapical lesions: a systematic review analysing studies on diagnostic efficacy by a hierarchical model. Int Endod J 2015; 48: 815–28. doi: 10.1111/iej.12388 [DOI] [PubMed] [Google Scholar]
  • 21. Rosenberg PA, Frisbie J, Lee J, Lee K, Frommer H, Kottal S, et al. Evaluation of pathologists (histopathology) and radiologists (cone beam computed tomography) differentiating radicular cysts from granulomas. J Endod 2010; 36: 423–28. doi: 10.1016/j.joen.2009.11.005 [DOI] [PubMed] [Google Scholar]
  • 22. Jones AV, Craig GT, Franklin CD. Range and demographics of odontogenic cysts diagnosed in a UK population over a 30-year period. J Oral Pathol Med 2006; 35: 500–507. doi: 10.1111/j.1600-0714.2006.00455.x [DOI] [PubMed] [Google Scholar]
  • 23. Natkin E, Oswald RJ, Carnes LI. The relationship of lesion size to diagnosis, incidence, and treatment of periapical cysts and granulomas. Oral Surg Oral Med Oral Pathol 1984; 57: 82–94. doi: 10.1016/0030-4220(84)90267-6 [DOI] [PubMed] [Google Scholar]
  • 24. Ng YL, Mann V, Gulabivala K. A prospective study of the factors affecting outcomes of non-surgical root canal treatment: Part 2: tooth survival. Int Endod J 2011; 44: 610–25. doi: 10.1111/j.1365-2591.2011.01873.x [DOI] [PubMed] [Google Scholar]
  • 25. Sönmez G, Kamburoğlu K, Yılmaz F, Koç C, Barış E, Tüzüner A. Versatility of high resolution ultrasonography in the assessment of granulomas and radicular cysts: a comparative in vivo study. Dentomaxillofacial Radiology 2019; 48: 20190082. doi: 10.1259/dmfr.20190082 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26. Trope M, Pettigrew J, Petras J, Barnett F, Tronstad L. Differentiation of radicular cyst and granulomas using computerized tomography. Endod Dent Traumatol 1989; 5: 69–72. doi: 10.1111/j.1600-9657.1989.tb00339.x [DOI] [PubMed] [Google Scholar]
  • 27. Hashemi RH, Bradley WG,Lisanti CJ.. MRI: the basics (4thedn).Philadelphia, PA: Lippincott Williams & Wilkins, 2019. [Google Scholar]
  • 28. Morrison WB, Schweitzer ME, Bock GW, Mitchell DG, Hume EL, Pathria MN, et al. Diagnosis of osteomyelitis: utility of fat-suppressed contrast-enhanced MR imaging. Radiology 1993; 189: 251–57. doi: 10.1148/radiology.189.1.8204132 [DOI] [PubMed] [Google Scholar]
  • 29. Konouchi H, Asaumi J, Yanagi Y, Hisatomi M, Kawai N, Matsuzaki H, et al. Usefulness of contrast enhanced-MRI in the diagnosis of unicystic ameloblastoma. Oral Oncol 2006; 42: 481–86. doi: 10.1016/j.oraloncology.2005.10.001 [DOI] [PubMed] [Google Scholar]
  • 30. Wamasing N, Watanabe H, Sakamoto J, Tomisato H, Kurabayashi T. Differentiation of cystic lesions in the jaw by conventional magnetic resonance imaging and diffusion-weighted imaging. Dentomaxillofac Radiol 2022; 51(1): 20210212. doi: 10.1259/dmfr.20210212 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31. Lam PD, Kuribayashi A, Imaizumi A, Sakamoto J, Sumi Y, Yoshino N, et al. Differentiating benign and malignant salivary gland tumours: diagnostic criteria and the accuracy of dynamic contrast-enhanced MRI with high temporal resolution. Br J Radiol 2015; 88(1049): 20140685. doi: 10.1259/bjr.20140685 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32. Yabuuchi H, Fukuya T, Tajima T, Hachitanda Y, Tomita K, Koga M. Salivary gland tumors: diagnostic value of gadolinium-enhanced dynamic MR imaging with histopathologic correlation. Radiology 2003; 226: 345–54. doi: 10.1148/radiol.2262011486 [DOI] [PubMed] [Google Scholar]
  • 33. Sakamoto J, Yoshino N, Okochi K, Imaizumi A, Tetsumura A, Kurohara K, et al. Tissue characterization of head and neck lesions using diffusion-weighted MR imaging with SPLICE. Eur J Radiol 2009; 69: 260–68. doi: 10.1016/j.ejrad.2007.10.008 [DOI] [PubMed] [Google Scholar]
  • 34. Lizio G, Salizzoni E, Coe M, Gatto MR, Asioli S, Balbi T, et al. Differential diagnosis between a granuloma and radicular cyst: effectiveness of magnetic resonance imaging. Int Endod J 2018; 51: 1077–87. doi: 10.1111/iej.12933 [DOI] [PubMed] [Google Scholar]
  • 35. Juerchott A, Pfefferle T, Flechtenmacher C, Mente J, Bendszus M, Heiland S, et al. Differentiation of periapical granulomas and cysts by using dental MRI: a pilot study. Int J Oral Sci 2018; 10: 17. doi: 10.1038/s41368-018-0017-y [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 36. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977; 33: 159–74. [PubMed] [Google Scholar]
  • 37. Rózyło-Kalinowska I. Digital radiography density measurements in differentiation between periapical granulomas and radicular cysts. Med Sci Monit 2007; 13 Suppl 1: 129–36. [PubMed] [Google Scholar]
  • 38. Sedlacik J, Kutzner D, Khokale A, Schulze D, Fiehler J, Celik T, et al. Optimized 14 + 1 receive coil array and position system for 3D high-resolution MRI of dental and maxillomandibular structures. Dentomaxillofac Radiol 2016; 45(1): 20150177. doi: 10.1259/dmfr.20150177 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 39. Ludwig U, Eisenbeiss A-K, Scheifele C, Nelson K, Bock M, Hennig J, et al. Dental MRI using wireless intraoral coils. Sci Rep 2016; 6: 23301. doi: 10.1038/srep23301 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 40. Flügge T, Hövener J-B, Ludwig U, Eisenbeiss A-K, Spittau B, Hennig J, et al. Magnetic resonance imaging of intraoral hard and soft tissues using an intraoral coil and FLASH sequences. Eur Radiol 2016; 26: 4616–23. doi: 10.1007/s00330-016-4254-1 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 41. Costello JR, Kalb B, Martin DR. Incidence and risk factors for gadolinium-based contrast agent immediate reactions. Top Magn Reson Imaging 2016; 25: 257–63. doi: 10.1097/RMR.0000000000000109 [DOI] [PubMed] [Google Scholar]
  • 42. Pasquini L, Napolitano A, Visconti E, Longo D, Romano A, Tomà P, et al. Gadolinium-Based contrast agent-related toxicities. CNS Drugs 2018; 32: 229–40. doi: 10.1007/s40263-018-0500-1 [DOI] [PubMed] [Google Scholar]
  • 43. Kanal E, Patton TJ, Krefting I, Wang C. Nephrogenic systemic fibrosis risk assessment and skin biopsy quantification in patients with renal disease following gadobenate contrast administration. AJNR Am J Neuroradiol 2020; 41: 393–99. doi: 10.3174/ajnr.A6448 [DOI] [PMC free article] [PubMed] [Google Scholar]

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