OBJECTIVES: To compare the image quality of deep learning-based Compressed SENSE (DL-based CS) reconstructed images with conventional algorithm-based Compressed SENSE (Alg-based CS) reconstructed images in contrast-enhanced 3D T1-weighted images of the maxillofacial region. METHODS: The cases of 32 patients who underwent two reconstructions, conventional Alg-based CS, and DL-based CS, were retrospectively analyzed. We set the reduction factors to 3 and 6. Thus, four types of images were obtained: Alg3, DL3, Alg6, and DL6. We calculated the signal-to-noise ratios (SNRs) of the muscle and spinal cord and the Structural Similarity Index Measure (SSIM) between the two reconstructions at both the level of the tongue and oral floor. Additionally, noise, visualization of anatomical structures, and motion artifacts were subjectively assessed on a 5-point scale. RESULTS: A significant difference was observed between Alg3 and Alg6, indicating that a higher reduction factor results in a lower SNR. DL was useful for improving image quality, and no significant difference was observed between DL6 and Alg3. The SSIM at a reduction factor of six was smaller than that at a reduction factor of three, and this tendency was markedly noticeable in the lower face, which shows that DL is beneficial for denoising under low SNR conditions. The qualitative assessment of the noise and anatomical structure showed similar trends to the SNR. CONCLUSIONS: Given the quantitative and qualitative analyses, DL-based CS reconstruction is useful, especially for high reduction factors and regions with low coil sensitivity.

Background/purposeRadiolucent lesions of the mandible, including ameloblastoma, odontogenic keratocyst (OKC), dentigerous cyst (DC) and simple bone cyst (SBC), are frequently encountered in clinical practice. However, they vary in type and occasionally in appearance. Each lesion needs a different treatment and approach; therefore, accurate diagnosis is crucial before treatment. However, the radiographic findings, including computed tomography (CT), are often similar. This study aimed to compare the CT findings of 41 ameloblastomas, 74 OKCs, 87 DCs, and 13 SBCs in the mandible.Materials and methodsPatients were evaluated on initial CT images focusing on features such as long/short diameters, relationship with adjacent teeth, cortex appearance, locularity, scalloped margins, and sclerotic rims. Multivariate logistic regression analysis was performed to determine the most useful features for differential diagnosis. Criteria for differential diagnosis were finally established for three lesions, excluding SBC, which had a relatively small number of cases.ResultsThe relationship with the affected tooth, short diameters, sclerotic rims, and locularity were found to be significant features in the differential diagnosis. Ameloblastomas were characterized by relatively larger short diameters, frequently accompanied by root resorption and adjacent tooth displacement, while SBCs lacked these features. Sclerotic rims were commonly observed in OKCs and DCs, and most DCs were unilocular, containing a crown within the lesion. Based on these results, criteria were established for differential diagnosis with a diagnostic accuracy of 84.2%.ConclusionThis is the first study to attempt to characterize each lesion's radiological features, and these criteria are likely to assist in clinical diagnosis.

Purpose: To compare the evaluation of temporomandibular joint bone changes and diagnosis of degenerative joint disease (DJD) using fast field echo resembling a CT using restricted echo-spacing (FRACTURE) magnetic resonance imaging (MRI) sequence, with that using computed tomography (CT). Methods: This study included 28 temporomandibular joints from 14 patients who underwent MRI, including FRACTURE sequence, and CT of the temporomandibular joint region. Three-axis cross-sectional images were prepared for both FRACTURE and CT. Two radiologists independently assessed temporomandibular joint bone changes across nine categories. The proportion of agreement between FRACTURE and CT assessments for bone changes was calculated separately for each observer using CT as the reference standard. Diagnostic agreement for detecting DJD was also assessed, and interobserver agreement for DJD diagnosis was measured using kappa statistics. Results: The proportion of agreement between FRACTURE and CT assessments for bone changes ranged from 0.750 to 1.000 for Observer 1, and from 0.786 to 1.000 for Observer 2. For DJD diagnosis, the FRACTURE technique demonstrated high agreement with CT assessments, with proportions of agreement of 1.000 for Observer 1 and 0.893 for Observer 2. The kappa statistic for interobserver agreement for DJD diagnosis was substantial with FRACTURE and almost perfect with CT. Conclusion: The FRACTURE technique may provide information comparable to CT assessments for evaluating temporomandibular joint bone changes and diagnosing DJD. Adding FRACTURE, a widely available sequence, to conventional MRI sequences may enable many institutions to diagnose both disc displacement and DJD without requiring CT.

Objective: To evaluate useful parameters for differentiating metastatic lymph nodes in oral squamous cell carcinoma using dual-energy computed tomography (DECT) in the venous phase. Methods: A total of 117 lymph nodes without visually obvious necrosis (83 non-metastatic and 34 metastatic) from 40 patients were retrospectively analyzed. The region of interest was defined at the area with the maximum short diameter. Nine parameters were calculated and correlated with the pathology images: CT values of virtual monochromatic X-ray images at 40, 70, and 100 key (HU40 key, HU70 key, HU100 key), iodine concentration (IC), CT value variation at 40-70 key (240-70 HU), 40-100 key (240-100 HU), lymph node long diameter, short diameter, and long-short diameter ratio. Results: Metastatic lymph nodes had lower CT and IC values than non-metastatic nodes. However, the short diameter had the highest the area under the receiver operating characteristic curve (AUC) with 0.846 (95 % confidence interval: 0.741-0.914), and the respective sensitivity and specificity were 82.4 % and 84.3 % at a cutoff of 7.54 mm. For parameters using CT values and IC, HU100 key had the highest AUC (0.737), followed by HU70 key (0.717), HU40 key (0.686), IC (0.660), 240-100 HU (0.659), and 240-70 HU (0.659). Six DECT-derived parameters showed the significant negative correlation to the short axis length. Conclusion: In the venous phase, although the significant differences were found in the DECT-derived parameters, the maximal short diameter was found to be the most useful parameter for the differentiation of metastatic lymph nodes.

RATIONALE:Composite lesions of neurogenic tumors with vascular malformations, which were once included among hemangiomas, are extremely rare and can be classified into 2 types: conjoined and discrete associations, with the former representing a single lesion of vascular malformation within tumor tissue. To date, we have found 24 composite lesions (conjoined association type) of schwannomas coexisting with vascular malformations. However, such composite lesions should be interpreted with caution. PATIENT CONCERNS:A 29-year-old woman had recognized swelling of the tongue 5 years prior to her initial hospital visit and the lesion had recently been slowly growing. DIAGNOSES:Based on clinical examinations, including imaging studies, the tumorous lesion was clinically diagnosed as a schwannoma, but a benign salivary gland tumor and venous malformation (VM) were not completely ruled out. INTERVENTIONS:The lesion was excised with safety margin. OUTCOMES:The excised sample revealed 2 intriguing features; however, the lesion was diagnosed as an ancient schwannoma with VM-like features because of the lack of definitive findings that would make these lesions a composite of independent lesions. There was no evidence of recurrence or distant metastasis at the 16-month follow-up after excision. LESSONS:Ancient schwannomas of the oral cavity are rare. In particular, schwannomas that appear as composite lesions of schwannomas with vascular malformations are extremely rare. Here, we report the first case of an ancient schwannoma with VM-like features of the tongue. It is important for clinicians to accumulate information on these rare cases to make an accurate preoperative diagnosis and to plan appropriate treatment.

Background and objective Oral metastases are rare. We experienced a case of oral metastasis of renal cell carcinoma (RCC) and discussed its characteristics with a systematic review to survey the literature for useful features for the diagnosis of oral metastatic RCC. Methods A systematic review was conducted according to the PRISMA 2020 statement. An electronic search was performed using three databases and the literature of cases of renal cancer metastasis to the jawbone and gingiva. Results Thirty studies were identified (male-to-female ratio, 2.75:1). The site of metastasis was the jawbone in 66.7% (mandible, 60%; maxilla, 6.7%) and the gingiva in 30%. Clinical symptoms were a mass in 86.7% and hypoesthesia in 23.3%. A total of 76.7% of oral metastases were clear cell type. In our case, the male patient showed a mass in the maxillary gingiva without hypoesthesia. Metastatic clear cell RCC was suspected by an oral biopsy, which was confirmed on clinical examinations, including a renal biopsy. Conclusion Oral metastases are rare, and the clinical and imaging findings for oral metastases of RCC are wide-ranged with low specificity, depending on the metastatic site. It is necessary to fully understand the key points in histopathological differentiation. Because the clinician plays a fundamental role in the early diagnosis of oral cancer and the identification of metastatic lesions, awareness of the possibility of rare tumors as in this study can facilitate an accurate preoperative diagnosis and the planning of appropriate treatment.

To summarize the ultrasonography (US) and magnetic resonance imaging (MRI) findings of lymphoepithelial cysts (LECs) and dermoid cysts (DCs) and to discuss the hyperinternal echo in LECs based on histopathological findings. Patients who underwent US and MRI before resection and whose lesions were pathologically diagnosed as LECs or DCs were included (January 2010 to December 2023). Internal echo, convective flow, and Doppler signals were evaluated on US, while on MRI, we measured the apparent diffusion coefficient (ADC). Surprisingly, all lesions (4 LECs and 7 DCs) had hyperinternal echoes. Convective flow and Doppler signals were observed in 2 of the 4 cases of LEC, and the ADC was high in these cases (2.4 × 10–3 and 2.0 × 10–3 mm2/s). In the two cases where they were not, the ADC was low (1.4 × 10–3 and 0.81 × 10–3 mm2/s). Various cells, such as lymphocyte cells, foam cells, erythroid cells, and keratin, have been found in the cystic cavity, which are thought to be the cause of hyperecho. Considering the ADC, the presence or absence of convection and Doppler signals is thought to reflect the ease of movement of the contents. In the DCs, neither internal convection nor obvious Doppler signals were observed. ADCs were quite low for cysts, which was a characteristic finding (1.1 ± 0.13–3 mm2/s). It is well known that DCs appear hyperechoic on US owing to the presence of keratin; however, it is necessary to recognize that some LECs are depicted as hyperechoic masses and have convective flow and Doppler signals depending on the content.

Primary intraosseous carcinoma not otherwise specified (PIOC NOS) is a rare tumor assumed to arise from the epithelium, such as odontogenic cysts or benign tumors. Its clinical and imaging diagnoses are often challenging, especially in the early stages, as it mimics jaw cysts and benign tumors, and no specific findings have been identified. This report presents the case of a 66-year-old male patient with mandibular PIOC, highlighting the imaging findings over time. Magnetic resonance imaging (MRI) before symptom onset showed a cystic lesion in the right mandible with a soft tissue component. Both the fluid component and soft tissue exhibited low apparent diffusion coefficient values (1.0 × 10–3 mm2/s and 1.3 × 10–3 mm2/s, respectively). Subsequent MRI approximately 5 months later during symptom onset showed a slight increase in the soft tissue component. Based on the clinical and imaging findings, ameloblastoma was suspected, prompting a biopsy for confirmation. However, the histopathological findings showed squamous cell carcinoma (SCC). MRI performed approximately 1 month later exhibited significant tumor growth and extension beyond the jawbone, consistent with a malignant tumor. Histopathological examination identified areas with a basal layer in a palisading arrangement, indicating a pre-existing odontogenic cyst, and showed a transition from epithelial dysplasia to SCC. In addition, carcinoma cell invasion and proliferation into the cyst were observed. Based on these findings, PIOC of the right mandible was determined to be the definitive diagnosis.

Background Diffusion-weighted imaging (DWI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) are widely used in the orofacial region. Furthermore, quantitative analyses have proven useful. However, a few reports have described the correlation between DWI-derived parameters and DCE-MRI-derived parameters, and the results have been controversial. Purpose To evaluate the correlation among parameters obtained by DWI and DCE-MRI and to compare them between benign and malignant lesions. Material and Methods Fifty orofacial lesions were analysed. The apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f) were estimated by DWI. For DCE-MRI, TK model analysis was performed to estimate physiological parameters, for example, the influx forward volume transfer constant into the extracellular-extravascular space (EES) (Ktrans) and fractional volumes of EES and plasma components (ve and vp). Results Both ADC and D showed a moderate positive correlation with ve (ρ = 0.640 and 0.645, respectively). Ktrans showed a marginally weak correlation with f (ρ = 0.296), while vp was not correlated with f or D*; therefore, IVIM perfusion-related parameters and TK model perfusion-related parameters were not straightforward. Both D and ve yielded high diagnostic power between benign lesions and malignant tumours with areas under the curve (AUCs) of 0.830 and 0.782, respectively. Conclusion Both D and ve were reliable parameters that were useful for the differential diagnosis. In addition, the true diffusion coefficient (D) was affected by the fractional volume of EES.

Objectives: The purpose of this study was to compare the image quality of ultra-high-resolution CT (U-HRCT) with that of conventional multidetector row CT (convCT) and demonstrate its usefulness in the dentomaxillofacial region. Methods: Phantoms were helically scanned with U-HRCT and convCT scanners using clinical protocols. In U-HRCT, phantoms were scanned in super-high-resolution (SHR) mode, and hybrid iterative reconstruction (HIR) and filtered-back projection (FBP) techniques were performed using a bone kernel (FC81). The FBP technique was performed using the same kernel as in convCT (reference). Two observers independently evaluated the 54 resulting images using a 5-point scale (5 = excellent diagnostic image quality; 4 = above average; 3 = average; 2 = subdiagnostic; and 1 = unacceptable). The system performance function (SPF) was calculated for a comprehensive evaluation of the image quality using the task transfer function and noise power spectrum. Statistical analysis using the Kruskal-Wallis test was performed to compare the image quality among the 3 protocols. Results: The observers assigned higher scores to images acquired with the SHRHIR and SHRFBP protocols than to those acquired with the reference (P < 0.0001 and P < 0.0001, respectively). The relative SPF value at 1.0 cycles/mm in SHRHIR and SHRFBP compared to the reference protocol were 151.5% and 45.6%, respectively. Conclusions: Through phantom experiments, this study demonstrated that U-HRCT can provide superior-quality images compared to conventional CT in the dentomaxillofacial region. The development of a better image reconstruction method is required to improve image quality and optimize the radiation dose.

We report an unusual case of carcinoma ex pleomorphic adenoma (CXPA) in the submandibular gland. The mass had a unique calcification. Panoramic tomography revealed sponge-like calcification. The central portion displayed heterogeneous high signal intensity on T1-weighted image (T1WI) and T2-weighted image (T2WI), and heterogeneously moderate signal intensity on a short-TI inversion recovery (STIR) image. The ADC was low (0.78 × 10−3mm2/sec). After surgical excision, a pathological examination revealed that the mass contained CXPA as a minor component. Tumor cells with large hyperchromatic nuclei and eosinophilic or clear cytoplasm proliferated in irregular small tubule formations or cribriform or Roman-bridge structures in hyalinized or focally ossified stroma. The entire mass was calcified, particularly in the central region. Taken together, the reduced T1 relaxation times were related to the surface effects of diamagnetic particles, which were observed at calcium particle concentrations of up to 30

Synovial sarcoma (SS) is a malignant soft tissue tumor that usually arises in the para-articular regions of the extremities. Only nine cases of SS in the mandible have been reported to date. The present study described a case of SS arising from the left mandible. A 54-year-old woman was referred to Kyushu University Hospital (Fukuoka, Japan) with a complaint of numbness in the left mental nerve area. Computed tomography revealed replacement of the left mandibular bone marrow with soft tissue and destruction of the mandibular canal. Magnetic resonance imaging revealed an isointense mass on T1-weighted images and hyperintensity on T2-weighted images. The tumor showed homogeneous enhancement. A biopsy was performed, and monophasic SS was diagnosed based on immunohistochemical staining features and genetic analysis. Hemimandible dissection and supraomophyoid neck resection were performed with fibular osteocutaneous flap reconstruction, followed by adjuvant chemotherapy. There was no evidence of recurrence or distant metastases. The present study also reviewed the clinical, imaging, histological, and immunohistochemical features of the SS in the mandible.

Metastatic tumors in the oral cavity are rare, accounting for only 1% of all oral malignancies. The most common site of metastatic tumors in the oral cavity is the mandibular molar region. The primary sites differ between the sexes. Among men, the primary sites are the lung, kidney, liver, and prostate in the order of frequency. Moreover, 11% of jawbone metastases among men originate from the prostate gland. Symptoms differ according to the location of the metastasis; besides, metastases-related imaging findings are nonspecific, making it difficult to reach an accurate diagnosis. Metastatic oral cancer has a poor prognosis; therefore, early diagnosis and treatment are important to improve the survival-rate and quality of life. A 76-year-old male patient was referred to our hospital with complaint of right-sided mandibular swelling and past medical history of adenocarcinoma of the prostate gland. Intraoral examination revealed a hard hemispherical mass on the right mandibular first molar region. Computed tomography showed a well-marginated radiopaque hemisphere mass with a typical sunburst periosteal reaction. Based on the imaging findings, we suspected primary osteosarcoma or metastatic prostate cancer. Histopathological examination of the mandible revealed a glandular structure with atypia similar to that of the primary prostate cancer cells. After prostate specific antigen monitoring therapy, the metastatic cancer did not grow. Metastatic cancers from other organs should be considered in the differential diagnosis of jawbone malignancies because the metastatic cancer might present similarities to the primary cancer in imaging findings, as in the present case that clinically mimicked osteosarcoma.

Objectives: Appropriate differential diagnosis between odontogenic keratocysts (OKCs) and ameloblastomas before treatment is crucial, but the radiographic findings, including computed tomography (CT), are often similar. This study, therefore, aimed to compare the CT findings of OKCs and ameloblastomas in the mandible.Methods: Forty-one OKC and 28 ameloblastoma patients were radiologically evaluated by using initial CT images focusing on features such as long/short diameters, CT values, the appearance of the cortex, locularity, scalloped margins, sclerotic rims, and high-density structures. Subtypes of ameloblastoma were also considered. Statistical analyses, including multivariate logistic regression analysis, were performed to determine the features that were helpful for differential diagnosis.Results: Short diameters and locularity were found to be significant features in the differential diagnosis. Between unicystic and conventional ameloblastomas, the frequency of sclerotic rims and buccal disappearance was significantly different. Based on these results, criteria were established for differential diagnosis between OKCs and ameloblastomas, and the diagnostic accuracy was 92.8 %. Conclusion: This finding indicates that several CT findings are strikingly different between OKCs and amelo-blastomas, and that these criteria for differential diagnosis are clinically useful.

OBJECTIVES:To compare the gamma distribution (GD), intravoxel incoherent motion (IVIM), and monoexponential (ME) models in terms of their goodness-of-fit, correlations among the parameters, and the effectiveness in the differential diagnosis of various orofacial lesions.METHODS:A total of 85 patients underwent turbo spin-echo diffusion-weighted imaging with six b-values. The goodness-of-fit of three models was assessed using Akaike Information Criterion. We analysed the correlations and compared the effectiveness in the differential diagnosis among the parameters of GD model (κ, shape parameter; θ, scale parameter; fractions of diffusion: ƒ1, cellular component; ƒ2, extracellular diffusion; ƒ3, perfusion component), IVIM model (D, true diffusion coefficient; D*, pseudodiffusion coefficient; f, perfusion fraction), and ME model (apparent diffusion coefficient, ADC).RESULTS:The GD and IVIM models showed a better goodness-of-fit than the ME model (p < 0.05). ƒ1 had strong negative correlations with D and ADC (ρ = -0.901 and -0.937, respectively), while ƒ3 had a moderate positive correlation with f (ρ = 0.661). Malignant entity presented significantly higher ƒ1 and lower D and ADC than benign entity (p < 0.0001). Malignant lymphoma had significantly higher ƒ1 in comparison to squamous cell carcinoma (p = 0.0007) and granulation (p = 0.0075). The trend in ƒ1 was opposite to the trend in D. Malignant lymphoma had significant lower ƒ3 than squamous cell carcinoma (p = 0.005) or granulation (p = 0.0075).CONCLUSIONS:The strong correlations were found between the GD- and IVIM-derived parameters. Furthermore, the GD model's parameters were useful for characterising the pathological structure in orofacial lesions.

OBJECTIVES:To compare the delineation of mandibular cancer by 3D T1 turbo field echo with compressed SENSE (CS-3D-T1TFE) images and MDCT images, and to compare both sets of images with histopathological findings, as the gold standard, to validate the accuracy and clinical usefulness of CS-3D-T1TFE reconstruction.METHODS:Twenty-four patients with mandibular squamous cell carcinoma (SCC) who underwent MRI including CS-3D-T1TFE and MDCT examinations before surgery were retrospectively included. For both examinations, 0.5-mm-thick coronal plane images and 0.5-mm-thick plane images perpendicular and parallel to the dentition were constructed. Two radiologists rated bone invasion in three categories indexed by cortical bone, cancellous bone, and mandibular canal (MC), and inter-rater agreement was assessed by weighted kappa statistics. In 20 of the 24 patients who underwent surgery, the correlation of bone invasion with the histopathological evaluation by pathologists was assessed using Pearson's correlation coefficient. Soft-tissue invasion was assessed by diagnosing the presence of invasion into the mylohyoid muscle, gingivobuccal fold, and masticator space, and inter-rater agreement was assessed by kappa statistics.RESULTS:The interobserver agreement for bone invasion assessment was almost perfect with CS-3D-T1TFE and substantial with MDCT. The image evaluations by both observers agreed with the pathological evaluations in 15 of the 20 cases, showing high correlation (r > 0.8). CS-3D-T1TFE also showed higher inter-rater agreement than MDCT for all measures of soft-tissue invasion.CONCLUSIONS:CS-3D-T1TFE reconstructed images were clinically useful in accurately depicting the extent of mandibular cancer invasion and potentially solving the problem of lesion overestimation associated with conventional MRI.KEY POINTS:• Reconstructed CS-3D-T1TFE images were useful for the diagnosis of mandibular cancer. • CS-3D-T1TFE images showed higher inter-rater agreement than MDCT and high correlation with pathological findings. • CS-3D-T1TFE images may solve the problem of overestimation of the tumor extent, which has been associated with MRI in the past.

OBJECTIVE:To determine whether the γ distribution (GD) model of diffusion MRI is useful in the evaluation of the isocitrate dehydrogenase (IDH) mutation status of glioblastomas. METHODS:12 patients with IDH-mutant glioblastomas and 54 patients with IDH-wildtype glioblastomas were imaged with diffusion-weighted imaging using 13 b-values from 0 to 1000 s/mm2. The shape parameter (κ) and scale parameter (θ) were obtained with the GD model. Fractions of three different areas under the probability density function curve (f1, f2, f3) were defined as follows: f1, diffusion coefficient (D) < 1.0×10-3 mm2/s; f2, D > 1.0×10-3 and <3.0×10-3 mm2/s; f3, D > 3.0 × 10-3 mm2/s. The GD model-derived parameters measured in gadolinium-enhancing lesions were compared between the IDH-mutant and IDH-wildtype groups. Receiver operating curve analyses were performed to assess the parameters' diagnostic performances. RESULTS:The IDH-mutant group's f1 (0.474 ± 0.143) was significantly larger than the IDH-wildtype group's (0.347 ± 0.122, p = 0.0024). The IDH-mutant group's f2 (0.417 ± 0.131) was significantly smaller than the IDH-wildtype group's (0.504 ± 0.126, p = 0.036). The IDH-mutant group's f3 (0.109 ± 0.060) was significantly smaller than the IDH-wildtype group's (0.149 ± 0.063, p = 0.0466). The f1 showed the best diagnostic performance among the GD model-derived parameters with the area under the curve value of 0.753. CONCLUSION:The GD model could well describe the pathological features of IDH-mutant and IDH-wildtype glioblastomas, and was useful in the differentiation of these tumors. ADVANCES IN KNOWLEDGE:Diffusion MRI based on the γ distribution model could well describe the pathological features of IDH-mutant and IDH-wildtype glioblastomas, and its use enabled the significant differentiation of these tumors. The γ distribution model may contribute to the non-invasive identification of the IDH mutation status based on histological viewpoint.

The preoperative imaging-based differentiation of primary central nervous system lymphomas (PCNSLs) and glioblastomas (GBs) is of high importance since the therapeutic strategies differ substantially between these tumors. In this study, we investigate whether the gamma distribution (GD) model is useful in this differentiation of PNCSLs and GBs. Twenty-seven patients with PCNSLs and 57 patients with GBs were imaged with diffusion-weighted imaging using 13 b-values ranging from 0 to 1000 sec/mm2. The shape parameter (κ) and scale parameter (θ) were obtained with the GD model. Fractions of three different areas under the probability density function curve (f1, f2, f3) were defined as follows: f1, diffusion coefficient (D) <1.0×10-3 mm2/sec; f2, D >1.0×10-3 and <3.0×10-3 mm2/sec; f3, D >3.0 × 10-3 mm2/sec. The GD model-derived parameters were compared between PCNSLs and GBs. Receiver operating characteristic (ROC) curve analyses were performed to assess diagnostic performance. The correlations with intravoxel incoherent motion (IVIM)-derived parameters were evaluated. The PCNSL group's κ (2.26 ± 1.00) was significantly smaller than the GB group's (3.62 ± 2.01, p = 0.0004). The PCNSL group's f1 (0.542 ± 0.107) was significantly larger than the GB group's (0.348 ± 0.132, p<0.0001). The PCNSL group's f2 (0.372 ± 0.098) was significantly smaller than the GB group's (0.508 ± 0.127, p<0.0001). The PCNSL group's f3 (0.086 ± 0.043) was significantly smaller than the GB group's (0.144 ± 0.062, p<0.0001). The combination of κ, f1, and f3 showed excellent diagnostic performance (area under the curve, 0.909). The f1 had an almost perfect inverse correlation with D. The f2 and f3 had very strong positive correlations with D and f, respectively. The GD model is useful for the differentiation of GBs and PCNSLs.

Background: Although magnetic resonance imaging (MRI) provides excellent soft-tissue contrast, long acquisition times are major disadvantages. Purpose: To evaluate the usefulness of compressed sensing (CS) for contrast-enhanced oral and maxillofacial MRI by comparing the 3D T1 turbo field echo with compressed SENSE (CS-3D-T1TFE) sequence with the multi-slice spin echo (MS-SE) sequence as the reference standard. Material and Methods: Thirty patients with orofacial lesions participated in this study. The scan times for MS-SE and CS-3D-T1TFE were 5 min 56 s and 1 min 43 s, respectively. The signal-to-noise ratio (SNR) was calculated for quantitative analysis and seven parameters (degree of lesion conspicuity, motion artifacts, metal artifacts, pulsation artifacts, quality of fat suppression, homogeneity of blood vessel signal intensity, and overall image quality) were evaluated using a 5-point scale (5 = excellent, 1 = unacceptable) by two observers for qualitative analysis. For comparisons between MS-SE and CS-3D-T1TFE, the paired t-test was used. Results: The SNR of CS-3D-T1TFE was higher than or equal to that of MS-SE. The CS-3D-T1TFE scores for motion artifacts, pulsation artifacts, and homogeneity of blood vessel signal intensity were higher than the corresponding MS-SE scores in assessments by both observers. The MS-SE scores for fat suppression were higher than or equal to the CS-3D-T1TFE scores. There were no significant differences in lesion conspicuity, metal artifacts, and overall image quality between the two sequences. Conclusion: CS-3D-T1TFE imaging, less than 30% of the scan time for MS-SE, showed no image degradation while retaining equal or higher SNR and image quality.

This study aims to quantitatively evaluate the effect of additional copper-filters (Cu-filters) on the radiation dose and contrast-to-noise ratio (CNR) in a dental cone beam computed tomography (CBCT). The Cu-filter thickness and tube voltage of the CBCT unit were varied in the range of 0.00-0.20 mm and 70-90 kV, respectively. The CBCT images of a phantom with homogeneous materials of aluminum, air, and bone equivalent material (BEM) were acquired. The CNRs were calculated from the voxel values of each homogeneous material. The CTDIvol was measured using standard polymethyl methacrylate CTDI test objects. We evaluated and analyzed the effects of tube current and various radiation qualities on the CNRs and CTDIvol. We observed a tendency for higher CNR at increasing tube voltage and tube current in all the homogeneous materials. On the other hand, the CNR reduced at increasing Cu-filter thickness. The tube voltage of 90 kV showed a clear advantage in the tube current-CNR curves in all the homogeneous materials. The CTDIvol increased as the tube voltage and tube current increased and decreased with the increase in the Cu-filter thickness. When the CNR was fixed at 9.23 of BEM at an exposure setting of 90 kV/5 mA without a Cu-filter, the CTDIvol at 90 kV with Cu-filters was 8.7% lower compared with that at 90 kV without a Cu-filter. The results from this study demonstrate the potential of adding a Cu-filter for patient dose reduction while ensuring the image quality.