Junichiro Sakamoto

Comparison of accuracy of intravoxel incoherent motion and apparent diffusion coefficient techniques for predicting malignancy of head and neck tumors using half-Fourier single-shot turbo spin-echo diffusion-weighted imaging.

PURPOSE To evaluate the use of the intravoxel incoherent motion (IVIM) technique in half-Fourier single-shot turbo spin-echo (HASTE) diffusion-weighted imaging (DWI), and to compare its accuracy to that of apparent diffusion coefficient (ADC) to predict malignancy in head and neck tumors. PATIENTS AND METHODS HASTE DW images of 33 patients with head and neck tumors (10 benign and 23 malignant) were evaluated. Using the IVIM technique, parameters (D, true diffusion coefficient; f, perfusion fraction; D*, pseudodiffusion coefficient) were calculated for each tumor. ADC values were measured over a range of b values from 0 to 1000s/mm(2). IVIM parameters and ADC values in benign and malignant tumors were compared using Students t test, receiver operating characteristics (ROC) analysis, and multivariate logistic regression modeling. RESULTS Mean ADC and D values of malignant tumors were significantly lower than those of benign tumors (P<0.05). Mean D* values of malignant tumors were significantly higher than those of benign tumors (P<0.05). There was no significant difference in mean f values between malignant and benign tumors (P>0.05). The technique of combining D and D* was the best for predicting malignancy; accuracy for this model was higher than that for ADC. CONCLUSIONS The IVIM technique may be applied in HASTE DWI as a diagnostic tool to predict malignancy in head and neck masses. The use of D and D* in combination increases the diagnostic accuracy in comparison with ADC.

Application of diffusion kurtosis imaging to odontogenic lesions: Analysis of the cystic component.

To assess the feasibility of applying diffusion kurtosis imaging (DKI) to common odontogenic lesions and to compare its diagnostic ability versus that of the apparent diffusion coefficient (ADC) for differentiating keratocystic odontogenic tumors (KCOTs) from odontogenic cysts.

Effects of compression force on elasticity index and elasticity ratio in ultrasound elastography

OBJECTIVES The purpose of this study was to investigate the relationship between compression force and hardness values in ultrasound elastography. METHODS Ultrasound elastography was performed using an elastography phantom, comprising inclusions with different elasticities and echogenicities. The compression force was set to approximately 100 gw (light force) and approximately 500 gw (heavy force). The elasticity index (EI) of the inclusion was measured. The EI was a relative hardness value of a structure within an elastographic image. Similarly, the EI of the background was measured as a reference. The elasticity ratio (ER) was calculated as the EI of the inclusion divided by the EI of the reference. RESULTS The hardness of the phantom could be discerned with both the EI and ER, regardless of the compression force. The EI and ER with heavy force tended to be higher than those with light force, but the difference was not significant. A strong correlation was observed between the EI and ER of soft structures, whereas the correlation between the EI and ER of hard structures was weak, and the ER values varied widely. CONCLUSIONS The EI offers potential as a good indicator for assessing the hardness.

Utility of fusion volumetric images from computed tomography and magnetic resonance imaging for localizing the mandibular canal

OBJECTIVES The purpose of this study was to investigate whether CT/MRI fusion volumetric images can improve the detectability of the mandibular canal (MC) compared with CT alone. METHODS Images of 31 lesions within or close to the mandible using both multislice CT (MSCT) and MRI were gathered from our imaging archives. All lesions underwent MSCT and three-dimensional volumetric interpolated breath-hold examination (3D-VIBE) MRI. Of the 62 hemimandibles, 13 hemimandibles were excluded because the MC passed through a lesion. The remaining 49 hemimandibles were included in this study. Each hemimandible was divided into 3 areas (premolar, molar and retromolar), and 147 areas were evaluated. First, the visibility of the MC on CT or its neurovascular bundle (NVB) on 3D-VIBE was evaluated. Second, in areas in which both the MC and NVB were visible, the relative locations of the NVB on MRI and the position of the MC on CT were assessed using CT/MRI fusion volumetric images. RESULTS The MC and NVB were clearly visible in 100 (68%) and 144 (98%) of 147 areas on CT and MRI, respectively. All NVBs and MCs were in identical locations, and the NVB on MRI was the same size or smaller than the MC on CT in 79 and 21 areas, respectively. CONCLUSIONS 3D-VIBE MRI can accurately depict the NVB. Compared with CT alone, CT/MRI fusion volumetric imaging improves MC detectability.

Imaging findings of childhood B-cell lymphoblastic lymphoma in the mental region: a case report

Lymphoblastic lymphoma (LBL) is an uncommon neoplasm that accounts for about 5% of all non-Hodgkins lymphomas. Approximately 90% of LBLs are of immature T-cell lineage, with B-cell lymphoblastic lymphoma (B-LBL) accounting for only about 10%. Owing to infrequency, the clinicopathological features and the imaging findings of B-LBL are not well defined. LBLs frequently affect extranodal sites. The most common site is the skin, followed by the bone, and the head and neck region is rarely involved. We report herein a case of childhood B-LBL occurring in the mental region, with emphasis on the findings of several imaging studies, including contrast-enhanced CT, MRI and fluorodeoxyglucose-positron emission tomography/CT.

Oral carcinoma: Clinical evaluation using diffusion kurtosis imaging and its correlation with histopathologic findings

PURPOSE In this study, we aimed to determine the usefulness of diffusion kurtosis imaging (DKI) as a noninvasive method for evaluation of the histologic grade and lymph node metastasis in patients with oral carcinoma. MATERIALS AND METHODS Twenty-seven patients with oral carcinoma were examined with a 3-T MR system and 16-channel coil. DKI data were obtained by a single-shot echo-planar imaging sequence with repetition time, 10,000 ms; echo time, 94 ms; field of view, 250 × 204.25 ms; matrix, 120 × 98; section thickness, 4 mm; four b values of 0, 500, 1000, and 2000 s/mm2; and motion-probing gradients in three orthogonal directions. Diffusivity (D) and kurtosis (K) were calculated using the equation: S = S0 ∙ exp(-b ∙ D + b2 ∙ D2 ∙ K/6). Conventional apparent diffusion coefficient (ADC) was also calculated. The MR images were compared with the histopathologic findings. RESULTS Relative to the histologic grades (Grades 1, 2, and 3) of the 27 oral carcinomas, D values showed a significant inverse correlation (r = -0.885; P < 0.001) and K values showed a significant positive correlation (r = 0.869; P < 0.001), whereas ADC values showed no significant correlation (r = -0.311; P = 0.115). When comparing between metastatic and non-metastatic lymph nodes, significant differences in the D values (P < 0.001) and K values (P < 0.001), but not the ADC values (P = 0.110) became apparent. CONCLUSIONS In patients with oral carcinoma, DKI seems to be clinically useful for the evaluation of histologic grades and lymph node metastasis.

Colorectal carcinoma: Ex vivo evaluation using q-space imaging; Correlation with histopathologic findings: q-Space Imaging of Colorectal Carcinoma

Although the prognosis of colorectal carcinoma (CRC) patients depends on the histologic grade (HG) and lymph node metastasis (LNM), accurate preoperative assessment of these prognostic factors is often difficult.

Mandibular canal visibility using a plain volumetric interpolated breath-hold examination sequence in MRI

OBJECTIVES To evaluate the validity of plain volumetric interpolated breath-hold examinations (VIBEs) for detecting the course of the mandibular canal, and to compare the results with contrast-enhanced (CE) VIBE images. METHODS From our imaging archives, we collected 28 cases taken with a VIBE sequence both before and after intravenous administration of gadolinium hydrate, and then two observers evaluated neurovascular bundle (NVB) visibility in the VIBE images. For the invisible NVB cases, we identified the invisible areas and analysed the causes of invisibility. For cases that also had corresponding CT thin slice images, we obtained a fusion image between MRI and CT, and investigated the relationship between the NVB in VIBE and the mandibular canal in CT images. RESULTS The visibility of the NVBs in plain VIBE was 89%, the same as on CE VIBE. There were three invisible cases in each plain and CE VIBE images. The invisible areas were premolar in three cases, and molar in one case, and the causes of the invisibility were a metallic artefact in one case and motion artefacts in the other two cases. CONCLUSIONS A plain VIBE can depict the NVB at the same rate as CE VIBE, and is suitable for detecting NVBs.

Imaging the bifid mandibular canal using high resolution MRI

OBJECTIVE: This study aimed to investigate the incidence of bifid mandibular canals (BMCs) using high-resolution MRI with a three-dimensional volumetric interpolated breath-hold examination sequence (3D-VIBE) through the neurovascular bundle (NVB). METHODS: In this retrospective study, we extracted 154 datasets from our archive of patients who underwent MRI examination with a 3D-VIBE sequence for mandible lesions from January 2015 to April 2016. The right and the left mandibles were treated independently with 59 cases excluded due to NVB morphology or artifacts, yielding 249 hemi-mandible cases classified among three subtypes: Type 0 with no BMC, Type one with one NVB and two NVBs on route to it, and Type two with two NVBs. We also investigated the incidence of nutrient canals (NCs) using MRI. Finally, we determined whether each BMC case could also be identified via panoramic radiography (PR) or CT. RESULTS: Of the 249 cases examined, 6.4% were found to have BMC (Types 1 and 2). Subtypes were classified as follows: 233 as Type 0 (93.6%), 11 as Type 1 (4.4%), and 5 as Type 2 (2.0%). The NC was identified on MRI in a majority of cases. No BMCs were identified using PR or CT except for one, which was identified by CT. CONCLUSION: The incidence rate of BMC per MRI was 6.4% in this study. NCs, including the retromolar canal, had an incidence rate of 58.4-97.6%. Further, BMCs were not verified by PR or CT, indicating that MRI should be used to assess BMCs.

The intravoxel incoherent motion MRI of lateral pterygoid muscle: a quantitative analysis in patients with temporomandibular joint disorders

OBJECTIVES To quantitatively evaluate diffusion and perfusion status of lateral pterygoid muscle (LPM) in patients with temporomandibular joint disorder (TMD) by intravoxel incoherent motion (IVIM) imaging and to correlate with findings on temporomandibular joints (TMJs) by conventional MRI. METHODS 42 patients with TMD underwent MRI. To assess IVIM parameters, diffusion-weighted imaging was obtained by spin-echo-based single-shot echoplanar imaging. Regions of interest were created on all diffusion-weighted images of the superior belly of the lateral pterygoid (SLP) and inferior belly of the lateral pterygoid (ILP) at b-values 0-500 s mm-2. Then, IVIM parameters, diffusion (D) and perfusion (f) were calculated using biexponential fittings. The correlation of these values with conventional MRI findings on TMJs was investigated. RESULTS For SLP, the f parameter in TMJs with anterior disc displacement without reduction was significantly higher than that in normal ones (p = 0.015). It was also significantly higher in TMJs with joint effusion than in those without (p = 0.016). On the other hand, for both SLP and ILP, the D parameter significantly increased in TMJs with osteoarthritis compared with those without (p = 0.015 and p = 0.022, respectively). CONCLUSIONS Pathological changes of LPM in patients with TMD may be quantitatively evaluated by IVIM parameters.