Imaging findings of liver resection using a bipolar radiofrequency electrosurgical device--initial observations

Objective

To assess contrast-enhanced US (CEUS), computed tomography (CT) and magnetic resonance (MR) imaging findings and serial changes of the treated area at follow-up in patients who underwent liver resection using a bipolar radiofrequency electrosurgical device.

Methods

Imaging findings of 27 patients with resected hepatocellular carcinomas (HCCs) (n = 24) and metastases (n = 3) (mean size: 2.6 cm), were retrospectively evaluated. Two readers assessed: the (a) presence, (b) thickness, (c) shape and (d) echogenicity (CEUS)/attenuation (CT)/signal intensity (MR imaging) at coagulated site and the (e) presence of residual tumor of the bipolar radiofrequency electrosurgical device resection margin.

Results

Follow-up was performed with either CT (n = 20) or MR imaging (n = 7) and repeated in 16 patients with CT (n = 7), MR imaging (n = 4), or both techniques (n = 5). Four patients also had a single CEUS examination. At first imaging follow-up a peripheral halo was depicted at resection site (100%). A fluid collection within the surgical area was found in 67% of patients. During the following imaging examinations a progressive involution of both findings was observed, respectively, in 81% and 62% of patients. Viable tissue was detected in three patients (11%).

Conclusions

After liver resection with bipolar radiofrequency electrosurgical device successfully ablated tumor is demonstrated at imaging by an unenhancing partial linear peripheral halo, in most cases, surrounding a fluid collection reducing in size during follow-up.     

Texture analysis in non-contrast enhanced CT: impact of malignancy on texture in apparently disease-free areas of the liver

Objectives

To determine whether texture analysis of non-contrast enhanced computed tomography (CT) images in apparently disease-free areas of the liver is altered by the presence of extra- and intra-hepatic malignancy in colorectal cancer patients.

Materials and methods

Hepatic attenuation and texture were assessed from non-contrast enhanced CT in three groups of colorectal cancer patients: (A) 15 controls with no malignancy; (B) nine patients with extra-hepatic malignancy but no liver involvement; (C) eight patients with hepatic metastases. Regions of interest were manually constructed only over apparently normal areas of liver tissue excluding major blood vessels and areas of intra-hepatic fat, which may otherwise alter CT texture irrespective of the presence of malignancy. Texture was analysed on unfiltered images and following band-pass image filtration to highlight image features at different spatial frequencies (fine: 2 pixels/1.68 mm in width, medium: 6 pixels/5.04 mm and coarse: 12 pixels/10.08 mm). The relative contributions made to the image by features at two different spatial frequencies were expressed as filter ratios (fine/medium, fine/coarse and medium/coarse). Texture was quantified as mean grey-level intensity, entropy and uniformity.

Results

Texture was not altered on unfiltered images whereas relative texture analysis following image filtration identified differences in fine to medium texture ratios in apparently disease-free areas of the liver in patients with hepatic metastases as compared to patients with no tumour (entropy, p = 0.0257) and patients with extra-hepatic disease (uniformity, p = 0.0143).

Conclusions

Relative texture analysis of unenhanced hepatic CT can reveal changes in apparently disease-free areas of the liver that have previously required more complex perfusion measurements for detection.     

Body diffusion-weighted MR imaging of uterine endometrial cancer: Is it helpful in the detection of cancer in nonenhanced MR imaging?

Objective

In this study, the authors discussed the feasibility and value of diffusion-weighted (DW) MR imaging in the detection of uterine endometrial cancer in addition to conventional nonenhanced MR images.

Methods and materials

DW images of endometrial cancer in 23 patients were examined by using a 1.5-T MR scanner. This study investigated whether or not DW images offer additional incremental value to conventional nonenhanced MR imaging in comparison with histopathological results. Moreover, the apparent diffusion coefficient (ADC) values were measured in the regions of interest within the endometrial cancer and compared with those of normal endometrium and myometrium in 31 volunteers, leiomyoma in 14 patients and adenomyosis in 10 patients. The Wilcoxon rank sum test was used, with a p < 0.05 considered statistically significant.

Results

In 19 of 23 patients, endometrial cancers were detected only on T2-weighted images. In the remaining 4 patients, of whom two had coexisting leiomyoma, no cancer was detected on T2-weighted images. This corresponds to an 83% detection sensitivity for the carcinomas. When DW images and fused DW images/T2-weighted images were used in addition to the T2-weighted images, cancers were identified in 3 of the remaining 4 patients in addition to the 19 patients (overall detection sensitivity of 96%). The mean ADC value of endometrial cancer (n = 22) was (0.97 ± 0.19) × 10⁻³ mm²/s, which was significantly lower than those of the normal endometrium, myometrium, leiomyoma and adenomyosis (p < 0.05).

Conclusion

DW imaging can be helpful in the detection of uterine endometrial cancer in nonenhanced MR imaging.     

Utility of the broccoli sign in the distinction of prolapsed uterine tumor from cervical tumor

Objective

To describe the utility, histopathological basis, and clinical correlates of the broccoli sign.

Methods

The committee on human research approved this HIPAA compliant study and waived written informed consent. Based on the records of the senior author and our multidisciplinary Gynecologic Oncology Tumor Board, we retrospectively identified thirteen women (mean age of 48.8 years; range, 34–74) with a cervical mass seen at MR imaging (n = 13) or CT (n = 5) that demonstrated the previously reported broccoli sign (i.e., a soft tissue stalk connecting the cervical mass to the uterine cavity) on one or other modality. All available clinical, imaging, and histopathological records were reviewed, with particular emphasis on initially suspected diagnosis, final proven diagnosis, and outcome.

Results

Cervical cancer was the initial clinically suspected diagnosis in 6 of 13 patients. Surgical resection demonstrated prolapsed uterine tumor in all patients, consisting of endometrioid adenocarcinoma (n = 7), carcinosarcoma (n = 2), adenosarcoma (n = 1), and leiomyoma (n = 3). Excluding the three patients with leiomyomas, currently, 7 patients with malignant tumors are disease free after a mean interval of 15 months (range, 3–45) and 3 patients have been lost to follow-up.

Conclusion

A stalk connecting an apparent cervical mass seen at CT or MR imaging to the endometrial cavity (“broccoli sign”) favors the diagnosis of a prolapsed uterine tumor; these prolapsed uterine tumors can often be malignant but appear to have a good prognosis.     

Assessment of colorectal hepatic metastases by quantitative T2 relaxation time

Aim

To determine the T₂ relaxation time of colorectal hepatic metastases and changes in T₂ relaxation times following chemotherapy.

Materials and methods

42 patients with 96 hepatic colorectal metastases underwent baseline MRI. Axial T₁, T₂ and multi-echo GRASE sequences were acquired. ROIs were drawn on T₂ relaxation maps, obtained from GRASE images, encompassing metastasis and normal liver to record T₂ relaxation time values. In 11 patients with 28 metastases, MRI was repeated using same protocol at 6 weeks following chemotherapy. The median pre-treatment T₂ values of metastases and normal liver were compared using the Mann–Whitney test. The pre- and post-treatment median T₂ values of metastases were compared using the Wilcoxon–Rank test for responding (n = 16) and non-responding (n = 12) lesions defined by RECIST criteria. The change in T₂ values (ΔT₂) were compared and correlated with percentage change in lesion size.

Results

There was no difference in the pre-treatment median T₂ of metastases between responding (67.3 ± 8.6) and non-responding metastases (71.4 ± 16.5). At the end of chemotherapy, there was a decrease in the median T₂ of responding lesions (61.6 ± 12.6) p = 0.83, and increase in non-responding lesions (76.2 ± 18.4) p = 0.03, but these were not significantly different from the pre-treatment values. There was no significant difference in ΔT₂ of responding and non-responding lesions (p = 0.18) and no correlation was seen between size change and ΔT₂ (coefficient = 0.3).

Conclusion

T₂ relaxation time does not appear to predict response of colorectal liver metastasis to chemotherapy.     

Assessment of acute cholangitis by MR imaging

Purpose

The purpose of this study is to assess the common MRI findings of acute cholangitis compared with those of non-acute cholangitis.

Materials and methods

During a 31-month period, we performed MRCP and contrast-enhanced MRI on 173 patients with biliary abnormalities including duct dilatation or stricture. The causes of the biliary abnormalities included biliary stone disease (n = 85), cholangiocarcinoma (n = 47), periampullary cancer (n = 20), GB cancer (n = 4), and others (n = 17). Among 173 patients, 66 consecutive patients were confirmed with acute cholangitis diagnosed according to the Tokyo guideline, and 107 patients were confirmed as having non-acute cholangitis. Two radiologists retrospectively and independently accessed the MR findings, including the cause of biliary abnormality, increased periductal signal intensity on T2-weighted images, the transient periductal signal difference, and the presence of abscess, thrombosis, and ragged duct. They also measured the dilated duct and the thickened wall. The Student t-test and the Pearson chi-square were used. The κ statistics were used to determine interobserver agreement. Logistic regression was used to identify the MR findings that predicted acute cholangitis.

Results

MRI correctly accessed the cause of biliary abnormality in 163 patients (94%). The statistically common findings for acute cholangitis were as follows: increased periductal signal intensity on T2-weighted imaging (n = 26, 39%, p < 0.05); transient periductal signal difference (n = 31, 47%, p < 0.05); abscess (n = 18, 27%, p < 0.05); thrombosis (n = 12, 18%, p < 0.05); and ragged duct (n = 11, 17%, p < 0.05). Interobserver agreement was good to excellent for each finding (κ = 0.74–0.97). The wall thickness showed a statistically significant difference between the acute cholangitis and the non-acute cholangitis group (2.65 mm:2.32 mm, p < 0.05), however, there was no significant difference in duct dilatation in the two groups. The periductal transient attenuation difference was an independent predictor of acute cholangitis (Exp (B) = 6.389, p = 0.018).

Conclusion

MRI accurately assesses the cause of biliary abnormality in patients with cholangitis. Using statistically common MR findings for acute cholangitis, MR imaging is very successful in predicting acute cholangitis.     

MRI of fat necrosis of the breast: the "black hole" sign at short tau inversion recovery

Objective

To describe MRI features of fat necrosis of the breast.

Materials and methods

Twenty-five lesions in 16 patients were retrospectively analyzed. MRI was performed due to equivocal findings at conventional imaging after surgical treatment of cancer (n = 14) or during anticoagulant therapy (n = 1), after focal mastitis treated with ductal resection (n = 1). In the 15 patients with previous surgery MRI was performed after a median interval of 24 months, using short tau inversion recovery (STIR) and contrast-enhanced dynamic T1-weighted sequences. Signal-to-noise ratio (SNR) inside the lesion and surrounding healthy fat was calculated on both STIR and unenhanced T1-weighted images. Maximal lesion diameter was measured on STIR images. All lesions had final clinical and imaging assessment in favor of fat necrosis and negative clinical and imaging follow-up (21–40 months; median 24 months).

Results

At STIR sequence, fat necrosis appeared as a “black hole”, being markedly hypointense (median SNR = 29) compared with surrounding fat (median SNR = 95) (P < 0.001), while no significant difference was found at unenhanced T1-weighted sequence. No significant correlation with time from treatment was found. Of 25 lesions, 15 showed ring enhancement, with continuous increase (n = 10), plateau (n = 2), or wash-out curve (n = 3). The 11 enhancing lesions in the 8 patients with previous radiation therapy showed an initial enhancement higher than that of the 4 enhancing lesions in the 2 patients who did not, although the difference was not significant (P = 0.104).

Conclusion

Fat necrosis of the breast exhibits a “black hole” sign on STIR images, allowing for an easier diagnosis in clinical practice.     

Hepatic hemangioma: correlation of enhancement types with diffusion-weighted MR findings and apparent diffusion coefficients

Purpose

To correlate hepatic hemangioma enhancement types in gadolinium-enhanced magnetic resonance (MR) images with diffusion-weighted MR findings and apparent diffusion coefficients (ADCs).

Materials and methods

Respiratory-triggered diffusion-weighted MR images (TR/TE, 2422/46 ms; parallel imaging factor, 2; b factor, 500 s/mm²; number of averaging, 6) obtained in 35 patients with 44 hepatic hemangiomas diagnosed by gadolinium-enhanced MR and by follow-up imaging were retrospectively evaluated. Hemangiomas were classified into three enhancement types based on gadolinium-enhanced MR imaging findings: type I, early-enhancement type; type II, peripheral nodular enhancement type; type III, delayed enhancement type. Two blinded readers qualitatively assessed lesion sizes and signal intensities on T2-weighted turbo spin-echo and diffusion-weighted images. The ADCs of hemangiomas were also measured.

Results

No significant difference was observed between the three enhancement types in terms of signal intensities on T2-weighted images. Signal intensities on diffusion-weighted images were lower in the order type I to III (P < .01), and mean ADCs were 2.18 × 10⁻³, 1.86 × 10⁻³, and 1.71 × 10⁻³ mm²/s for types I, II, and III, respectively (P < .01). No correlation was found between lesion sizes and ADCs.

Conclusion

Hepatic hemangiomas were found to have enhancement type dependent signal intensities and ADCs on diffusion-weighted MR images. Further studies will have to substantiate that these diffusion patterns might reflect intratumoral blood flow or perfusion.     

Primary adrenal lymphoma: radiological; pathological, clinical correlation

Objective

The purpose of this study was to analyze CT and MR imaging (MRI) manifestation of primary adrenal lymphoma in order to better understand of this rare disease.

Materials and methods

Six patients (4 men, 2 women; median age, 65.5 years) with pathologically proven primary adrenal lymphoma were retrospectively reviewed. Imaging findings (CT&;MRI, n = 3; only CT, n = 3) were analyzed and correlated with clinical and pathologic findings.

Results

All cases were pathologically proven primary adrenal diffuse large B-cell lymphoma with bilateral lesions in 3 cases respectively. Maximum diameters of the 9 lesions were 6.1–14.8 cm, median 10.5 cm. Seven lesions were round, oval or oblong, and 2 lesions irregular. Seven lesions were well-defined and 2 had ill-defined margins. Unenhanced CT density of 9 lesions and MR signal intensity of T1 weighted images of 6 lesions were similar to that of muscle, and all 6 lesions were hyperintense on T2-weighted MR images. Following intravenous injection of contrast media, 6 lesions had mild enhancement and 3 lesions had moderate enhancement on parenchymal phase imaging. Enhancement was homogenous in three, slightly inhomogeneous in four, and heterogeneous in two. Seven lesions, in 5 cases, infiltrated the adjacent tissues or organs in patients with large tumors.

Conclusion

Primary adrenal lymphoma usually manifests as large, well-defined, soft-tissue masses replacing the adrenal gland with homogeneous or slightly inhomogeneous enhancement. Large tumors especially tend to infiltrate adjacent structures.     

Contribution of thin slice (1 mm) oblique coronal proton density-weighted MR images for assessment of anteromedial and posterolateral bundle damage in anterior cruciate ligament injuries

Purpose

To evaluate the diagnostic efficacy of using additional oblique coronal 1 mm proton density-weighted (PDW) MR imaging of the knee for detection and grading anterior cruciate ligament (ACL), anteromedial bundle (AMB) and posterolateral bundle (PLB) injuries.

Materials and methods

We prospectively assessed preoperative MR images of 50 patients (36 men, 14 women; age range, 18–62 years). First, we compared the diagnostic performance of routine sagittal (3 mm) and additional oblique coronal images (1 mm) for ACL tears. Then, we compared the tear types (AMB or PLB) and grade presumed from oblique coronal MR imaging with arthroscopy.

Results

Arthroscopy revealed ACL tear in 24 (48%) patients. There was significant difference between sagittal images and arthroscopy results for ACL tear recognition (p < 0.001). No significant difference was detected for oblique coronal images when compared with arthroscopy results (p = 0.180). Sensitivity and specificity values for ACL tear diagnosis were 37.04% and 95.65% for sagittal images; 74.07% and 91.30% for oblique coronal images. There was no significant difference between arthroscopy and oblique coronal MR images in grading AMB and PLB injuries (p > 0.05).

Conclusion

Addition of thin slice oblique coronal images to conventional sequences could better contribute to better verifying the presence of ACL tear and in determining its grade.     

Comparison of clinical and MR imaging outcomes after uterine fibroid embolization with Bead Block and Embosphere

Purpose

To compare clinical and imaging outcomes after uterine fibroid embolization (UFE) with Embosphere versus Bead Block microspheres.

Materials and methods

Our institutional review board approved this HIPAA-compliant study. We conducted a retrospective review of all consecutive UFEs performed for symptomatic uterine fibroids at our academic institution from 2001 to 2008. UFE was performed using Embosphere (n = 70) or Bead Block (n = 55) microspheres. Patient symptoms and MR images were reviewed before and following UFE. The MR images were analyzed for changes in the size and contrast enhancement of the dominant fibroid and the uterus.

Results

125 patients underwent UFE. Pre-treatment characteristics (patient age, presenting symptoms, fibroid location, and volume of the largest fibroid) were similar across groups. Procedure endpoint (near-stasis, reached in 94% of cases), duration, and sedation medication doses were also similar. Clinical follow-up was available in 69 (55%) patients (mean duration: 13.6 months). Of these, 92% had clinical improvement of their main presenting symptom(s) and 3% developed early menopause. MRI follow-up was available in 105 (84%) patients (mean 7.8 months). Mean volume reduction of the largest fibroid was similar after Embosphere (48%) and Bead Block (53%, p = NS). Residual enhancement ≥5% in the dominant fibroid was similarly uncommon after Bead Block (19%) or Embosphere (16%, p = NS). Mean uterine volume reduction was similar across groups (38%); no myometrial infarction occurred.

Conclusion

This retrospective study showed no superiority of Embosphere over Bead Block microspheres in terms of clinical and imaging outcomes after UFE.     

Evaluation of MR diffusion-weighted imaging in differentiating endometriosis infiltrating the bowel from colorectal carcinoma

Objective

Endometriosis infiltrating the bowel may be difficult to differentiate from colorectal carcinoma in cases that present with non-specific clinical and imaging features. The aim of this study is to assess the value of MR diffusion-weighted imaging (DWI) in differentiating endometriosis infiltrating the bowel from colorectal carcinoma.

Methods

In 66 patients, MR DWI was added to the standard imaging protocol in patients visiting our outdoor MR clinic for the analysis of suspected or known deep infiltrating endometriosis (DIE). In patients diagnosed with DIE infiltrating the bowel on MR imaging, high b-value diffusion-weighted images were qualitatively assessed by two readers in consensus and compared to high b-value diffusion weighted images in 15 patients evaluated for colorectal carcinoma. In addition, ADC values of lesions were calculated, using b-values of 50, 400 and 800 s/mm².

Results

A total of 15 patients were diagnosed with DIE infiltrating the bowel on MR imaging. Endometriosis infiltrating the bowel showed low signal intensity on high b-value diffusion-weighted images in all patients, whereas colorectal carcinoma showed high signal intensity on high b-value diffusion-weighted images in all patients. Mean ADC value in endometriosis infiltrating the bowel (0.80 ± 0.06 × 10⁻³ mm²/s) was significantly lower compared to mean ADC value in colorectal carcinoma (0.86 ± 0.06 × 10⁻³ mm²/s), but with considerable overlap between ADC values.

Conclusion

Only qualitative assessment of MR DWI may be valuable to facilitate differentiation between endometriosis infiltrating the bowel and colorectal carcinoma.     

Assessment of liver tumor response by high-field (3T) MRI after radiofrequency ablation: Short- and mid-term evolution of diffusion parameters within the ablation zone

Purpose

To compare the apparent diffusion coefficient (ADC) values of malignant liver lesions on diffusion-weighted MRI (DWI) before and after successful radiofrequency ablation (RF ablation).

Materials and methods

Thirty-two patients with 43 malignant liver lesions (23/20: metastases/hepatocellular carcinomas (HCC)) underwent liver MRI (3.0 T) before (<1 month) and after RF ablation (at 1, 3 and 6 months) using T2-, gadolinium-enhanced T1- and DWI-weighted MR sequences. Jointly, two radiologists prospectively measured ADCs for each lesion by means of two different regions of interest (ROIs), first including the whole lesion and secondly the area with the visibly most restricted diffusion (MRDA) on ADC map. Changes of ADCs were evaluated with ANOVA and Dunnett tests.

Results

Thirty-one patients were successfully treated, while one patient was excluded due to focal recurrence. In metastases (n = 22), the ADC in the whole lesion and in MRDA showed an up-and-down evolution. In HCC (n = 20), the evolution of ADC was more complex, but with significantly higher values (p = 0.013) at 1 and 6 months after RF ablation.

Conclusion

The ADC values of malignant liver lesions successfully treated by RF ablation show a predictable evolution and may help radiologists to monitor tumor response after treatment.     

Usefulness of contrast-enhanced three-dimensional MR angiography using time-resolved imaging of contrast kinetics applied to description of Extracranial Arteriovenous Malformations: initial experience

Purpose

The purpose of this study was to evaluate the usefulness of contrast-enhanced three-dimensional MR angiography using time-resolved imaging of contrast kinetics (TRICKS-MRA) to demonstrate extracranial arteriovenous malformations (E-AVMs).

Materials and methods

TRICKS-MRA was performed in 33 patients (adults; n = 30, children; n = 3) with E-AVMs. Four different scan protocols were arranged based on the size of E-AVM, and serial images were acquired from the start of contrast injection with a time frame ranging from 1.2 to 7.1 s. Demonstration of feeding arteries and drainage veins, and the extent of nidus was qualitatively graded using a three-point scale. In sixteen patients who underwent DSA 3 days to 15 months after TRICKS-MRA, the comparability of TRICKS-MRA to DSA was evaluated using a three-point scale. In each category, score of 3 or excellent was defined as the positive result.

Results

Demonstration of the feeding arteries, the drainage veins, and the extent of nidus were graded as excellent in 68%, 65%, and 58% of the patients, respectively. Comparability of TRICKS-MRA to DSA was excellent in 75%, 88%, and 88% of the sixteen patients who underwent DSA.

Conclusion

TRICKS-MRA is a feasible and useful vascular imaging technique to provide time-resolved analysis of angioarchitecture of E-AVMs.     

Hepatic hemangiomas: difference in enhancement pattern on 3T MR imaging with gadobenate dimeglumine versus gadoxetate disodium

Purpose

To compare intraindividual differences in enhancement pattern of hepatic hemangiomas between gadobenate dimeglumine (Gd-BOPTA) and gadoxetate disodium (Gd-EOB-DTPA)-enhanced 3T MR imaging.

Materials and methods

This is a HIPAA-compliant, IRB-approved retrospective study with waiver for informed consent granted. From 10/07 to 5/09, 10 patients (2 males, 8 females; mean age, 57.3 years) with 15 hepatic hemangiomas (mean diameter, 4.4 ± 5.6 cm) underwent both Gd-BOPTA- and Gd-EOB-DTPA-enhanced 3T MR imaging (mean interval, 266 days; range, 38–462 days). Diagnosis of hemangioma was based on strict imaging criteria. MR imaging was obtained during three arterial, portal venous, and up to four delayed phases. During each phase, hemangioma-to-liver contrast-to-noise ratio (CNR) was measured for each lesion on both examinations. Statistical analysis was performed using paired Student's t-test.

Results

Hemangioma-to-liver CNR peaked during the portal venous phase (Gd-BOPTA: 48.9 ± 65.8, Gd-EOB-DTPA: 0.7 ± 3.8). During all imaging phases except the first arterial phase, hemangioma-to-liver CNR was significantly lower on Gd-EOB-DTPA-enhanced compared to Gd-BOPTA-enhanced MR images (p < 0.05). Notably, Gd-EOB-DTPA yielded negative hemangioma-to-liver CNR (−2.5 ± 2.4) compared to Gd-BOPTA (40.7 ± 56.4) during the first delayed phase (7–8 min after contrast administration), remaining negative for the rest of the delayed phases (up to 26 min after contrast administration).

Conclusion

The enhancement patterns of hepatic hemangiomas differs significantly between Gd-BOPTA and Gd-EOB-DTPA-enhanced 3T MR imaging. The smaller dose, shorter plasma half-life, and increased hepatobiliary uptake of Gd-EOB-DTPA leads to a negative CNR of hemangioma-to-liver on delayed phases and could create an imaging pitfall with this agent.     

Hepatic MR imaging for in vivo differentiation of steatosis, iron deposition and combined storage disorder: single-ratio in/opposed phase analysis vs. dual-ratio Dixon discrimination

Objective

To assess whether in vivo dual-ratio Dixon discrimination can improve detection of diffuse liver disease, specifically steatosis, iron deposition and combined disease over traditional single-ratio in/opposed phase analysis.

Methods

Seventy-one patients with biopsy-proven (17.7 ± 17.0 days) hepatic steatosis (n = 16), iron deposition (n = 11), combined deposition (n = 3) and neither disease (n = 41) underwent MR examinations.Dual-echo in/opposed-phase MR with Dixon water/fat reconstructions were acquired. Analysis consisted of: (a) single-ratio hepatic region-of-interest (ROI)-based assessment of in/opposed ratios; (b) dual-ratio hepatic ROI assessment of in/opposed and fat/water ratios; (c) computer-aided dual-ratio assessment evaluating all hepatic voxels.Disease-specific thresholds were determined; statistical analyses assessed disease-dependent voxel ratios, based on single-ratio (a) and dual-ratio (b and c) techniques.

Results

Single-ratio discrimination succeeded in identifying iron deposition (I/O_{Iron threshold} < 0.88) and steatosis (I/O_{Fat threshold>1.15}) from normal parenchyma, sensitivity 70.0%; it failed to detect combined disease.Dual-ratio discrimination succeeded in identifying abnormal hepatic parenchyma (F/W_{Normal threshold} > 0.05), sensitivity 96.7%; logarithmic functions for iron deposition (I/O_{Iron discriminator} < e^{(0.01−F/W_Iron)/0.48}) and for steatosis (I/O_{Fat discriminator} > e^{(F/W_Fat−0.01)/0.48}) differentiated combined from isolated diseases, sensitivity 100.0%; computer-aided dual-ratio analysis was comparably sensitive but less specific, 90.2% vs. 97.6%.

Conclusion

MR two-point-Dixon imaging using dual-ratio post-processing based on in/opposed and fat/water ratios improved in vivo detection of hepatic steatosis, iron deposition, and combined storage disease beyond traditional in/opposed analysis.     

Comparative survival analysis in patients with pulmonary metastases from nasopharyngeal carcinoma treated with radiofrequency ablation

Purpose

The aim of this retrospective study was to evaluate technical efficacy and the impact of CT-guided pulmonary radiofrequency ablation (RFA) on survival in patients with pulmonary metastases from nasopharyngeal carcinoma (NPC).

Materials and methods

Between 2000 and 2009, 480 patients were pathologically or clinically confirmed pulmonary metastases from NPC. And ten included patients of them had a total of 23 pulmonary metastases treated with percutaneous RFA under the real-time CT fluoroscopy. Safety, local tumor progression, and survival were evaluated in our institutions. Matched-pair survival was compared using Kaplan–Meier analysis.

Results

A total of 25 ablations were performed to 23 pulmonary metastases in 13 RFA sessions. Pneumothorax requiring chest tube placement developed in 3 of 13 (23.1%) RFA sessions. The median metastatic overall survival was 36.1 months for all the 480 NPC patients with pulmonary metastases. Furthermore, matched-pair analysis demonstrated patients with RFA treatment had a greater metastatic overall survival than patients without RFA treatment (77.1 months vs 32.4 months, log-rank test, p = 0.009). There were no statistically significant differences in the survival probability of patients with RFA treatment (n = 10) and surgical resection of pulmonary metastases (n = 27) (log-rank test, p = 0.75).

Conclusion

CT-guided pulmonary RFA is safe and offers a treatment alternative for local tumor control, providing promising survival in selected patients with pulmonary metastases from NPC.     

Comparison of arterial and venous coronary artery bypass flow measurements using 3-T magnetic resonance phase contrast imaging

Objective

Comparison of arterial and venous coronary artery bypass flow measurements using 3-T magnetic resonance (MR) phase contrast in correlation with intraoperative Doppler flow measurements.

Methods

Fifty-six coronary bypasses (right coronary artery n = 18, left internal mammary artery to left anterior descending artery n = 16, marginal artery n = 7, circumflex artery n = 7, diagonal artery n = 6, left anterior descending artery n = 1, and right internal mammary artery to right coronary artery n = 1) were studied in 27 asymptomatic patients. In this prospective study, each bypass was studied intra-operatively using Doppler flow measurement. Within one week post surgery, patients were studied using a 3-T MR scanner (Magnetom Verio, Siemens, Erlangen, Germany) using velocity encoded phase-contrast flow measurements.

Results

Intraoperative Doppler flow measurements demonstrated regular flow patterns in all vascular territories supplied. All bypasses were patent on MRI and flow measurement results were as follows: median flow 60 ml/min (interquartile range (IQR): 37.5–78.5 ml/min). For comparison, the corresponding median intraoperative flow was 58 ml/min (IQR: 41–80 ml/min) (p < 0.001; R = 0.44). Linear regression analysis demonstrated a significant correlation for venous bypasses (p = 0.0002; R = 0.48), but not for arterial bypasses (p = 0.09; R = 0.24).

Conclusion

This study demonstrated that MR flow measurements of venous bypass grafts agreed more with Doppler than arterial bypass grafts. However, bypass patency was confirmed for all patients. In the future, this technique may be used for non invasive coronary bypass graft follow-up.     

CT and MR imaging findings of sinonasal angiomatous polyps

Objective

To characterize the CT and MR imaging findings of patients with sinonasal angiomatous polyps (SAPs) and evaluate their respective clinical value in the diagnosis of SAP.

Methods

CT and MR imaging findings of 15 patients with pathologically proven SAP were examined. Assessed image features included location, size, margin, attenuation, and change of the bony walls of the sinonasal cavity on CT, and signal intensity and enhancement pattern on MR.

Results

On CT, the SAP was mostly isoattenuated with patches of slight hyperattenuation. Most lesions caused changes in the adjacent bone, including expansile remodeling (n = 8), defect or destruction (n = 7), and hyperostosis (n = 6). All lesions examined by MR showed heterogeneous isointense signal intensity on T1-weighted images and mixed obvious hyperintense and hypointense signal intensity with linear hypointense septum internally (n = 10), and hypointense peripheral rim on T2-weighted images (n = 10). Postcontrast MR images demonstrated areas of heterogeneous and marked enhancement with an unenhanced hypointense rim and septa (n = 7).

Conclusions

CT and MR imaging have respective advantages in the diagnosis of SAP. Combined application of CT and MR examinations is necessary for patients with suspected SAP.     

Detection and classification of focal liver lesions in patients with colorectal cancer: retrospective comparison of diffusion-weighted MR imaging and multi-slice CT

Objectives

To compare the diagnostic performance of diffusion-weighted MR imaging (DWI) with multi-slice CT (MS-CT) in the detection and classification of focal liver lesions in patients with colorectal cancer.

Methods

In a retrospective study 68 patients who underwent DWI at 1.5 T (b-values of 50, 300 and 600 s/mm²) and contrast-enhanced MS-CT were analysed by two radiologists blinded to the clinical results. Imaging results were correlated with intraoperative surgical and ultrasound findings (n = 24), imaging follow-up or PET (n = 44). Sensitivity of DWI and MS-CT in detection of focal liver lesions was compared on a per-lesion and a per-segment basis. Receiver operator-characteristic (ROC) curves to determine the diagnostic performance and the sensitivities of correctly identifying liver metastases on a segmental base were calculated.

Results

For lesion detection, DWI was significantly superior to MS-CT both on a per-lesion (difference in sensitivities for reader 1 and 2 22.65% and 19.06%, p < 0.0001) and a per-segment basis (16.86% and 11.76%, p < 0.0001). Especially lesions smaller than 10 mm were better detected with DWI compared to MS-CT (difference 41.10% and 29.45%, p < 0.0001). ROC-analysis showed superiority for lesions classification (p < 0.0001) of DWI (AUC: 0.949 and 0.951) as compared to MS-CT (AUC: 0.879 and 0.892, p < 0.0001 and p = 0.005). DWI was able to filter out metastatic segments with a higher sensitivity (88.2 and 86.5%) compared to MS-CT (68.0 and 67.4%, p < 0.0001 and p = 0.005, respectively).

Conclusion

Compared to MS-CT DWI is both more sensitive in the detection of liver lesions and more accurate in determining the extent of metastatic disease in patients with colorectal cancer and therefore might help to optimize therapeutic management in those patients.