Iodine overlays to improve differentiation between peritoneal carcinomatosis and benign peritoneal lesions.

OBJECTIVES: Peritoneal carcinomatosis (PC) is a prognostically relevant metastatic disease which may be difficult to depict in postoperative patients, particularly in early stages. This study aimed to determine whether PC could be diagnosed more accurately when using a combination of spectral detector CT (SDCT)-derived conventional images (CI) and iodine overlay images (IO) compared with CI only. METHODS: Thirty patients with PC and 30 patients with benign peritoneal alterations (BPA) who underwent portal-venous abdominal SDCT were included. Four radiologists determined the presence/absence of PC for each patient and assessed lesion conspicuity, diagnostic certainty, and image quality using 5-point Likert scales. Subjective assessment was conducted in two sessions comprising solely CI and CI/IO between which a latency of 6 weeks was set. Iodine uptake and HU attenuation were determined ROI-based to analyze quantitative differentiation of PC/BPA. RESULTS: Specificity for PC was significantly higher when using CI/IO compared with using CI only (0.86 vs. 0.78, p ≤ 0.05), while sensitivity was comparable (0.79 vs. 0.81, p = 1). In postoperative patients, the increase in specificity was the highest (0.93 vs. 0.80, p ≤ 0.05). Lesion conspicuity was rated higher in CI/IO (4 (3-5)) compared with that in CI only (3 (3-4); p ≤ 0.05). Diagnostic certainty was comparable (both 4 (3-5); p = 0.5). CI/IO received the highest rating for overall image quality and assessability (CI/IO 5 (4-5) vs. CI 4 (4-4) vs. IO 4 (3-4); p ≤ 0.05). Area under the receiver operating characteristics curve (AUC) for quantitative differentiation between PC and BPA was higher for iodine (AUCIodine = 0.95, AUCHU = 0.90). CONCLUSIONS: Compared with CI, combination of CI/IO improves specificity in the assessment of peritoneal carcinomatosis at comparable sensitivity, particularly in postoperative patients. KEY POINTS: • Combination of iodine overlays and conventional images improves specificity when assessing patients with peritoneal carcinomatosis at comparable sensitivity. • Particularly in postsurgical patients, iodine overlays could help to avoid false-positive diagnosis of peritoneal disease. • Iodine overlays alone provided inferior image quality and assessability than conventional images, while the combination of both received the highest ratings. Iodine overlays should therefore be used in addition to and not as a substitute for conventional images.

Value of spectral detector computed tomography for assessment of pancreatic lesions.

PURPOSE: Dual energy CT (DECT) can contribute to the diagnosis of benign and malignant pancreatic lesions. This study examined whether a novel, detector-based spectral CT scanner (SDCT) may improve subjective assessment of different types of pancreatic lesions and if various quantitative maps may improve lesion contrast and differentiation. MATERIALS AND METHODS: 61 consecutive patients who underwent clinical, contrast-agent enhanced, abdominal SDCT scans and showed pancreatic lesions of different origins were included. Subjective image analysis was performed by two readers who assessed image quality, lesion conspicuity and diagnostic confidence on 5-point Likert scales for conventional polyenergetic reconstructions (polyE), virtual monoenergetic images (monoE), virtual non-contrast images, iodine density, iodine overlay, and Z effective (Zeff) maps. Two readers acquired quantitative values from these maps ROI-based from which contrast-to-noise and lesion-to-parenchyma ratios were calculated. RESULTS: MonoE images at low keV levels yielded highest Likert scores regarding lesion conspicuity and reader confidence; iodine overlays facilitated lesion delineation. Inter-observer agreement ranged between substantial and excellent (kappa values 0.73-0.81). Contrast-to-noise-ratios for low keV monoE images were significantly higher, compared to polyE images (e.g. monoE 40 keV p < 0.0001). Marked overlap between PDAC and miscellaneous non-PDAC lesions was present in various spectral reconstructions. CONCLUSIONS: In line with previous studies, monoE images at low keV levels and iodine overlay maps facilitated subjective lesion delineation which was substantiated by the quantitative analysis. Hence, spectral detector CT improves pancreatic lesion conspicuity, while its value for lesion differentiation needs to be further evaluated in larger study cohorts.

Low-dose computed tomography of urolithiasis in obese patients: a feasibility study to evaluate image reconstruction algorithms.

Purpose: Retrospective evaluation and comparison of image quality generated by low-dose computed tomography (LDCT) from obese patients with urolithiasis using alternative reconstruction algorithms. Materials and methods: Twenty-five obese patients (body mass index [BMI]>25 kg/m2) underwent LDCT scans for suspected urolithiasis. The scans were recompiled using filtered-back projection (FBP), statistical iterative reconstruction (iDose) and iterative model-based reconstruction (IMR). Dose-length product (DLP) and patient details were obtained from the CT dose report and clinical charts, respectively. Objective image noise was assessed by measuring the SD of Hounsfield units (HUs) in defined locations. Additionally, subjective image evaluation was independently performed by two radiologists using a 3-point Likert scale. The inter-reviewer agreement of image quality was calculated. Results: Ureteral concretions were observed in all CT scans, two of which revealed bilateral stones. The assessed patients' mean BMI was 29.29±3.74 kg/m2, and the DLP of the CT scans was 100.04±10.00 mGy*cm. All scans were rated diagnostic with the iDose and iterative model-based reconstructions, whereas 41% of the scans performed with FBP reconstruction were nondiagnostic. With respect to image quality, IMR was superior to iDose and FBP, both in the objective (P<0.001) and overall subjective (P≤0.008) evaluation of the respective data sets. The inter-reviewer agreement for overall image quality was "almost perfect" for IMR, "substantial" for iDose and "moderate" for FBP (κ values of 1.0, 0.6 and 0.46, respectively). Conclusion: Using iterative image reconstruction algorithms, LDCT of urolithiasis is feasible in overweight patients with a BMI between 25 and 35 kg/m2. Due to higher image quality, IMR is the preferred algorithm for scan reconstruction as it may help to avoid repeated examinations due to initial nondiagnostic scans.

MRI detects peripheral nerve and adjacent muscle pathology in non-systemic vasculitic neuropathy (NSVN).

BACKGROUND: Diagnosis and disease monitoring of non-systemic vasculitic neuropathy (NSVN) are based on electrophysiological and clinical measures. However, these methods are insensitive to detect subtle differences of axonal injury. We here assessed the utility of a multiparametric MRI protocol to quantify axonal injury and neurogenic muscle damage in NSVN. METHODS: Ten NSVN patients and ten age-matched controls were investigated in this single-center prospective study. All participants were assessed by diffusion tensor imaging (DTI) of the tibial nerve and multiecho Dixon MRI of soleus and gastrocnemius muscles. These data were correlated with clinical and electrophysiological data. RESULTS: DTI scans of the tibial nerves of patients with NSVN showed significantly lower mean fractional anisotropy (FA) values (0.32 ± 0.02) compared to healthy controls (0.42 ± 0.01). FA values of NSVN patients correlated negatively with clinical measures of pain. Multiecho Dixon MRI scans revealed significantly higher intramuscular fat fractions in the soleus muscle (19.86 ± 6.18% vs. 5.86 ± 0.74%, p = 0.0015) and gastrocnemius muscle (26.09 ± 6.21% vs. 3.59 ± 0.82%, p = 0.0002) in NSVN patients compared to healthy controls. CONCLUSION: Our data provide a proof of concept that MRI can render information about nerve integrity and muscle pathology in NSVN. Further studies are warranted to evaluate DTI and multiecho Dixon MRI as surrogate markers in NSVN.

MRI biomarkers of proximal nerve injury in CIDP.

Objective: To evaluate the utility of nerve diffusion tensor imaging (DTI), nerve cross-sectional area, and muscle magnetic resonance imaging (MRI) multiecho Dixon for assessing proximal nerve injury in chronic inflammatory demyelinating polyneuropathy (CIDP). Methods: In this prospective observational cohort study, 11 patients with CIDP and 11 healthy controls underwent a multiparametric MRI protocol with DTI of the sciatic nerve and assessment of muscle proton-density fat fraction of the biceps femoris and the quadriceps femoris muscles by multiecho Dixon MRI. Patients were longitudinally evaluated by MRI, clinical examination, and nerve conduction studies at baseline and after 6 months. Results: In sciatic nerves of CIDP patients, mean cross-sectional area was significantly higher and fractional anisotropy value was significantly lower, compared to controls. In contrast, muscle proton-density fat fraction was significantly higher in thigh muscles of patients with CIDP, compared to controls. MRI parameters showed high reproducibility at baseline and 6 months. Interpretation: Advanced MRI parameters demonstrate subclinical proximal nerve damage and intramuscular fat accumulation in CIDP. Data suggest DTI and multiecho Dixon MRI might be useful in estimating axonal damage and neurogenic muscle changes in CIDP.

Implementation of ultra-low-dose lung protocols in CT-guided lung biopsies: feasibility and safety in the clinical setting.

Objective To evaluate the use of ultra-low-dose computed tomography (ULDCT) for CT-guided lung biopsy versus standard-dose CT (SDCT). Methods CT-guided lung biopsies from 115 patients (50 ULDCT, 65 SDCT) were analyzed retrospectively. SDCT settings were 120 kVp with automatic mAs modulation. ULDCT settings were 80 kVp with fixed exposure (20 mAs). Two radiologists evaluated image quality (i.e., needle artifacts, lesion contouring, vessel recognition, visibility of interlobar fissures). Complications and histological results were also evaluated. Results ULDCT was considered feasible for all lung interventions, showing the same diagnostic accuracy as SDCT. Its mean total radiation dose (dose-length product) was significantly reduced to 34 mGy-cm (SDCT 426 mGy-cm). Image quality and complication rates ( P = 0.469) were consistent. Conclusions ULDCT for CT-guided lung biopsies appears safe and accurate, with a significantly reduced radiation dose. We therefore recommend routine clinical use of ULDCT for the benefit of patients and interventionalists.

Incidental Findings in Abdominal Dual-Energy Computed Tomography: Correlation Between True Noncontrast and Virtual Noncontrast Images Considering Renal and Liver Cysts and Adrenal Masses.

PURPOSE: To assess correlation between attenuation measurements of incidental findings in abdominal second generation dual-energy computed tomography (CT) on true noncontrast (TNC) and virtual noncontrast (VNC) images. MATERIALS AND METHODS: Sixty-three patients underwent arterial dual-energy CT (Somatom Definition Flash, Siemens; pitch factor, 0.75-1.0; gantry rotation time, 0.28 seconds) after endovascular aneurysm repair, consisting of a TNC single energy CT scan (collimation, 128 × 0.6 mm; 120 kVp) and a dual-energy arterial phase scan (collimation, 32 × 0.6 mm, 140 and 100 kVp; blended, 120 kVp data set). Attenuation measurements in Hounsfield units (HU) of liver parenchyma and incidental findings like renal and hepatic cysts and adrenal masses on TNC and VNC images were done by drawing regions of interest. Statistical analysis was performed by paired t test and Pearson correlation. RESULTS: Incidental findings were detected in 56 (89%) patients. There was excellent correlation for both renal (n = 40) and hepatic cysts (n = 12) as well as adrenal masses (n = 6) with a Pearson correlation of 0.896, 0.800, and 0.945, respectively, and mean attenuation values on TNC and VNC images of 10.6 HU ± 12.8 versus 5.1 HU ± 17.5 (attenuation value range from -8.8 to 59.1 HU vs -11.8 to 73.4 HU), 6.4 HU ± 5.8 versus 6.3 HU ± 4.6 (attenuation value range from 2.0 to 16.2 HU vs -3.0 to 15.9 HU), and 12.8 HU ± 11.2 versus 12.4 HU ± 10.2 (attenuation value range from -2.3 to 27.5 HU vs -2.2 to 23.6 HU), respectively. As proof of principle, liver parenchyma measurements also showed excellent correlation between TNC and VNC (n = 40) images with a Pearson correlation of 0.839 and mean attenuation values on TNC and VNC images of 47.2 HU ± 10.5 versus 43.8 HU ± 8.7 (attenuation value range from 21.9 to 60.2 HU vs 4.5 to 65.3 HU). CONCLUSIONS: In conclusion, attenuation measurements of incidental findings like renal cysts or adrenal masses on TNC and VNC images derived from second generation dual-energy CT scans show excellent correlation providing considerable dose savings, favorable for future application in clinical routine.

High-pitch carbon dioxide contrasted CT angiography: pilot study.

PURPOSE: This study was designed to evaluate CO2 computed tomography angiography (CO2-CTA) of the iliac and lower limb arteries in patients with contraindications for iodinated contrast agent (ICA). METHODS: Five patients with contraindications for ICA were examined using CO2-fluoroscopic enhanced angiography (CO2-FLA) and CO2-CTA using a high-pitch examination protocol. Objective (vessel diameter) and subjective (visual score) image quality parameters were evaluated. Pathological findings in both modalities were compared. RESULTS: CO2-CTA was feasible in all patients without adverse side effects, except for CO2 injection-associated pain. Objective vessel analysis revealed no significant difference in diameters as determined by CO2-CTA and CO2-FLA (0.44 ± 0.4 and 0.46 ± 0.41 mm, p = 0.93). CO2-CTA had on average a higher image-quality score (2.6 ± 1.0 vs. 2.3 ± 1.0, p = 0.009). While for pelvic and upper leg CO2-CTA advantageous (3.1 ± 0.74 vs. 2.7 ± 0.9, p = 0.0014) at good quality scores, for calf vessels no significant improvement was visible (1.9 ± 1.0 vs. 1.7 ± 0.9, p = 0.49) and scores were poorer. CONCLUSIONS: CO2-CTA with high-pitch CT was feasible in a limited number of patients. Image-quality scores were on average higher for CO2-CTA than for CO2-FLA, while limited imaging quality in the vessels below the knee needs further work on the CT protocol. An added value of cross-sectional imaging was apparent but needs further quantification.