Michael A. Patak

Patient Exposure and Image Quality of Low-Dose Pulmonary Computed Tomography Angiography : Comparison of 100-and 80-kVp Protocols

Objective:Measures to reduce radiation exposure and injected iodine mass are becoming more important with the widespread and often repetitive use of pulmonary CT angiography (CTA) in patients with suspected pulmonary embolism. In this retrospective study, we analyzed the capability of 2 low-kilovoltage CTA-protocols to achieve these goals. Materials and Methods:Ninety patients weighing less than 100 kg were examined by a pulmonary CTA protocol using either 100 kVp (group A) or 80 kVp (group B). Volume and flow rate of contrast medium were reduced in group B (75 mL at 3 mL/s) compared with group A (100 mL at 4 mL/s). Attenuation was measured in the central and peripheral pulmonary arteries, and the contrast-to-noise ratios (CNR) were calculated. Entrance skin dose was estimated by measuring the surface dose in an ovoid-cylindrical polymethyl methacrylate chest phantom with 2 various dimensions corresponding to the range of chest diameters in our patients. Quantitative image parameters, estimated effective dose, and skin dose in both groups were compared by the t test. Arterial enhancement, noise, and overall quality were independently assessed by 3 radiologists, and results were compared between the groups using nonparametric tests. Results:Mean attenuation in the pulmonary arteries in group B (427.6 ± 116 HU) was significantly higher than in group A (342.1 ± 87.7 HU; P < 0.001), whereas CNR showed no difference (group A, 20.6 ± 7.3 and group B, 22.2 ± 7.1; P = 0.302). Effective dose was lower by more than 40% with 80 kVp (1.68 ± 0.23 mSv) compared with 100 kVp (2.87 ± 0.88 mSv) (P < 0.001). Surface dose was significantly lower at 80 kVp compared with 100 kVp at both phantom dimensions (2.75 vs. 3.22 mGy; P = 0.027 and 2.22 vs. 2.73 mGy; P = 0.005, respectively). Image quality did not differ significantly between the groups (P = 0.151). Conclusions:Using 80 kVp in pulmonary CTA permits reduced patient exposure by 40% and CM volume by 25% compared with 100 kVp without deterioration of image quality in patients weighing less than 100 kg.

MR motility imaging in Crohn’s disease improves lesion detection compared with standard MR imaging

ObjectiveTo evaluate retrospectively in patients with Crohn’s disease (CD) if magnetic resonance (MR) motility alterations correlate with CD typical lesions leading to an increased detection rate.MethodsForty patients with histologically proven CD underwent MR enterography (MRE), including coronal cine sequences (cine MRE), in addition to the standard CD MR protocol. Two blinded readings were performed with and without cine MRE. Locations presenting motility alterations on the cine sequences were analysed on standard MRE for CD-related lesions. This was compared with a second reading using the standard clinical MRE protocol alone.ResultsThe number of lesions localised by cine MRE and identified on standard MRE compared with standard MRE alone were 35/24 for wall thickening (p = 0.002), 24/20 for stenoses (p = 0.05), 17/11 for wall layering (p = 0.02), 5/3 for mucosal ulcers (p = 0.02) and 21/17 for the comb sign (p = 0.05). Overall, cine MRE detected 35 more CD-specific findings than standard MRE alone (124/89; p = 0.007) and significantly more patients with CD-relevant MR findings (34/28; p = 0.03).ConclusionCD lesions seem to be associated with motility changes and this leads to an increased lesion detection rate compared with standard-MRE imaging alone.

Thoracoabdominal-aortoiliac Multidetector-row Ct Angiography at 80 and 100 kvp: Assessment of Image Quality and Radiation Dose

Objective:To compare image quality and radiation dose of thoracoabdominal computed tomography (CT) angiography at 80 and 100 kVp and to assess the feasibility of reducing contrast medium volume from 60 to 45 mL at 80 kVp. Materials and Methods:This retrospective study had institutional review board approval; informed consent was waived. Seventy-five patients who had undergone thoracoabdominal 64-section multidetector-row CT angiography were divided into 3 groups of 25 patients each. Patients of groups A (tube voltage, 100 kVp) and B (tube voltage, 80 kVp) received 60 mL of contrast medium at 4 mL/s. Patients of group C (tube voltage, 80 kVp) received 45 mL of contrast medium at 3 mL/s. Mean aortoiliac attenuation, image noise, and contrast-to-noise ratio were assessed. The measurement of radiation dose was based on the volume CT dose index. Three independent readers assessed the diagnostic image quality. Results:Mean aortoiliac attenuation for group B (621.1 ± 90.5 HU) was significantly greater than for groups A and C (485.2 ± 110.5 HU and 483.1 ± 119.8 HU; respectively) (P < 0.001). Mean image noise was significantly higher for groups B and C than for group A (P < 0.05). The contrast-to-noise ratio did not significantly differ between the groups (group A, 35.0 ± 13.8; group B, 31.7 ± 10.1; group C, 27.3 ± 11.5; P = 0.08). Mean volume CT dose index in groups B and C (5.2 ± 0.4 mGy and 4.9 ± 0.3 mGy, respectively) were reduced by 23.5% and 27.9%, respectively, compared with group A (6.8 ± 0.8 mGy) (P < 0.001). The average overall diagnostic image quality for the 3 groups was graded as good or better. The score for group A was significantly higher than that for group C (P < 0.01), no difference was seen between group A and B (P = 0.92). Conclusions:Reduction of tube voltage from 100 to 80 kVp for thoracoabdominal CT angiography significantly reduces radiation dose without compromising image quality. Reduction of contrast medium volume to 45 mL at 80 kVp resulted in lower but still diagnostically acceptable image quality.

Faecal tagging to avoid colonic cleansing before MRI colonography.

Colonic cleansing is unpleasant and has low acceptance by patients. We show the feasibility of faecal tagging, which obviates the need for colonic cleansing, in conjunction with internal magnetic resonance imaging colonography.

MRI of the small and large bowel

Abstract. Driven by the improvements in gradient technology, breathhold T1- and T2-weighted imaging of the abdominal structures has become possible. These techniques allow exploitation of the advantages inherent to the MR imaging experiment: unsurpassed soft tissue contrast and multiplanar imaging capabilities. Magnetic resonance imaging of the small and large bowel has thus moved from a hypothetical possibility to a practical reality. This manuscript describes some of the underlying fast imaging techniques for display of the small and large bowel. Furthermore, it discusses the plethora of available oral and rectal contrast agents. Finally, clinical indications for MR of the small and large bowel as well as the rectum are decribed in light of the available literature. Advantages and disadvantages relative to computed tomography and othe imaging techniques are discussed.

Detection of Pulmonary Emboli With CT Angiography at Reduced Radiation Exposure and Contrast Material Volume: Comparison of 80 kVp and 120 kVp Protocols in a Matched Cohort

Objective:The detection rate of pulmonary emboli (PE) with computed tomography angiography (CTA) using either a standard or a low-dose protocol, combining reduced radiation exposure and iodine delivery rate, was retrospectively analyzed in a matched cohort of 120 patients. Materials and Methods:The study was performed according to the regulations of the institutional review board. Four groups of 30 patients each, with a body weight of less than 100 kg and receiving pulmonary CTA were matched by age (range, 21–87 years), gender (female/male, 48/72), weight (range, 41–99 kg), and cross sectional area of the chest (range, 468–885 cm2). Sixty patients had PE and 60 patients had no PE at CTA. The CT tube voltage was either 80 kVp (group A, with PE and group B, with no PE) or 120 kVp (group C, with PE and group D, with no PE). Volume and flow rate of injected contrast medium was lower with the 80 kVp protocol (75 mL at 3 mL/s) compared with the 120 kVp protocol (100 mL at 4 mL/s). Contrast-to-noise ratio (CNR) for the pulmonary trunk was calculated. Two independent readers analyzed all CTAs in a randomized order for the localization of emboli, diagnostic confidence, and image quality. The reference standard for the presence of emboli involved consensus reading and assessment of available clinical data and findings with additional imaging modalities. CNR, subjective image quality, diagnostic confidence, sensitivity, and specificity for emboli at both tube voltages were compared. Results:All patients with PE were correctly identified with both protocols, corresponding to a sensitivity of 100% at the patient level. For the localizations with emboli, both the sensitivity (83.7% at 80 kVp and 83.6% at 120 kVp; P = 0.921) and the specificity (97.2% at 80 kVp and 97.8% at 120 kVp; P = 0.463) were not significantly different at the 2 tube voltages. The diagnostic confidence was not different at all ramification levels (P = 0.216–1.0). CNR did not differ between the groups (P = 0.202). The overall subjective image quality was higher at 120 kVp compared with 80 kVp (P = 0.017). Conclusion:Detection rate and diagnostic confidence for the presence of pulmonary emboli with low-dose pulmonary CTA using 80 kVp and reduced iodine delivery rate may be equal to that at 120 kVp in patients weighing less than 100 kg.

MR imaging in Crohn's disease: correlation of MR motility measurement with histopathology in the terminal ileum

The objective of the study was to correlate MR‐detectable motility alterations of the terminal ileum with biopsy‐documented active and chronic changes in Crohns disease.

Temperature mapping of magnetic resonance-guided laser interstitial thermal therapy (LITT) in lymphangiomas of the head and neck.

Lymphangiomas of the tongue and neck are uncommon benign congenital lymphatic tumors. These vascular lesions are difficult to treat, frequently recur, and can cause patients significant morbidity. Treatment may also be complicated by adjacent vital anatomic structures. Magnetic resonance (MR)‐controlled laser‐induced interstitial thermotherapy (LITT) has been proven to be a noninvasive safe treatment. Real‐time monitoring of tissue temperature with thermosensitive sequences allows controlled coagulation necrosis.

Crohn's disease: small bowel motility impairment correlates with inflammatory-related markers C-reactive protein and calprotectin

To evaluate the correlation between the levels of C‐reactive protein (CRP), calprotectin, and small bowel motility in patients with Crohns disease assessed with MRI.

New frontiers of MRI in Crohn’s disease: motility imaging, diffusion-weighted imaging, perfusion MRI, MR spectroscopy, molecular imaging, and hybrid imaging (PET/MRI)

This article reviews the latest diagnostic advances in the evaluation of the CD, including functional studies on intestinal motility and molecular characterization of the inflammatory process at the level of the involved bowel. Molecular changes related to inflammation of the intestinal wall may be evaluated by different MRI techniques, including diffusion-weighted imaging, perfusion weighted imaging, in vivo spectroscopy, molecular imaging, and fusion imaging (PET–MRI).