Riccardo Iannaccone

Detection of colorectal lesions with virtual computed tomographic colonography

BACKGROUND The aim of our study was to compare the performance of virtual computed tomographic colonography with that of conventional colonoscopy in a blinded, prospective study in 165 patients with suspected colorectal lesions. METHODS There were 165 patients, all referred for conventional colonoscopy, who underwent preliminary virtual computed tomographic colonography. Computed tomograhic images of all suspected lesions were analyzed and subsequently compared with conventional colonoscopy findings. RESULTS There were 30 colorectal cancers and 37 polyps identified at conventional colonoscopy. Virtual computed tomographic colonography correctly detected all cancers, as well as 11 of 12 polyps of 10 mm in diameter or larger (sensitivity, 92%); 14 of 17 polyps between 6 and 9 mm (sensitivity, 82%); and 4 of 8 polyps of 5 mm or smaller (sensitivity, 50%). The per-patient sensitivity and specificity were 92% and 97%, respectively. CONCLUSIONS Virtual computed tomographic colonography has a diagnostic sensitivity similar to that of conventional colonoscopy for the detection of colorectal lesions larger than 6 mm in diameter.

Peliosis Hepatis: Spectrum of Imaging Findings

OBJECTIVE It is important to recognize the imaging characteristics of peliosis hepatis because peliotic lesions may mimic several different types of focal hepatic lesions CONCLUSION We illustrate the spectrum of imaging findings of peliosis hepatis, including sonography, CT, MR, and angiography.

Local staging of rectal cancer with MRI using a phased array body coil

Surgery is the method of choice for the treatment of rectal cancer. Optimization of therapeutic strategies (i.e., preor postoperative radiotherapy and chemotherapy) is fundamental to prevent local recurrence and increase survival rates of patients. Local recurrence varies from 3% to 32% of cases depending on the study [1] and is related mostly to incomplete removal of lateral spread of the tumor [2, 3]. Moreover, local recurrence is reduced when the histologic specimen shows a tumor-free circumferential resection margin larger than 1 mm. Thus, total mesorectal excision, with resection of the tumor and the surrounding mesorectal fat, is the surgically accepted treatment of choice; this procedure is associated with a recurrence rate of less than 10% without radiotherapy. Therefore, the use of preor postoperative radiotherapy may be limited to cases in which involvement of mesorectal fascia is diagnosed. This therapeutic approach demands accurate preoperative tumor staging. Goals of an imaging method are represented by (a) accurate staging of rectal wall infiltration, (b) evaluation of spreading into mesorectal fat and involvement of mesorectal fascia, and (c) nodal involvement. Endorectal ultrasonography is considered as the most accurate imaging modality for T-staging of rectal cancers, with accuracies ranging between 64% and 94% [4, 5]. However, it is limited in the evaluation of stenosing lesions and tumors located at the rectosigmoid junction; moreover, it does not identify mesorectal fascia and lymph nodes far from the rectal wall due to its limited field of view. Computed tomography, even with the use of spiral scanners, cannot demonstrate rectal wall layers. Moreover, it has limitations in the assessment of tumor infiltration in surrounding structures for locally advanced primary and recurrent rectal cancers, with a sensitivity approaching 70% and a specificity of approximately 85%. However, it remains an useful imaging modality for identification of distant metastases (i.e., liver lesions and mesenteric lymph nodes) [6–9]. The use of magnetic resonance imaging (MRI) has been advocated in recent years. Initial results were disappointing due to technical limitations. Advancements in terms of MR equipment, coils, and sequences have progressively optimized the technique, with a parallel increase in accuracy. Thanks to the high-contrast spatial resolution and large field of view, MRI has the potential to fulfill the requirements for the ideal imaging technique for the preoperative staging of rectal cancer.

Hepatocellular carcinoma treated with radio frequency ablation: An early evaluation with magnetic resonance imaging

To determine the usefulness of nonenhanced T1‐weighted spoiled gradient‐recalled acquisition in the steady‐state (SPGR) MRI in the early assessment of the efficacy of radio frequency (RF) therapy for hepatocellular carcinoma (HCC).

Multislice CT angiography of mesenteric vessels

Due to several distinct advantages over conventional angiography (including minimal invasiveness, lower cost, and lower ionizing radiation exposure for patients and staff), computed tomography (CT) angiography has replaced diagnostic conventional angiography in several clinical situations. The recent introduction of multislice CT (MSCT) scanners has significantly improved CT angiographic applications, especially in the evaluation of the mesenteric vasculature. Thin-slice collimation protocols associated with powerful postprocessing procedures allow the display of mesenteric circulation with excellent detail. The purposes of this presentation are (a) to illustrate the imaging technique that can be used to obtain state-of-the-art MSCT angiographic images of the mesenteric vasculature, (b) to review the normal anatomy and anatomic variants of mesenteric vessels, and (c) to illustrate some of the potential clinical applications of MSCT angiography of the mesenteric vessels.

Multislice CT colonography: Technical developments

The introduction of multislice spiral computed tomography (CT) offers increased spatial resolution along the longitudinal axis, resulting in improved image quality, and dramatically reduced acquisition times, with the capability of examining large anatomic regions in a single breath hold. Dedicated protocols are still under optimization to reduce radiation exposure and to take full advantage of the new technology. This article presents a review of the literature; the impact of multislice CT on virtual colonoscopy is also discussed.

Determining the optimal timing for early arterial phase hepatic CT imaging by measuring abdominal aortic enhancement in variable contrast injection protocols

Objective: To find the optimal scan timing for early arterial phase hepatic CT with adequate arterial enhancement after the aortic contrast arrival. Methods: Sixty patients were divided randomly into three groups, each of which received 2.0 mL/kg of the 300 mgI/mL contrast medium with an injection duration of 30 seconds (Group A, mean rate 3.6 mL/sec); of 25 seconds (B, 4.6 mL/sec); of 30 seconds (3.6 mL/sec) followed by a saline chaser (C). Results: After the contrast arrival, aortic enhancement increased rapidly for 6-15 seconds (mean, 10 seconds) to the initial peak enhancement in all groups, and then, increased moderately to the maximum aortic enhancement over the following 19, 13, and 21 seconds, respectively. The mean maximum aortic enhancement in Group B (392 HU) and C (360 HU) were significantly higher than that in A (326 HU), respectively. The difference between the initial and maximum aortic enhancement was less than 50 HU. Conclusion: The optimal timing of the early arterial phase for hepatic CT arteriography is 10-15 seconds after the aortic arrival.

Assessment of Two 3D MDCT Colonography Protocols for Observation of Colorectal Polyps

OBJECTIVE The objective of our study was to assess the value of two-way interpretation (i.e., from rectum to cecum and vice versa) compared with one-way interpretation (i.e., from rectum to cecum only) in terms of polyp detection and interpretation time on MDCT colonography. MATERIALS AND METHODS Fifty consecutive patients underwent both CT colonography and conventional colonoscopy. Three radiologists independently analyzed the CT colonographic examinations of each patient using a primary 3D method. All examinations were analyzed using two techniques: navigation from rectum to cecum only (one-way) and navigation from rectum to cecum and vice versa (two-way). Sensitivity and positive predictive value were calculated on both a per-polyp basis and a per-patient basis. Alternative free-response receiver operating characteristic (ROC) curve analysis was estimated, and image interpretation time was documented. RESULTS One hundred fifty-five polyps were depicted in 45 patients by colonoscopy. The mean sensitivity of CT colonography for polyp detection with two-way (88.4%) was significantly superior to that with one-way (78.1%) (p < 0.01). The mean positive predictive value of each observer with one-way was 66.7%, whereas that with two-way was 65.8%. The mean area under the alternative free-response ROC curve (A(z) value) with two-way (0.827) was higher than that with one-way (0.816), but there was not a statistically significant difference. The average interpretation time of each observer with two-way (39 min) was statistically significantly longer than that with one-way (25 min) (p < 0.01). CONCLUSION When using a primary 3D interpretation technique at CT colonography, complete 3D navigation from rectum to cecum and from cecum to rectum is mandatory to maximize polyp detection. The image interpretation time for two-way interpretation is statistically significantly longer than that with one-way interpretation.

Colorectal carcinoma: detection and staging with multislice CT (MSCT) colonography.

In Western countries, colorectal cancer (CRC) is the third most common malignant tumor and the third leading cause of cancer-related deaths for men and women [1]. By detecting and removing precursor adenomas, screening tests play a major role in the prevention of CRC [2]. However, despite these efforts, approximately 50% of patients die within 5 years after the surgical procedure [3]. Early diagnosis is of paramount importance for curative surgical resection. At the same time, there is evidence that the overall prognosis and outcome depend on disease stage at initial diagnosis [3]. Accurate preoperative staging also is essential for a correct therapeutic plan, including surgery (limited or extensive resection), radiotherapy, or chemotherapy (advanced stage disease). With regard to CRC, currently there is no ideal preoperative diagnostic test in terms of diagnostic accuracy and staging. For many years, conventional colonoscopy and double-contrast barium enema (DCBE) constituted the sole available diagnostic examinations [4]. However, these techniques cannot assess the depth of bowel wall invasion or the presence of lymphadenopathies and/or distant metastases. In addition, in case of obstructive neoplasms, conventional colonoscopy (and in many cases DCBE) cannot be used to evaluate the proximal colon [5–7]. Several studies have investigated the potential role of computed tomography (CT) and magnetic resonance imaging in the diagnosis and staging of CRC, with conflicting results [8–15]. However, previous reports were often limited by the use of past-generation scanners (i.e., non-spiral CT technology) and by the preparation of the patients (i.e., the colon was neither cleaned nor distended before CT). In the past decade, CT colonography, a technique that applies advanced imaging software to volumetric CT datasets obtained from spiral CT acquisitions to produce two-dimensional and three-dimensional images of the colon [16], has been extensively investigated. Results from the literature are promising, with a sensitivity for the detection of colorectal carcinoma approaching 100% [16–20]. This article describes the role of multislice CT (MSCT) colonography in the diagnosis and staging of CRC.

Multinodular focal fatty infiltration of the liver: atypical imaging findings on delayed T1-weighted Gd-BOPTA-enhanced liver-specific MR images.

We report a case of pathologically confirmed multinodular focal fatty infiltration. MRI was performed after bolus injection of gadobenate dimeglumine (Gd‐BOPTA, MultiHance®; Bracco, Milan, Italy), a liver‐specific paramagnetic, gadolinium (Gd)‐based MR contrast agent that concomitantly enables the acquisition of a standard dynamic phase with timing strategies similar to those used for other extracellular fluid contrast agents, followed by a delayed T1‐weighted liver‐specific phase (the so‐called hepatobiliary phase). In the present case, multiple rounded areas of fatty infiltration, although confidently diagnosed using chemical shift sequences due to a significant signal intensity reduction on out‐of‐phase images, were unexpectedly hypointense during the delayed liver‐specific phase of Gd‐BOPTA. Reduced Gd‐BOPTA concentration during the liver‐specific phase is generally correlated with liver malignancy. Since such lesions can be prospectively mistaken for metastatic disease, we performed a hepatic biopsy to establish a definitive diagnosis. Our empirical observations suggest that Gd‐BOPTA uptake may be impaired in fatty infiltrated liver tissue. Because at present there is no report evaluating the kinetics of Gd‐BOPTA in fatty liver, further studies are needed to specifically investigate this issue. J. Magn. Reson. Imaging 2006.