Luís Curvo-Semedo

Rectal Cancer: Assessment of Complete Response to Preoperative Combined Radiation Therapy with Chemotherapy--Conventional MR Volumetry versus Diffusion-weighted MR Imaging.

PURPOSE To determine diagnostic performance of diffusion-weighted (DW) magnetic resonance (MR) imaging for assessment of complete tumor response (CR) after combined radiation therapy with chemotherapy (CRT) in patients with locally advanced rectal cancer (LARC) by means of volumetric signal intensity measurements and apparent diffusion coefficient (ADC) measurements and to compare the performance of DW imaging with that of T2-weighted MR volumetry. MATERIALS AND METHODS A retrospective analysis of 50 patients with LARC, for whom clinical and imaging data were retrieved from a previous imaging study approved by the local institutional ethical committee and for which all patients provided informed consent, was conducted. Patients underwent pre- and post-CRT standard T2-weighted MR and DW MR. Two independent readers placed free-hand regions of interest (ROIs) in each tumor-containing section on both data sets to determine pre- and post-CRT tumor volumes and tumor volume reduction rates (volume). ROIs were copied to an ADC map to calculate tumor ADCs. Histopathologic findings were the standard of reference. Receiver operating characteristic (ROC) curves were generated to compare performance of T2-weighted and DW MR volumetry and ADC. The intraclass correlation coefficient (ICC) was used to evaluate interobserver variability and the correlation between T2-weighted and DW MR volumetry. RESULTS Areas under the ROC curve (AUCs) for identification of a CR that was based on pre-CRT volume, post-CRT volume, and volume, respectively, were 0.57, 0.70, and 0.84 for T2-weighted MR versus 0.63, 0.93, and 0.92 for DW MR volumetry (P = .15, .02, .42). Pre- and post-CRT ADC and ADC AUCs were 0.55, 0.54, and 0.51, respectively. Interobserver agreement was excellent for all pre-CRT measurements (ICC, 0.91-0.96) versus good (ICC, 0.61-0.79) for post-CRT measurements. ICC between T2-weighted and DW MR volumetry was excellent (0.97) for pre-CRT measurements versus fair (0.25) for post-CRT measurements. CONCLUSION Post-CRT DW MR volumetry provided high diagnostic performance in assessing CR and was significantly more accurate than T2-weighted MR volumetry. Post-CRT DW MR was equally as accurate as volume measurements of both T2-weighted and DW MR. Pre-CRT volumetry and ADC were not reliable.

Diffusion-weighted MRI in rectal cancer: Apparent diffusion coefficient as a potential noninvasive marker of tumor aggressiveness

To assess the value of diffusion‐weighted MR imaging (DWI) as a potential noninvasive marker of tumor aggressiveness in rectal cancer, by analyzing the relationship between tumoral apparent diffusion coefficient (ADC) values and MRI and histological prognostic parameters.

USPIO-enhanced magnetic resonance imaging for nodal staging in patients with head and neck cancer.

To determine the accuracy of ultrasmall superparamagnetic iron oxide (USPIO)‐enhanced magnetic resonance imaging (MRI) for nodal staging in patients with head and neck cancer.

Congenital Cystic Lesions of the Biliary Tree

OBJECTIVE The purpose of this essay is to illustrate the imaging findings of congenital cystic lesions of the biliary tract. CONCLUSION Congenital cystic lesions of the biliary tract include ductal plate malformations and choledochal cysts and can be recognized with characteristic imaging findings and basic knowledge of the embryologic development of the biliary tree.

Usefulness of Perfusion CT to Assess Response to Neoadjuvant Combined Chemoradiotherapy in Patients with Locally Advanced Rectal Cancer

RATIONALE AND OBJECTIVES To prospectively evaluate perfusion computed tomography (CT) for assessment of changes in tumor vascularity after chemoradiation therapy (CRT) in locally advanced rectal cancer and to analyze the correlation between baseline perfusion parameters and tumor response. MATERIALS AND METHODS Twenty patients with rectal cancer underwent baseline perfusion CT before CRT, and in 11 an examination after CRT was also performed. For each tumor, blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability-surface area product (PS) were quantified. The Mann-Whitney U test compared baseline perfusion parameters of responders and nonresponders and pre- and post-CRT measurements were compared by the Wilcoxon signed-rank test (P < .05 statistically significant for both tests). RESULTS Baseline BF was significantly lower (P = .013) and MTT was significantly higher (P = .006) in responders. Both were able to discriminate responders from nonresponders with a sensitivity of 80% and 100% and a specificity of 73.3% and 86.7%, respectively, for BF and MTT. Baseline BV and PS were not significantly different in responders and nonresponders. Perfusion parameters changed significantly in post-CRT scans compared to baseline: BF (P = .003), BV (P = .003), and PS (P = .008) decreased, whereas MTT increased (P = .006). CONCLUSION Baseline BF and MTT can discriminate patients with a favorable response from those that fail to respond to CRT, potentially selecting high-risk patients with resistant tumors that may benefit from an aggressive preoperative treatment approach.

The Hypointense Liver Lesion on T2-Weighted MR Images and What It Means

The vast majority of focal liver lesions are hyperintense on T2-weighted magnetic resonance (MR) images. Rarely, however, hepatic nodules may appear totally or partially hypointense on those images. Causes for this uncommon appearance include deposition of iron, calcium, or copper and are related to the presence of blood degradation products, macromolecules, coagulative necrosis, and other conditions. Although rare, low signal intensity relative to surrounding liver on T2-weighted images may be seen in a wide spectrum of lesions. Examples include cases of focal nodular hyperplasia, hepatocellular adenoma, hepatocellular carcinoma, metastases, leiomyoma, siderotic or dysplastic nodules, nodules in Wilson disease, granuloma, and hydatid cyst. On fat-suppressed T2-weighted images, nodules with a lipomatous component, such as lipoma, angiomyolipoma, hepatocellular adenoma, and hepatocellular carcinoma may also appear partially or totally hypointense. The conjunction of other MR imaging findings and their integration in the clinical setting may allow a correct diagnosis in a considerable proportion of cases. The cause for T2-weighted hypointensity may not be, however, always recognized, and only pathologic correlation may provide the answer. The aims of this work are to discuss the causes and mechanisms of hypointensity of liver lesions on T2-weighted images and proposing an algorithm for classification that may be useful as a quick reminder for the interested reader.

Imaging the postoperative patient: long-term complications of gastrointestinal surgery

AbstractObjectivesThe objectives of this review are (1) to become acquainted with the long-term complications of surgery of the gastrointestinal tract, and (2) to appreciate the appropriate use of imaging in the assessment of long-term complications.BackgroundGastrointestinal tract surgery comprises a group of procedures performed for a variety of both benign and malignant diseases. In the late postoperative setting, adhesions and internal hernias are the most important complications. and they can be further complicated by volvulus and ischemia. At present, computed tomography (CT) is the workhorse for evaluating late postoperative complications. Accurate imaging assessment of patients is essential for adequate treatment planning.Imaging findings or procedure detailsIn this pictorial essay we will review the most frequent long-term complications after gastrointestinal surgery, including adhesions, afferent loop syndrome, closed-loop obstruction, strangulated obstruction, internal hernias, external hernias, anastomotic strictures and disease recurrence. Examples will be depicted using iconography from the authors’ imaging department.ConclusionsKnowledge of the most frequent complications after gastrointestinal surgery in the late postoperative period is of paramount importance for every radiologist, so that potentially life-threatening situations can be promptly diagnosed and adequate therapy can be planned.Teaching points• Long-term postoperative complications of gastrointestinal tract surgery can be divided intoprocedure-relatedanddisease-relatedcategories. • The most commonprocedure-relatedcomplications are internal hernias and adhesions. • The most frequentdisease-relatedcomplications are mainly associated with neoplastic or inflammatory recurrence. • Computed tomography is the most useful examination when such complications are suspected.

An unusual cause of intra-abdominal calcification: A lithopedion

We report a case of a 77-year-old female who was admitted to the emergency department complaining of diffuse abdominal pain for five days, associated with nausea, vomiting and constipation. Physical examination disclosed a large incarcerated umbilical hernia, which was readily apparent on supine abdominal plain films. These also showed a calcified heterogeneous mass in the mid-abdominal region, which was further characterized by CT as a lithopedion (calcified ectopic pregnancy). This is one of the few cases studied on a MDCT equipment, and it clearly enhances the post-processing abilities of this imaging method which allows diagnostic high-quality MIP images. Lithopedion is a rare entity, with less than 300 cases previously described in the medical literature. However, many reported cases corresponded to cases of skeletonization or collections of fetal bone fragments discovered encysted in the pelvic region at surgery or autopsy. It is thus estimated that true lithopedion is a much rarer entity. The diagnosis may be reached by a suggestive clinical history and a palpable mass on physical examination, while the value of modern cross-sectional techniques is still virtually unknown. Ultrasonography may depict an empty uterine cavity and a calcified abdominal mass of non-specific characteristics, and computed tomography or magnetic resonance imaging are able to reach a conclusive diagnosis and may additionally define the involvement of adjacent structures. The differential diagnosis includes other calcified pathologic situations, including ovarian tumors, uterine fibroids, urinary tract neoplasms, inflammatory masses or epiploic calcifications.

MR Contrast Agents

Despite the excellent soft tissue contrast provided by plain MRI, the use of intravascular contrast agents is often performed in a variety of clinical settings being an instrumental component of many MR studies. Several compounds have been developed for contrast-enhanced MR imaging of the abdomen, with the purpose of increasing tumor detection and differentiation between normal and pathological tissues. MR contrast agents can be divided according to their magnetic properties into paramagnetic and superparamagnetic agents. They are also classified as interstitial, nonspecific, or liver-specific contrast media, with the latter subdivided according to their target-cell population: hepatocyte-selective or Kupffer cell contrast agents.

Diffuse Fatty Liver Disease: From Diagnosis to Quantification

Even though liver biopsy is considered to be the gold standard for diagnosis and quantification of liver steatosis, it is not devoid of problems, since it implicates an invasive maneuver which carries a certain amount of risk of hemorrhage. Furthermore, it suffers from sampling errors and is very dependent on the experience of the reader for quantification.