David D. Casalino

Wavelet-packet-based texture analysis for differentiation between benign and malignant liver tumours in ultrasound images

The purpose of this study was to apply a novel method of multiscale echo texture analysis for distinguishing benign (hemangiomas) from malignant (hepatocellular carcinomas (HCCs) and metastases) focal liver lesions in B-mode ultrasound images. In this method, regions of interest (ROIs) extracted from within the lesions were decomposed into subimages by wavelet packets. Multiscale texture features that quantify homogeneity of the echogenicity were calculated from these subimages and were combined by an artificial neural network (ANN). A subset of the multiscale features was selected that yielded the highest performance in the classification of lesions measured by the area under the receiver operating characteristic curve (Az). In an analysis of 193 ROIs consisting of 50 hemangiomas, 87 hepatocellular carcinomas and 56 metastases, the multiscale features yielded a high A: value of 0.92 in distinguishing benign from malignant lesions, 0.93 in distinguishing hemangiomas from HCCs and 0.94 in distinguishing hemangiomas from metastases. Our new multiscale texture analysis method can effectively differentiate malignant from benign lesions, and thus has the potential to increase the accuracy of diagnosis of focal liver lesions in ultrasound images.

Utility of Diffusion-Weighted MRI in Characterization of Adrenal Lesions

OBJECTIVE The purpose of our study was to evaluate the utility of apparent diffusion coefficient (ADC) values for characterizing adrenal lesions and determine if diffusion-weighted imaging (DWI) can distinguish lipid-rich from lipid-poor adenomas. MATERIALS AND METHODS We retrospectively evaluated 160 adrenal lesions in 156 patients (96 women and 60 men; mean age, 63 years). ADCs and signal intensity (SI) decrease on chemical shift imaging were measured in adrenal lesions with a wide variety of pathologies. Lipid-rich and lipid-poor adenomas were identified by unenhanced CT. The overall predictive power of ADC, SI decrease, and lesion size were determined by receiver operating characteristic (ROC) analysis. Areas under the ROC curve (AUC) were compared for equivalence using nonparametric methods. Sensitivity, specificity, and positive and negative predictive values were calculated. Correlation coefficients were used to assess ADCs versus percentage SI decrease and ADCs versus CT attenuation. RESULTS ADCs of adrenal malignancies (median, 1.67 x 10(-3) mm(2)/s; interquartile range, 1.41-1.84 x 10(-3) mm(2)/s) were not different compared with those of benign lesions (1.61 x 10(-3) mm(2)/s; 1.27-1.96 x 10(-3) mm(2)/s; p > 0.05). Cysts (2.93 x 10(-3) mm(2)/s; 2.70-3.09 x 10(-3) mm(2)/s) showed higher ADCs than the remaining adrenal lesions (p < 0.05). The median ADCs of lipid-rich adenomas did not differ from those of lipid-poor ones (p > 0.05). The CT attenuation had no negative or positive correlation with the ADCs of adrenal adenomas (r = -0.05, p = 0.97). CONCLUSION Unlike lesion size and percentage decrease in SI, the ADCs were not useful in distinguishing benign from malignant adrenal lesions. Lipid-poor adenomas could not be distinguished from lipid-rich adenomas and all other nonfatty lesions of the adrenal gland with DWI.

ACR Appropriateness Criteria prostate cancer--pretreatment detection, staging, and surveillance.

Prostate cancer is the most common noncutaneous male malignancy in the United States. The use of serum prostate-specific antigen as a screening tool is complicated by a significant fraction of nonlethal cancers diagnosed by biopsy. Ultrasound is used predominately as a biopsy guidance tool. Combined rectal examination, prostate-specific antigen testing, and histology from ultrasound-guided biopsy provide risk stratification for locally advanced and metastatic disease. Imaging in low-risk patients is unlikely to guide management for patients electing up-front treatment. MRI, CT, and bone scans are appropriate in intermediate-risk to high-risk patients to better assess the extent of disease, guide therapy decisions, and predict outcomes. MRI (particularly with an endorectal coil and multiparametric functional imaging) provides the best imaging for cancer detection and staging. There may be a role for prostate MRI in the context of active surveillance for low-risk patients and in cancer detection for undiagnosed clinically suspected cancer after negative biopsy results. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

CT and MR Imaging for Evaluation of Cystic Renal Lesions and Diseases

Cystic renal lesions are commonly encountered in abdominal imaging. Although most cystic renal lesions are benign simple cysts, complex renal cysts, infectious cystic renal disease, and multifocal cystic renal disease are also common phenomena. The Bosniak classification system provides a useful means of categorizing cystic renal lesions but places less emphasis on their underlying pathophysiology. Cystic renal diseases can be categorized as focal, multifocal, or infectious lesions. Diseases that manifest with focal lesions, such as cystic renal cell carcinoma, mixed epithelial and stromal tumor, and cystic nephroma, are often difficult to differentiate but have differing implications for follow-up after resection. Multifocal cystic renal lesions can be categorized as acquired or heritable. Acquired entities, such as glomerulocystic kidney disease, lithium-induced nephrotoxicity, acquired cystic kidney disease, multicystic dysplastic kidney, and localized cystic renal disease, often have distinct imaging and clinical features that allow definitive diagnosis. Heritable diseases, such as autosomal dominant polycystic kidney disease, von Hippel-Lindau disease, and tuberous sclerosis, are usually easily identified and have various implications for patient management. Infectious diseases have varied imaging appearances, and the possibility of infection must not be overlooked when assessing a cystic renal lesion. A thorough understanding of the spectrum of cystic renal disease will allow the radiologist to make a more specific diagnosis and provide the clinician with optimal recommendations for further diagnostic testing and follow-up imaging.

ACR Appropriateness Criteria Indeterminate Renal Mass

Renal masses are increasingly detected in asymptomatic individuals as incidental findings. An indeterminate renal mass is one that cannot be diagnosed confidently as benign or malignant at the time it is discovered. CT, ultrasonography, and MRI of renal masses with fast-scan techniques and intravenous (IV) contrast are the mainstays of evaluation. Dual-energy CT, contrast-enhanced ultrasonography, PET/CT, and percutaneous biopsy are all technologies that are gaining traction in the characterization of the indeterminate renal mass. In cases in which IV contrast cannot be used, whether because of IV contrast allergy or renal insufficiency, renal mass classification with CT is markedly limited. In the absence of IV contrast, ultrasonography, MRI, and biopsy have some advantages. Owing to the low malignant and metastatic potential of small renal cell carcinomas (≤4 cm in diameter), active surveillance is additionally emerging as a diagnostic strategy for patients who have high surgical risk or limited life expectancy. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and application by the panel of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Segmentation of liver tumors in ultrasound images based on scale-space analysis of the continuous wavelet transform

We have developed a simple, yet robust method for segmentation of low-contrast objects embedded in noisy images. Our technique has been applied to segmenting of liver tumors in B-scan ultrasound images with hypoechoic rims. In our method, first a B-scan image is processed by a median filter for removal of speckle noise. Then several one-dimensional profiles are obtained along multiple radial directions which pass through the manually identified center of the region of a tumor. After smoothing by a Gaussian kernel smoother, these profiles are processed by Sombreros continuous wavelets to yield scalograms over a range of scales. The modulus maxima lines, which represent the degree of regularity at individual points on the profiles, are then utilized for identifying candidate points on the boundary of the tumor. These detected boundary points are fitted by an ellipse and are used as an initial configuration of a wavelet snake. The wavelet snake is then deformed so that the accurate boundary of the tumor is found. A preliminary result for several metastases with various sizes of hypoechoic rims showed that our method could extract boundaries of the tumors which were close to the contours drawn by expert radiologists. Therefore, our new method can segment the regions of focal liver disease in sonograms with accuracy, and it can be useful as a preprocessing step in our scheme for automated classification of focal liver disease in sonography.

ACR Appropriateness Criteria ® acute onset of scrotal pain--without trauma, without antecedent mass.

Men or boys, who present with acute scrotal pain without prior trauma or a known mass, most commonly suffer from torsion of the spermatic cord; epididymitis or epididymoorchitis; or torsion of the testicular appendages. Less common causes of pain include a strangulated hernia, segmental testicular infarction, or a previously undiagnosed testicular tumor. Ultrasound is the study of choice to distinguish these disorders; it has supplanted Tc-99 m scrotal scintigraphy for the diagnosis of spermatic cord torsion. MRI should be used in a problem solving role if the ultrasound examination is inconclusive. The ACR Appropriateness Criteria ® are evidence-based guidelines for specific clinical conditions that are reviewed every two years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Lithium-Associated Kidney Microcysts

Long-term lithium therapy is associated with impairment in concentrating ability and, occasionally, progression to advanced chronic kidney disease from tubulointerstitial nephropathy. Biopsy findings in patients with lithium-induced chronic tubulointerstitial nephropathy include tubular atrophy and interstitial fibrosis interspersed with tubular cysts and dilatations. Recent studies have shown that cysts are seen in 33–62.5% of the patients undergoing lithium therapy. MR imaging is highly capable of defining renal morphological features and has been demonstrated to be superior to US and CT scan for the visualization of small renal cysts. The microcysts are found in both cortex and medulla, particularly in the regions with extensive atrophy and fibrosis, and can be multiple and bilateral. They tend to be sparse and do not normally exceed 12 mm in diameter. The renal microcysts in the image here reported are subtle, but consistent with lithium-induced chronic nephropathy. An MRI of the kidneys provides noninvasive evidence that strengthens the diagnosis of lithium-induced nephropathy.

ACR Appropriateness Criteria Post-Treatment Follow-Up of Renal Cell Carcinoma

Although localized renal cell carcinoma can be effectively treated by surgery or ablative therapies, local or distant metastatic recurrence after treatment is not uncommon. Because recurrent disease can be effectively treated, patient surveillance after treatment of renal cell carcinoma is very important. Surveillance protocols are generally based on the primary tumors size, stage, and nuclear grade at the time of resection, as well as patterns of tumor recurrence, including where and when metastases occur. Various imaging modalities may be used in the evaluation of these patients. Literature on the indications and usefulness of these radiologic studies is reviewed. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Adrenal Gland Hemangioma

A 53-year-old female presenting with microscopic hematuria underwent a triple phase (pre-contrast and post-contrast) computerized tomography (CT) examination of the pelvis and abdomen. In addition to urolithiasis, which likely explained the hematuria, a 2 cm, well-defined nodule of the right adrenal gland was discovered. On pre-contrast CT the mass appeared predominately low density. Calcification or macroscopic fat was not present. The mass showed brisk peripheral enhancement with a nodular pattern on early post-contrast images (fig. 1). These nodular foci progressively increased in size on the delayed images with progressive, but incomplete, filling of the adrenal mass (fig. 2). Based on these imaging findings, diagnosis was benign adrenal hemangioma. Given its small size and lack of associated symptoms or signs of malignancy, the mass was followed with annual magnetic resonance imaging (MRI) and remained unchanged for several years. Adrenal hemangioma is a rare, benign, nonfunctioning tumor that is most often discovered incidentally on imaging studies. There have been approxi-