Magnetic resonance (MR) imaging plays an increasingly important role in the evaluation of patients with liver disease because of its high contrast resolution, lack of ionizing radiation, and the possibility of performing functional imaging sequences. With advances in hardware and coil systems, diffusion-weighted (DW) MR imaging can now be applied to liver imaging with improved image quality. DW MR imaging enables qualitative and quantitative assessment of tissue diffusivity (apparent diffusion coefficient) without the use of gadolinium chelates, which makes it a highly attractive technique, particularly in patients with severe renal dysfunction at risk for nephrogenic systemic fibrosis. In this review, acquisition parameters, postprocessing, and quantification methods applied to liver DW MR imaging will be discussed. The current clinical uses of DW MR imaging (liver lesion detection and characterization, compared and combined with conventional sequences) and the emerging applications of DW MR imaging (tumor treatment response and diagnosis of liver fibrosis and cirrhosis) will be reviewed. Also, limitations, mainly image quality and reproducibility of diffusion parameters, and future directions of liver DW MR imaging will be discussed.

Diffusion-weighted MR imaging of the liver.

In applying diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) technique, DW-MR images are acquired during free breathing, which results in images with high signal-to-noise ratio using relatively thin image sections (4–5 mm). Image acquisition during free breathing is possible because bulk tissue motion, including respiratory motion, may be considered as types of coherent motion, which do not result in significant signal loss unlike intravoxel incoherent motion, which reflects random water motion at a cellular level. The concept of DWIBS allows handling of the acquired images as a volumetric dataset and it exploits both prolonged T2 relaxation time and impeded diffusion that the majority of solid lesions (both benign and malignant) exhibit as mechanisms for image contrast, which is used for clinical evaluation of diseases.

Diffusion-Weighted Whole-Body Imaging with Background Body Signal Suppression (DWIBS)

Diagnosis, Evaluation and Follow-Up of Asymptomatic Microhematuria (AMH) in Adults: AUA Guideline

OBJECTIVE. The purpose of our study was to assess the reliability and usefulness of parallel imaging for apparent diffusion coefficient (ADC) measurement of abdominal organs and lesions.MATERIALS AND METHODS. Single-shot spin-echo echo-planar diffusion-weighted MRI (TE = 66, b = 0, 600 s/mm2) was performed in phantom and clinical studies. The b value was set to minimize the effects of perfusion in tissue and to maintain signal-to-noise ratio. Bottle phantoms were scanned with and without parallel imaging and with various parallel imaging factors and at various positions to evaluate the effects of parallel imaging on ADCs. In 200 consecutive clinical patients (122 men and 78 women: mean age, 61.9 years), ADCs were calculated for liver (four segments), spleen, pancreas (head, body, tail), gallbladder, renal parenchyma, and back muscle, and then compared to evaluate the reliability of clinical ADC measurements with parallel imaging. ADCs were also calculated for diffuse diseases and focal lesions (94 maligna...

https://www.ajronline.org/doi/pdfplus/10.2214/AJR.05.0778

ADC Measurement of Abdominal Organs and Lesions Using Parallel Imaging Technique

Study Type – Prognosis (retrospective cohort) Level of Evidence 2b



What’s known on the subject? and What does the study add?



Upper-tract urothelial carcinoma (UTUC) is a relatively uncommon urological malignancy with survival and outcomes data largely determined from single-centre series which can be limited by relatively small case numbers.



Through review of a large population based cohort, this study provides valuable information regarding epidemiological and survival patterns for over 13,000 patients with UTUC diagnosed over the past three decades.



OBJECTIVE

• To evaluate epidemiological and survival patterns of upper-tract urothelial carcinoma (UTUC) over the past 30 years through a review of a large, population-based database.



PATIENTS AND METHODS

• Data from the Surveillance, Epidemiology and End Results (SEER) database from 1973 to 2005 were reviewed in 10-year increments to evaluate disease trends.



• Univariate and multivariate survival analyses identified prognostic variables for outcomes.



RESULTS

• In total, 13 800 SEER-registered cases of UTUC were included. The overall incidence of UTUC increased from 1.88 to 2.06 cases per 100 000 person-years during the period studied, with an associated increase in ureteral disease (0.69 to 0.91) and a decrease in renal pelvic cancers (1.19 to 1.15).



• The proportion of in situ tumours increased from 7.2% to 31.0% (P < 0.001), whereas local tumours declined from 50.4% to 23.6% (P < 0.001).



• There was no change in the proportion of patients presenting with distant disease.



• In multivariate analysis, increasing patient age (P < 0.001), male gender (P < 0.001), black non-Hispanic race (P < 0.001), bilateral UTUC (P= 0.001) and regional/distant disease (P < 0.001) were all associated with poorer survival outcomes.



CONCLUSIONS

• The incidence of UTUC has slowly risen over the past 30 years.



• Increased use of bladder cancer surveillance regimens and improved abdominal cross-sectional imaging may contribute to the observed stage migration towards more in situ lesions.



• Although pathological disease characteristics impact cancer outcomes, certain sociodemographic factors also appear to portend worse prognosis.

Incidence and survival of patients with carcinoma of the ureter and renal pelvis in the USA, 1973-2005.

The purpose of this study was to measure apparent diffusion coefficient values of normal liver parenchyma and focal liver lesions utilizing a respiratory gated diffusion sequence with multiple b-values and to investigate whether apparent diffusion coefficient (ADC) measurements may be utilized to characterize and differentiate between malignant and benign focal hepatic lesions. Thirty-eight consecutive patients underwent MRI of the liver including diffusion-weighted imaging (DWI). A single-shot echo planar imaging sequence was applied in coronal orientation with multiple b-values (0, 50, 500, 1,000 s/mm2) and respiratory gating. ADC values were recorded on corresponding maps utilizing region of interest measurements in patients with benign (group A), malignant (group B) focal lesions and liver parenchyma (group C). Statistical analysis was applied to check whether differences in mean ADC values were significant (p<0.05). No focal lesions were detected in 11 patients, with a mean ADC value (CI 95%) of liver parenchyma 1.25×10−3 mm2/s (1.21×10−3 mm2/s−1.29×10−3 mm2/s). Differences in mean ADC of liver parenchyma between group A and B were not significant (p=0.054, 1.30×10−3 mm2/s and 1.31×10−3 mm2/s, respectively). Mean ADC value (95% CI) of 22 benign lesions found in 18 patients was 2.55×10−3 mm2/s (2.35×10−3 mm2/s−2.74×10−3 mm2/s), while the mean ADC value (95% CI) of 16 malignant lesions recorded in 9 patients was 1.04×10−3 mm2/s (0.9×10−3 mm2/s−1.17×10−3 mm2/s). The difference between mean ADC values of benign and malignant focal lesions was statistically significant (p<0.0001). Respiratory gated diffusion-weighted imaging in the liver is technically feasible. Apparent diffusion coefficient measurements can be useful in differentiating malignant from benign focal liver lesions.

Respiratory gated diffusion-weighted imaging of the liver: value of apparent diffusion coefficient measurements in the differentiation between most commonly encountered benign and malignant focal liver lesions.

Performance of computed tomographic urography in diagnosis of upper urinary tract urothelial carcinoma, in patients presenting with hematuria: Systematic review and meta-analysis.

Comparison between two-point and four-point methods for quantification of apparent diffusion coefficient of normal liver parenchyma and focal lesions. Value of normalization with spleen

Carcinomas of the rectum are associated with a significant local and distant recurrence rate. Not all patients are appropriate candidates for preoperative radiation therapy. Preoperative identification of those most likely to benefit from neoadjuvant therapy is important. There is no general consensus on the role of endorectal ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) in staging patients with rectal cancer. Although the tumor stage is an important prognostic factor, preoperative assessment is associated with prediction of the circumferential resection margin. Newer developments such as coils, sequences and gradients in MRI, evolution of multidetector CT and new contrast media, allow for an algorithm selection aiming at the best diagnostic options for patients. The present review will discuss the current role of the various imaging modalities in staging carcinomas of the rectum.

/pdf/preoperative-imaging-staging-of-rectal-cancer-nfbz6zi02a.pdf

Spyros Yarmenitis

Papers

Respiratory gated diffusion-weighted imaging of the liver: value of apparent diffusion coefficient measurements in the differentiation between most commonly encountered benign and malignant focal liver lesions.

Performance of computed tomographic urography in diagnosis of upper urinary tract urothelial carcinoma, in patients presenting with hematuria: Systematic review and meta-analysis.

Comparison between two-point and four-point methods for quantification of apparent diffusion coefficient of normal liver parenchyma and focal lesions. Value of normalization with spleen

Preoperative imaging staging of rectal cancer.

Ultrasound of the gallbladder and the biliary tree