Russell N. Low

Diffusion-weighted MRI (DWI) in the oncology patient: Value of breathhold DWI compared to unenhanced and gadolinium-enhanced MRI

To evaluate the feasibility and added value of single breathhold diffusion‐weighted (DW) imaging (DWI) in oncology patients undergoing abdominal MRI.

Crohn's disease evaluation: Comparison of contrast-enhanced MR imaging and single-phase helical CT scanning

The purpose of this study was to evaluate the use of gadolinium and barium‐enhanced magnetic resonance (MR) imaging in detecting intestinal and extraintestinal Crohns disease and compare MRI with contrast‐enhanced helical computed tomography (CT). Twenty‐six patients with Crohns disease underwent imaging examinations, including gadolinium‐enhanced, fat suppressed fast multiplanar spoiled gradient‐recalled (FMPSPGR) MR imaging with oral 2% barium sulfate and rectal water and with helical CT using IV and positive (13) or negative (13) intestinal contrast material. MR images and CT scans were reviewed separately by two radiologists for bowel wall thickness and enhancement, presence of abscess, phlegmon, and fistula. MR images and CT scans were then compared side by side. Surgical, endoscopic, and histopathologic findings and results of barium studies were reviewed to determine the location and severity of involvement of intestinal Crohns disease. Depiction of mural thickening and/or enhancement was superior on the MR images, which showed 55 (85%) and 52 (80%) of 65 abnormal bowel segments for the two observers, compared with helical CT, which showed 39 (60%) and 42 (65%; P < 0.001, P < 0.05) of bowel segments affected by Crohns disease. Segments of bowel with moderate or marked mural thickening were depicted equally on MR imaging and helical CT. In mildly diseased segments of bowel, with only slight thickening and enhancement, MR imaging depicted 22 (79%) and 19 (68%) of 28 segments, compared with helical CT, which depicted 9 (32%; P < 0.01), and 13 (46%; P > 0.05) of 28 segments. In the side‐by side comparison, MR imaging was preferred over helical CT for depicting normal bowel wall (MR 71%, CT 4%, equal 25%; P < 0.001), mural thickening (MR 41%, CT 11% equal 48%; P < 0.01), mural enhancement (MR 89%, equal 11%; P < 0.001), and overall GI tract evaluation (MR 52%, CT 10%, equal 38%; P < 0.001). Gadolinium‐enhanced MR imaging with oral dilute barium sulfate and rectal water depicts intestinal and extraintestinal changes of Crohns disease and shows promise as a clinically useful tool. J. Magn. Reson. Imaging 2000;11:127–135.

Diffusion-Weighted MRI of Peritoneal Tumors: Comparison With Conventional MRI and Surgical and Histopathologic Findings—A Feasibility Study

OBJECTIVE The purpose of our study was to evaluate the utility of single-shot spin-echo echo-planar diffusion-weighted imaging (DWI) using a b value of 400-500 s/mm(2) for depicting peritoneal tumors. MATERIALS AND METHODS Thirty-four consecutive oncology patients underwent preoperative abdominal and pelvic MRI for tumor staging. MRI included breath-hold DWI with a b value of 400-500 s/mm(2), T1-weighted spoiled gradient-echo, T2-weighted fast spin-echo, and 0- and 5-minute delayed gadolinium-enhanced imaging. At three separate sessions, two observers independently reviewed images for peritoneal tumors at 16 anatomic sites. First DWI alone was reviewed, followed by conventional MRI alone, and then conventional MRI, including DWI, was reviewed. Results of laparotomy and histopathologic evaluation were compared with MRI results. Sensitivity, specificity, and accuracy were calculated for DWI, conventional MRI, and combined DWI and conventional MRI for peritoneal tumor depiction. RESULTS Two-hundred fifty-five sites of peritoneal tumor were proven by surgical and histopathologic findings. The combination of DWI and conventional MRI was most sensitive and accurate for peritoneal tumors, depicting 230 and 214 tumor sites for the two observers (sensitivity, 0.90, 0.84; and accuracy, 0.91, 0.88) compared with DWI alone, which depicted 182 and 182 tumor sites with sensitivity (0.71, 0.71; and accuracy, 0.81, 0.81), and conventional MRI alone, which depicted 185 and 132 tumor sites (sensitivity, 0.73, 0.52; and accuracy, 0.81, 0.72). Peritoneal tumor showed restricted diffusion on DWI and ascites was of low signal intensity, increasing tumor conspicuity. CONCLUSION Adding DWI to routine MRI improves the sensitivity and specificity for depicting peritoneal metastases. Breath-hold DWI is now routinely used in all oncology patients referred for abdominal MRI at our institution.

Extrahepatic abdominal imaging in patients with malignancy: Comparison of MR imaging and helical CT in 164 patients

The purpose of this study was to compare the performance of magnetic resonance (MR) imaging using currently available techniques with contrast‐enhanced single‐phase helical computed tomography (CT) in depicting extrahepatic disease in patients with malignancy. At two institutions, 164 patients with known or suspected malignancy underwent abdominal imaging with contrast‐enhanced helical CT and MR imaging. The prospective interpretations of the CT scans and MR examinations were used to assess the sensitivity of each imaging test in detecting benign and malignant extrahepatic disease at 17 anatomic sites. Imaging findings were compared with results of surgery in 57 patients and with the combined results of image‐guided biopsy, follow‐up cross‐sectional imaging studies, other concurrent imaging tests, and clinical follow‐up. For the 164 patients, helical CT scans depicted 221 of 316 (70%) sites of proven extrahepatic tumor compared with 288 sites (91%) (P < 0.0001) for MR imaging. For the 57 patients who underwent exploratory laparotomy, helical CT scans depicted 101 of 154 (66%) findings of surgically confirmed extrahepatic tumor compared with MR imaging, which depicted 139 sites (90%) (P < 0.0001). Anatomic sites at which MR imaging showed a significantly greater detection of extrahepatic tumor included the peritoneum, bowel, and vascular and osseous structures. For depiction of benign extrahepatic disease, there was no significant difference between helical CT and MR imaging. MR imaging, using currently available T1‐weighted, RARE T2‐weighted, and gadolinium‐enhanced imaging, is effective in depicting extrahepatic disease in patients with malignancy. Compared with single‐phase helical CT scanning, MR imaging shows an advantage in depicting tumor involving the peritoneum, omentum, bowel, and osseous and vascular structures. J. Magn. Reson. Imaging 2000;12:269–277.

MR staging of primary colorectal carcinoma: comparison with surgical and histopathologic findings.

AbstractBackground: We retrospectively evaluated the accuracy of magnetic resonance (MR) imaging in staging colorectal cancer and assessing local tumor extent, nodal involvement, and distant abdominal and pelvic metastases. Methods: Forty-eight patients with primary colorectal carcinoma were referred for presurgical abdominal and pelvic MR imaging. MR imaging included T1-weighted, fat-suppressed T2-weighted, and fat-suppressed gadolinium-enhanced spin gradient-echo imaging. The prospective interpretations of the MR examinations were reviewed. MR depiction of local tumor extent, nodal involvement, and distant metastases at 18 anatomic locations was noted and compared with subsequent surgical and histopathologic findings. Results: Overall TNM MR staging agreed with surgical and pathologic staging in 41 (85%) of 48 patients, including 21 (78%) of 27 colon cancers and 20 (95%) of 21 rectal cancers. For depth of tumor penetration, which was evaluable in 44 patients, MR imaging agreed with pathologic results in 38 (86%) of 44 patients, including 22 (88%) of 25 colon cancers and 16 (84%) of 19 rectal cancers. In 42 (95%) of 44 patients, MR images correctly distinguished tumor confined to the bowel wall (T0, T1, and T2) from tumor with transmural tumor extension (T3 and T4). Regional nodal metastases were depicted in 15 of 22 patients (sensitivity, 68%; accuracy, 83%). Nodal metastases were better depicted for rectal cancer in eight of nine patients, compared with colon cancer in seven of 13 patients. Distant metastases were correctly depicted on MR imaging in 13 of 14 patients (sensitivity, 93%; accuracy, 98%). In the site-by-site analysis, MR imaging prospectively depicted 66 of 77 sites of surgically confirmed metastatic tumor in the abdomen and pelvis (sensitivity, 86%; specificity, 99%; accuracy, 98%). Conclusion: MR imaging using currently available techniques can effectively image local tumor extent and distant metastases in patients with colorectal carcinoma. Especially for colon cancer, incomplete depiction of nodal metastases in normal-size lymph nodes remains a limitation of cross-sectional imaging studies.

Fast spin-echo triple echo dixon: Initial clinical experience with a novel pulse sequence for simultaneous fat-suppressed and nonfat-suppressed T2-weighted spine magnetic resonance imaging

To evaluate a prototype fast spin‐echo (FSE) triple‐echo Dixon (FTED) technique for T2‐weighted spine imaging with and without fat suppression compared to conventional T2‐weighted fast recovery (FR) FSE and short‐tau inversion recovery (STIR) imaging.

Dynamic Gadolinium-Enhanced Perfusion MRI of Prostate Cancer: Assessment of Response to Hypofractionated Robotic Stereotactic Body Radiation Therapy

OBJECTIVE The purpose of this study was to evaluate the utility of dynamic gadolinium-enhanced perfusion MRI for monitoring the response to robotic stereotactic body radiation therapy for prostate cancer. MATERIALS AND METHODS Eighty-seven patients with prostate cancer underwent dynamic gadolinium-enhanced MRI before robotic stereotactic body radiation therapy, and prostate volume was calculated. Pharmacokinetic analysis postprocessing software was used to generate colorized parametric maps showing perfusion of enhancing tumors. The transfer constant K(trans) was calculated for identified tumors. Follow-up MRI was performed 2 months after treatment for 22 patients, 6 months for 71 patients, 12 months for 54 patients, and 24 months for 27 patients with repeated measurements of prostate volume and K(trans). RESULTS Perfusion MRI depicted focal enhancing prostate tumors that correlated with the biopsy results in 82 of 87 patients (94%). The median K(trans) of tumors before robotic stereotactic body radiation therapy was 1.79 minutes(-1). Follow-up MRI showed decreases in the size and degree of enhancement of tumors. The median tumor K(trans) decreased to 1.21 minutes(-1) 2 months, 0.39 minutes(-1) 6 months, 0.30 minutes(-1) 12 months, and 0.22 minutes(-1) 24 months after treatment. Prostate volume had decreased 23% 2 months, 26% 6 months, 33% 12 months, and 37% 24 months after robotic stereotactic body radiation therapy. The corresponding median prostate-specific antigen concentration before treatment was 6.45 ng/mL. After treatment, the concentration was 2.90 ng/mL at 2 months, 1.30 ng/mL at 6 months, 1.10 ng/mL at 12 months, and 0.59 ng/mL at 24 months. CONCLUSION Dynamic gadolinium-enhanced MRI is a useful tool for monitoring the response of prostate cancer to robotic stereotactic body radiation therapy, yielding both qualitative and quantitative data.

Fast spin‐echo triple‐echo Dixon: Initial clinical experience with a novel pulse sequence for fat‐suppressed T2‐weighted abdominal MR imaging

To evaluate a prototype fast spin echo (FSE) triple‐echo‐Dixon (fTED) technique for breath‐hold, fat‐suppressed, T2‐weighted abdominal imaging.

High-Resolution Double Arterial Phase Hepatic MRI Using Adaptive 2D Centric View Ordering: Initial Clinical Experience

OBJECTIVE The objective of our study was to evaluate a new 3D fast spoiled gradient-recalled echo (FSPGR) sequence referred to as modified liver acceleration volume acquisition (LAVA) for high-resolution gadolinium-enhanced dual arterial phase liver MRI and to determine the effect of this technique on the timing of the contrast bolus and lesion detection. MATERIALS AND METHODS Gadolinium-enhanced dual arterial phase liver MRI was performed in 109 patients using a modified LAVA sequence that supports adaptive 2D centric view ordering, efficient 2D autocalibrated acceleration, and partial-Fourier to achieve faster scan times while maintaining the same slice thickness, resolution, and coverage as single-phase imaging. After a fixed 20-second scan delay, a modified LAVA acquisition required a single 24- to 26-second breath-hold for two arterial phases with 56-60 slices per pass. Images were reviewed for timing relative to liver enhancement, lesion conspicuity, and lesion detection. Liver lesion depiction was evaluated qualitatively and quantitatively. A control group of 109 patients underwent imaging using a single arterial phase 3D FSPGR sequence, which was also performed with a fixed 20-second scan delay. RESULTS The single arterial phase images produced optimal timing in the middle or late arterial phase in 79 (72%) of the 109 control group patients compared with 99 (91%) of the 109 study group patients who underwent imaging using a dynamic modified LAVA dual arterial phase sequence. For the modified LAVA sequence, the first-pass images were obtained during the mid arterial phase in 34 patients (31%). The second-pass images were obtained during the mid arterial phase in 51 patients (47%) and late arterial phase in 26 patients (24%). Sixty-two patients had liver lesions showing greater conspicuity--on the first phase in 17 patients (27%) and second phase in 45 patients (73%). Hypovascular lesions were more conspicuous on second-phase images in 24 (86%) of 28 patients. Hypervascular lesions were more conspicuous on first-phase images in 13 patients (38%) and on second-phase images in 21 (62%) of 34 patients. The first-phase images detected 165 and 155 liver lesions, respectively, for two observers compared with 233 and 224 lesions on the second-phase images, whereas the combined dual arterial phase images detected 256 and 248 hepatic lesions. CONCLUSION High-resolution dual arterial phase 3D FSPGR MRI improves the timing of the arterial phase of liver enhancement and provides additional information for liver lesion detection.

A flexible fast spin echo triple-echo Dixon technique

To develop a flexible fast spin echo (FSE) triple‐echo Dixon (FTED) technique.