ABDOMINAL DIFFUSION WEIGHTED MR

ABDOMINAL DIFFUSION WEIGHTED MR Frank Miller, M.D. FACR Professor of Radiology Chief, Body Imaging Section Medical Director, MR Imaging Northwestern University Feinberg School of Medicine fmiller@northwestern.edu

DISCLOSURES No disclosures related to presentation

OBJECTIVES Demonstrate utility of DWI in abdomen Show advantages and limitations of DWI

ORGANS Liver Pancreas Adrenal Kidney Lymph nodes/peritoneum Problem-based approach and not able to cover nearly everything

DIFFUSION WEIGHTED IMAGING Used in neuroimaging for many years Used routinely in our body MR imaging practice Recommend starting DWI for abdominal applications if not already doing it Need to recognize the strengths and limitations

DIFFUSION WEIGHTED IMAGING Does not require contrast helpful when renal dysfunction and concern of NSF or allergy Relatively quick to perform Provides functional information in addition to anatomic Improved lesion conspicuity-better than T2 Best sequence for lymph node detection Some HCC (especially infiltrative lesions) and metastases better seen on DWI than on contrast-enhanced MR

IMPROVED CONSPICUITY: LIVER PECOMA b50 b500 ADC T1WI post

SOMETIMES LESS CONSPICUOUS HCC Arterial phase Delayed b500 ADC

DWI Normal cells have water mobility differences Theory-tumors less water mobility and therefore restricted diffusion: lower ADC Apparent diffusion coefficient (ADC): measure of diffusion which removes the T2 effects lesion which is bright on DWI may relate to T2 shine through and are bright on ADC map unlike true diffusion which is dark on ADC

WHICH B VALUE SHOULD YOU USE? b value-strength of diffusion sensitizing gradient No consensus on b values for abdomen-probably best between 0 and 1000 s/mm 2 At least 2 b values if calculating ADC We use 50, 400/500 and 800 s/mm 2

LOW B VALUE IMAGES 50-100 SEC/MM 2 Low b value: less diffusion gradient but higher SNR Signal loss in highly mobile water molecules (e.g. vessels): black blood images b>50 to minimize capillary perfusion b50

High b value IMAGES Higher b values-more diffusion component but when too high have lower signal to noise Highly cellular tissues such as tumors-water is restricted Additional b values for research or more accurate ADC b1000

Log (Relative SI) ADC MAP b50 b500 Slope of line represents ADC: relative signal intensity on y axis and b value on x axis b1000 ADC = log(s 0 / S 1 ) / (b 1 - b 0 ) b-values (s/mm 2 )

DIFFUSION MR Theory: malignant lesions have restricted diffusion and are bright while benign lesions do not although in practice not always true Diffusion MR only adds few minutes in total

T1 FS POST GAD T2

T1 FS POST GAD Better than T2 b500 Diffusion

T1 FS POST GAD Restricted ADC

PHYSIOLOGIC RESTRICTED DIFFUSION Impeded water diffusion from high cellularity Spleen Adrenal Lymph nodes Kidneys Testes Penis Hematopoietic bone marrow

DWI OF KIDNEY, ADRENAL AND SPLEEN Ciliated hepatic foregut cyst LA S LA S LA S LK LK LK B50 B500 B800 LA = left adrenal LK = left kidney S = spleen ADC

IMPROVED CONSPICUITY: UNKNOWN PRIMARY HASTE T2 T1 post B500 ADC

QUALITATIVE AND QUANTITATIVE EVALUATION OF DWI Qualitative-observe visually based on DWI and ADC map use routinely more than quantitatively High signal on high b value images (dark ADC map) suggest restricted diffusion generally from greater cellularity and integrity of cell membranes Tumor with necrosis, hypocellular or cystic tumors restrict less

DIFFUSION MRI-LIVER We use DWI routinely in all liver MR cases Helpful in detection of hepatic lesions similar to bone scan or PET scan detect additional lesions directs to re-review the conventional imaging to identify lesions Helpful but has limitations in characterization of hepatic lesions can confirm true lesion and not pseudolesion

CARCINOID METASTASES AND LIVER CYST ARTERIAL PHASE VENOUS PHASE

CARCINOID METASTASES AND LIVER CYST Metastases bright on DWI (and dark on ADC) from restricted diffusion and cyst is darker (bright on ADC) b500 ADC mets cyst cyst

METASTATIC MELANOMA WITH PRIOR THERAPY T1 FS CE T1 FS CE T1 FS CE T1 FS

METASTATIC MELANOMA WITH PRIOR THERAPY DWI b500 DWI b500 DWI b500 CE T1 FS

LESION CHARACTERIZATION Especially helpful for cysts and hemangiomas which may have free water Limitations in distinguishing solid benign lesions (FNH and adenomas) from malignant lesions (HCC and mets) Restricted diffusion not only seen in tumors but also abscesses restricted diffusion distinguish from simple cysts

T2 SHINE THROUGH EFFECT Pitfall-signal intensity on DWI depends on both water diffusion and T2 relaxation time Lesions with long T2 relaxation times (cysts, hemangiomas) may remain high signal on DWI and be mistaken for restricted diffusion Referred to as T2 shine-through

T2 SHINE THROUGH EFFECT IN CYST To avoid misinterpretation, should look at the high b value images and ADC map Lesions that are high signal on high b value images and ADC are from T2 shine through effect b0 b500 ADC = 4.4

WHY NOT JUST LOOK AT THE ADC IMAGES? Poor signal to noise ratio Use DWI to detect Use ADC map image to differentiate restricted diffusion from T2 shine through ADC

WHY NOT JUST LOOK AT THE ADC IMAGES? Poor signal to noise ratio Use DWI to detect Use ADC map image to differentiate restricted diffusion from T2 shine through ADC DWI

WHY NOT JUST LOOK AT THE ADC IMAGES? Poor signal to noise ratio Use DWI to detect Use ADC map image to differentiate restricted diffusion from T2 shine through ADC DWI

GIST: NONSPECIFIC LIVER LESION

RENAL DISEASE COULD NOT RECEIVE GADOLINIUM

RESTRICTED DIFFUSION b500 ADC

T2

b500 ADC

T2 T1 FS Post GAD T1 FS T2 FS DWI b50 b800 ADC b500 ADC 32 YEAR OLD WITH MELANOMA AND UNSUSPECTED LIVER LESIONS

1 YEAR LATER: LESIONS LARGER AND NEW LESIONS WITH MORE DEFINITIVE FEATURES POST GAD b50 b500 Art Phase Venous Phase B50 New Lesion Art Phase Delayed Phase Washout

HEPATOCELLULAR CARCINOMA POST GAD T1 FS T2 b500 ADC ADC = 1.6

RESTRICTED DIFFUSION LOW ADC = 1.26 b500 ADC MALIGNANT? FNH

FNH: NEED ANATOMIC IMAGES IN ADDITION TO DWI T1 FS ARTERIAL PHASE POST GAD T2 DELAYED POST GAD

ABSCESSES Not only tumors have restricted diffusion and low ADC Abscesses can have restricted diffusion DWI help distinguish abscesses from cysts b400 ADC

LIVER CYST VS. LIVER ABSCESS T2 T1 post contrast T2 T1 post contrast

LIVER CYST VS. LIVER ABSCESS T2 T1 post contrast b1000 T2 T1 post contrast b1000 ADC

ADC (x10-3 mm 2 /s) ADC OF LIVER LESIONS BOX AND WHISKERS PLOT 5.5 4.5 5 3.5 4 2.5 3 1.5 2 0.5 1 0 Metastasis HCC FNH Adenoma Abscess Hemangioma Cyst Miller FH, Hammond N, Siddiqi AJ et al. J Magn Reson Imaging. 2010 Jul;32:138-47

LACK OF SPECIFICITY Hemangioma Metastases HCC Adenoma

INTERPRETATION OF IMAGES AFTER IR TREATMENT Among the most difficult in radiology No one fights to read these cases Paradoxical increase in size is seen with ablative therapies such as RF ablation, TACE and Y90 radioembolization-result of hemorrhage and necrosis No uniform standard of interpretation Ring enhancement mistaken for tumor and may be post treatment changes including scar tissue or reactive edema

DIFFUSION MR Lesions often don t change in size or may grow following effective changes Diffusion MR can play role in diagnosing response Following therapy, tumors with restricted diffusion (dark on ADC maps) become less restricted diffusion (bright on ADC maps) increase in ADC values Some of changes in ADC may precede changes in size of lesion

LIMITATIONS OF ANATOMIC ASSESSMENT Anatomic response lags behind functional changes Difficult to prospectively predict tumor response Pre Tx 610 15 3 months Salem et al JVIR Dec 2005

FUNCTIONAL IMAGING: DIFFUSION Anatomic T1 post-gadolinium Functional Percentage enhancement on arterial and portal venous phases Extracellular space Tumor vascularity Detects altered water mobility Cellularity Integrity of the cell membrane Diffusion-weighted (DWI)

DIFFUSION: OVERSIMPLIFICATION Bright on diffusion images (dark ADC)-restricted diffusion-live tumor Dark on diffusion images-favorable response Successful treatment-dark on DWI and shows increase in ADC

HCC PRETREATMENT Bright

HCC POST TREATMENT Dark Post contrast Post Treatment DWI Post Treatment Post Treatment DWI Pretreatment

Pre-Treatment Arterial Phase Venous Phase DWI b50 Post-Treatment Arterial Phase Venous Phase DWI b50

T1 in Phase T2 Post GAD T1 FS

DWI PET

PANCREATIC IMAGING DWI may help in detecting solid pancreatic neoplasms with restricted diffusion May not be able to distinguish chronic pancreatitis from cancer because of overlap i.e. poorly differentiated adenoca and mass-forming pancreatitis have low ADC from dense fibrosis

PANCREATIC CANCER Critical to detect early Desmoplastic reaction accounts for low SI on T1FS images, hypoenhancement and restricted diffusion DWI especially helpful in detection and characterization of liver and lymph node and peritoneal mets

DIFFUSION EXAMPLE PANC CA T2 MR T1 FS MR CE T1 FS MR

DIFFUSION EXAMPLE PANC CA DIFFUSION B500 ADC

DIFFUSION EXAMPLE: ENDOCRINE TUMOR BEST SEEN ON DW NCCT Early Post Contrast Venous Post Contrast

ENDOCRINE TUMOR: DWI b0 b500 T1 FS CE CT

INSULINOMA

b0 b1000 ADC

BACKGROUND Pancreatic adenocarcinoma and mass-forming focal pancreatitis can have similar imaging findings on anatomic MRI Would be helpful for DWI to distinguish Contradictory results have been seen using DWI in the literature and wanted to determine why ADC values of pancreatic adenocarcinoma have been shown to be both higher and lower than mass-forming focal pancreatitis Fattahi et al. J Magn Reson Imaging 2009;29:350-6 Lee et al J Magn Reson Imaging 2008;28:928-36

MAY NOT BE ABLE TO DISTINGUISH Mass-forming pancreatitis b500 (ADC = 1.27) Adenocarcinoma b500 (ADC = 1.55)

EXTRACELLULAR FIBROSIS Mass-forming pancreatitis b500 (ADC=1.27) Poorly differentiated adenocarcinoma b500 (ADC =1.55) Extra-cellular fibrosis in both pancreatitis and adenocarcinoma No significant difference in ADC Wang Y, Miller FH, Chen Zongming E et al. Radiographics. 2011

ADC (x10-3 mm 2 /s) RESULTS: ADCs OF LESION AFTER SUBDIVISION 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Neuroendocrine Carcinoma (malignant) P=0.001 0.98 1.77 1.33 1.53 2.32 Well-differentiated Neuroendocrine Tumor (nonmalignant) Mass-forming focal Pancreatitis Poorly differentiated Adenocarcinoma Well/Moderately differentiated Adenocarcinoma

MALIGNANT ENDOCRINE: LOWER ADC VALUES Malignant endocrine carcinoma ADC=0.87 Well-differentiated endocrine tumor ADC= 2.22 High density of cellularity Cells with scant cytoplasm Lower ADC values

OVERLAP ONLY IN SMALL WELL DIFFERENTIATED WITH FIBROSIS Malignant endocrine carcinoma ADC=1.17 Well-differentiated endocrine tumor ADC= 1.02 High density of cellularity High density of fibrosis Low ADC values

ADC (x10-3 mm 2 /s) RESULTS: ADCs OF LESION AFTER SUBDIVISION 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Neuroendocrine Carcinoma (malignant) Well-differentiated Neuroendocrine Tumor (nonmalignant) Mass-forming focal Pancreatitis P=0.02 0.98 1.77 1.33 1.53 2.32 Poorly differentiated Adenocarcinoma Well/Moderately differentiated Adenocarcinoma

POOR DIFFERENTIATED TUMORS WITH MORE FIBROSIS: LOWER ADC Poorly differentiated adenoca ADC=1.48 Moderately differentiated adenoca ADC=2.27 Extra-cellular fibrosis Limited glandular formation Lower ADC values Wang Y, Miller FH, Chen Zongming E et al. Radiographics. 2011

DWI DWI did not distinguish mass-forming pancreatitis and adenocarcinoma fibrosis in both Grades of differentiation of tumors may be distinguished because of differences in cellularity, glandular differentiation and extracellular fibrosis

b500 ADC

RENAL IMAGING Especially helpful when concern of NSF and cannot give gadolinium Helps detect and confirm solid mass-suspect RCC Other lesions can have restricted diffusion-abscesses, angiomyolipomas, oncocytomas DWI images help guide to the anatomic abnormality which may be subtle

UNSUSPECTED SMALL RCC b800 ADC

NCCT Axial CECT Coronal CECT Axial Postgad Coronal Postgad b500 ADC

PCKD IN HORSESHOE KIDNEY WITH FEVERS; COULDN T GIVE GAD AS CONCERN OF NSF-LOW GFR Coronal T2 Coronal T2

Axial T2 b800

ADC Map CT Guided Biopsy

51 YR OLD MYELODYSPLASTIC SYNDROME AND FEVERS T1 FS T2

Post GAD T1 FS T2 Post GAD Sag T1 FS

RESTRICTED DIFFUSION: DARK ADC b800 ADC

DWI BETTER THAN T2

PYONEPHROSIS 64 year old male with rectal cancer: Worsening renal function Could not give GAD UNENHANCED CT T2WI DWI b500 ADC

ADRENAL GLAND Most important lesions to distinguish are not cystic from solid lesions but adrenal adenomas from metastases or adrenal cell carcinoma DWI is nonspecific; need very high specificity in the diagnosis of adenomas While malignant adrenal masses show restricted diffusion, adrenal adenomas also may show restricted diffusion

CARCINOMA: ADC 0.99 B500 B0 ADC Mean of carcinomas was 1.47 without difference from other lesions except cysts being higher.

ADENOMA: ADC 0.64 / SI DECREASE 46% IN PHASE OUT PHASE b500 b0

ADC (x10-3 mm 2 /s) ADCS OF ADRENAL LESIONS 5.50 5.00 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 Myelolipoma 1.16 1.75 1.60 2.93 1.55 1.84 1.64 Hemorrhage Adenoma Cyst Carcinoma Pheochromocytoma Metastasis Miller FH, Wang Y, McCarthy RJ, et al. Am. J. Roentgenol 2010; 194: W179-W185

1.0 0.8 0.6 0.4 0.2 Signal intensity (% Decrease), AUC = 0.93 Lesion size (cm), AUC = 0.82 ADC (x10-3 mm2/sec), AUC = 0.55 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1 - Specificity Miller FH, Wang Y, McCarthy RJ, et al. Am. J. Roentgenol 2010; 194: W179-W185

LYMPH NODE AND PERITONEAL IMPLANTS One of best uses for DWI-lymph node metastases and small peritoneal implants Conventional MR is not always ideal for showing lymph nodes and peritoneal implants-distinguishing from bowel can be difficult DWI helps direct radiologist to pathology on conventional imaging

LYMPH NODE AND PERITONEAL IMPLANTS In my opinion, DWI often does not distinguish benign from malignant lymph nodes but great sequence to show nodes Increasing use of MR because of radiation concerns when doing multiple CT scans for followup imaging especially when young patients (testicular cancer and lymphoma) where lymph nodes and DWI are important

TESTICULAR CANCER RECURRENCE: LYMPH NODES T2 T1 FS Diffusion b1000 b1000

TESTICULAR CANCER WITH RECURRENCE BEST SEEN ON B800 b50 b500

FALLOPIAN TUBE CANCER T1 FS T2 DWI b1000

FALLOPIAN TUBE CANCER T1 FS DWI b1000

VULVAR CANCER: DWI CRITICAL FOR METS Sag Post GAD T1 FS Axial Post GAD T1 FS

VULVAR CANCER: DWI CRITICAL FOR METS Axial Post GAD T1 FS DWI b500 Sag Post GAD T1 FS

VULVAR CANCER: DWI CRITICAL FOR METS Axial Post GAD T1 FS DWI b500

APPENDICITIS IN PREGNANT PT T2 True FISP T1 FS

APPENDICITIS IN PREGNANT PT T2 True FISP T1 FS b800 ADC

TUBO-OVARIAN ABSCESSES (TOA) T2 T1FS POSTGAD T1FS

TUBO-OVARIAN ABSCESSES (TOA) T2 T1FS POSTGAD T1FS DWI b800 ADC

28 YEAR OLD PELVIC PAIN AND FEVER T2 T1 FS Post GAD T1 FS T1 FS Post GAD

DWI-TUBOOVARIAN ABSCESS (TOA) DWI b800 ADC

INTER-LOOP ABSCESS: 73 YEAR OLD W RECTAL CANCER PRIOR RT AND FEVER AND PAIN T2 T1 post gad DWI b800 ADC

MR TO EVALUATE LIVER LESIONS

60 YEAR OLD WOMAN: FOLLOW UP COMPLEX RENAL CYST JULY 2014 T1 Post Gad CECT b500 ADC

AUG 2013 T1 Post Gad b800 Fungating, ulcerated partially obstructing adenocarcinoma in the distal transverse colon

MR FOR FIBROID EVALUATION PRE UFE Sagittal T2 Axial T2

DIFFUSION-WEIGHTED IMAGES b500

UNSUSPECTED RECTAL CANCER Sagittal T2 Axial T2

UNSUSPECTED RECTAL CANCER Sagittal Post Contrast Axial Post Contrast

T2 Post GAD T1 FS

BOTH ARE BRIGHT ON B50 IMAGE b50

B800 INFECTED BARTHOLIN GLAND CYST ADC

CONCLUSIONS DWI should be added to routine protocols Helpful in detection of lesions in liver, kidney, pancreas, lymph nodes and peritoneal implants Can be helpful in characterization Solid from cystic masses Abscesses from simple cysts Assess therapy response prior to size changes

ACKNOWLEDGEMENTS Dr. Shawn Haji-Momenian Dr. Laura Kulik Dr. Andrew Larson Dr. Robert J Lewandowski Dr. Reed Omary Dr. Tom Rhee Dr. Riad Salem Dr. Yi Wang