MRI Atlas of the Abdomen (a self-guided tutorial) Jeff Velez HMS3 Eric Chiang, MD Gillian Lieberman, MD.

MRI Atlas of the Abdomen (a self-guided tutorial) Jeff Velez HMS3 Eric Chiang, MD Gillian Lieberman, MD

2 Goals The purpose of this atlas is to provide students with; an outline of the anatomy of the abdomen via MR imaging. an outline of the anatomy of the abdomen via MR imaging. an introduction to how an MR image is created. an introduction to how an MR image is created. a basic understanding of how the manipulation of various parameters (TR,TE, pulse sequence) of an MR scan yield desired tissue differentiation. a basic understanding of how the manipulation of various parameters (TR,TE, pulse sequence) of an MR scan yield desired tissue differentiation. a list of some basic sequences used in abdominal MR. a list of some basic sequences used in abdominal MR. By coupling this review of how an MR image is created and manipulated with a thorough tour of abdominal anatomy seen through MRI, this tutorial can serve as an instructive tool in preparing students for their likely future clinical encounters with abdominal MRI in evaluating and managing abdominal disease.

3 Introduction Magnetic resonance (MR) imaging has been in widespread clinical use for well over a decade. Its use was primarily localized to the evaluation of the central nervous system and then more recently, the musculoskeletal system. Motion during the cardiac cycle, respiration, and peristalsis made MR imaging of the thorax and abdomen a major challenge. MR imaging of the abdomen started with the evaluation of solid visceral organs such as the liver and kidney. With technologic developments in MR hardware and software occurring at a swift and steady pace, MR imaging of the abdomen is beginning to expand beyond the solid viscera into the entire abdomen, including the hollow viscus of the GI tract.

4 Basics of MRI In order to read and understand an MR image, one must gain a basic understanding of the principles underlying its production. In order to read and understand an MR image, one must gain a basic understanding of the principles underlying its production. MR imaging is based on the naturally occurring magnetic moment that exists within the nuclei of a hydrogen atom, as well as its ubiquitous presence in organic tissue. When an external magnetic field is applied to organic tissue, protons within hydrogen nuclei align themselves in parallel with this field and also begin to resonate. When a radiofrequency (RF) pulse is applied to these aligned protons, it provides enough energy to dislodge (or excite) them from this orientation. However, this is a temporary phenomenon, and the nuclei relax back into realignment with the external magnetic field. Upon relaxation, energy is released in the form of RF waves. This “echo” is detected and a signal of variable intensity for a given location is produced. MR imaging is based on the naturally occurring magnetic moment that exists within the nuclei of a hydrogen atom, as well as its ubiquitous presence in organic tissue. When an external magnetic field is applied to organic tissue, protons within hydrogen nuclei align themselves in parallel with this field and also begin to resonate. When a radiofrequency (RF) pulse is applied to these aligned protons, it provides enough energy to dislodge (or excite) them from this orientation. However, this is a temporary phenomenon, and the nuclei relax back into realignment with the external magnetic field. Upon relaxation, energy is released in the form of RF waves. This “echo” is detected and a signal of variable intensity for a given location is produced. Tissue contrast is created because different tissues have different relaxation times. This is attributable to the different microenvironments surrounding the magnetized nuclei. Tissue contrast is created because different tissues have different relaxation times. This is attributable to the different microenvironments surrounding the magnetized nuclei.

5 4 Key Parameters of MRI T1 T1 T2 T2 Echo Time (TE) Echo Time (TE) Repetition Time (TR) Repetition Time (TR) The relaxation times of protons shifting from a higher to lower energy level, are referred to as T1 and T2 and are tissue specific. The relaxation times of protons shifting from a higher to lower energy level, are referred to as T1 and T2 and are tissue specific. The TE and TR are variables that can be controlled by an MR scanner operator. The TE and TR are variables that can be controlled by an MR scanner operator.

6 T1 and T2 T1 and T2 represent relaxation time constants. T1 and T2 represent relaxation time constants. Each tissue has a specific, inherent T1 and T2 value. Each tissue has a specific, inherent T1 and T2 value. For example: fat has a short T1 and T2, whereas fluid has a long T1 and T2. For example: fat has a short T1 and T2, whereas fluid has a long T1 and T2. These values are measured in milliseconds. These values are measured in milliseconds. T1 – the time it takes nuclei in a particular tissue that has been excited or “dislodged” from its parallel orientation to return to its nonexcited state. (The time when about 63% of the original longitudinal magnetization is reached). T1 – the time it takes nuclei in a particular tissue that has been excited or “dislodged” from its parallel orientation to return to its nonexcited state. (The time when about 63% of the original longitudinal magnetization is reached). T2 – the time it takes nuclei in a particular tissue that has been excited into a (phase coherent) transverse or perpendicular orientation to return to its non excited (non phase coherent) state. (The time when transverse magnitization decreases to 37% of the original value). T2 – the time it takes nuclei in a particular tissue that has been excited into a (phase coherent) transverse or perpendicular orientation to return to its non excited (non phase coherent) state. (The time when transverse magnitization decreases to 37% of the original value).

7 TR and TE These are two major parameters that can be adjusted (unlike T1 and T2) to create the desired tissue differentiation. These are two major parameters that can be adjusted (unlike T1 and T2) to create the desired tissue differentiation. When an MR image is taken, it begins with a magnetic field being established that is parallel with the bore of the scanner. This field has a strength on the order of 1-2 Teslas, depending on the scanner. Once this is established, and protons have aligned with the field, a sequence of radiofrequency (RF) pulses are administered. This excites the protons to a higher energy level. This is then followed by relaxation back into a low energy state. This relaxation time is constant (T1 and T2). What can be changed however is the repetition time (TR) or time between administered RF pulses. What also can be manipulated is the time that the RF “echo” is received by the RF detector. This time is referred to as TE, or echo time. When an MR image is taken, it begins with a magnetic field being established that is parallel with the bore of the scanner. This field has a strength on the order of 1-2 Teslas, depending on the scanner. Once this is established, and protons have aligned with the field, a sequence of radiofrequency (RF) pulses are administered. This excites the protons to a higher energy level. This is then followed by relaxation back into a low energy state. This relaxation time is constant (T1 and T2). What can be changed however is the repetition time (TR) or time between administered RF pulses. What also can be manipulated is the time that the RF “echo” is received by the RF detector. This time is referred to as TE, or echo time. By adjusting TE and TR, according to a tissue’s T1 and T2, the various tissues in a region of interest can be differentiated. By adjusting TE and TR, according to a tissue’s T1 and T2, the various tissues in a region of interest can be differentiated.

8 T1 weighted images vs. T2 weighted images The following 2 slides offer graphs to help explain tissue contrast on T1 vs. T2 weighted images. The following 2 slides offer graphs to help explain tissue contrast on T1 vs. T2 weighted images. These graphs are depictions of the signal intensity as function of time for two tissues types (fat and fluid) in an external magnetic field. These graphs are depictions of the signal intensity as function of time for two tissues types (fat and fluid) in an external magnetic field. A helpful way to analyze these graphs is to identify which curve provides the higher signal intensity (red or blue) at the time point indicated by the dashed vertical line (detection time). That point represents the tissue that will appear brighter on the MR image. A helpful way to analyze these graphs is to identify which curve provides the higher signal intensity (red or blue) at the time point indicated by the dashed vertical line (detection time). That point represents the tissue that will appear brighter on the MR image. Keep in mind that the TR and TE (along with the sequence of RF pulses) are what we can manipulate, while T1 and T2 are constant and tissue dependent. They are represented by the degree of line curvature (exponential relationship) on the graphs to follow. Keep in mind that the TR and TE (along with the sequence of RF pulses) are what we can manipulate, while T1 and T2 are constant and tissue dependent. They are represented by the degree of line curvature (exponential relationship) on the graphs to follow.

9 T1 Weighted Image TR Signal Intensity — fat — fluid TR = repetition time TE = echo time TE T1 Weighted Image—short TR and TE Although this is a gross oversimplification, when an image is T1 weighted, this means that the protocol used to scan a patient involves adjusting the TE and TR (shortening their times) in a manner that will cause tissues with fast T1 and T2 relaxation times (e.g. fat) to appear brighter. In this graph fat has a greater signal intensity than fluid. Tissues with short T1 and T2 (fat) will appear brighter than those with longer T1 and T2 (fluid).

10 T2 Weighted Image TR Signal Intensity — fat — fluid TR = repetition time TE = echo time TE T2 Weighted Image—long TR and TE In this graph fluid has a greater signal intensity than fat. Tissues with long T1 and T2 (fluid) will appear brighter than those with short T1 and T2 (fat). On a T2 weighted image the protocol used is one that will result in tissue with long T1 and T2 (fluid) having a higher signal intensity. This is illustrated in the following slides. On a T2 weighted image the protocol used is one that will result in tissue with long T1 and T2 (fluid) having a higher signal intensity. This is illustrated in the following slides. This protocol involves using a TR and TE that are relatively longer than the T1 weighted sequence. This protocol involves using a TR and TE that are relatively longer than the T1 weighted sequence.

11 Beyond T1 and T2—Abdominal MRI Along with the advancements in MR scanner hardware technology, developments in the pulse sequences used have led to the growing role of MRI in abdominal imaging. Along with the advancements in MR scanner hardware technology, developments in the pulse sequences used have led to the growing role of MRI in abdominal imaging. The fundamental principle behind these sequences is to maximize contrast, resolution, speed, and coverage while keeping motion and noise (relative to signal) at a minimum. The fundamental principle behind these sequences is to maximize contrast, resolution, speed, and coverage while keeping motion and noise (relative to signal) at a minimum. A list of commonly used sequences (acronyms provided) that capture abdominal anatomy and pathology include: VIBE, HASTE, STIR, TSE, and GRE sequences. A list of commonly used sequences (acronyms provided) that capture abdominal anatomy and pathology include: VIBE, HASTE, STIR, TSE, and GRE sequences. Although a description of all of these sequences is beyond the scope of this atlas, a brief discussion of the VIBE sequence can provide an introduction to the MR parameters that are manipulated to achieve maximal contrast, resolution, speed, and coverage. Although a description of all of these sequences is beyond the scope of this atlas, a brief discussion of the VIBE sequence can provide an introduction to the MR parameters that are manipulated to achieve maximal contrast, resolution, speed, and coverage.

12 Volumetric Interpolated Breath-hold Examination (VIBE) The VIBE Sequence is T1 based (short TR and TE). It is a complex 3D Fourier transform sequence that allows for fast acquisition time, thus reducing motion artifact and allowing for adequate coverage of the abdomen. In a given amount of time the VIBE sequence can provide better tissue contrast by utilizing a technique known as fat saturation. Given the relatively high resolution and coverage, VIBE sequences can be reconstructed and used for angiographic examinations. The axial, coronal, sagittal, and selected 3D reconstructions of the abdomen to follow were performed using the VIBE sequence.

13 Anatomy of the Abdomen Throughout this atlas, in axial, coronal, sagittal, and oblique 3D planes, we will highlight; Liver Liver Biliary System Biliary System Pancreas Pancreas Spleen Spleen Gastrointestinal Tract Gastrointestinal Tract Kidneys Kidneys Retroperitoneum Retroperitoneum Peritoneum Peritoneum

14 We have used images from 3 different patients: Patient A - 32 year old female Patient A - 32 year old female MR settings: VIBE sequence, MR abdomen Planes: Axial, coronal, and sagittal; coronal MRCP image Patient B - 54 year old female Patient B - 54 year old female MR settings: VIBE sequence, MRA abdomen (focused on celiac/SMA) Planes: Maximum intensity projection (MIP) 3D reconstruction Patient C - 27 year old male Patient C - 27 year old male MR Settings: VIBE sequence, MRA abdomen (focused on renal arteries) Planes: Maximum intensity projection 3D reconstruction

15 Pt A - Axial VIBE Plate 1

17 Pt A - Axial VIBE - Dome of the Liver Liver R. Ventricle L. Ventricle Esophagus Azygos v. Aorta Inferior Vena Cava R. Lower lobe of lung L. Lower lobe of lung Plate 3

23 Pt A - Axial VIBE - Hepatic Veins L. hepatic v. M. hepatic v. R. hepatic v. Inferior vena cava Spleen Hemiazygos v. Aorta Gastroesophageal junction Gastric fundus Azygos v. L. lower lobe of lung L. Lobe of liver (lateral segment) R. lobe of liver (posterior segment) Plate 8 R. lobe of liver (anterior segment) L. Lobe of liver (medial segment)

26 Pt A - Axial VIBE - Hepatic Divisions Plate 10 LLS LMS RPS RAS LLS—Lateral segment of left lobe LMS—Medial segment of left lobe RAS—Anterior segment of right lobe RPS—Posterior segment of right lobe M. hepatic vein R. hepatic vein L. hepatic vein Inferior vena cava The superior aspect of the liver serves as a good reference point when inspecting axial images of the liver. It can be divided into 4 segments based on the alignment of the hepatic veins draining into the inferior vena cava. The dashed line indicates the respective course of the three hepatic veins. These segments can be further divided into superior and inferior segments.

29 Pt A - Axial VIBE - Splenic Hilum Plate 12 Splenic vein Splenic artery Splenic flexure Posterior aspect of stomach Posterior chest wall Tail of pancreas The spleen is an intraperitoneal structure, enclosed by peritoneum except at its hilum where the splenic vessels enter and leave. It can be readily differentiated from the kidney by its location adjacent to the posterolateral chest wall. Important relationships of the spleen include abutment of the posterior aspect of the stomach as well as the tail of the pancreas

32 Pt A - Axial VIBE - Adrenal Gland and Spleen Spleen Ascending lumbar veins Body of pancreas Aorta Inferior vena cava Gastric fundus R. portal vein L. portal vein R. crus of diaphragm L. crus of diaphragm Spinal cord Vertebral body L. adrenal gland Ascending lumbar veins Plate 14 R. adrenal gland

34 Pt A - Axial VIBE - Adrenal Glands Plate 15 This image illustrates the characteristic “inverted Y” appearance of the adrenal glands. The adrenal glands reside on the anteromedial and superior aspect of the kidneys.

37 Pt A - Axial VIBE - Celiac Trunk Celiac TrunkCommon hepatic a. Aorta Hepatic a. fossa Portal vein Inferior vena cava L. adrenal gland Spleen Caudate lobe L. kidney R. kidney Splenic flexure Desc. colon Ligamentum teres Body of Pancreas Gastric body Plate 17

39 Pt A - Axial VIBE Plate 18 Hepatic artery Portal vein Caudate lobe Inferior vena cava R. Adrenal gland (see plates 20-24) A notable anatomic relationship exists at the level of the right adrenal gland that involves a posterior to anterior sequence of structures that line up in a relatively linear fashion. These include, from posterior to anterior—R. adrenal gland, IVC, caudate lobe, portal vein, and hepatic artery.

41 Pt A - Axial VIBE - Body of Pancreas Ligamentum teres L. lobe (medial) L. lobe (lateral) Porta hepatis Portal vein Hepatic artery Inferior vena cava Superior mesenteric artery Splenic vein Gastric body Descending colon Small bowel R. kidney L. kidney Neck of gallbladder Body of pancreas Spleen Aorta Pancreatic duct Plate 19

44 Pt A - Axial VIBE - Origin of SMA Descending colon Neck of gallbladder Body of pancreas L. kidney R. kidney Small bowel Gastric body Splenic vein Inferior vena cava Hepatic artery Neck of pancreas Ligamentum teres Portal vein Superior mesenteric artery Porto-splenic confluence Gastric antrum R. renal vein Aorta Plate 21

46 Pt A - Axial VIBE - Relationships of the Superior Mesenteric Artery Plate 22 Body of pancreas Superior mesenteric artery (SMA) L. Renal vein Aorta Splenic vein This slide shows another important relationship that exists surrounding the SMA. There are four structure to be aware of. These include the body of the pancreas and splenic artery, which pass over the SMA anteriorly. Posteriorly, the duodenum and left renal vein cross behind the SMA. In this particular image, the transverse aspect of the duodenum is out of plane leaving a small distal portion visible. Distal duodenum

49 Pt A - Axial VIBE - Origin of the Renal Arteries L. renal artery Hilum of right kidney Gastric body Gastric antrum Small bowel Body of gallbladder Inferior vena cava Superior mesenteric vein Ligamentum teres fissure Superior mesenteric artery Head of pancreas Hilum of left kidney Hepatic flexure L. renal vein Duodenum (1 st part) Duodenum (2 nd part) Falciform ligament Plate 24

51 Pt A - Axial VIBE - Clinical Relationships of the GallBladder An important clinical relationship exists between the gallbladder and the GI tract. In this image the hepatic flexure lies adjacent and medial to the body of the gallbladder. As the gallbladder ascends its neck abuts the superior and/or descending duodenum (which in this image lies medial to the flexure, see plate 59). In gallstone ileus, a stone from the gallbladder tracks through the wall of the gallbladder and enters the duodenum causing obstruction at the narrow lumen of the ileocecal valve. If the stone forms a fistula with the hepatic flexure, and enters the colon, ileus is unlikely due to the wide colonic lumen. Gallbladder Hepatic flexure Duodenum (descending) Plate 25

54 Pt A - Axial VIBE - Renal Hilum Quadratus lumborum Hilum of right kidney Hilum of left kidney Duodenum (2 st part) Small bowel L. renal vein Body of gallbladder Inferior vena cava Ligamentum teres fissure Head of pancreas Duodenum (3 nd part) R. renal pelvis Renal pelvis fat Transverse colon Deep back muscles Hepatic flexure Psoas muscle Superior mesenteric artery Hepatorenal recess (Morrison’s pouch) Superior mesenteric vein Plate 27

57 Pt A - Axial VIBE - Kidney and Retroperitoneum Plate 29 The kidneys are retroperitoneal structures that reside at the level of T12 to L3, with the right typically being lower than the left due to the presence of the liver. It is encapsulated and housed, along with the adrenal glands, within the perirenal space. This space is surrounded by Gerota’s fascia. The anterior and posterior pararenal space surround Gerota’s fascia with an additional layer of adipose tissue (see slide 74 for a more detailed look at the retroperitoneum). These retroperitoneal locations have clinical relevance when staging for renal cell carcinoma or assessing for renal infection or trauma. In terms of relations, the kidney is well connected, coming into contact (through peri- and pararenal spaces) bilaterally with the adrenals and diaphragm superiorly and the quadratus lumborum and psoas muscles inferomedially. On the right side the kidney is adjacent to the liver, duodenum, and ascending colon. On the left side the kidney is in contact with spleen, stomach, pancreas, jejunum, and descending colon. Posterior pararenal space Perirenal space Kidney Perirenal space Anterior pararenal space

59 Pt A - Axial VIBE - Hepatic Flexure Transverse colon Deep back muscles Ureter Hepatic flexure Quadratus lumborum Psoas muscle Superior mesenteric artery Small bowel Superior mesenteric vein Fundus of gallbladder Anterior pararenal space* Posterior pararenal space* Perirenal space* Lumbar vessels Inferior vena cava Aorta Flank stripe* Duodenum * Marked structures of retroperitoneum will be discussed in the following slide. Plate 30

60 A Simplified Overview of the Retroperitoneal Spaces Gastric body Spleen Liver Inferior vena cava Anterior Pararenal space Posterior Pararenal space Perirenal space Pancreas Flank stripe Right kidney Left kidney Transversalis fascia Gerota’s fascia

64 Pt A - Axial VIBE - Lower Poles of Kidneys Transverse colon Quadratus lumborum Psoas muscle Small bowel Inferior vena cava Fundus of gall bladder Aorta L. ureter Erector spinae Liver R. ureter Plate 33

72 Pt A - Coronal Plane - VIBE Reformatted Plate 41

74 Pt A - Coronal Plane - VIBE Reformatted Gallbladder Hepatic flexure Gastric body Liver Gallbladder Diaphragm Ligamentum teres R. ventricle Small bowel Falciform ligament Transverse colon Plate 42

77 Pt A - Coronal Plane - VIBE Reformatted Transverse Colon Hepatic flexure Gastric body Gastric antrum Splenic flexure Diaphragm L. ventricle R. ventricle Small bowel Portal vein Transverse colon R. lobe of liver Fundus of gallbladder L. lobe of liver Gastric fundus Plate 44

80 Pt A - Coronal Plane - VIBE Reformatted Pancreas and Splenic and Superior Mesenteric Vein Neck of pancreas Body of pancreas Superior mesenteric vein The pancreas is a retroperitoneal structure that has many close anatomic relations. One such relation occurs posterior to the neck of the pancreas, and involves the union of the splenic vein and superior mesenteric vein (SMV) to form the portal vein. This image is in the plane of the pancreas and the more anteriorly situated SMV. The pancreas can be subdivided into five segments. They include a head, neck, uncinate process, body and tail. In this image, the body and neck of the pancreas are located centrally, anterior to the splenic vein (out of plane). Plate 46

82 Pt A - Coronal Plane - VIBE Reformatted Union of Splenic and Superior Mesenteric Veins Splenic v. Gastric body/fundus Hepatic flexure Superior mesenteric a. Portal vein R. and L. hepatic arteries Abdominal aorta R. ventricle L. ventricle Small bowel Neck of pancreas Body of pancreas Duodenum (descending) Splenic flexure Diaphragm Head of pancreas Gallbladder Ascending colon Superior mesenteric v. Plate 47

84 Pt A - Coronal Plane - VIBE Reformatted Branching of the Celiac artery Inferior vena cava R. ventricle L. ventricle Small bowel Aorta Portal vein Superior mesenteric artery Hepatic flexure Celiac artery Gastric body/fundus Splenic v. L. gastric artery Body of pancreas Ligamentum teres Hepatic artery Plate 48

86 Pt A - Coronal Plane - VIBE Reformatted Portal Vein Portal vein Superior mesenteric a. Hepatic flexure Celiac artery Spleen L. ventricle Gastric fundus Splenic v. Right hepatic vein Small bowel R. atrium Abdominal aorta Body of pancreas L. renal vein Inferior vena cava Plate 49

88 Pt A - Coronal Plane - VIBE Reformatted Course of the Inferior Vena Cava (IVC) Ascending from the confluence of the common iliac veins the IVC travels parallel and a few centimeters to the right of the vertebral column. The IVC crosses anterior to the right renal artery, receiving the right and left renal vein. The left renal vein crosses over the aorta anterior and parallel to the left renal artery. Along with also receiving gonadal, suprarenal, and lumbar veins along this course, the IVC next passes along the inferior visceral border of the liver where it receives input from the three hepatic veins. Following this the IVC passes through the vena caval foramen to then enter the right atrium. This image illustrates the IVC passing the right renal artery anteriorly, the liver posteriorly, and entering the right atrium of the heart. Right atrium IVC Right renal artery IVC Plate 50

90 Pt A - Coronal Plane - VIBE Reformatted Esophagogastric Junction Body of pancreas Inferior vena cava Spleen Psoas muscles Aorta Splenic v. Superior branch of portal vein Inferior branch of portal vein Esophagus Small bowel Gastric cardia Celiac artery Hepatic flexure R. atrium L. renal arteries Plate 51

93 Pt A - Coronal Plane - VIBE Reformatted Adrenal Glands Thoracic aorta Hepatic vein Hepatorenal recess R. kidney Spleen Psoas m. L. kidney Splenic v. Right renal arteries L. renal arteries Inferior vena cava R. adrenal gland L. adrenal gland Gastric cardia Abdominal aorta Plate 53

97 Pt A - Coronal Plane - VIBE Reformatted Renal Hilum and T12 Vertebral Body Thoracic aorta Hemiazygos v Hepatic vein Serratus anterior m. Renal sinus fat Hepatorenal recess R. kidney R. lower lobe of lung L. lower lobe of lung Spleen R. psoas m. L. renal pelvis L. kidney L. renal calyx Splenic hilum L. psoas m. Plate 56

99 Pt A - Coronal Plane - VIBE Reformatted Splenic Hilum Right lobe of liver (posterior segment) Serratus anterior m. Renal calyx Hepatorenal recess R. kidney R. lower lobe of lungL. lower lobe of lung Spleen Splenic hilum Splenic artery Spinal canal Thoracic aorta L. kidney R. psoas m.L. psoas m. Plate 57

103 Pt A - Coronal Plane - VIBE Reformatted Spinal Canal at T10/Posterior Kidneys Right lobe of liver (posterior segment) Spinal canal Spleen Spinal cord Perirenal fat Erector spinae m. Hepatorenal recess R. lower lobe of lung R. kidney L. lower lobe of lung L. kidney Plate 60

104 Pt A - Sagittal Plane - VIBE Reformatted Plate 61

107 Pt A - Sagittal Plane - VIBE Reformatted Right Lobe of Liver Liver (vertical span) Anterior ribs Subcutaneous fat R. lung Posterior ribs Intercostal m. Plate 63

110 Pt A - Sagittal Plane - VIBE Reformatted Gallbladder Gallbladder Perirenal fat Posterior pararenal fat Hepatorenal recess Ascending colon R. kidney R. lobe of liver (posterior segment) R. lobe of liver (anterior segment) Branch of portal vein Transverse colon Hepatic veins Plate 65

112 Pt A - Sagittal Plane - VIBE Reformatted Hepatorenal Recess 30 Hepatorenal Recess The peritoneal recess between the liver and kidney occupies an important clinical location in the abdomen. In the supine position this recess, also known as “Morrison’s pouch”, is the lowest point where fluid (e.g ascites) can collect. Superior Anterior Superior Plate 66

114 Pt A - Sagittal Plane - VIBE Reformatted Medulla of Right Kidney Body of gallbladder Hepatic veins Renal calyx Pararenal fat R. kidney (cortex) R. Kidney (medulla) Portal vein R. Lobe of liver (anterior segment) R. Lobe of liver (posterior segment) Hepatic flexure Plate 67

116 Pt A - Sagittal Plane - VIBE Reformatted Porta hepatis Hepatic artery Common bile duct Portal vein The porta hepatis is the “port” of entrance and exit to and from the liver for the portal triad—portal vein, hepatic artery, and common bile duct. This sagittal MR image provides a cross section of the portal triad. Plate 68

118 Pt A - Sagittal Plane - VIBE Reformatted Inferior Vena Cava Inferior vena cava Hepatic artery Psoas m. R. lumbar vessels Portal vein Plate 69

121 Pt A - Sagittal Plane - VIBE Reformatted Superior Mesenteric Vein Superior mesenteric vein Liver Thoracic aorta Head of pancreas Spinal canal Hepatic flexure Duodenum Uncinate process Hepatic artery Abdominal aorta Inferior vena cava Plate 71

123 Pt A - Sagittal Plane - VIBE Reformatted Aorta, Celiac Artery, and Superior Mesenteric Artery Splenic vein Duodenum (transverse) Neck of pancreas Left lobe of liver Superior mesenteric artery Celiac artery Duodenum (superior) L. renal vein Ascending colon Transverse colon Esophago- gastric junction Aorta Hepatic artery Plate 72

127 Pt A - Sagittal Plane - VIBE Reformatted Medulla of Left Kidney Gastric body Left lobe of liver (lateral segment) Left kidney (medulla) Transverse colon Left kidney (cortex) Spleen Gastric fundus Renal calyx Pancreatic body and tail Small bowel Perirenal fat Plate 75

129 Pt A - Sagittal Plane - VIBE Reformatted Lesser Sac Gastric fundus Gastric body Body and tail of pancreas In this image, the lesser sac can be seen on end as a thin hypointense area between the stomach and the pancreas. The lesser sac is a blind pouch of peritoneum that is bordered antero-superiorly by the posterior wall of the stomach and the lesser omentum and postero-inferiorly by the peritoneum overlying the body of the pancreas. Plate 76

131 Pt A - Sagittal Plane - VIBE Reformatted Spleen Spleen Splenic flexure Small bowel Apex of heart Splenic vein Gastric body Left kidney Plate 77

132 Pt B - MRA with contrast, maximum intensity projection 3D reconstruction of superior mesenteric and celiac arteries Plate 78

133 Pt B - MRA with contrast, maximum intensity projection 3D reconstruction of superior mesenteric and celiac arteries Aorta Hepatic artery R. renal artery Superior mesenteric artery Celiac trunk Splenic artery Gastroduodenal artery Plate 78

135 Pt B - MRA with contrast, maximum intensity projection 3D reconstruction of superior mesenteric and celiac arteries Aorta Hepatic artery Splenic artery Celiac trunk Superior mesenteric artery Lumbar arteries L. renal artery R. renal artery Plate 79

138 Pt B - MRA with contrast, maximum intensity projection 3D reconstruction of superior mesenteric and celiac arteries Plate 82 Superior mesenteric artery Celiac trunk Inferior mesenteric artery

140 Pt B - MRA with contrast, maximum intensity projection 3D reconstruction of superior mesenteric and celiac arteries Celiac trunk Superior mesenteric artery Hepatic artery Left gastric artery Splenic artery Lumbar arteries Plate 83

141 Pt C - MRA with contrast, maximum intensity projection 3D reconstruction of renal arteries Plate 84

142 Pt C - MRA with contrast, maximum intensity projection 3D reconstruction of renal arteries Right renal artery Left renal artery Aorta Superior mesenteric artery Lumbar arteries L. ureter Plate 84

145 Pt C - MRA with contrast, maximum intensity projection 3D reconstruction of renal arteries Superior mesenteric artery Aorta L. Ureter Right renal artery Left renal artery Plate 86

147 Pt C - MRA with contrast, maximum intensity projection 3D reconstruction of renal arteries Aorta Superior mesenteric artery L. Renal artery Branches of L. renal artery Plate 87

148 Correlation of Axial, Coronal, and Sagittal MR Plate 1 Liver and Gastroesophageal junction When examining the GI tract, a useful tool for orientation is the stomach. If one follows axial slices in the caudal direction from the diaphragm and GE junction downward, an easy landmark of the stomach is its characteristic longitudinally oriented rugae. These provide an initial reference point from which one can follow the GI tract distally through the duodenum to its distal transverse and ascending segments.

149 Correlation of Axial, Coronal, and Sagittal MR Plate 2 Spleen Given its location immediately adjacent to the posterior and lateral ribs and its lack of surrounding adipose tissue (unlike the kidneys), the spleen is very susceptible to trauma. MR imaging of the abdomen can serve as a useful tool in assessing splenic trauma.

150 Correlation of Axial, Coronal, and Sagittal MR Plate 3 Celiac Trunk The celiac artery arises off of the aorta at the level of T12. It trifurcates into the splenic, hepatic and left gastric arteries. These arteries supply the foregut of the GI tract—distal esophagus, stomach, duodenum, pancreas, liver, gall bladder, and spleen.

151 Correlation of Axial, Coronal, and Sagittal Plate 4 Pancreas Together these images capture the body and tail of the pancreas. To image the entire view of the pancreas an oblique section can be helpful.

152 The Pancreas This image illustrates four main segments of the pancreas in one plane. These include the tail, body, neck, and head of the pancreas. Due to the fact that the pancreas typically slopes inferiorly from the tail at the splenic hilum to its head adjacent to the duodenum, this image was reconstructed in an oblique plane. Head Neck Body Tail

153 Correlation of Axial, Coronal, and Sagittal MR Plate 5 Gallbladder Fluid is hypointense (dark) on these T1 weighted VIBE images. The fluid-filled gallbladder illustrates this appearance. To further examine the gallbladder and biliary tree, T2 weighted MRCP (MR cholangiopancreatography) can be used.

154 MRCP of the Biliary Tree Pancreatic duct L. Hepatic duct Common bile duct Common hepatic duct R. hepatic duct Gallbladder Cystic duct

155 Correlation of Axial, Coronal, and Sagittal MR Plate 6 Kidney (Right Upper Pole)

156 Correlation of Axial, Coronal, and Sagittal Plate 7 Kidney (Left Hilum)

157 Correlation of Axial, Coronal, and Sagittal MR Plate 8 Kidneys (Left Lower Pole) and Vertebral Musculature Vertebral body Quadratus lumborum Erector spinae Psoas muscle Ureter The lower poles of the kidneys lie adjacent and antero-lateral to the muscles of the back. These include the psoas, quadratus lumboratum, deep back muscles, and intermediate (erector spinae) back muscles. Notice the small hypointense circular slice of the left ureter lying on the left psoas muscle. Deep back mm.

158 References Christofordis, A Atlas of Axial, Sagittal, and Coronal Anatomy with CT and MRI 1988 Novelline, RA Novelline, RA Living Anatomy: A Working Atlas Using Computed Tomography, Magnetic Resonance, and Angiography Images 1 st edition, 1987 Moore, K and Dalley, A Clinically Oriented Anatomy 4 th edition, 1999 Fleckenstein, P Anatomy in Diagnostic Imaging 2 nd edition, 2001

159 Special Thanks Pamela Lepkowski, Education Coordinator at Beth Israel Deaconess Medical Center for technical assistance and editing.

MRI Atlas of the Abdomen (a self-guided tutorial) Jeff Velez HMS3 Eric Chiang, MD Gillian Lieberman, MD.

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MRI Atlas of the Abdomen (a self-guided tutorial) Jeff Velez HMS3 Eric Chiang, MD Gillian Lieberman, MD.

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