MRI Atlas of the Abdomen (a self-guided tutorial) Jeff Velez HMS 3 Eric Chiang, MD Gillian Lieberman, MD
Goals The purpose of this atlas is to provide students with; • • an outline of the anatomy of the abdomen via MR imaging. 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 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. 2
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. 3
Basics of MRI • 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. Tissue contrast is created because different tissues have different relaxation times. This is attributable to the different microenvironments surrounding the magnetized nuclei. 4
4 Key Parameters of MRI • T 1 • T 2 • Echo Time (TE) • Repetition Time (TR) • The relaxation times of protons shifting from a higher to • lower energy level, are referred to as T 1 and T 2 and are tissue specific. The TE and TR are variables that can be controlled by an MR scanner operator. 5
T 1 and T 2 • • • T 1 and T 2 represent relaxation time constants. Each tissue has a specific, inherent T 1 and T 2 value. For example: fat has a short T 1 and T 2, whereas fluid has a long T 1 and T 2. These values are measured in milliseconds. T 1 – 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). T 2 – 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). 6
TR and TE • These are two major parameters that can be adjusted (unlike T 1 and T 2) 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 (T 1 and T 2). 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 T 1 and T 2, the various tissues in a region of interest can be differentiated. 7
T 1 weighted images vs. T 2 weighted images • The following 2 slides offer graphs to help explain tissue contrast on • • • T 1 vs. T 2 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. 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 T 1 and T 2 are constant and tissue dependent. They are represented by the degree of line curvature (exponential relationship) on the graphs to follow. 8
T 1 Weighted Image—short TR and TE Signal Intensity — fat — fluid TR = repetition time TE = echo time TR In this graph fat has a greater signal intensity than fluid. Tissues with short T 1 and T 2 (fat) will appear brighter than those with longer T 1 and T 2 (fluid). TE Although this is a gross oversimplification, when an image is T 1 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 T 1 and T 2 relaxation times (e. g. fat) to appear brighter. 9
T 2 Weighted Image—long TR and TE Signal Intensity — fat — fluid TR = repetition time TE = echo time TR In this graph fluid has a greater signal intensity than fat. Tissues with long T 1 and T 2 (fluid) will appear brighter than those with short T 1 and T 2 (fat). TE • On a T 2 weighted image the protocol used is one that will result in tissue with long T 1 and T 2 (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 T 1 weighted sequence. 10
Beyond T 1 and T 2—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. 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. 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. 11
Volumetric Interpolated Breath-hold Examination (VIBE) • The VIBE Sequence is T 1 based (short TR and TE). • It is a complex 3 D 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 3 D reconstructions of the abdomen to follow were performed using the VIBE sequence. 12
Anatomy of the Abdomen Throughout this atlas, in axial, coronal, sagittal, and oblique 3 D planes, we will highlight; • • Liver Biliary System Pancreas Spleen Gastrointestinal Tract Kidneys Retroperitoneum Peritoneum 13
We have used images from 3 different patients: • 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 MR settings: VIBE sequence, MRA abdomen (focused on celiac/SMA) Planes: Maximum intensity projection (MIP) 3 D reconstruction Patient C - 27 year old male MR Settings: VIBE sequence, MRA abdomen (focused on renal arteries) Planes: Maximum intensity projection 3 D reconstruction 14
Pt A - Axial VIBE Plate 1 15
Pt A - Axial VIBE Plate 2 16
Pt A - Axial VIBE - Dome of the Liver R. Ventricle L. Ventricle Inferior Vena Cava Esophagus Aorta L. Lower lobe of lung R. Lower lobe of lung Azygos v. Plate 3 17
Pt A - Axial VIBE Plate 4 18
Pt A - Axial VIBE Plate 5 19
Pt A - Axial VIBE Plate 6 20
Pt A - Axial VIBE Plate 7 21
Pt A - Axial VIBE Plate 8 22
Pt A - Axial VIBE - Hepatic Veins L. Lobe of liver (lateral segment) Gastric fundus L. hepatic v. L. Lobe of liver (medial segment) M. hepatic v. Inferior vena cava R. lobe of liver (anterior segment) R. hepatic v. Aorta R. lobe of liver (posterior segment) Plate 8 Azygos v. Gastroesophageal junction Hemiazygos v. L. lower lobe of lung Spleen 23
Pt A - Axial VIBE Plate 9 24
Pt A - Axial VIBE Plate 10 25
Pt A - Axial VIBE - Hepatic Divisions LMS LLS L. hepatic vein M. hepatic vein RAS Inferior vena cava R. hepatic vein LLS—Lateral segment of left lobe RPS LMS—Medial segment of left lobe RAS—Anterior segment of right lobe RPS—Posterior segment of right lobe Plate 10 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. 26
Pt A - Axial VIBE Plate 11 27
Pt A - Axial VIBE Plate 12 28
Pt A - Axial VIBE - Splenic Hilum 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. Splenic flexure Posterior aspect of stomach Tail of pancreas Splenic vein Splenic artery Posterior chest wall Important relationships of the spleen include abutment of the posterior aspect of the stomach as well as the tail of the pancreas Plate 12 29
Pt A - Axial VIBE Plate 13 30
Pt A - Axial VIBE Plate 14 31
Pt A - Axial VIBE - Adrenal Gland Spleen Gastric fundus L. portal vein Inferior vena cava Aorta R. portal vein R. adrenal gland Body of pancreas L. adrenal gland Spleen R. crus of diaphragm L. crus of diaphragm Vertebral body Ascending lumbar veins Spinal cord Ascending lumbar veins Plate 14 32
Pt A - Axial VIBE Plate 15 33
Pt A - Axial VIBE - Adrenal Glands 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. Plate 15 34
Pt A - Axial VIBE Plate 16 35
Pt A - Axial VIBE Plate 17 36
Pt A - Axial VIBE - Celiac Trunk Common hepatic a. Ligamentum teres Celiac Trunk Gastric body Hepatic a. fossa Splenic flexure Caudate lobe Body of Pancreas Portal vein L. adrenal gland Desc. colon Spleen Inferior vena cava L. kidney R. kidney Aorta Plate 17 37
Pt A - Axial VIBE Plate 18 38
Pt A - Axial VIBE Hepatic artery Portal vein Caudate lobe Inferior vena cava R. Adrenal gland (see plates 20 -24) Plate 18 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. 39
Pt A - Axial VIBE Plate 19 40
Pt A - Axial VIBE - Body of Pancreas Gastric body Small bowel Splenic vein Pancreatic duct L. lobe (lateral) Ligamentum teres L. lobe (medial) Neck of gallbladder Porta hepatis Portal vein Hepatic artery Inferior vena cava R. kidney Superior mesenteric artery Plate 19 Aorta Body of pancreas L. kidney Descending colon Spleen 41
Pt A - Axial VIBE Plate 20 42
Pt A - Axial VIBE Plate 21 43
Pt A - Axial VIBE - Origin of SMA Gastric body Small bowel Descending colon Ligamentum teres Body of pancreas Gastric antrum Hepatic artery Neck of gallbladder Porto-splenic confluence Portal vein Neck of pancreas Splenic vein R. kidney Plate 21 Inferior vena cava R. renal vein Superior mesenteric artery Aorta L. kidney 44
Pt A - Axial VIBE Plate 22 45
Pt A - Axial VIBE - Relationships of the Superior Mesenteric Artery Body of pancreas This slide shows another Splenic vein 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. Plate 22 Superior mesenteric artery (SMA) Distal duodenum L. Renal vein Aorta 46
Pt A - Axial VIBE Plate 23 47
Pt A - Axial VIBE Plate 24 48
Pt A - Axial VIBE - Origin of the Renal Arteries Falciform ligament Ligamentum teres fissure Gastric antrum Gastric body Superior mesenteric vein Hepatic flexure Superior mesenteric artery Small bowel L. renal vein L. renal artery Body of gallbladder Duodenum (1 st part) Head of pancreas Duodenum (2 nd part) Hilum of left kidney Hilum of right kidney Inferior vena cava Plate 24 49
Pt A - Axial VIBE Plate 25 50
Pt A - Axial VIBE - Clinical Relationships of the Gall. Bladder Gallbladder Hepatic flexure 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. Duodenum (descending) Plate 25 51
Pt A - Axial VIBE Plate 26 52
Pt A - Axial VIBE Plate 27 53
Pt A - Axial VIBE - Renal Hilum Duodenum (3 nd part) Ligamentum teres fissure Head of pancreas Body of gallbladder Superior mesenteric vein Hepatic flexure Transverse colon Duodenum (2 st part) Superior mesenteric artery Small bowel L. renal vein R. renal pelvis Hepatorenal recess (Morrison’s pouch) Hilum of left kidney Inferior vena cava Renal pelvis fat Deep back muscles Hilum of right kidney Quadratus lumborum Psoas muscle Plate 27 54
Pt A - Axial VIBE Plate 28 55
Pt A - Axial VIBE Plate 29 56
Pt A - Axial VIBE - Kidney and Retroperitoneum The kidneys are retroperitoneal structures that reside at the level of T 12 to L 3, 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. Anterior pararenal space Perirenal space 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. Kidney Perirenal space Posterior pararenal space Plate 29 57
Pt A - Axial VIBE Plate 30 58
Pt A - Axial VIBE - Hepatic Flexure Superior mesenteric artery Superior mesenteric vein Aorta Transverse colon Duodenum Small bowel Anterior pararenal space* Flank stripe* Perirenal space* Posterior pararenal space* Fundus of gallbladder Hepatic flexure Inferior vena cava Lumbar vessels Quadratus lumborum Deep back muscles Ureter Psoas muscle Plate 30 * Marked structures of retroperitoneum will be discussed in the following slide. 59
A Simplified Overview of the Retroperitoneal Spaces Gastric body Liver Pancreas Anterior Pararenal space Flank stripe Perirenal space Right kidney Inferior vena cava Spleen Transversalis fascia Gerota’s fascia Left kidney Posterior Pararenal space 60
Pt A - Axial VIBE Plate 31 61
Pt A - Axial VIBE Plate 32 62
Pt A - Axial VIBE Plate 33 63
Pt A - Axial VIBE - Lower Poles of Kidneys Transverse colon Aorta Fundus of gall bladder Small bowel Inferior vena cava L. ureter Liver R. ureter Psoas muscle Quadratus lumborum Erector spinae Plate 33 64
Pt A - Axial VIBE Plate 34 65
Pt A - Axial VIBE Plate 35 66
Pt A - Axial VIBE Plate 36 67
Pt A - Axial VIBE Plate 37 68
Pt A - Axial VIBE Plate 38 69
Pt A - Axial VIBE Plate 39 70
Pt A - Axial VIBE Plate 40 71
Pt A - Coronal Plane - VIBE Reformatted Plate 41 72
Pt A - Coronal Plane - VIBE Reformatted Plate 42 73
Pt A - Coronal Plane - VIBE Reformatted Gallbladder R. ventricle Diaphragm Falciform ligament Liver Ligamentum teres Gallbladder Hepatic flexure Gastric body Transverse colon Small bowel Plate 42 74
Pt A - Coronal Plane - VIBE Reformatted Plate 43 75
Pt A - Coronal Plane - VIBE Reformatted Plate 44 76
Pt A - Coronal Plane - VIBE Reformatted Transverse Colon L. ventricle Diaphragm R. ventricle Gastric fundus L. lobe of liver Portal vein R. lobe of liver Gastric body Fundus of gallbladder Hepatic flexure Transverse colon Small bowel Splenic flexure Gastric antrum Plate 44 77
Pt A - Coronal Plane - VIBE Reformatted Plate 45 78
Pt A - Coronal Plane - VIBE Reformatted Plate 46 79
Pt A - Coronal Plane - VIBE Reformatted Pancreas and Splenic and Superior Mesenteric Vein 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). 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. Plate 46 80
Pt A - Coronal Plane - VIBE Reformatted Plate 47 81
Pt A - Coronal Plane - VIBE Reformatted Union of Splenic and Superior Mesenteric Veins L. ventricle Diaphragm R. ventricle Gastric body/fundus Splenic flexure Body of pancreas Portal vein R. and L. hepatic arteries Neck of pancreas Gallbladder Duodenum (descending) Hepatic flexure Plate 47 Ascending colon Head of pancreas Superior mesenteric v. Splenic v. Superior mesenteric a. Abdominal aorta Small bowel 82
Pt A - Coronal Plane - VIBE Reformatted Plate 48 83
Pt A - Coronal Plane - VIBE Reformatted Branching of the Celiac artery R. ventricle Ligamentum teres L. ventricle L. gastric artery Hepatic artery Portal vein Celiac artery Hepatic flexure Aorta Inferior vena cava Gastric body/fundus Body of pancreas Small bowel Splenic v. Superior mesenteric artery Plate 48 84
Pt A - Coronal Plane - VIBE Reformatted Plate 49 85
Pt A - Coronal Plane - VIBE Reformatted Portal Vein R. atrium Inferior vena cava Right hepatic vein L. ventricle Gastric fundus Celiac artery Portal vein Superior mesenteric a. Abdominal aorta Hepatic flexure Spleen Body of pancreas Splenic v. Small bowel Inferior vena cava L. renal vein Plate 49 86
Pt A - Coronal Plane - VIBE Reformatted Plate 50 87
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. Right atrium IVC Right renal artery IVC This image illustrates the IVC passing the right renal artery anteriorly, the liver posteriorly, and entering the right atrium of the heart. Plate 50 88
Pt A - Coronal Plane - VIBE Reformatted Plate 51 89
Pt A - Coronal Plane - VIBE Reformatted Esophagogastric Junction Spleen R. atrium Esophagus Gastric cardia Body of pancreas Superior branch of portal vein Inferior branch of portal vein Plate 51 Celiac artery Splenic v. Aorta Hepatic flexure Inferior vena cava L. renal arteries Psoas muscles Small bowel 90
Pt A - Coronal Plane - VIBE Reformatted Plate 52 91
Pt A - Coronal Plane - VIBE Reformatted Plate 53 92
Pt A - Coronal Plane - VIBE Reformatted Adrenal Glands Thoracic aorta Hepatic vein Gastric cardia Inferior vena cava Abdominal aorta R. adrenal gland Right renal arteries R. kidney Hepatorenal recess Spleen Splenic v. L. adrenal gland L. kidney L. renal arteries Psoas m. Plate 53 93
Pt A - Coronal Plane - VIBE Reformatted Plate 54 94
Pt A - Coronal Plane - VIBE Reformatted Plate 55 95
Pt A - Coronal Plane - VIBE Reformatted Plate 56 96
Pt A - Coronal Plane - VIBE Reformatted Renal Hilum and T 12 Vertebral Body Thoracic aorta R. lower lobe of lung Serratus anterior m. Hepatic vein Renal sinus fat R. kidney Hepatorenal recess R. psoas m. L. lower lobe of lung Hemiazygos v Spleen Splenic hilum L. renal calyx L. renal pelvis L. kidney L. psoas m. Plate 56 97
Pt A - Coronal Plane - VIBE Reformatted Plate 57 98
Pt A - Coronal Plane - VIBE Reformatted Splenic Hilum Thoracic aorta R. lower lobe of lung L. lower lobe of lung Serratus anterior m. Splenic hilum Spleen Right lobe of liver (posterior segment) R. kidney Splenic artery L. kidney Hepatorenal recess R. psoas m. Renal calyx L. psoas m. Spinal canal Plate 57 99
Pt A - Coronal Plane - VIBE Reformatted Plate 58 100
Pt A - Coronal Plane - VIBE Reformatted Plate 59 101
Pt A - Coronal Plane - VIBE Reformatted Plate 60 102
Pt A - Coronal Plane - VIBE Reformatted Spinal Canal at T 10/Posterior Kidneys L. lower lobe of lung Right lobe of liver (posterior segment) Hepatorenal recess Spinal canal Spleen Perirenal fat L. kidney Erector spinae m. R. kidney Spinal cord Plate 60 103
Pt A - Sagittal Plane - VIBE Reformatted Plate 61 104
Pt A - Sagittal Plane - VIBE Reformatted Plate 62 105
Pt A - Sagittal Plane - VIBE Reformatted Plate 63 106
Pt A - Sagittal Plane - VIBE Reformatted Right Lobe of Liver R. lung Intercostal m. Liver (vertical span) Posterior ribs Anterior ribs Subcutaneous fat Plate 63 107
Pt A - Sagittal Plane - VIBE Reformatted Plate 64 108
Pt A - Sagittal Plane - VIBE Reformatted Plate 65 109
Pt A - Sagittal Plane - VIBE Reformatted Gallbladder Hepatic veins R. lobe of liver (anterior segment) Branch of portal vein Gallbladder Transverse colon R. lobe of liver (posterior segment) Hepatorenal recess R. kidney Posterior pararenal fat Perirenal fat Ascending colon Plate 65 110
Pt A - Sagittal Plane - VIBE Reformatted Plate 66 111
Pt A - Sagittal Plane - VIBE Reformatted Hepatorenal Recess Superior 30 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. Anterior Superior Hepatorenal Recess Plate 66 112
Pt A - Sagittal Plane - VIBE Reformatted Plate 67 113
Pt A - Sagittal Plane - VIBE Reformatted Medulla of Right Kidney R. Lobe of liver (anterior segment) Hepatic veins R. Lobe of liver (posterior segment) Pararenal fat Portal vein Renal calyx R. kidney (cortex) Body of gallbladder R. Kidney (medulla) Hepatic flexure Plate 67 114
Pt A - Sagittal Plane - VIBE Reformatted Plate 68 115
Pt A - Sagittal Plane - VIBE Reformatted Porta hepatis Common bile duct Portal vein Hepatic artery Plate 68 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. 116
Pt A - Sagittal Plane - VIBE Reformatted Plate 69 117
Pt A - Sagittal Plane - VIBE Reformatted Inferior Vena Cava Hepatic artery R. lumbar vessels Portal vein Inferior vena cava Psoas m. Plate 69 118
Pt A - Sagittal Plane - VIBE Reformatted Plate 70 119
Pt A - Sagittal Plane - VIBE Reformatted Plate 71 120
Pt A - Sagittal Plane - VIBE Reformatted Superior Mesenteric Vein Thoracic aorta Inferior vena cava Liver Abdominal aorta Hepatic artery Head of pancreas Hepatic flexure Superior mesenteric vein Spinal canal Duodenum Uncinate process Plate 71 121
Pt A - Sagittal Plane - VIBE Reformatted Plate 72 122
Pt A - Sagittal Plane - VIBE Reformatted Aorta, Celiac Artery, and Superior Mesenteric Artery Aorta Esophago-gastric junction Hepatic artery Left lobe of liver Celiac artery Neck of pancreas Duodenum (superior) Splenic vein Transverse colon Plate 72 L. renal vein Ascending colon Superior mesenteric artery Duodenum (transverse) 123
Pt A - Sagittal Plane - VIBE Reformatted Plate 73 124
Pt A - Sagittal Plane - VIBE Reformatted Plate 74 125
Pt A - Sagittal Plane - VIBE Reformatted Plate 75 126
Pt A - Sagittal Plane - VIBE Reformatted Medulla of Left Kidney Gastric fundus Left lobe of liver (lateral segment) Gastric body Spleen Pancreatic body and tail Left kidney (medulla) Renal calyx Transverse colon Perirenal fat Small bowel Left kidney (cortex) Plate 75 127
Pt A - Sagittal Plane - VIBE Reformatted Plate 76 128
Pt A - Sagittal Plane - VIBE Reformatted Lesser Sac 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. Gastric fundus Body and tail of pancreas Gastric body In this image, the lesser sac can be seen on end as a thin hypointense area between the stomach and the pancreas. Plate 76 129
Pt A - Sagittal Plane - VIBE Reformatted Plate 77 130
Pt A - Sagittal Plane - VIBE Reformatted Spleen Apex of heart Splenic flexure Splenic vein Gastric body Spleen Small bowel Left kidney Plate 77 131
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Plate 78 132
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Aorta Hepatic artery Celiac trunk Splenic artery Gastroduodenal artery R. renal artery Superior mesenteric artery Plate 78 133
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Plate 79 134
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Aorta Hepatic artery Lumbar arteries Splenic artery R. renal artery Celiac trunk Superior mesenteric artery L. renal artery Plate 79 135
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Plate 80 136
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Plate 81 137
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Celiac trunk Superior mesenteric artery Inferior mesenteric artery Plate 82 138
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Plate 83 139
Pt B - MRA with contrast, maximum intensity projection 3 D reconstruction of superior mesenteric and celiac arteries Left gastric artery Hepatic artery Celiac trunk Splenic artery Superior mesenteric artery Lumbar arteries Plate 83 140
Pt C - MRA with contrast, maximum intensity projection 3 D reconstruction of renal arteries Plate 84 141
Pt C - MRA with contrast, maximum intensity projection 3 D reconstruction of renal arteries Lumbar arteries Right renal artery Aorta Left renal artery L. ureter Superior mesenteric artery Plate 84 142
Pt C - MRA with contrast, maximum intensity projection 3 D reconstruction of renal arteries Plate 85 143
Pt C - MRA with contrast, maximum intensity projection 3 D reconstruction of renal arteries Plate 86 144
Pt C - MRA with contrast, maximum intensity projection 3 D reconstruction of renal arteries Aorta Superior mesenteric artery L. Ureter Left renal artery Right renal artery Plate 86 145
Pt C - MRA with contrast, maximum intensity projection 3 D reconstruction of renal arteries Plate 87 146
Pt C - MRA with contrast, maximum intensity projection 3 D reconstruction of renal arteries Aorta Superior mesenteric artery Branches of L. renal artery L. Renal artery Plate 87 147
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. 148
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. 149
Correlation of Axial, Coronal, and Sagittal MR Plate 3 Celiac Trunk The celiac artery arises off of the aorta at the level of T 12. 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. 150
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. 151
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 152
Correlation of Axial, Coronal, and Sagittal MR Plate 5 Gallbladder Fluid is hypointense (dark) on these T 1 weighted VIBE images. The fluid-filled gallbladder illustrates this appearance. To further examine the gallbladder and biliary tree, T 2 weighted MRCP (MR cholangiopancreatography) can be used. 153
MRCP of the Biliary Tree R. hepatic duct Cystic duct Common bile duct Gallbladder L. Hepatic duct Common hepatic duct Pancreatic duct 154
Correlation of Axial, Coronal, and Sagittal MR Plate 6 Kidney (Right Upper Pole) 155
Correlation of Axial, Coronal, and Sagittal Plate 7 Kidney (Left Hilum) 156
Correlation of Axial, Coronal, and Sagittal MR Plate 8 Kidneys (Left Lower Pole) and Vertebral Musculature Ureter Vertebral body Psoas muscle Deep back mm. Quadratus lumborum Erector spinae 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. 157
References Christofordis, A Atlas of Axial, Sagittal, and Coronal Anatomy with CT and MRI 1988 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 158
Special Thanks Pamela Lepkowski, Education Coordinator at Beth Israel Deaconess Medical Center for technical assistance and editing. 159
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