الفهرس 
MRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRI ANATOMY OF THE LIVERMRIOnly 14 pages are availabe for public view
 |  | from | 32 |  |  |
| | | from | 32 | | |
Abstract
radia.tion exp.osure. I.n som.e hos.pitals, imm.ediately af.ter t.he trea.tment, a positron
Hepatocel.lular carcinoma (HCC) is an ag.gressive primary liver ma.lignancy, repr.esents over 90% of all primary liver ma.lignancy. It is the 6th most com.mon cancer world.wide leading to the 3rd caus.e of cancer relat.ed deaths with incre.asing incidence nowa.days which is posing a major health.care problem.
Ima.ging plays a critical role in the diagn.osis, staging, surveillance, and treatment monitoring of hepat.ocellular carcinoma (HCC). Early diagn.osis is crucial for optim.izing treatment outcome. Ultraso.und is now the first and only screeni.ng exam for HCC and if a mas.s is questioned in screening ultras.ound, a subsequent MRI is the exa.m of choice for diagnosis of HCC.
Unlike most maligna.ncies, which typically require biopsy for diagnosis, HCC can be diagnosed based on MRI char.acteristics alone due to the relatively high specificity of this mod.ality and once the imaging diagnosis is made, therapy is chosen based on extent of disease, liver fun.ction, patient age and co morbidities. Thus, imaging is crucial for patient-managem.ent options, which include liver transplantation or vari.ous loco regional or systemic therapies.
HCC most comm.only presents late in the disease cou.rse. As a result, the majority of patients are not candidates for curative therapies. Loco regio.nal thera.pies including Yttri.um-90 (Y-90) Radioem.bo.lization play an import.ant role in management of the vast maj.ority of patients with HCC.
Trans art.erial Radioemboli.zation (TARE) is a directed techn. .ique that embeds Yttri.um-90 (Y-90) microsp.heres into branches of the hep.atic artery. As long all intra.hepatic malign.ancies derive the vast majority of their blood supply from the hep.atic artery rather than the portal circu.lation, selective cath.eter-based administration of Y-90 microsph.eres into the hepatic artery is thought to prefere.ntially deliver therapy to tumor, sparing normal liver parenchyma. This techni.que allows delivery of high radiat.ion doses up to 50 to 150 Gy with m.ean pene.tration ran.ge of 2.5 mm, so it deliver tumoricidal doses of radiation within the tumor capi.llary bed, sparing uninvolved liver tissue with a min.or role of emb.olic occlusion of the tumor blo.od supply.
Post TARE imag.ing generally begins with contr.ast-enhanc.ed MRI, and/or PET/CT. This should preferably match the pre-treatment imag.ing in modality and technique. The initial post-treatment imaging is usually at 1 month after treatment, and is followed by serial examinations every 3 months. Although response to treatment evolves gradually, early imaging is important to identify the non-responders who tend to have poor survival.
As Radioem.bolization i.s un.ique i.n t.hat its prim.ary m.ode o.f tu.mor kil.ling i.s b.y int.ernal radia.tion a.nd n.ot ind.uced isch.emia, th.e imaging find.ings follow.ing therapy aren’t the same to the radio.logic findings that measure therapeutic effectiveness for most tradit.ional ther.a.pies and the use of st.rict anatomic (size ) crite.ria alo.ne h.as bee.n sho.wn t.o b.e a.n im.perfect eva.luation o.f th.erapeutic res.ponse. Howe.ver, after TARE, the tumor may shrink, remain the same, or even increase in size. Treatment-related ne.crosis, edema, and hemorrhage may cause an initial increase in the size of a tumor that is other.wise responding to therapy.
Reducti.on in tumor size, necros.is and la.ck of tumor enha.nce.ment as seen at MRI are primary surrogates of a favor.able response to 90Y treat.ment. Use of fun.ctional MR im.aging tech.niques such as DWI and P.ET/CT can be helpful in solving certain dia.gnostic dilemmas that may be encoun.tered durin.g post-TARE foll.ow-up imaging. Radi.ologists need to be aware of certain benign findings that are uni.que to post-TARE livers, such as peritumoral edema, perilesional thin rim of enhanc.e.ment and geo.graphic areas of hypoden.sity in non-tumorous liver. This kno.wledge would en.sure that there is a low rate of false-positive diagnosis of progressive disease. Similarly, knowle.dge of the comm.on complica.tions that follow 90Y treatment and their pathoge.nesis would empower the radiologist in generati.ng more informed and intell.igent impres.sions from their observat.ions.