Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

923 results found
Article

Primary mediastinal large B-cell lymphoma

Primary mediastinal large B-cell lymphoma is a distinct entity, recognized in the WHO classification of lymphoma. Epidemiology Primary mediastinal large B-cell lymphoma accounts approximately 5% of large B-cell lymphoma, which is usually disseminated or found in the abdomen. There appears to b...
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Primary non-cutaneous melanoma

Primary non-cutaneous melanomas are much less common than primary cutaneous melanomas 1. These include meningeal melanoma primary uveal malignant melanoma primary prostatic malignant melanoma primary urethral malignant melanoma mucosal melanoma sinonasal mucosal melanoma
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Primary osteosarcoma (breast)

Primary osteosarcoma of the breast, a.k.a. extraskeletal osteosarcoma of breast, is an uncommon breast malignancy and is a subtype of extraskeletal osteosarcoma. Epidemiology While it can present in a wide are group, the peak age at presentation is around the 6th decade 7. Pathology  The pre...
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Primary ovarian lymphoma

Primary ovarian lymphoma (POL) refers to involvement of the ovary with lymphoma but without the involvement of any other site. It is an extremely rare yet well-recognized condition. Epidemiology POL accounts for ~1.5% of ovarian tumors 5. Pathology The rarity of this condition is probably in...
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Primary pleural lymphoma

Primary pleural lymphoma is extremely rare, especially in immunocompetent patients. Epidemiology Primary pleural lymphoma accounts for <0.5% of all non-Hodgkin lymphoma 2 and ~2.5% of primary chest wall tumors 4.  Pathology Primary pleural lymphoma may be Hodgkin or non-Hodgkin lymphoma with...
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Primary prostatic malignant melanoma

Primary melanoma of the prostate is rare, and usually cannot be diagnosed on imaging alone. In many cases, it is believed that in fact, the tumor represents prostatic involvement by melanoma of the urethra. Epidemiology Primary malignant melanoma of the prostate represents both a tiny fraction...
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Primary pulmonary chondrosarcoma

Primary pulmonary chondrosarcoma is an extremely rare form of chondrosarcoma, in terms of location. The majority of intrathoracic chondrosarcomas occur in relation to the chest wall. Epidemiology While the exact incidence is unknown, only a handful of cases have been reported in the literature...
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Primary pulmonary lymphoma

Primary pulmonary lymphomas refer to clonal lymphoid proliferation affecting the lungs without any detectable extrapulmonary involvement. It is much rarer than secondary pulmonary lymphoma and is most frequently represented by lymphoma of B-cell lineage - often marginal zone B-cell lymphoma of m...
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Primary pulmonary meningioma

A primary pulmonary meningioma is a very rare from of an ectopic meningioma. Clinical presenation They are generally asymptomatic and incidentally discovered although rarely patients with symptoms have also been reported. Pathology Histologically, they comprise of whorls of spindle cells int...
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Primary pulmonary synovial sarcoma

Primary pulmonary synovial sarcoma is an extremely rare tumor and refers to a situation where a synovial sarcoma arises from the lung as a primary site. It together with a pleural synovial sarcoma comes under the broader category of pleuro-pulmonary synovial sarcomas 3. Epidemiology It account...
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Primary sarcomatoid carcinoma of the lung

Primary sarcomatoid carcinomas of the lung refer to a heterogeneous group of rare and poorly differentiated types of non-small cell lung carcinomas (NSCLC). Epidemiology They are thought to account for 0.2 to 1% of all lung cancers 1. Sarcomatoid histology may be present in 0.1-0.4% of non-sma...
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Primary urethral cancer

Primary urethral cancer, in most cases a urethral carcinoma, is a rare urological malignancy. It can be divided in female urethral cancer and male urethral cancer. Epidemiology It has an incidence of 4.3 per million for males and 1.5 per million for females. It usually manifests in the fifth d...
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Primary urethral cancer (staging)

Primary urethral cancer staging often uses the TNM system and is as follows: TNM staging Primary tumor staging (T) Tx: primary tumor cannot be assessed T0: no evidence of primary tumor Tis: carcinoma in situ Ta: non-invasive papillary, polypoid, or verrucous carcinoma T1: invasion of sube...
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Primary urethral malignant melanoma

Melanoma of the urethra is a very rare tumor of the male urethra and often presents as an invasive prostatic mass. As such it is usually referred to as primary prostatic malignant melanoma.
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Primary uveal malignant melanoma

Malignant uveal melanomas, also referred to as choroidal melanomas, are the most common primary tumor of the adult eye 3.  Epidemiology Malignant melanoma of the uvea is the most common primary intraocular malignancy and is predominantly seen in Caucasians 5. The incidence of these tumors incr...
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Prostate atrophy

Prostatic atrophy is characterized by reduced cytoplasm prostatic acinar cells and constitutes a benign mimic of prostate cancer not only on imaging but also histologically. Terminology The term 'proliferative inflammatory atrophy (PIA)' is used if it is associated with inflammation. Epidemio...
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Prostate cancer

Prostate cancer ranks as the most common primary malignant tumor in men and the second most common cause of cancer-related deaths in men. Prostatic adenocarcinoma is by far the most common histological type and is the primary focus of this article. ICD-11: 2C82Z Epidemiology It is primarily a...
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Prostate cancer (staging)

Prostate cancer staging takes into account TNM (primary site, nodal and distant metastases), pretreatment PSA and histological grading. The Gleason score is used to determine the Grade Group.  An old, superseded staging system is the Whitmore-Jewett staging system. Additionally, there is some ...
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Prostate imaging recurrence reporting

Prostate imaging recurrence reporting (PI-RR) or prostate MRI for local recurrence reporting is a structured reporting scheme similar to the Prostate Imaging-Reporting and Data System (PIRADS) v2.1 on multiparametric prostate MRI for the detection of local recurrence after radical prostatectomy ...
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Prostate Imaging-Reporting and Data System (PI-RADS)

PI-RADS (Prostate Imaging–Reporting and Data System) is a structured reporting scheme for multiparametric prostate MRI in the evaluation of suspected prostate cancer in treatment naive prostate glands. This article reflects version 2.1 (v2.1), published in 2019 and developed by an internationall...
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Prostate MRI (an approach)

Prostate MRI has become an increasingly frequent examination faced in daily radiological practice and is mainly conducted for the detection, active surveillance and staging of prostate cancer. This approach is an example of how to create a radiological report of a prostate MRI (usually mpMRI) wi...
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Prostate MRI protocol

Prostate MRI has become an increasingly frequent examination faced in daily radiological practice and is usually acquired as either multiparametric or biparametric MRI of the prostate. This article aims to outline the concept of an MRI protocol for the assessment of the prostate. Recommendatio...
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Prostate sarcoma

Prostate sarcomas are an uncommon and heterogeneous group of tumors arising from mesenchymal cells in and around the prostate (as opposed to the more common prostate adenocarcinoma which derives from the glandular tissue).  Pathology In children, the most common tumor type is a prostatic rhabd...
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Prostate specific antigen

Prostate specific antigen (PSA) is currently used as a tumor marker for prostate adenocarcinoma. PSA is a 33 kilodalton glycoprotein produced in prostate epithelial cells. Its normal physiologic role is as a liquefying agent for seminal fluid; only a tiny amount leaks into the blood, therefore ...
Article

Prostate-specific membrane antigen

Prostate-specific membrane antigen (PSMA) (also known as glutamate carboxypeptidase II) is a type II transmembrane glycoprotein that has become an increasingly prominent imaging biomarker 1. PSMA has emerged as a useful target in PET imaging of prostate cancer, especially in the evaluation of sm...
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Prostatic acid phosphatase

Prostatic acid phosphatase (PAP) also known as prostatic specific acid phosphatase (PSAP) is an enzyme generated by prostatic glandular tissue. Usage It can be used in immunohistochemistry to identify prostatic tissue including prostatic epithelium and prostatic ducts and is usually expressed ...
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Prostatic leiomyoma

Prostatic leiomyomas are benign mesenchymal tumors of the prostate. Epidemiology Prostatic leiomyomas are very rare 1-3. Clinical presentation Prostatic leiomyomas can present with voiding difficulties or obstructive symptoms 1. Complications Complications of prostatic leiomyomas include a...
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Proton therapy

Proton therapy, also referred to as proton-beam therapy, is the most common type of particle therapy. It represents one of the highly conformal radiation therapy techniques that, differing from the other external-beam photon therapies, uses the proton particle properties to minimize the toxic ef...
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Protoplasmic astrocytoma

Protoplasmic astrocytoma is a rare variant of diffuse low-grade astrocytomas with histological and imaging features which overlap with other entities.  Until recently, they were classified as a subtype of low-grade diffuse astrocytoma. However, in the latest (2016) update to WHO classification ...
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PSA density

The PSA density (PSAD), is a calculation performed at diagnosis and is the serum prostate specific antigen (PSA) level (ng/mL) divided by the volume of the prostate gland (mL), resulting in a value with the units, ng/mL2 1. Prostate volume is calculated from TRUS measurements 2,3.  Alternativel...
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Pseudocirrhosis

Pseudocirrhosis is a radiological term used to convey the imaging findings of cirrhosis, but emphasize that it occurs in the setting of hepatic metastases. It is most commonly reported following chemotherapeutic treatment of breast cancer metastases, although has also been reported before treatm...
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Pseudo Meigs syndrome

Pseudo Meigs syndrome refers to a clinical syndrome of pleural effusion, ascites associated with an ovarian tumor that is not a fibroma or a fibroma-like tumor. Pathology Entities that have been reported to result in pseudo Meigs syndrome include Krukenberg tumors colon carcinoma metastases ...
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Pseudomyogenic hemangioendothelioma

Pseudomyogenic hemangioendotheliomas, also known as epithelioid sarcoma-like hemangioendotheliomas, are locally aggressive and rarely metastasizing vascular neoplasms with histological similarities to myoid tumors and epithelioid sarcomas.  Epidemiology Pseudomyogenic hemangioendotheliomas are...
Article

Pseudomyxoma peritonei

Pseudomyxoma peritonei refers to syndrome of progressive intraperitoneal accumulation of mucinous ascites related to a mucin-producing neoplasm. It is most commonly caused by a mucinous tumor of the appendix 10. Much less commonly, mucinous tumors of colon, rectum, stomach, pancreas, and urachu...
Article

Pulmonary artery sarcoma

Pulmonary artery sarcomas are extremely rare tumors that originate from the intimal mesenchymal cells of the pulmonary artery. It is frequently misdiagnosed as pulmonary thromboembolism.  Epidemiology  Primary malignant tumors of the pulmonary arteries are very rare with an incidence of 0.001–...
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Pulmonary chondroma

Pulmonary chondromas are rare, benign cartilaginous tumors of the lungs, and form part of the Carney triad although they can also arise sporadically. Epidemiology Sporadic pulmonary chondromas occur most frequently in middle-aged males, while those associated with Carney triad occur most frequ...
Article

Pulmonary hamartoma

Pulmonary hamartomas (alternative plural: hamartomata) are benign neoplasms composed of cartilage, connective tissue, muscle, fat, and bone. It is one of the most common benign tumors of the lung and accounts for ~8% of all lung neoplasms and 6% of solitary pulmonary nodules. Terminology Pulmo...
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Pulmonary lymphoma

Pulmonary lymphoma refers to lung parenchymal involvement with lymphoma. Pathology It can be broadly divided as primary or secondary: primary pulmonary lymphoma: (rare) usually non-Hodgkin lymphoma which is limited to the lung with or without mediastinal lymph node involvement and with no evi...
Article

Pulmonary mesenchymal cystic hamartoma

Pulmonary mesenchymal cystic hamartomas (PMHCs) are a rare subtype of pulmonary hamartomas. Pathology They usually comprise multiple bilateral cysts and nodules. The cyst walls are lined with normal respiratory epithelium and the nodules are permeated by scattered airways that are also lined w...
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Pulmonary metastases

Pulmonary metastases are common and the result of metastatic spread from a variety of primary tumors via blood or lymphatics. This article describes hematogenous pulmonary metastases with lymphangitis carcinomatosis discussed separately. Epidemiology The epidemiology will match that of the un...
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Pulmonary neuroendocrine tumors

Pulmonary neuroendocrine tumors are a group of lung tumors which are of neuroendocrine cell lineage. These are thought to arise from Kulchitzky cells and range from being low to high grade. These include: carcinoid tumors of the lung bronchial carcinoid tumors typical bronchial carcinoids a...
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Pulmonary opacification

Pulmonary opacification represents the result of a decrease in the ratio of gas to soft tissue (blood, lung parenchyma and stroma) in the lung. When reviewing an area of increased attenuation (opacification) on a chest radiograph or CT it is vital to determine where the opacification is. The pat...
Article

Pulmonary pneumocytoma

Pulmonary pneumocytomas, previously known as pulmonary sclerosing hemangiomas (PSH), are rare benign neoplasms of the lung. Epidemiology Typically presents in middle age (30-50 years of age). There is a recognized female predilection.  Clinical presentation  Most patients are asymptomatic. S...
Article

Pulmonary venous obstructive syndrome

Pulmonary vein obstructive syndrome (PVOS) is a form of pulmonary venous stenosis which can occur as a result of pulmonary venous infiltration by a tumor or compression by affected lymph nodes with resultant venous stasis +/- subsequent thrombosis. It can occur to a variable extent. Terminology...
Article

Pure ground glass nodules

Pure ground glass lung nodules are a subtype of ground glass lung nodules where there is no associated solid component. Pathology Etiology They have been shown to represent various pathologies such as 1,3 adenocarcinoma in situ of lung minimally-invasive adenocarcinoma of lung invasive ad...
Article

Pyrexia

Pyrexia (or fever) is a clinical sign, indicated by an abnormally elevated core body temperature, which is defined by several medical societies as ≥38.3°C (≥≈101°F). The temperature elevation may be persistent or episodic. If the body temperature is greater than 41.5°C - a rare phenomenon - it i...
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Pyrexia of unknown origin

A pyrexia of unknown origin, commonly shortened to PUO and also known as a fever of unknown origin (FUO), was originally defined in 1961 as the condition in which the core body temperature is >38.3oC for a period of three weeks or more, with no diagnosis reached after one week of inpatient inves...
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Raccoon eyes sign (base of skull fracture)

Raccoon eyes sign (or panda eyes in the UK and Ireland) refers to periorbital ecchymosis with sparing of the tarsal plate 3 and is a physical examination finding indicative of a base of skull fracture of the anterior cranial fossa. However it is not pathognomonic for trauma, and there are sever...
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Radial scar

Radial scar, or complex sclerosing lesion, is a rosette-like proliferative breast lesion. It is not related to surgical scarring. Some authors, however, reserve the latter term to lesions over 1 cm 5.  It is an idiopathic process with sclerosing ductal hyperplasia.  Its significance is that it...
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Radiation-induced breast cancer

Radiation-induced breast cancers are a potential long-term complication of radiotherapy to the chest, in particular, in those patients receiving irradiation for breast cancer or Hodgkin lymphoma.  Besides breast cancer, sarcomas (breast angiosarcoma or osteosarcomas arising from the irradiated ...
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Radiation-induced breast changes

Radiation-induced breast changes are a consequence of radiotherapy toxicity over the breast tissues either related to targeted breast cancer treatment or other thoracic malignancies (eg. lung cancer).  Radiographic features The radiation-induced breast changes may be seen in either dedicated b...
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Radiation-induced carcinogenesis

Radiation-induced carcinogenesis is widely but not universally believed to occur at exposures from ionizing radiation used in medical imaging. It is thought to be a stochastic effect of ionizing radiation, with the linear no-threshold theory (LNT) proposing no "safe" level of radiation exposure,...
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Radiation-induced cerebral vasculopathy

Radiation-induced cerebral vasculopathy or cranial arteritis encompasses a complex and broad range of effects on the intra- and extracranial vessels resulting from injury from radiation exposure. Manifestations can include hemorrhages and ischemic strokes, cavernoma and capillary telangiectasias...
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Radiation-induced glioma

Radiation-induced gliomas are a rare complication of cranial irradiation, occurring in less than 3% of cases 15 years post-treatment. Glioblastomas correspond to three-quarters of all radiation-induced gliomas.  The risk of developing a secondary CNS cancer following radiation exposure has been...
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Radiation-induced heart disease

Radiation-induced heart disease, also known as radiation cardiotoxicity, describes an uncommon constellation of potential cardiac complications of thoracic radiotherapy. Epidemiology The demographics of patients affected by radiation-induced heart disease are those of the underlying condition ...
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Radiation-induced liver disease

Radiation-induced liver disease (RILD), also referred to as radiation hepatitis, represents the toxic effect of radiation therapy on normal hepatocytes.   This article will discuss liver toxicity appearances after external beam radiotherapy techniques. Please refer to the dedicated article on s...
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Radiation-induced lung cancer

Radiation-induced lung cancers are a potential long-term complication of radiotherapy to the chest.  Besides lung cancer, sarcomas (osteosarcomas are the most common arising from the irradiated bones, and malignant fibrous histiocytomas the most frequently arising from the soft tissues), breast...
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Radiation-induced neuritis

Radiation-induced neuritis is a complication of radiotherapy that may present with visible changes on MRI. It is likely to be most relevant in the head and neck region. There is only scarce radiology literature on the subject and radiation-induced optic neuritis is best documented. Radiographic...
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Radiation-induced esophagitis

Radiation-induced esophagitis is a consequence of radiotherapy toxicity over the esophagus resulting in both acute or chronic complications:  acute esophagitis: usually 2 to 4 weeks after radiotherapy start 1 extending within ≤ 3 months after completion of the radiotherapy 3 chronic esophagiti...
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Radiation-induced pulmonary fibrosis

Radiation-induced pulmonary fibrosis is the late manifestation of radiation-induced lung disease and is relatively common following radiotherapy for chest wall or intrathoracic malignancies. This article does not deal with the changes seen in the acute phase. Please refer to the article on radi...
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Radiation-induced sarcoma

Radiation-induced sarcoma (RIS) can originate in either the irradiated bone or soft tissues after a period of latency. They are usually high-grade tumors with a poor prognosis when compared with primary sarcomas. Malignant fibrous histiocytoma and osteosarcoma are the two most common histologica...
Article

Radiation-induced thyroid cancer

Radiation-induced thyroid cancer is an important etiology of thyroid cancer.  Epidemiology Information about radiation-induced thyroid malignancies comes from several long-term cohort studies along with some case-controlled studies and their subsequent meta-analyzes. Although these studies var...
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Radiation recall pneumonitis

Radiation recall pneumonitis (RRP) is a rare reaction occurring in previously irradiated areas of pulmonary tissue after the application of triggering agents (e.g. chemotherapeutic agents or immunomodulators etc). It is not thought to be due to the direct effect of radiation. Classically this ha...
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Radiation therapy

Radiation therapy, or radiotherapy, is a common oncologic treatment modality utilizing ionizing radiation to control or eliminate malignant cells. Radiotherapy plays a role in primary curative treatment (eg. head and neck cancer), adjuvant therapy (e.g. reducing recurrence rate after local breas...
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Radioembolization

Radioembolization is the delivery of radioactive microspheres to cancers using an endovascular approach. It is often performed as an outpatient procedure.  Indications hepatocellular carcinoma hepatic metastases from colorectal carcinoma Contraindications Absolute contraindications excessi...
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Radiologically inserted gastrostomy (RIG)

A radiologically inserted gastrostomy (RIG) is a procedure where a tube is inserted percutaneously in the stomach, principally to provide nutritional support for patients with swallowing disorders 1. Indications inadequate oral intake due to dysphagia (neurologic disorder, oesophagal obstructi...
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Radiomics

Radiomics (as applied to radiology) is a field of medical study that aims to extract a large number of quantitative features from medical images using data characterization algorithms. The data is assessed for improved decision support. It has the potential to uncover disease characteristics tha...
Article

Raindrop skull

The raindrop skull appearance of calvarial multiple myeloma is the presence of multiple, well-defined lytic lesions (punched out lesions) of various size scattered throughout the skull. This term is applied as an analogy to rain hitting a surface and splashing, where it leaves a random pattern o...
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RANO criteria for glioblastoma

Response assessment in neuro-oncology criteria (RANO), published in 2010 1, are used to assess response to first-line treatment of glioblastoma (as well as lower grade astrocytoma 3) and have largely superseded the older Macdonald criteria (which only dealt with glioblastoma multiforme) 2. For ...
Article

RASopathy

RASopathies are a class of developmental disorders caused by germline mutations in genes that encode for components or regulators of the Ras/mitogen-activated protein kinase (MAPK) pathway. Epidemiology As a group, RASopathies represent one of the most common malformation syndromes, with an in...
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RECIST 1.1: comparison with RECIST 1.0

Response Evaluation Criteria In Solid Tumors (RECIST) was updated to version 1.1 in 2009. For both RECIST 1.0 and 1.1, the requirement for measurable disease at baseline depends on the endpoints of the clinical trial. The fundamental concept common to both versions of RECIST is that measurable...
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Rectal cancer

Rectal cancer, although sharing many of the features of generic colorectal carcinoma (CRC), has different preoperative imaging assessment, with MRI rectum as the mainstay for local staging, and distinct surgical techniques (i.e. total mesorectal excision).  Epidemiology Rectal cancer is genera...
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Rectal cancer response assessment

Assessment of rectal cancer response to therapy, which may be chemotherapy, radiotherapy, or a combination, relies on the synthesis of clinical, endoscopic and radiologic evaluation.  The purpose of neoadjuvant therapy is to downstage the tumor, to facilitate surgical resection and reduce local...
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Rectal cancer (staging)

Staging of rectal cancer strongly predicts the success of and rate of local recurrence following rectal cancer resection. MRI is the modality of choice for the staging of rectal cancer, to guide surgical and non-surgical management options. MRI is used at diagnosis, following downstaging chemora...
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Renal cell carcinoma

Renal cell carcinomas (RCC) (historically also known as hypernephroma or Grawitz tumor) are primary malignant adenocarcinomas derived from the renal tubular epithelium and are the most common malignant renal tumor. They usually occur in 50-70-year old patients and macroscopic hematuria occurs in...
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Renal cell carcinoma (TNM staging)

Renal cell carcinoma staging using the TNM staging system for renal cell carcinoma. Older but still widely used system in some practices is the Robson staging system. TNM staging (7th edition) T T1 T1a: tumor confined to kidney, <4 cm T1b: tumor confined to kidney, >4 cm but <7 cm T2: limi...
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Renal leiomyoma

Renal leiomyomas are benign tumors of the kidney originating from smooth muscle cells of the renal capsule, pelvis, calyces, or blood vessels. There is a 4-5.5% prevalence based on autopsy findings 1. Clinical presentation Renal leiomyomas are usually incidental findings. In symptomatic cases...
Article

Renal lymphoma

Renal lymphoma is usually a part component of multi-systemic lymphoma. Primary renal lymphoma, which is defined as lymphoma involving the kidney exclusively without any manifestation of extra-renal lymphatic disease 3-5. Typical imaging findings are multiple bilateral hypodense or infiltrative r...
Article

RENAL nephrometry scoring system

The RENAL nephrometry scoring system was developed to categorize renal masses into low, intermediate and high complexity, based on cross-sectional imaging findings. Its purpose is to aid in decision making, patient counseling, surgical planning, and patient follow-up, as well as academic reporti...
Article

Renal oncocytoma

Renal oncocytomas are relatively benign renal tumors. The main clinical importance of this lesion is the difficulty in pre-operatively distinguishing it from renal cell carcinomas, as epidemiology, presentation, imaging and even histology can be very similar.  Epidemiology Renal oncocytomas ac...
Article

Renal osteodystrophy

Renal osteodystrophy (ROD), also known as uremic osteopathy, is a constellation of musculoskeletal abnormalities that occur in patients with chronic renal failure, due to concurrent and superimposed: osteomalacia (adults)/rickets (children) secondary hyperparathyroidism: abnormal calcium and p...
Article

Reporting and Data Systems (disambiguation)

In recent years there has been a proliferation of Reporting and Data Systems (RADS), which have been proposed - and in many cases widely adopted - as standardized systems for the reporting of imaging of various body organs, often, but certainly not always, with a focus on oncological disease 2. ...
Article

Residual breast cancer

A residual breast cancer is a remaining portion of the original primary breast cancer after an incomplete resection or following radiotherapy or chemotherapy. The term is particularly used in assessing patients who have had neo-adjuvant chemo +/- radiotherapy.
Article

Response evaluation criteria in solid tumors

Response evaluation criteria in solid tumors or RECIST refers to a set of published rules used to assess tumor burden in order to provide an objective assessment of response to therapy. They were initially introduced in 2000 and have undergone subsequent revision in 2009 (RECIST 1.1). For the ev...
Article

Retroperitoneal leiomyosarcoma

Retroperitoneal leiomyosarcoma, leiomyosarcoma arising within the retroperitoneum, is one of the commonest primary retroperitoneal neoplasms. The retroperitoneum is considered the most common extrauterine site for leiomyosarcoma.  Epidemiology They are more common in women. Clinical presentat...
Article

Rhabdoid meningioma

Rhabdoid meningioma is a rare and aggressive subtype of meningioma, it is classified as WHO grade III. Rhabdoid morphology is associated with a poor prognosis, regardless of tumor histogenesis. It resembles other types of rhabdoid tumors with a great tendency for recurrence 1,2. Extensive necros...
Article

Rhabdomyosarcoma (genitourinary tract)

Rhabdomyosarcomas of the genitourinary tract are uncommon tumors occurring in pelvic organs.  It is a disease nearly exclusive to the pediatric population.  For a general discussion of this type of tumor, please refer to the article on rhabdomyosarcomas. Epidemiology The peak incidence of tum...
Article

Rhabdomyosarcomas (biliary tract)

Rhabdomyosarcomas of the biliary tract are rare tumors, usually identified in children, with a very poor prognosis. They are usually grouped under botryoid rhabdomyosarcomas. For a general discussion of this type of tumor, please refer to the article on rhabdomyosarcomas. Epidemiology Rhabdom...
Article

Right hemicolectomy

A right hemicolectomy is a surgical procedure to remove the cecum and ascending colon. Indications cancer of the appendix, cecum or ascending colon (most common) 1 inflammatory bowel disease, particularly Crohn disease complicated appendicitis cecal volvulus perforation of the right colon ...
Article

ROS1 mutation

The ROS1 mutation is a mutation occurring in the ROS1 oncogene on chromosome 6 resulting in a defective receptor tyrosine kinase which has structural similarity to the anaplastic lymphoma kinase (ALK) protein. It is thought to be present in several cancers of the subtype non-small cell lung can...
Article

Rotational/helical/arc intensity-modulated radiation therapy

Rotational/helical/arc intensity-modulated radiation therapy (IMRT) is the most advanced form of IMRT is conceptually similar to helical or cone-beam CT 1. The radiation beam remains turned on throughout the treatment while the gantry is moved around the patient at variable speed and the multi-l...
Article

Rubinstein-Taybi syndrome

Rubinstein-Taybi syndrome (RTS) is a very rare genetic multi-system disorder primarily characterized by intellectual disability, broad and often angulated thumbs and halluces, and distinctive facial features. Epidemiology The estimated incidence is 1 in 100,000-125,000 live births 5. Clinical...
Article

Rule of 10s (Wilms tumor)

Wilms tumor classically follows a "rule of 10s" 1,2: up to 10% may have unfavorable histology 10% are bilateral 10% have vascular invasion 10% have calcifications on CT 10% have pulmonary metastases at presentation See also Wilms tumor

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