Rothmund-Thomson Syndrome

Rothmund-Thomson syndrome (poikiloderma congenitale) is a rare autosomal recessive disorder that presents in infancy with skeletal issues (see below), skin rash (poikiloderma), partial or total alopecia, eye issues (photophobia, cataract, microphthalmia, microcornea, strabismus, and glaucoma), and hormonal issues (hypogonadism, growth hormone deficiency). The patients are also predisposed to developing osteosarcoma and basal and squamous cell carcinoma of the skin.

Skeletal problems that can be seen on radiographs include mineralization disorders (osteoporosis or osteosclerosis), radial hypoplasia or agenesis, absent thumb, mild epiphysial dysostosis and metaphyseal sclerosis, knee subluxation, and flattened and elongated vertebral bodies.

References

• Gelaw B, Ali S, Becker J. Rothmund-Thomson syndrome, Klippel-Feil syndrome, and osteosarcoma. Skeletal Radiol. 2004 Oct;33(10):613-5.
• Mehollin-Ray AR, Kozinetz CA, Schlesinger AE, Guillerman RP, Wang LL. Radiographic abnormalities in Rothmund-Thomson syndrome and genotype-phenotype correlation with RECQL4 mutation status. AJR Am J Roentgenol. 2008 Aug;191(2):W62-6.

Focal Nodular Hyperplasia on F-18 FDG-PET

Focal nodular hyperplasia (FNH) characteristically has FDG avidity similar to (more common) or lower than the surrounding liver. In rare circumstances, FNH can present as a hypermetabolic lesion, creating some confusion.

The case above shows the typical appearance of focal nodular hyperplasia on CT. FDG-PET shows that the uptake of the lesion (arrow) is similar to the adjacent liver.

Differential considerations on FDG-PET include adenoma, hemangioma, and hepatocellular carcinoma.

References

• Aznar DL, Ojeda R, Garcia EU, Aparici F, Sánchez PA, Flores D, Martínez C, Sopena R. Focal nodular hyperplasia (FNH): a potential cause of false-positive positron emission tomography. Clin Nucl Med. 2005 Sep;30(9):636-7.
• Kurtaran A, Becherer A, Pfeffel F, Müller C, Traub T, Schmaljohann J, Kaserer K, Raderer M, Schima W, Dudczak R, Kletter K, Virgolini I. 18F-fluorodeoxyglucose (FDG)-PET features of focal nodular hyperplasia (FNH) of the liver. Liver. 2000 Dec;20(6):487-90.

Focal Pure Ground-Glass Opacities in the Setting of Primary Lung Carcinoma

A focal pure ground-glass opacity (GGO) is defined on HRCT as an area of homogeneously increased opacity of the lung without a solid component and with preservation of the underlying bronchial and vascular margins.

One or more of these focal pure ground-glass opacities are often seen in the lungs, sometimes in more than one lobe, in addition to the primary lung cancer. These can represent neoplastic lesions (e.g., atypical adenomatous hyperplasia, bronchioloalveolar carcinoma, lymphoma, and even metastases) or inflammatory lesions and fibrosis.

Most focal pure ground-glass opacities associated with lung cancer do not change in size during follow-up. In addition, the prognosis of patients with a primary lung cancer and coexisting atypical adenomatous hyperplasia or bronchoalveolar carcinoma is related more to the primary lung cancer than the atypical adenomatous hyperplasia or bronchoalveolar carcinoma. Therefore, it has been suggested that therapy be directed at resection of the primary tumor without intervention in the remaining focal pure ground-glass opacities.

The case above is from a patient with a resected primary lung carcinoma and with multiple focal pure ground-glass opacities (pink arrows). These had not changed in size over a 4-year period. A more solid lesion (blue arrow) had mild FDG avidity (not shown) and had grown slightly in the same interval.

References

Tsutsui S, Ashizawa K, Minami K, Tagawa T, Nagayasu T, Hayashi T, Uetani M. Multiple focal pure ground-glass opacities on high-resolution CT images: Clinical significance in patients with lung cancer. AJR Am J Roentgenol. 2010 Aug;195(2):W131-8.

Cystic Lymph Nodes in Head and Neck Squamous Cell Carcinomas

Cystic cervical nodal metastases are specific and easily recognizable manifestation of a subset of head and neck squamous cell carcinomas (SCC) arising from the Waldeyer ring and associated with human papillomavirus (HPV).

Cystic lymph nodes can be seen in as many as 50% of squamous cell carcinomas arising from the Waldeyer ring, and about 50% of all tonsil/base of tongue squamous cell carcinomas are positive for human papillomavirus. These cystic nodal metastases are typically located in the jugulodigastric region and can be moderately large and associated with relatively small or occult primary tumors.

The cyst formation in these lymph nodes is thought to be due to spontaneous degradation of keratin and cellular debris inside the lymph node or formation of a true epithelium-lined cyst in the center of the lymph node. It is not thought to be due to central necrosis as can be seen in cystic nodal metastases elsewhere.

Other head and neck cancers, notably papillary thyroid carcinoma, can result in cystic lymph node metastasis. Carcinoma arising in a branchial cleft cyst is now considered to be exceedingly rare. Indeed, many lesions previously diagnosed as branchial cleft carcinomas are now thought to have represented cystic metastasis from a tonsillar primary squamous cell carcinoma.

References

Goldenberg D, Begum S, Westra WH, Khan Z, Sciubba J, Pai SI, Califano JA, Tufano RP, Koch WM. Cystic lymph node metastasis in patients with head and neck cancer: An HPV-associated phenomenon. Head Neck. 2008 Jul;30(7):898-903.

F18-FDG PET and Hepatocellular Carcinoma

FDG-PET is relatively insensitive for hepatocellular carcinoma. Well-differentiated tumors can have metabolic activity that can be similar to the normal liver parenchyma, resulting in reported sensitivities of at most ~65%. The sensitivity falls to 0% in patients with end-stage liver disease awaiting transplantation.

However, there may be a role for FDG-PET in prognosis, with FDG-avid lesions representing poorly differentiated tumors and poorer prognosis.

The image above shows extensive hepatocellular carcinoma in the liver with a right adrenal metastasis (arrows). The FDG uptake pattern is essentially normal in both the liver and the right adrenal gland.

References

• Ahn SG, Kim SH, Jeon TJ, Cho HJ, Choi SB, Yun MJ, Lee JD, Kim KSJ. The role of preoperative [18F]fluorodeoxyglucose positron emission tomography in predicting early recurrence after curative resection of hepatocellular carcinomas. Gastrointest Surg. 2011 Nov;15(11):2044-52. Epub 2011 Sep 9.
• Hustinx R. PET imaging in assessing gastrointestinal tumors. Radiol Clin North Am. 2004 Nov;42(6):1123-39, ix.

Role of Radiography in Diagnosis of Rheumatoid Arthritis

The most recent guidelines by the American College of Rheumatology and European League Against Rheumatism have dropped radiography from their diagnostic criteria and instead rely on physical examination findings and laboratory data.

The reason for this change is that modern therapy relies on early diagnosis and treatment with disease-modifying antirheumatic drugs (DMARDs), and radiographs are painfully insensitive in this setting (~70% of patients with early disease have normal radiographs).

MRI or ultrasound are much more sensitive, but the guidelines limit their use to confirmation of the clinical findings after clinical classification of a patient.

Radiography still has a role in excluding other joint diseases (e.g., osteoarthritis) and to assess joint damage in established cases of rheumatoid arthritis.

References

• Aletaha D, Neogi T, Silman AJ, et al. 2010 rheumatoid arthritis classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Ann Rheum Dis. 2010 Sep;69(9):1580-8. Erratum in: Ann Rheum Dis. 2010 Oct;69(10):1892.
• Rowbotham EL, Grainger AJ. Rheumatoid arthritis: ultrasound versus MRI. AJR Am J Roentgenol. 2011 Sep;197(3):541-6.
• Tan YK, Conaghan PG. Imaging in rheumatoid arthritis. Best Pract Res Clin Rheumatol. 2011 Aug;25(4):569-84.

FDG and Lactating Women

Lactating women have increased uptake in the breast(s) used for breastfeeding. For example, a breast that is consistently refused by baby or breasts in non-breastfeeding women, do not have significantly increased uptake.

No significant radiotracer is excreted in the breast milk, and the radiation dose received by the baby is more from close contact with the breast than from ingestion of radioactive milk.

References

Hicks RJ, Binns D, Stabin MG. Pattern of uptake and excretion of (18)F-FDG in the lactating breast. J Nucl Med. 2001 Aug;42(8):1238-42.

Environmental Risk Factors for Rheumatoid Arthritis

The current thinking is that rheumatoid arthritis (RA) occurs when genetic and environmental factors combine to trigger immunopathological changes that lead to an inflammatory arthritis.

Cigarette smoking is the one environmental factor with an unequivocal association. The impact seems to be limited to patients with seropositive disease, and its influence is greater in men compared to women.

Other strong associations include low alcohol use (alcohol is protective) and periodontitis (increased risk in edentulous patients and those with periodontal disease).

Weaker environmental risk factors include vitamin D intake (protective), obesity (increases risk), social status (socioeconomic status and education are inversely associated with risk of developing RA), breast-feeding (protects mother), and high birth weight (higher risk).

There are contradictory reports in the literature about the association of oral contraceptive pill use and history of blood transfusions, with some finding protective effects and others finding an increased risk.

References

Scott IC, Steer S, Lewis CM, Cope AP. Precipitating and perpetuating factors of rheumatoid arthritis immunopathology: linking the triad of genetic predisposition, environmental risk factors and autoimmunity to disease pathogenesis. Best Pract Res Clin Rheumatol. 2011 Aug;25(4):447-68.

Infradiaphragmatic Brown Fat Uptake

Brown fat uptake in FDG-PET is usually fairly characteristic in the neck, shoulder and costovertebral regions: bilateral, symmetric, intense uptake that is usually multifocal although linear uptake is also possible.

Infradiaphragmatic brown fat uptake poses a challenge when asymmetrical or focal, and may be mistaken for adrenal malignancy or misregistration due to respiration. Correlation with PET images shows the uptake to be located in infradiaphragmatic fat.

References

• Bar-Shalom R, Gaitini D, Keidar Z, Israel O. Non-malignant FDG uptake in infradiaphragmatic adipose tissue: a new site of physiological tracer biodistribution characterised by PET/CT. Eur J Nucl Med Mol Imaging. 2004 Aug;31(8):1105-13.
• Reddy MP, Ramaswamy MR. FDG uptake in brown adipose tissue mimicking an adrenal metastasis: source of false-positive interpretation. Clin Nucl Med. 2005 Apr;30(4):257-8.

Multiple Intraparotid Calcifications

Differential considerations for multiple intraparotid calcifications includes

• Sialolithiasis: Isolated or in association with Sjögren syndrome or cystic fibrosis.
• Tuberculosis:
• Mucoepidermoid tumors:
• Osteochondroma:
• Inflammatory pseudotumor:
• MALT lymphoma:

References

• Konstantinidis I, Paschaloudi S, Triaridis S, Fyrmpas G, Sechlidis S, Constantinidis J. Bilateral multiple sialolithiasis of the parotid gland in a patient with Sjögren's syndrome. Acta Otorhinolaryngol Ital. 2007 Feb;27(1):41-4.
• Tagnon BB, Theate I, Weynand B, Hamoir M, Coche EE. Long-standing mucosa-associated lymphoid tissue lymphoma of the parotid gland: CT and MR imaging findings. AJR Am J Roentgenol. 2002 Jun;178(6):1563-5.

Calcium Pyrophosphate Deposition: Terminology and Classification

An expert panel put together by the European League Against Rheumatism (EULAR) has come up with consensus definitions for the spectrum of conditions associated with calcium pyrophosphate crystals.

They define calcium pyrophosphate deposition (CPPD) as an umbrella term for all instances of calcium pyrophosphate crystal occurrence. Chondrocalcinosis is defined as cartilage calcification and stress that it is not always due to calcium pyrophosphate deposition. Radiograogic chondrocalcinosis is neither sensitive nor specific for diagnosis of calcium pyrophosphate deposition.

Four clinical presentations can be associated with calcium pyrophosphate deposition:

• Asymptomatic CPPD: May be isolated chondrocalcinosis or associated with osteoarthritis. Often an incidental finding during imaging for another indication.
• Osteoarthritis with CPPD: CPPD in a joint that also shows changes of osteoarthritis. The knees are typically involved, although the distribution may be atypical for osteoarthritis elsewhere (e.g., radiocarpal or midcarpal, glenohumeral, hindfoot or midfoot). Cyst and osteophyte formation tends to be more prominent than in osteoarthritis without CPPD. Patients may have chronic symptoms and/or acute attacks of crystal-induced inflammation. In contrast to osteoarthritis without CPPD, there may be more inflammatory symptoms and signs.
• Acute CPP crystal arthritis: Acute-onset, self-limiting synovitis with CPPD (formerly known as pseudogout). Patients typically present with severe, rapid-onset joint pain, tenderness, swelling, and overlying erythema. The symptoms peak within 6–24 hours. May coexist with a septic joint.
• Chronic CPP crystal inflammatory arthritis: Chronic inflammatory oligoarthritis or polyarthritis associated with CPPD. Patients have occasional systemic upset with elevation of CRP and ESR and superimposed flares with characteristics of crystal inflammation (see above). Differential considerations include rheumatoid arthritis and other chronic inflammatory joint diseases in older adults.

Imaging findings are similar to those of osteoarthritis, but the dirstribution within the joint is different, with CPPD affecting non-weight-bearing surfaces of joints. It is also usually bilateral and symmetric. Synovial inflammation and joint effusions can also be seen. Osteophytes and osteochondral bodies are commonly present. Subchondral cysts are more prominent than in osteoarthritis, and may form before cartilage loss is radiographically evident. Risk factors for calcium pyrophosphate arthropathy are aging, osteoarthritis, previous joint trauma, metabolic diseases (e.g., the four Hs: hemochromatosis, primary hyperparathyroidism, hypophosphatasia, hypomagnesemia), and hereditary predisposition.

References

• Steinbach LS, Resnick D. Calcium pyrophosphate dihydrate crystal deposition disease revisited. Radiology. 1996 Jul;200(1):1-9.
• Zhang W, Doherty M, Bardin T, Barskova V, Guerne PA, Jansen TL, Leeb BF, Perez-Ruiz F, Pimentao J, Punzi L, Richette P, Sivera F, Uhlig T, Watt I, Pascual E. European League Against Rheumatism recommendations for calcium pyrophosphate deposition. Part I: terminology and diagnosis. Ann Rheum Dis. 2011 Apr;70(4):563-70.

Os Vesalianum Pedis

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The os vesalianum pedis (to be differentiated from the os vesalianum manius in the hand) is an uncommon accessory bone that is seen in less than 0.5% of the population. It is located within the peroneus brevis tendon adjacent to the tip of a well-developed tuberosity of the fifth metatarsal and articulates with the cuboid. It is rarely symptomatic.

Differential considerations include:

• Avulsion fracture: Oriented in the transverse plane.
• Normal ossification center: The normal ossification center of the tuberosity of the fifth metatarsal is oriented parallel to the metatarsal shaft.
• Iselin disease: Traction apophysitis at the base of the fifth metatarsal. Similar to Osgood Schlatter disease, ossicles can break free, resulting in a fragmented appearance.

References

• Gillespie H. Osteochondroses and apophyseal injuries of the foot in the young athlete. Curr Sports Med Rep. 2010 Sep-Oct;9(5):265-8.
• Mellado JM, Ramos A, Salvadó E, Camins A, Danús M, Saurí A. Accessory ossicles and sesamoid bones of the ankle and foot: imaging findings, clinical significance and differential diagnosis. Eur Radiol. 2003 Dec;13 Suppl 4:L164-77. Review.

FDG Embolism

Thrombus formation during intravenous administration of FDG can result in small pulmonary emboli that present as a focus (or foci) of intense FDG activity in the lung without a corresponding CT abnormality. These generally resolve after a few days and can even be seen to migrate peripherally in scans obtained on the same day.

The mechanism is thought to be related to FDG uptake by platelets at the site of injection and by neutrophils at the site of embolism. Vascular injury during FDG injection can lead to thrombus formation and platelet activation. Activated platelets have increased energy requirements and glucose uptake (5–6 times normal), which can lead to concentration of FDG in the thrombus. Activated neutrophils that respond to vascular injury after pulmonary embolism also have increased glucose uptake and can cause focal FDG uptake at the site of embolism.

References

• Farsad M, Ambrosini V, Nanni C, Castellucci P, Boschi S, Rubello D, Fabbri M, Franchi R, Fanti S. Focal lung uptake of 18F-fluorodeoxyglucose (18F-FDG) without computed tomography findings. Nucl Med Commun. 2005 Sep;26(9):827-30.
• Ha JM, Jeong SY, Seo YS, Kwon SY, Chong A, Oh JR, Song HC, Bom HS, Min JJ. Incidental focal F-18 FDG accumulation in lung parenchyma without abnormal CT findings. Ann Nucl Med. 2009 Aug;23(6):599-603.
• Kavanagh PV, Stevenson AW, Chen MY, Clark PB. Nonneoplastic diseases in the chest showing increased activity on FDG PET. AJR Am J Roentgenol. 2004 Oct;183(4):1133-41.

Colonic Lipoma

Colonic lipomas can be seen in up to ~4% of autopsy examinations of the colon. About 1/3 are located in the ascending colon, with incidence dropping the more distal you go down the colon.

They are the most most common benign tumors causing colo-colonic intussusception in adults. About 90% of colonic lipomas are submucosal. The rest are subserosal and related to the epiploic appendices.

Colonic lipomas are usually asymptomatic when smaller than 2 cm. Lesions larger than 2 cm are thought to be more likely to cause acute abdominal pain, changes in bowel habits, gastrointestinal bleeding (from ulceration of the colonic mucosa overlying the tumor), intussusception, or bowel obstruction. About 50% of patients with lipomas between 3 cm - 4 cm in diameter are symptomatic, while 75% of patients with lipomas larger than 4 cm are symptomatic.

Radiographs may reveal a focal radiolucency, but are usually not helpful. Contrast enema can also be nonspecific, revealing a smooth filling defect; however, changes in the lesion's shape and size on real-time fluoroscopy during peristalsis or with compression ("squeeze sign") can suggest the diagnosis.

CT or MRI can be diagnostic, by showing characteristic fat attenuation and intensity, respectively.

References

• Fernandez MJ, Davis RP, Nora PF. Gastrointestinal lipomas. Arch Surg. 1983 Sep;118(9):1081-3.
• Gollub MJ. Colonic intussusception: clinical and radiographic features. AJR Am J Roentgenol. 2011 May;196(5):W580-5.
• Gould DJ, Anne Morrison C, Liscum KR, Silberfein EJ. A lipoma of the transverse colon causing intermittent obstruction: a rare cause for surgical intervention. Gastroenterol Hepatol (N Y). 2011 Jul;7(7):487-90.

Feline Injection-Site Sarcomas

Foreign material injected in the subcutis or muscle of predisposed cats can induce a chronic inflammatory response that can lead to neoplastic transformation. The tumors are mesenchymal tumors, most commonly fibrosarcomas, but malignant fibrous histiocytoma, osteosarcoma, chondrosarcoma, rhabomyosarcoma and undifferentiated sarcoma have also been reported.

The most common inciting agent is vaccination, with an incidence of between 1/1000–1/10,000 vaccinated cats. Other reported inciting factors include injections of long acting antibiotics or steroids, pesticides, non-absorbable suture material, and microchip implants

The latency period can be as long as 10 years; however, periods as short as 3 months have been observed. Once the tumor appears, however, growth can be dramatic, often reaching several centimeters in diameter within a few weeks, and leading to central necrosis.

Biopsy is recommended for these lesions, as fine needle aspiration and cytology evaluation can be nondiagnostic in about 50% of cases. As the masses can be quite heterogeneous, incisional biopsy is preferred to avoid issues with sampling error (small tissue samples can lead to misdiagnosis as a granuloma).

The mainstay of therapy is wide surgical excision with macroscopically free margins of 3 cm – 5 cm, with overall median disease-free intervals of ~10 months. Adjuvant chemotherapy and radiation therapy has also been used.

Current guidelines recommend administration of FeLV vaccination in the left rear leg, as distal as possible, the rabies vaccine in the right rear leg, as distal as possible, and the four-in-one vaccine FVRCP ± C2 in the right shoulder.

References

Martano M, Morello E, Buracco P. Feline injection-site sarcoma: past, present and future perspectives. Vet J. 2011 May;188(2):136-41. Epub 2010

Bone Infarction on FDG-PET

Bone infarction/avascular necrosis can have increased FDG activity, likely from peri-infarct inflammation. This hasn't been very well studied in the literature and can sometimes result in a false-positive interpretation in the evaluation of metastatic disease. The image above shows mild FDG activity in the left femoral head, corresponding to avascular necrosis seen on the coronal T1-weighted image.

References

Grigolon MV, Delbeke D. F-18 FDG uptake in a bone infarct: a case report. Clin Nucl Med. 2001 Jul;26(7):613-4.

Diffusely Increased FDG Activity in the Thyroid

The thyroid may occasionally have diffusely increased uptake on FDG-PET scans obtained for malignancy elsewhere. Between 1%-3% of patients undergoing a PET scan will have such uptake. This finding can be seen as a normal variant or associated with chronic lymphocytic (Hashimoto) thyroiditis, with or without the presence of hypothyroidism and can be seen even in patients receiving thyroid hormone replacement therapy.

Focal uptake in the thyroid should raise concern for carcinoma or metastasis.

References

• Chen YK, Chen YL, Cheng RH, Yeh CL, Lee CC, Hsu CH. The significance of FDG uptake in bilateral thyroid glands. Nucl Med Commun. 2007 Feb;28(2):117-22.
• Karantanis D, Bogsrud TV, Wiseman GA, Mullan BP, Subramaniam RM, Nathan MA, Peller PJ, Bahn RS, Lowe VJ. Clinical significance of diffusely increased 18F-FDG uptake in the thyroid gland. J Nucl Med. 2007 Jun;48(6):896-901.
• Shreve PD, Anzai Y, Wahl RL. Pitfalls in oncologic diagnosis with FDG PET imaging: physiologic and benign variants. Radiographics. 1999 Jan-Feb;19(1):61-77; quiz 150-1.

Perirectal Artifact on FDG PET/CT

Differences in position of rectal gas between acquisition of CT and PET images can lead to a perirectal artifact on attenuation-corrected PET images.

The artifact is caused by localized attenuation over-correction at the margin of the rectum due to movement of gas: There is soft tissue attenuation in the rectum at CT acquisition, and gas during PET acquisition. The proximity of the high-signal urinary bladder results in a high-intensity region extending posterior to the bladder and around the rectum immediately adjacent to a region of rectal gas. The artifact is not observed when rectal gas is absent.

This artifact is reportedly seen in 15% of PET/CTs and has a maximum standardized uptake value of ~5.

References

Lodge MA, Chaudhry MA, Udall DN, Wahl RL. Characterization of a perirectal artifact in 18F-FDG PET/CT. J Nucl Med. 2010 Oct;51(10):1501-6.

PEComa

PEComas are a family of neoplasms with perivascular epithelioid cell (PEC) differentiation, and are defined by the WHO as "mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells (PECs)."

The best known member of the PEComa family is the angiomyolipoma. Other members of the family include clear cell "sugar" tumor of the lung; lymphangioleiomyomatosis; clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres; and unusual clear tumors of the pancreas, rectum, abdominal serosa, uterus, vulva, thigh, and heart.

The uterus is the most common site of involvement, accounting for about half of the documented cases in the literature, but PEComas can occur anywhere. While more common in women, they can also occur in men.

References

• Pathology and Genetics of Tumours of Soft Tissue and Bone. Fletcher CDM, Unni KK, Mertens F (eds). IARCPress Lyon, 2002.
• Prasad SR, Sahani DV, Mino-Kenudson M, Narra VR, Humphrey PA, Menias CO, Chintapalli KN. Neoplasms of the perivascular epithelioid cell involving the abdomen and the pelvis: cross-sectional imaging findings. J Comput Assist Tomogr. 2007 Sep-Oct;31(5):688-96.

Lateral Recess of the Sphenoid Sinus

Pneumatization of the sphenoid sinus can extend laterally, creating a lateral recess. Pneumatization can then further extend into the pterygoid process, the great wing of the sphenoid bone (as seen abvoe) or both. This can be clinically relevant, as surgical access to lesions in this lateral recess can be challenging.

Coronal images reveal projection of the sphenoid sinus sidewall beyond the foramen rotundum (r). The lateral recess extends into the greater wing of the sphenoid bone above the vidian canal (v) and below the foramen rotundum (r), separating the two. There may be normal side-to-side asymmetry of the vidian-rotundum distance.

The main differential consideration in an opacified sinus is an expansile or erosive process in the sphenoid sinus (e.g., mucoceles or polyps). The most specific evidence of such a process is gross sinus wall erosion and flattening or erosion of the rims of vidian canal or the foramen rotundum.

The patient above has bilateral lateral recesses, with the one on the right extending to the sphenoid wing. The patient also has multiple facial fractures.

References

• Giannetti AV, Guimarães RE, Santiago AP, Perpétuo FO, Machado MA. A tomographic study of the skull base in primary spontaneous cerebrospinal fluid leaks. Neuroradiology. 2011 Jul 8.
• Lewin JS, Curtin HD, Eelkema E, Obuchowski N. Benign expansile lesions of the sphenoid sinus: differentiation from normal asymmetry of the lateral recesses. AJNR Am J Neuroradiol. 1999 Mar;20(3):461-6.
• Tami TA. Surgical management of lesions of the sphenoid lateral recess. Am J Rhinol. 2006 Jul-Aug;20(4):412-6.

Demineralized Bone Matrix Putty

Demineralized bone matrix putty (DBM) is a malleable substance that is used for packing material, either by itself or mixed with other grafting material to increase volume.

Bone matrix contains small amounts of bone morphogenetic proteins (BMPs), and demineralization increases their bioavailabilty for interaction with mesenchymal stem cells. Bone morphogenetic proteins recruit these stem cells and modulate their conversion to bone-forming cells that produce new bone.

By itself, demineralized bone matrix putty is mostly osteoinductive (recruits and modulates mesenchymal stem cells to produce new bone). Combination with cancellous bone allograft, which is mainly osteoconductive (functions as a scaffold for bone growth), gives the mixture both osteoinductive and osteoconductive properties. Bone autograft by itself has both osteoinductive and osteoconductive properties. Using putty with bone allograft avoids harvest site

The putty by itself is barely perceptible post-operative radiographs. The combination with allograft (seen above) gives it a density on radiographs higher than medullary bone, but lower than cortical bone. On CT, the combination also has attenuation between that of medullary bone and cortical bone (~500–1000 HU).

References

• Beaman FD, Bancroft LW, Peterson JJ, Kransdorf MJ, Menke DM, DeOrio JK. Imaging characteristics of bone graft materials. Radiographics. 2006 Mar-Apr;26(2):373-88.
• Pietrzak WS, Perns SV, Keyes J, Woodell-May J, McDonald NM. Demineralized bone matrix graft: a scientific and clinical case study assessment. J Foot Ankle Surg. 2005 Sep-Oct;44(5):345-53.

Osteoma Cutis

Osteoma cutis, more simply called cutaneous ossification, is an uncommon condition. It can be classified as primary and secondary forms.

Primary Osteoma Cutis

Primary osteoma cutis is further divided into two subclasses based on whether or not it is associated with Albright hereditary osteodystrophy.

Albright hereditary osteodystrophy has a poor long-term prognosis. Cases of primary osteoma cutis associated with Albright hereditary osteodystrophy can either have pseudohypoparathyroidism or pseudopseudohypoparathyroidism. Patients are generally obese and have short stature, developmental disabilities, round facies, and basal ganglia calcifications.

Cases of primary osteoma cutis not associated with Albright hereditary osteodystrophy can be further divided as multiple miliary osteoma of the face (usually women), isolated osteoma (single site), widespread osteoma (occurs in the neonatal period), and congenital plaque-like osteoma.

Secondary Osteoma Cutis

Secondary osteoma cutis is relatively more common than primary osteoma cutis and occurs in association with prior skin inflammation (e.g., syphilis, pyogenic granuloma, folliculitis), injury, or tumor. Tumors associated with secondary osteoma cutis include metastatic bronchogenic carcinoma, basal cell carcinoma, hemangioma, and pilomatricoma, among others.

References

Fazeli P, Harvell J, Jacobs MB. Osteoma cutis (cutaneous ossification). West J Med. 1999 Oct;171(4):243-5.

Pencil on CT

The CT appearance of the typical pencil containing graphite and wood is shown above in cross section in a patient with a penetrating injury. The attenuation of wood is negative (~-400 HU in this case), seen best on the lung windows. The graphite has much higher attenuation (~500 in this case), but lower than that of cortical bone.

The paint seems to have higher attenuation than the wood. Two old papers from 1971 raise concerns about the lead content of paints used on pencils, but I can't find any recent data on the contents of the paint.

References

• Pichirallo J. Lead poisoning: risks for pencil chewers? Science. 1971 Aug 6;173(3996):509-10.
• Tenenholz T, Baxter AB, McKhann GM. Orbital assault with a pencil: evaluating vascular injury. AJR Am J Roentgenol. 1999 Jul;173(1):144.
• Schaplowsky AF. Lead in paint on pencils. HSMHA Health Rep. 1971 Nov;86(11):961-2.

Radiation-Induced Coronary Artery Disease in Breast Cancer

Radiation-induced heart disease includes a spectrum of pathology affecting the pericardium, coronary arteries, myocardium, and heart valves. Of these, coronary artery disease may be the most significant cause of mortality from radiation-induced heart disease.

Women who have received adjuvant radiation therapy for left-sided breast cancer have been shown to have an increased incidence of coronary artery disease. The vast majority involve the left anterior descending artery. Indeed, myocardial perfusion defects have been shown to develop in the left anterior descending artery territory following radiation therapy for left-sided breast cancer.

The etiology may be related to damage to capillaries supplying myocytes or to the major epicardial arteries themselves (mimicking the pathological process of atherosclerosis).

Patients with radiation-induced coronary artery disease present in the same way as those without a history of radiation and are usually treated in the same way. Surgical management, however, may be complicated by mediastinal and pericardial fibrosis, concurrent radiation-induced injury to the left internal mammary artery (which is usually used as a graft), and impaired post-operative healing of radiation-damaged tissues.

Modern radiation therapy techniques have reduced the amount of heart that is included in the radiation field, and there is some data to suggest that there may not be an increased risk of mortality related to coronary artery with these newer techniques.

References

• Filopei J, Frishman W. Radiation-Induced Heart Disease. Cardiol Rev. 2012 Feb 6.
• Park CK, Li X, Starr J, Harris EE. Cardiac morbidity and mortality in women with ductal carcinoma in situ of the breast treated with breast conservation therapy. Breast J. 2011 Sep-Oct;17(5):470-6.

Posttraumatic Subchondral Injuries

Posttraumatic subchondral injuries affect the articulating surface with intact articular cartilage. They are both associated with lysis and liquefaction of medullary fat and can be further classified as contusions (bruises) and fractures (impaction).

• Subchondral bone contusions: These are trabecular microfracture or infractions with hemorrhage and edema. MRI reveals poorly defined, reticulated, heterogeneous T1-hypointensity and T2-hyperintensity. The area of signal abnormality is usually larger on T2-weighted images compared to T1-weighted images.
  
  Differential considerations for this appearance include:
  • Osteonecrosis
  • Fat necrosis
  • Osteoarthritis
  • Normal variant (e.g., in children)
  
  
  
• Subchondral fractures: These are linear or curvilinear fractures that extend through the subchondral bone without violation or depression of the subchondral bone plate. There may be thickening of the black line of the subchondral bone plate and/or geographic or linear areas of signal abnormality in the subchondral bone marrow. When geographic, there is a coalescent area of low T1 signal that abuts the subchondral plate. When linear (shown above), the signal abnormality can be vertical, oblique or parallel to the cartilage.
  
  Differential considerations include:
  • Osteonecrosis
  • Stress fracture
  • "Spontaneous osteonecrosis of the knee"

References

• Bohndorf K. Imaging of acute injuries of the articular surfaces (chondral, osteochondral and subchondral fractures). Skeletal Radiol. 1999 Oct;28(10):545-60.
• Vellet AD, Marks PH, Fowler PJ, Munro TG. Occult posttraumatic osteochondral lesions of the knee: prevalence, classification, and short-term sequelae evaluated with MR imaging. Radiology. 1991 Jan;178(1):271-6.

Surveillance for Local Recurrence of Colon Cancer

A comparison of different surveillance strategies for locally recurrent colorectal cancer:

Modality	Sensitivity	Specificity	PPV	NPV	Accuracy
CEA	44.4%	92.5%	66.7%	83.1%	80.3%
PET-CT	94.4%	73.6%	54.8%	97.5%	78.9%
MRI	88.9%	73.6%	53.3%	95.1%	77.5%

The National Comprehensive Cancer Network (NCCN) also has new surveillance guidelines (2012) for colon and rectal cancer patients. For colon cancer patients, these guidelines include:

• History and physical examination every 3-6 months for the first 2 years, then every 6 months for a total of 5 years.
• CEA every 3-6 months for the first 2 years. If the original tumor was T2 or greater or N1-N2, CEA every 6 months for a total of 5 years after that.
• CT Chest, abdomen, pelvis every year for node positive patients and node negative patients at high risk for recurrence (e.g., vascular invasion and poorly differentiated tumors).
• Colonoscopy in 1 year (if the patient did not have a pre-operative colonoscopy due to an obstructive lesion, colonoscopy in 3-6 months). Repeat colonoscopy in 1 year if advanced adenoma. If no advanced adenoma was present, repeat in 3 years then every 5 years.
• PET-CT is not routinely recommended.

References

• Desch CE, Benson AB 3rd, Somerfield MR, Flynn PJ, Krause C, Loprinzi CL, Minsky BD, Pfister DG, Virgo KS, Petrelli NJ; American Society of Clinical Oncology. Colorectal cancer surveillance: 2005 update of an American Society of Clinical Oncology practice guideline. J Clin Oncol. 2005 Nov 20;23(33):8512-9.
• Fiocchi F, Iotti V, Ligabue G, Malavasi N, Luppi G, Bagni B, Torricelli P. Role of carcinoembryonic antigen, magnetic resonance imaging, and positron emission tomography-computed tomography in the evaluation of patients with suspected local recurrence of colorectal cancer. Clin Imaging. 2011 Jul-Aug;35(4):266-73.

Leiomyosarcoma vs. Leiomyoma on FDG-PET

While uterine leiomyosarcomas usually have moderate to intense FDG uptake and uterine leiomyomas usually have low to moderate FDG uptake, there is overlap in findings on FDG-PET. This, unfortunately, means that FDG PET cannot reliably differentiate leiomyosarcoma from leiomyoma.

The image above shows a uterine leiomyoma (arrow) with intense FDG activity (maximum SUV of around 10). It has remained stable in size and activity on 4 years of follow-up PET/CT.

References

• Kitajima K, Murakami K, Kaji Y, Sugimura K. Spectrum of FDG PET/CT findings of uterine tumors. AJR Am J Roentgenol. 2010 Sep;195(3):737-43.

Notch on the Lateral Aspect of the Radial Metaphysis

A notch can be seen as a normal variant on the lateral aspect of the radial metaphysis. This notch will eventually fill in by overgrowth of the epiphysis of the radial head.

References

McCarthy SM, Ogden JA. Radiology of postnatal skeletal development. VI. Elbow joint, proximal radius, and ulna. Skeletal Radiol. 1982;9(1):17-26.