Scedosporium apiospermum causing otomycosis in an immunocompetent child with tympanostomy tubes: Management of this rare entity

Infection following a tympanostomy tube insertion is a common occurrence. Scedosporium apiospermum is a filamentous fungus mainly isolated in water and soil. There have been no reported cases of S. apiospermum infection of an immunocompetent individual with a tympanostomy tube in situ. A child was referred with unilateral otorrhoea failing to respond to conventional treatment in the community. S. apiospermum was identified following specialist testing. An extended course of anti-fungal treatment led to complete resolution. Due to the rare occurrence of aural S. apiospermum and unreported nature, it should be managed in a multidisciplinary setting.

Use of magnetic resonance imaging as the primary imaging modality in the diagnosis and follow-up of malignant external otitis

Malignant external otitis (MEO) is a severe infection of the external auditory meatus caused by Pseudomonas aeruginosa. Classical features include unrelenting deep otalgia, otorrhoea and granulations in the floor of the ear canal. Treatment is generally protracted antibiotic therapy and monitoring of inflammatory markers; the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Traditionally computed tomography (CT) has been the imaging modality of choice. The authors present a case where magnetic resonance imaging (MRI) has been crucial in the diagnosis and follow up of a patient with MEO.

Pulmonary embolism. Is the clinical history a useful adjunct to aid the interpretation of the equivocal lung scan?

Pulmonary embolism is commonly fatal, yet notoriously difficult to detect. Diagnosis often relies on the ventilation-perfusion radionuclide scan, which itself is frequently equivocal. It has been suggested that if the equivocal ventilation-perfusion scan is interpreted in the light of clinical information, diagnostic accuracy can be improved. However, which features in the history should be considered? In this study of 197 patients undergoing ventilation-perfusion scanning, the clinical data of the 98 patients with either high-probability or normal scans were compared to the scan findings. The presence of a deep vein thrombosis was significantly associated with a high probability scan, whereas the presence of constant chest pain was significantly associated with a negative scan. Classical symptoms for pulmonary embolism, namely pleuritic chest pain and hemoptysis, were poor predictors of high-probability scans. Consequently, the authors advise considerable caution when using the clinical data to aid the interpretation of the equivocal lung scan in the individual case.

Duplex ultrasound scanning for diagnosing lower limb deep vein thrombosis

BACKGROUND

Traditionally, venography is used to investigate deep vein thrombosis (DVT), though duplex ultrasound offers a challenging, noninvasive alternative method and previous reports have described the use of duplex ultrasound for detecting proximal lesions.

OBJECTIVE

To compare duplex ultrasound imaging with venography for both proximal and distal lesions using the probe compression technique and a different protocol.

METHODS

Duplex scans were done by the same operator prior and blind to venography, which was performed using a standard protocol with the films being reviewed blindly by a second radiologist at a later date.

RESULTS

In 74 patients, 21 of 22 above-knee lesions present on venography were detected by duplex scanning and there was complete agreement in the 52 of 52 venogram negatives. For lesions below the knee, duplex detected 26 of 27 lesions also present on venography and agreed on 37 of 43 venogram negatives. These figures give duplex ultrasound overall accuracies of 99% and 90% (Kappa 98% and 89%) for above- and below-knee lesions, respectively.

CONCLUSION

These figures suggest duplex ultrasound technique compares favorably with venography for diagnosing both proximal and distal lesions.

Dosimetric assessment of radiolabelled lipiodol as a potential therapeutic agent in colorectal liver metastases using combined CT and SPECT

Lipiodol has previously been used as an agent for targeted radiotherapy by selective retention in primary hepatic tumours following direct hepatic arterial infusion. We have considered the potential dosimetry of 131I-labelled lipiodol in treating colorectal liver metastases. Fifteen patients with multiple colorectal liver metastases underwent selective hepatic angiography when 5 ml lipiodol labelled with 40 MBq 131I were infused. All patients underwent planar scintigraphy of the abdomen and thorax, single photon emission computed tomography (SPECT) of the liver and whole body counting on at least two occasions following lipiodol injection. Computed tomographic (CT) images of the liver were also taken typically 7 days postinjection. The lipiodol was found to deposit on the periphery of metastases of less than 10 cm diameter. In one patient a metastasis of diameter greater than 15 cm failed to infuse. In two patients the lobe of the liver containing metastases was not successfully infused. Overlay of CT and SPECT images confirmed concentration in metastases. Quantification of SPECT images indicated that between 55 and 100% (median 86%) of the injected activity was retained in the liver following injection, and tumour to liver ratios of dose delivered ranged from 1.21:1 to 4.7:1 (median 3.1:1). Tumour does ranged from 11.8 to 43.3 mGy MBq-1 injected. Dose to the lungs ranged from 0 to 46% of the liver dose (median 16%). Lipiodol has potential for treatment of colorectal liver metastases in targeted radiotherapy.

Biodistribution of Lipiodol following hepatic arterial injection

Thirteen patients undergoing selective coeliac angiography before insertion of an indwelling hepatic arterial cannula underwent injection of 3 ml radiolabelled Lipiodol (2 MBq 131I) into the hepatic artery at the end of the procedure. At subsequent laparotomy 1-9 days later, biopsies were taken from normal liver and metastases. The radioactivity of this material was measured to establish the tumour:liver ratios. Two patients with large metastases (> 10 cm in diameter) had low ratios. In the remainder, the median ratio at 24 h was 1.5:1 (range 1.1-2.5:1; n = 5) and 2.6:1 (range 1.5-64.0:1; n = 6) at 3-9 days. Four patients underwent single photon emission computed tomography, which confirmed selective retention of Lipiodol in small metastases, although no activity was detected in a large deposit (> 15 cm) 10 days after injection. The tumour:liver ratio in the other three patients increased from 3.0-5.6:1 on day 1 to 4.5-7.2:1 on day 6. This study suggests that Lipiodol may be a useful therapeutic delivery agent to small colorectal liver metastases.

Biodistribution of lipiodol following hepatic arterial injection

Lipiodol, a derivative of poppy seed oil, has been used angiographically to improve visualisation of small liver tumours. We have utilised this finding to determine whether intrahepatic arterial injection of lipiodol can be used as a vehicle to deliver selectively 131I into liver tumours. Two groups of rats were studied. Group 1 (control, no liver tumour) received 0.1 ml 131I-lipiodol (1 microCi) into the hepatic artery. Animals were killed at regular time intervals over 30 days and organs were submitted to well-counting. Over 90% of activity remained in the liver at 6 h. Eighty per cent activity was lost from the normal liver, to be excreted in the urine over 30 days. Group 2 animals received intraportal injections of 7.5 x 10(5) MC28 sarcoma cells. Multiple liver metastases were present after 14 days. Animals were similarly studied at each time interval and samples from tumour and normal liver were submitted to well-counting. Lipiodol was selectively retained within tumour and cleared from normal liver. 131I-lipiodol may prove valuable as a delivery agent for radio/chemotherapy to liver metastases.

Measurement of radiation dose to the thyroid using positron emission tomography

Measurements of the functioning volume of thyroid tissue have been made in 22 patients undergoing radioiodine therapy for thyrotoxicosis, using a prototype multiwire proportional counter positron camera. Tomographic images were produced of the distribution of 124I in the thyroid. Functioning volumes were found to be in the range 21-79 cm3 with volume errors of the order of +/- 4% to +/- 14%. Radioiodine uptake varied from 28% to 98%. Using a value of 6 days for the effective half-life of radioiodine in hyperactive thyroids, radiation doses from a standard therapy administration of 75 MBq of 131I varied from 11 to 48 Gy (compared with a recommended 50-70 Gy). In five cases PET imaging showed a non-uniform distribution of radioiodine in thyroids thought to have uniform uptake from conventional pinhole scintigraphy.