Imaging appearances for recurrent nasopharyngeal carcinoma and post-salvage nasopharyngectomy.

Nasopharyngeal carcinoma (NPC) is a head and neck neoplasm that occurs in endemic numbers among people of southern Chinese descent. External beam radiation to the nasopharyngeal bed and primary draining lymph node echelons is the mainstay of treatment with concurrent cisplatin-based chemotherapy for more advanced disease. Detection of residual and/or recurrent NPC has important clinical implications, as salvage protocols are available. The review aims to increase awareness of the imaging features of NPC recurrences at local and distant sites using computed tomography (CT), magnetic resonance imaging (MRI), and positron-emission tomography (PET). Important changes in imaging seen in patients after nasopharyngectomy are also discussed.

Dynamic contrast-enhanced MRI of neuroendocrine hepatic metastases: A feasibility study using a dual-input two-compartment model.

Neuroendocrine hepatic metastases exhibit various contrast uptake enhancement patterns in dynamic contrast-enhanced MRI. Using a dual-input two-compartment distributed parameter model, we analyzed the dynamic contrast-enhanced MRI datasets of seven patient study cases with the aim to relate the tumor contrast uptake patterns to parameters of tumor microvasculature. Simulation studies were also performed to provide further insights into the effects of individual microcirculatory parameter on the tumor concentration-time curves. Although the tumor contrast uptake patterns can be influenced by many parameters, initial results indicate that hepatic blood flow and the ratio of fractional vascular volume to fractional interstitial volume may potentially distinguish between the patterns of neuroendocrine hepatic metastases.

Metastatic angiosarcoma to the thyroid.

BACKGROUND: Angiosarcoma (AS) in non-alpine areas is exceptionally rare, and so is metastatic AS to the thyroid. The difficulties and controversies associated with its diagnosis and management are highlighted in this case report. METHOD: Case report. RESULTS: A Chinese gentleman with AS metastatic to the thyroid presented a year after radiotherapy to his scalp AS. There was rapid expansion of the metastasis over 2 weeks and invasion of the pyriform fossa caused dysphagia and haemoptysis. The diagnosis was established by paraffin histology of the tumour post-hemithyroidectomy, after repeated fine-needle aspiration cytology was not diagnostic. Patient opted for external beam radiotherapy to the pyriform fossa instead of pharyngolaryngectomy. Residual pyriform tumour was treated with brachytherapy delivered via nasogastric tube. Unfortunately, the patient died 4 months later due to cardiac failure which was unrelated to his oncologic condition. CONCLUSION: AS metastatic to the thyroid is possible. The unexpectedly acute presentation and difficulties associated with diagnosis and management are highlighted. A useful method of delivering brachytherapy to the pyriform fossa is described.

Neurological changes following radiation therapy for head and neck tumours.

Radiation therapy is widely used in the treatment of head and neck tumours either as a primary form of treatment or a supplementary modality. Although the benefits of radiation therapy are well established, this treatment modality is not without untoward consequences and complications. The intent of this paper is to highlight the neurological complications that may follow the treatment for head and neck malignancies, in particular, following radiation therapy for nasopharyngeal carcinoma.

Clinics in diagnostic imaging (85). Mandible osteoradionecrosis complicated by infection.

Mandibular osteoradionecrosis is a rare but well-known complication that may be seen in patients with head and neck tumours following radiation therapy. A 42-year-old man presented with painful soft tissue swelling and a discharging sinus over the right mandible. Radiographs showed osteolytic destruction. Computed tomography confirmed bony destruction and fragmentation, as well as signs of soft tissue infection. The diagnosis of mandible osteoradionecrosis complicated by infection was confirmed by biopsy and surgically. The clinical and imaging features of osteoradionecrosis are highlighted.

Diffusion weighted MR imaging in acute stroke: the SGH experience.

Cerebrovascular accident (CVA) is a leading cause of death and disability in many countries. Diffusion-weighted (DW) magnetic resonance (MR) imaging has been reported to be useful in the detection of acute strokes and as an investigative tool evaluating the therapeutic effects of neuroprotective and thrombolytic agents. The objectives of this study are to share our experience using the commercially available isotropic DW scan in imaging of acute stroke, assess its usefulness over conventional T2-weighted (T2W) scans in a busy clinical radiology unit and highlight it pitfalls. We found the rapid sub-minute DW technique well suited for ill and restless stroke patients and superior to T2W scans in many ways. It was highly sensitive to acute ischaemic lesions, made lesions easily identifiable and readily differentiated the acute lesion from a background of multiple chronic infarcts. However, there are potential pitfalls in the evaluation of small hyperacute posterior fossa strokes and venous infarcts. The major strength of this MR technique lies in its ability to diagnose hyperacute strokes and thence the potential for therapeutic thrombolysis, but unfortunately patients qualifying for the "therapeutic window" were a minority. More efforts need to be focused on public education in order for this powerful imaging modality to find its true value and contribute to viability of an effective thrombolytic programme.

Assessment of tumor blood flow distribution by dynamic contrast-enhanced CT.

A distinct feature of the tumor vasculature is its tortuosity and irregular branching of vessels, which can translate to a wider dispersion and higher variability of blood flow in the tumor. To enable tumor blood flow variability to be assessed in vivo by imaging, a tracer kinetic model that accounts for flow dispersion is developed for use with dynamic contrast-enhanced (DCE) CT. The proposed model adopts a multiple-pathway approach and allows for the quantification of relative dispersion in the blood flow distribution, which reflects flow variability in the tumor vasculature. Monte Carlo simulation experiments were performed to study the possibility of reducing the number of model parameters based on the Akaike information criterion approach and to explore possible noise and tissue conditions in which the model might be applicable. The model was used for region-of-interest analysis and to generate perfusion parameter maps for three patient DCE CT cases with cerebral tumors, to illustrate clinical applicability.

Interpretation and applicability of empirical tissue enhancement metrics in dynamic contrast-enhanced MRI based on a multiple pathway model.

Computer simulations based on a physiologically realistic tracer kinetic model with multiple pathways was used to provide insights on the applicability and interpretation of tissue enhancement metrics such as the maximum slope, peak enhancement and area under curve, commonly used in dynamic contrast-enhanced (DCE) MRI. Results show that physiological conditions of the tissue that could affect the accuracy of the maximal slope method include a high blood flow, increased variability of flow within the vasculature or a low vascular volume. Interestingly, changes in permeability and interstitial volume might not affect the accuracy of the maximal slope method. Time-to-peak and peak value of the tissue enhancement curve are not strictly properties of the tissue alone, and they cannot be linearly related to intrinsic tissue parameters such as blood flow, blood volume, capillary permeability, interstitial volume and mean transit time. Similar to the normalized initial area under tissue concentration curve, an alternative estimate of the total tracer distribution volume can be simply given by the ratio of tracer concentration in the tissue and artery sampled at the final DCE scan.

Oligodendroglial tumor chemotherapy using "decreased-dose-intensity" PCV: a Singapore experience.

The authors propose "decreased-dose-intensity" PCV (procarbazine, lomustine [CCNU], and vincristine) chemotherapy for Asian patients with oligodendroglial tumors. In this study, all seven patients with oligodendroglioma (OD) and eight with anaplastic oligodendroglioma (AO) had objective responses or stable disease. Median progression-free survival was greater than 29 months (OD) and 36.5 months or greater (AO); 86% of patients with OD and 63% with AO remain progression-free. Twenty-four Common Toxicity Criteria Grade 3/4 adverse events were noted.

CT evaluation of nasolacrimal relapse of nasopharyngeal carcinoma.

AIM: The aim of the current study was to elucidate the anatomy of the nasolacrimal apparatus using computed tomography (CT), and to investigate the CT findings suggestive of recurrent nasopharyngeal carcinoma (NPC) involving the nasolacrimal apparatus. MATERIALS AND METHODS: CT images of five patients with clinical or radiological findings suggestive of recurrent NPC who presented with nasolacrimal involvement were reviewed. Involvement of the lacrimal fossa, nasolacrimal canal (NLC), and adjacent anatomic structures including orbit and sinonasal cavities were noted. RESULTS: CT in all patients demonstrated findings of NLC invasion and ostiomeatal complex obliteration. Four of the five patients showed medial canthal mass or pre-septal thickening, ethmoid bulla opacification and inferior nasal meatal involvement. CONCLUSION: Knowledge of the anatomy of the nasolacrimal apparatus using CT is critical for evaluating images for tumour recurrence at this site. NLC invasion, a medial canthal mass and pre-septal thickening are important primary indicators for potential involvement of the nasolacrimal apparatus by recurrent NPC. Secondary signs suggesting this distinct form of relapse are obliteration of ostiomeatal channel, ethmoid bulla opacification and inferior nasal meatus involvement.

Radiologists' detection of mammographic abnormalities with and without a computer-aided detection system.

The aim of this study was to to evaluate the role of a computer-aided program (CAD) in assisting detection of mammographic lesions by radiologists not specifically trained in mammography and its potential utility in breast screening. Mammograms were evaluated by radiologists not specifically trained in mammography first without, and then with, the CAD. Finally, the mammograms were evaluated by experienced mammographers who formed the reference standard. Two hundred and ninety four breasts were studied. In 257 breasts (87.4%), the CAD system did not help with the detection of abnormalities. It assisted radiologists in detecting abnormalities in 21 breasts (7.1%) with potential for detecting abnormalities in a further 13 breasts (4.4%). Only in three cases (1%) did it cause confusion in interpretation. There is overall increased sensitivity in detecting mammographic abnormalities with the aid of the CAD system from 74.4 to 87.2%, which is statistically significant. However, it failed to detect suspicious abnormalities in 71 breasts (24.1%). The CAD system improved detection of suspicious mammographic abnormalities by radiologists who are not specifically trained in mammography. However, there is also a substantial failure to detect suspicious mammographic features that cautions against over-reliance on the system, emphasizing its role as a second reader at best.