Module 1

Reading the prostate mpMRI

MRI basics, the multi-parametric sequences, zonal anatomy and PI-RADS in plain terms.

Honestly, the first time a radiologist talked me through a prostate MRI it looked like grey soup and everyone else seemed fluent. If that is you, you are normal, and you are in the right place. We build it up from "what even is an MRI".

MRI slices live

The raw multi-parametric scan.

3D reconstruction live

Segmented gland, zones and lesion as a rotatable model.

Beside-patient spatial teaching future spatial workflow

Future spatial-computing workflows for placing the anatomy model in clinical space.

01 What an MRI actually is 4 min

Let us start from the very beginning, because nobody explained this to me and I was too embarrassed to ask.

An MRI uses no radiation at all. It uses a strong magnet and radio waves, which make the water in your body give off tiny signals that a computer turns into pictures. That is most of it.

The idea that unlocked everything for me: the same prostate looks different on two images side by side. That is on purpose. They are different T2 "sequences", each tuned to show different tissue.

Key point MRI = magnet + radio waves + water signal. No radiation. Different sequences show different things deliberately.

You can now explain why an MRI has no radiation and why one scan shows several different images. More than most people on the ward can do.

A patient asks if their prostate MRI involves radiation like a CT. The honest answer?

02 What makes it multi-parametric 5 min

The "mp" means multi-parametric: we look through several lenses and combine them. Three matter.

1. T2 - the anatomy lens

Shows the shape and zones. Your map.

2. DWI and its ADC map - the cellularity lens

Measures how freely water moves. Cancer crams cells together, so water movement is restricted.

The thing nobody told me: restricted diffusion is bright on DWI but dark on ADC. Same finding, opposite look, because ADC is a calculated mirror image.

3. DCE - the blood-flow lens

A small gadolinium injection; tumours tend to light up early. A supporting, tie-breaking role in modern scoring.

A line to remember "Bright on DWI, dark on ADC, makes the radiologist twitchy."

You can now name the three sequences and say what each is for. That is the vocabulary of an MDT.

Which sequence tells you how tightly packed the cells are?

03 Zonal anatomy: where cancer lives 5 min

The bit urologists most need and are quietly shakiest on. Bear with me, it is satisfying once it clicks.

PZ - outer shell, mostly at the back. Prime real estate for cancer.
TZ - the middle, around the urethra. Where BPH enlarges, and where some cancers hide.

Around 70% of prostate cancers start in the PZ, so "lesion in the peripheral zone" should raise your antennae.

See it in 3D. Rotate a real segmented gland and fade the peripheral and transition zones in and out. Open in 3D

Key point ~70% of prostate cancers arise in the peripheral zone. The transition zone is BPH territory but not innocent.

You can picture the gland in zones and say where most cancers live.

Roughly what proportion of prostate cancers arise in the peripheral zone?

04 Which sequence matters where 4 min

The rule that makes you sound like you know what you are doing in MDT. Different zones, different dominant sequences.

In the PZ, the dominant sequence is DWI. The zone is uniform, so restriction stands out.
In the TZ, the dominant sequence is T2. It is a lumpy BPH mess, so we lean on shape and texture. A suspicious TZ lesion looks like a smudged "erased charcoal" area.

Mnemonic "Peripheral, look at Diffusion. Transition, Trust T2." The double letters help: P-D and T-T.

You can say which sequence drives the decision in each zone.

A lesion is in the transition zone. Which sequence is dominant for judging it?

05 From image to a PI-RADS score 5 min

The score everyone quotes. PI-RADS (or the very similar Likert scale used widely in the UK) boils it down to 1 to 5. You do not assign it as a urologist, but you must read it intelligently.

1-2 reassure.
3 the honest "not sure" score.
4-5 this needs a biopsy.

See it in 3D. Compare a peripheral-zone lesion case with a normal gland and a BPH-pattern gland. Open in 3D

Key point PI-RADS reflects suspicion, not certainty. 3 is the deliberately uncomfortable middle ground.

You can read a PI-RADS or Likert score and know roughly what it implies. End of Module 1.

Which PI-RADS scores generally prompt a biopsy?

That is Module 1. You can now follow the imaging half of an MDT conversation, which is a genuine milestone.

Next: Why and when we biopsy →